BACTERIAL CELL WALL SYNTHESIS INHIBITORS/BACTERIAL PROTEIN SYNTHESIS INHIBITORS/INHIBITORS OF BACTERIAL NUCLEIC ACID SYNTHESIS OR FUNCTION/ANTIMYCOBACTERIAL DRUGS

Trimethoprim-sulfamethoxazole

A 59-year-old man complained to his physician that his skin itched all over his body. Two weeks earlier, he had begun oral antibiotic therapy for acute pharyngitis. Physical examination showed a diffuse maculopapular rash. Which of the following drugs most likely caused the patient's dermatitis?

Decreased drug oral bioavailability

A 25-year-old man recently diagnosed with severe acne involving the face, back, and chest started a treatment that included tetracycline. The physician instructed the patient to avoid milk or dairy products within 2 hours of taking the medication, because dairy products can interact with tetracycline. Which of the following best explains the outcome of the interaction between tetracycline and dairy products?

Tetracycline

A 25-year-old woman presented to the clinic because of vulvar itching and burning and a thick, cheesy vaginal discharge for the past 5 days. The woman had been taking an oral antibiotic for 2 months to treat moderate acne. Gram stain of a vaginal smear indicated Candida albicans as the offending pathogen. Which of the following drugs most likely contributed to the appearance of the patient's infection?

Penicillin G

A 26-year-old man presented to the emergency department with sudden onset of fever (101.1°F, 38.5°C), oliguria, and a skin rash. The man had been receiving systemic pharmaco-therapy for primary syphilis. Laboratory findings showed eosinophiluria and proteinuria. Further exams led to the diagnosis of drug-induced tubulointerstitial nephritis. Which of the following antibiotics most likely caused the patient's disease?

Isoniazid

A 28-year-old man underwent a tuberculin skin test (Mantoux method) that turned out to be positive. The man was the husband of a woman who had uncomplicated pulmonary tuberculosis treated at home with a multiple-drug regimen. The man was prescribed a drug to be taken daily for 6 months. Which of the following drugs was most likely given?

Sulfamethoxazole

A 28-year-old woman late in her third trimester of pregnancy complained to her physician of persistent burning upon urination. The patient's medical history was significant for recurrent urinary tract infections. An antibiotic treatment was prescribed. Which of the following drugs would be contraindicated in this patient because of a risk of kernicterus in the newborn?

Rifampin

A 47-year-old Hispanic man recently diagnosed with pulmonary tuberculosis started a multi-drug treatment. One of the drugs he was given is active against most mycobacteria, many gram-positive and -negative bacteria, chlamydiae, rickettsiae, and poxviruses. Which of the following drugs has such a broad antibacterial spectrum?

Macrolides

A 53-year-old man was admitted to the hospital with the admitting diagnosis of pneumonia. Further exams indicated that the pneumonia was due to Mycoplasma pneumonia,and treatment with an appropriate bacteriostatic antibiotic was started. The given drug most likely belonged to which of the following classes?

Erythromycin

A 58-year-old woman complained to her physician of bruising and nose bleeds. The woman, diagnosed with atrial fibrillation, had been taking warfarin for 1 year. One week earlier, she was diagnosed with mycoplasmal pneumonia and was started on antibiotic therapy. Which of the following drugs most likely mediated the patient's bleeding?

Rifampin

A 10-year-old girl was brought to the emergency department by her mother, who said that her daughter had high fever (103.3°F, 39.6°C) and was irritable and lethargic. Physical examination showed nuchal rigidity and a positive Brudzinski sign. Subsequent exams led to the diagnosis of meningo-coccal meningitis. Which of the following drugs would have been appropriate prophylaxis for the health personnel assisting this girl?

Gene-induced changes in bacterial RNApolymerase

A 13-year-old boy had been receiving a multidrug treatment for bone tuberculosis. After 4 months of therapy, susceptibility testing showed that the mycobacterium was resistant to isoniazid and rifampin. Which of the following was most likely the mechanism of mycobacterial resistance to rifampin in this patient?

Blockade of translocation reaction

A 14-year-old girl diagnosed with a respiratory tract infection started treatment with erythromycin. Which of the following molecular actions on bacterial cells most likely mediated the therapeutic effect of the drug in the patient's disease?

Erythromycin

A 15-day-old baby boy was admitted to the pediatric ward with mucopurulent ocular discharge, edema of the eyelids, and peudomembrane formation. A Gram stain of the exudate revealed no microorganisms, but a Giemsa stain showed cells with cytoplasmic inclusions. Both topical and systemic treatments were prescribed. Which of the following drugs was most likely administered?

Linezolid

A 15-year-old girl was admitted to the hospital because of fever (103.2°F, 39.5°C) and severe pain in her left leg. A bone scan showed in ammation in her left distal femur. Two blood cultures were positive for Staphylococcus aureus, and susceptibility testing showed that the bacterium was methicillin- and vancomycin-resistant. Therapy was started with an antibiotic that binds to the 23S portion of the 50S ribosomal subunit and inhibits the formation of the initiation complex. Which of the following drugs was most likely given?

Activation of motilin receptors in the gut

A 17-year-old girl complained to her physician of watery diarrhea. Three days ago, she was diagnosed with streptococcal pharyngitis, and treatment with erythromycin was started. Which of the following best explains the most likely reason for this adverse effect of erythromycin?

Ciprofloxacin

A 22-year-old man who was on vacation in Mexico was seen at a local clinic because of malaise, fever (103.2°F, 39.5°C), tachycardia, nausea and vomiting, abdominal cramps and six loose, unformed, and bloody stools. The symptoms started 24 hours after a dinner at a local restaurant. A presumptive diagnosis was made, and pharmacotherapy was started. Which of the following drugs would be appropriate for this patient?

Methicillin-resistant Staphylococcus aureus

A 22-year-old woman consulted her physician because of a postpartum breast infection. A Gram stain of the pus re- vealed gram-positive bacteria, and a susceptibility test showed resistance to all β-lactam antibiotics. Which of the following bacteria was most likely the offending pathogen?

Alteration of the ribosomal binding site that prevents drug binding

A 23-year-old man complained to his physician of a severe sore throat and fever. Because the man was allergic to penicillin, erythromycin was prescribed, but 3 days later, the clinical picture was not improved. The physician changed the antibiotic because he suspected bacterial resistance to erythromycin. Which of the following mechanisms can ac- count for resistance to macrolides?

Azithromycin

A 23-year-old woman complained to her physician of pain during urination and a mucoid-like vaginal discharge that started about 14 days after her last intercourse. A Gram stain of the exudate revealed gram-negative cocci. Treatment with ceftriaxone was prescribed. Which of the following drugs would be appropriate to add to the patient's regimen?

Ceftriaxone

A 23-year-old woman complained to her physician of urinary frequency, pain upon urination, and a mucopurulent vaginal discharge. One year earlier, the patient had undergone an anaphylactic reaction to penicillin. A Gram stain of the exudate revealed gram-negative cocci. Which of the following drugs would be contraindicated for this patient?

Doxycycline

A 24-year-old man was admitted to the hospital because of severe erythema that occurred a few minutes after exposure to sunlight. He reported that past and more prolonged exposures to sun had caused only a mild erythema. A few days earlier, the man had started on antibiotic treatment for non-gonococcalurethritis. Which of the following antibiotics most likely caused the patient's erythema?

Streptococcus pyogenes

A 24-year-old woman came to the clinic with a sore throat and low-grade fever.Physical examination showed tonsil exudates and tender cervical adenopathy. A Gram stain of the tonsil exudate demonstrated the presence of a high number of bacteria.A diagnosis was made,and penicillin G was prescribed, as the physician knew that the most likely offending pathogen was sensitive to the antibiotic. Which of the fol- lowing bacteria did the physician most likely believe caused the patient's infection?

Bartonella enselae: erythromycin

A 3-year-old boy was brought to the pediatrician's office by his mother because of a low-grade fever and a painful, enlarged inguinal lymph node. On questioning, the mother stated that the boy was scratched on his right leg by his pet cat 1 week earlier. A Gram stain of pus aspirated from the lymph node revealed many small,gram-negative rods.Which of the following correctly pairs the most likely offending pathogen with the appropriate treatment?

Erythromycin

A 3-year-old girl developed whooping cough. Parents and other close contacts of the patient should receive a 10-day course of which of the following drugs?

Haemophilus influenzae

A 30-year-old man recently diagnosed with otitis media started treatment with ciprofloxacin. A 7-day course was able to completely heal the disease. Which of the following bacteria most likely caused the patient's infection?

Relapsing fever: doxycycline

A 30-year-old man was admitted to the hospital with fever (103°F, 39.4°C), chills, tachycardia, vomiting, and muscle pain. He had the same symptoms 10 days earlier, just after a camping trip near the United States−Mexico border. The fever remained high for 3 days,then cleared abruptly. A thick blood smear with Giemsa stain revealed many threadlike bacteria with large, irregular coils. Which of the following correctly pairs the most likely disease with the appropriate treatment?

To delay the emergence of drug resistance

A 30-year-old man with AIDS was recently diagnosed with pulmonary tuberculosis and started a multidrug treatment with isoniazid, rifampin, pyrazinamide, and ethambutol. Which of the following best explains why ethambutol was added to the therapeutic regimen?

Ampicillin

A 30-year-old woman was in labor with her second child. Her first baby had contracted neonatal meningitis due to contamination with Streptococcus agalactiae during delivery. To prevent recurrence of this infection in the second child, which of the following drugs would be most appropriate for treatment of both the mother and the baby?

Mycolic acids

A 31-year-old homosexual man was found to be HIVpositive. Currently, he did not have symptoms of tuberculosis, but his tuberculin skin test was positive. A treatment with isoniazid was prescribed. The inhibition of synthesis of which of the following endogenous compounds most likely mediated the therapeutic effect of the drug in this patient?

Vibrio cholerae

A 31-year-old man was hospitalized because of severe watery diarrhea, vomiting, and altered mental status. The man returned 1 day earlier from Latin America, where he visited with relatives, several of whom were recovering from an intestinal infection. Physical examination showed a critically ill patient with marked loss of tissue turgor, sunken eyes, and wrinkled skin. Lab tests on admission revealed hemo-concentration and severe metabolic acidosis. A diagnosis was made, and an emergency treatment was initiated that included the parenteral administration of doxycycline. Which of the following bacteria most likely caused the patient's disease?

Impairment of fetal growth

A 31-year-old pregnant woman who recently arrived from Uganda was diagnosed with lymphogranuloma venereum. The physician prescribed a treatment with erythromycin, as tetracyclines are contraindicated during pregnancy. Which of the following drug-induced adverse effects best describes the reason for this contraindication?

Activation of autolytic enzymes in the bacterial cell wall

A 31-year-old woman recently diagnosed with acute tonsillitis started a treatment with amoxicillin. Which of the following molecular actions most likely contributed to the therapeutic effect of the drug in the patient's disease?

Ceftazidime and tobramycin

A 32-year-old male heroin addict was admitted to the hospital with a 2-day history of fever, shaking chills, rigors, and night sweats. His vital signs were blood pressure 100/60 mm Hg, pulse 120 bpm, respirations 24/min, temperature 102.2°F (39°C). Two-dimensional echocardiography revealed three small vegetations on the tricuspid valve. Three blood cultures were drawn, and empiric therapy was initiated. The cultures turned out to be positive for Pseudomonas aeruginosa, with the following antibiotic susceptibilities: Gentamicin - (minimum inhibitory concentration: 16 μg/mL) Tobramycin - (minimum inhibitory concentration: 2 μg/mL) Piperacillin - (minimum inhibitory concentration: 64 μg/mL) Ceftazidime - (minimum inhibitory concentration: 4 μg/mL) Imipenem - (minimum inhibitory concentration: 2 μg/mL) Surgical excision of the infected valve and a 6-week post- operative treatment were planned. Which of the following drug combinations would be most appropriate for the patient at this time?

Transpeptidation reaction

A 32-year-old man recently diagnosed with cellulitis caused by Streptococcus pyogenes started a treatment with ampicillin. The drug acts by binding to penicillin-binding proteins. Which of the following molecular actions is catalyzed by penicillin-binding proteins?

Blockade of the transpeptidation reaction of protein synthesis

A 32-year-old woman on a vacation trip in East Asia was diagnosed with acute conjunctivitis. A topical treatment with chloramphenicol was able to completely heal the disease. Which of the following molecular actions most likely mediated the therapeutic efficacy of the drug in the patient's disease?

Penicillin G

A 32-year-old woman was seen at a clinic because of 2 days of headache with joint and muscle pain. Physical examination revealed nuchal rigidity and a petechial rash on the lower extremities.A Gram stain of her spinal fluid showed many neutrophils and many gram-negative, bean-shaped diplococci. Which of the following drugs would be most appropriate for the therapy of this patient?

Gene-induced changes in bacterial arabinosyl transferase

A 33-year-old man had been receiving a multidrug treatment for pulmonary tuberculosis. After 3 months of therapy, susceptibility testing showed that the mycobacterium was resistant to isoniazid and ethambutol. Which of the following was most likely the mechanism of mycobacterial resistance to ethambutol in this patient?

Penicillin G

A 33-year-old man presented to the clinic because he had noticed a red, painless nodule on the glans of his penis 1 week earlier. Three days after it appeared, the nodule be- came ulcerated, but only minimally painful. Physical examination showed an ulcer with an indurated base that exuded clear serum. Darkfield microscopy from the exudate showed numerous slender spiral microorganisms that were actively motile. A diagnosis was made, and a suitable therapy was prescribed. Which of the following drugs would be most appropriate for this patient?

Doxycycline

A 33-year-old woman was hospitalized with fever (103.5°F, 39.7°C), chills, mental confusion, vomiting, and diarrhea. One week earlier, the woman had returned from a vacation in central Africa. A Giemsa stain confirmed the diagnosis of Plasmodium falciparum malaria. Because the patient came from a region with multidrug-resistant strains of P. falciparum, parenteral quinidine therapy was started. Which of the following would be a useful agent to add to her therapeutic regimen?

Isoniazid and rifampin

A 34-year-old HIV-positive woman was admitted to the hospital because of a 4-week history of fatigue, increasing abdominal girth, exertional dyspnea, nocturnal dyspnea, and peripheral edema. Vital signs were pulse 80, blood pressure 90/70 mm Hg. Physical examination revealed prominent external jugular veins that became more distended during inspiration. The heart was slightly enlarged, and a third sound was noted in early diastole. A computed tomography scan showed a large pericardial effusion, and pericardiocentesis removed 500 mLof bloody fluid with a high protein content. A diagnosis of hemorrhagic pericarditis was made, and an appropriate therapy was prescribed. Which of the following pairs of drugs would be most appropriately included in the patient's regimen?

Ceftriaxone

A 34-year-old man presented to the clinic with a painful ulcer on his penis. Regional lymph nodes were enlarged and painful. The man admitted to unprotected intercourse with a new partner while on a recent vacation. Darkfield micros- copy and an FTA-ABS (fluorescent treponemal antibody absorption) test for syphilis were negative. A Gram stain of pus revealed short gram-negative bacilli in parallel chains.Which of the following would be the most appropriate pharmaco-therapy for this patient?

Penicillin G

A 34-year-old man was admitted to the emergency department because of flushing, itching, nausea, sneezing, and abdominal cramps. Five days earlier, the patient was diagnosed with syphilis and started on antibiotic treatment. Vital signs on admission were blood pressure 98/56 mm Hg, pulse 125 bpm, respirations 22/min. Physical examination showed a cyanotic patient with urticaria, angioedema, and wheezing. Which of the following antibiotics most likely caused the patient's signs and symptoms?

Erythromycin

A 34-year-old pregnant woman developed severe pharyngitis that turned out to be due to Streptococcus pyogenes. Past history of the patient was signifcant for an anaphylactic reaction to ampicillin. Which of the following antibiotics would be most appropriate for this patient?

Doxycycline

A 34-year-old woman presented to the clinic with mild fever (99.5°F, 37.5°C), fatigue, muscle and joint pain, and multiple red rashes with a clear center. She reported that 10 days ago she was bitten on the arm by a tiny tick. A circular skin lesion started at the bite site, expanded to 15 cm (about 6 inches) or so, and was followed by multiple, painless rashes. Physical examination confirmed the diagnosis of erythema migrans. Which of the following drugs would be appropriate for the patient at this stage?

Metronidazole

A 34-year-old woman recently diagnosed with salpingitis due to Bacteroides fragilis started a treatment with a drug that is reduced by anaerobes to a highly reactive nitro radical anion able to damage bacterial DNA. Which of the following drugs did the patient most likely take?

Clarithromycin

A 34-year-old woman who was HIV positive presented with fever (100.8°F, 38.2°C), profuse night sweats, poor appetite, and a 20-lb (4.5-kg) weight loss over the past 5 months. Physical examination revealed a cachectic female with prominent oral thrush and mild splenomegaly. Her CD4+ lymphocyte count was 45 cells/mm3 (normal > 500 cells/mm3), and a DNA probe test confirmed the diagnosis of Mycobacterium avium complex infection. An appropriate multidrug regimen was started. Which of the following drugs was most likely included in the patient's pharmacotherapy?

Cephalexin

A 34-year-old woman with no previous history of disease complained to her physician of burning on urination, bladder pain, and frequent urination of a small volume. A microorganism isolated from her urine grew on EMB (eosin methylene blue) agar, produced green colonies, was motile, and was urease-negative. A diagnosis of urinary tract infection was made, and antibiotic therapy was prescribed. Which of the following drugs would be appropriate for the patient's disease?

Enterobacter aerogenes

A 35-year-old man presented with fever (101°F, 38.3°C), cough, and dyspnea. The man was hospitalized 1 week ago because he was found to be HIV positive, but no antiviral therapy had been initiated yet. Further exams led to the diagnosis of pneumonia, and 10 days of gentamicin therapy was able to cure the disease. Which of the following micro- organisms was most likely the cause of the patient's acute illness?

Streptomycin and moxifloxacin

A 35-year-old man recently diagnosed with pulmonary tuberculosis started a treatment with isoniazid, rifampin, pyrazinamide, and ethambutol, but 2 months later, susceptibility testing revealed a Mycobacterium tuberculosis resistant to isoniazid and pyrazinamide. These drugs were discontinued, and two other drugs were prescribed. Which of the following

DNA-dependent RNApolymerase

A 36-year-old Black man recently diagnosed with pulmonary tuberculosis started a drug treatment that included rifampin. Inhibition of which of the following enzymes most likely mediated the therapeutic efficacy of rifampin in the patient's disease?

Metronidazole

A 36-year-old woman complained to her physician that she became dizzy and suffered flushing and vomiting after drinking a double scotch. The woman, recently diagnosed with bacterial vaginosis, started an oral antibiotic therapy 1 week ago. Which of the following drugs most likely caused this interaction with alcohol?

Ciprofloxacin

A 37-year-old woman with AIDS was admitted to the hospital because of fever (100.4°F, 38°C), drenching night sweats, poor appetite, and an 18-lb (about 8-kg) weight loss over the past 3 months. She had a past medical history of intestinal candidiasis and cryptococcal meningitis. Physical examination revealed a cachectic woman with hepatospenomegaly. Chest radiography was unremarkable, and lab results showed a CD4+ lymphocyte count of 50 cells/mm3. A presumptive diagnosis of Mycobacterium avium complex infection was made and later confirmed by a DNA probe test.Which of the following drugs should be included in the initial therapy of this patient?

Doxycycline

A 38-year-old man presented to the hospital with fever (102.7°F, 39.2°C), severe retrobulbar headache, chills, photophobia, muscular pains, and prostration. He reported he found a tick attached to his scalp 7 days earlier while camping in the mountains of Colorado. Physical examination revealed a rash of pink macules 2 to 5 mm (0.08−0.2 inch) spread all over his body. Apresumptive diagnosis was made, and an empiric therapy was started. Which of the following antibiotics would be appropriate for this patient?

Dicloxacillin

A 4-year-old boy was brought to the pediatrician by his mother because of respiratory difficulties. Medical history of the boy was signifcant for recurrent pulmonary infections. A Gram stain of the sputum revealed gram-positive cocci in grapelike clusters. Which of the following drugs would be an appropriate empiric treatment at this early stage?

Penicillin G and clindamycin

A 41-year-old woman collapsed at home and was brought to the emergency department. Her husband stated she had complained recently of severe abdominal cramping, nausea, vomiting, and diarrhea. Vital signs on admission were temperature 103°F(39.4°C),pulse 134 bpm,blood pressure 85/52 mm Hg,respirations28/min.Physical examination showed a critically ill patient with an abdominal erythematous indurated area below the umbilicus and an 8-mm (0.31-inch) central ulcer. A fluorescent antibody test of a specimen from the ulcer identied group A streptococci. Which of the fol- lowing pairs of drugs would be most appropriate for the emergency treatment of this patient?

Streptomycin and doxycycline

A 42-year-old farmer presented to his physician because he had fever that usually rose in the afternoon, subsided during the night, and was followed by drenching sweats. Further exams led to the diagnosis of brucellosis, and a suitable pharmacotherapy was prescribed. Which of the following pairs of drugs would be appropriate for the patient at this time?

Vancomycin

A 42-year-old man hospitalized for staphylococcal endocarditis developed hypotension, tachycardia, generalized pruritus, and facial flushing 15 minutes after receiving an intravenous injection of an antibiotic. Which of the following drugs most likely caused the patient's syndrome?

Inhibition of relaxation of supercoiled bacterial DNA

A 42-year-old man recently diagnosed with mycoplasma pneumonia started a treatment with ciprofloxacin. Which of the following molecular actions most likely mediated the therapeutic effect of the drug in the patient's disease?

Dihydropteroate synthetase

A 44-year-old man recently diagnosed with nocardiosis started a treatment with a high dose of sulfadiazine. Inhibition of which of the following bacterial enzymes most likely mediated the therapeutic effect of the drug in the patient's disease?

Dapsone

A 44-year-old man who recently moved from Mexico to Los Angeles presented to the hospital because of a diffuse skin disease.Skin examination showed macules,nodules,and plaques over his face and thorax. Further exams led to the diagnosis of lepromatous leprosy, and an appropriate therapy was started. Which of the following drugs should be included in the therapeutic regimen of this patient?

Ethambutol

A 44-year-old woman complained of blurred vision and inability to distinguish green objects from red objects. The woman, recently diagnosed with cavitary pulmonary tuberculosis, had been receiving a three-drug combination regimen for 2 months.An eye examination indicated a narrowing of her visual field. Which of the following drugs most likely caused these adverse effects?

Sulfadiazine

A 44-year-old woman presented to the clinic with fever (101°F, 38.3°C) and cough productive of a small amount of greenish, thick sputum. The woman, suffering from pemphigus, had been receiving high-dose prednisone for 6 months. Physical examination revealed coarse breath sounds in the right lower lung, and a chest x-ray showed a 4-cm (1.6-inch) nodule with central cavitation. Examination of the sputum showed long branching filaments of gram-positive, acid-fast rods. Which of the following drugs would be appropriate to treat the patient's infection?

Gentamicin

A 45-year-old diabetic woman complained to her physician of pain in her right ear for the past 5 hours. Further exams led to the diagnosis of external otitis, and later the culture of ear exudate showed Pseudomonas aeruginosa as the main offending pathogen. The patient was given an antibiotic that causes misreading of the bacterial messenger RNA template leading to the production of aberrant bacterial proteins. Which of the following drugs was most likely administered?

Chlamydia psittaci: doxycycline

A 45-year-old farmer presented to the clinic with fever (103.2°F, 39.5°C), chills, headache, and a dry cough. Chest x-ray showed extensive nodular infiltrates radiating from the hilum. History revealed that the man raised chickens and that approximately 2 weeks ago he had lost a large number of them to an undiagnosed disease. The presumptive diagnosis of pneumonia was made, and an appropriate drug was prescribed. Which of the following correctly pairs the most likely offending pathogen with the appropriate treatment?

Tobramycin

A 45-year-old woman was diagnosed with a urinary tract infection due to gram-negative rods. The woman had been suffering from myasthenia gravis for 5 years. Which of the following antibiotics would be relatively contraindicated in this patient?

Ciprofloxacin

A 46-year-old woman complained of burning on urination and bladder pain. Her medical history was significant for re- current urinary tract infections and for a congenital long QT syndrome detected during a routine visit 1 year ago. A clean catch midstream urine sample showed many gram-negative rods. Which of the following antibiotics would be contra-indicated for this patient?

They decrease quinolone oral bioavailability.

A 46-year-old woman with a long history of recurrent urinary tract infection complained to her physician of burning on urination and bladder pain. The woman used antacids from time to time to treat annoying heartburn. The physician prescribed ciprofloxacin for 1 week and instructed the patient to avoid the use of antacids during the therapy. Which of the following statements best explains why antacids are contraindicated in patients taking fluoroquinolones?

Metronidazole

A 47-year-old man was admitted to the hospital because of fever (103.1°F, 39.5°C), severe headache, weakness in his right arm and leg, and increasing drowsiness. The patient had a history of chronic sinusitis treated with a variety of oral antibiotics. His last episode of sinusitis occurred 1 month ago and apparently resolved with clindamycin therapy. A computed tomography scan revealed a left frontal lesion with a small amount of surrounding cerebral edema. A diagnosis of brain abscess was made, and the patient underwent stereo- tactic aspiration of the abscess under local anesthesia. Which of the following antibiotics would have been most appropriately included in the initial postsurgical therapy of this patient?

Metronidazole

A 47-year-old woman suffering from ulcerative colitis was admitted to the hospital with fever (103.5°F, 39.7°C) and severe abdominal pain. Physical examination showed an extremely ill patient with diffuse abdominal tenderness, pro- found dehydration, and bloody diarrhea. Further exams led to the diagnosis of fulminant colitis, and an emergency therapy was started. Which of the following antibiotics should be included in the treatment of this patient?

Erythromycin

A 48-year-old woman was hospitalized with the admitting diagnosis of polymorphic ventricular tachycardia. The woman had been suffering from depression and had been on amitriptyline for 3 months. Three days earlier, she complained of fever and sore throat and was started on antibiotics. Which of the following antibiotics most likely triggered the patient's tachycardia?

Campylobacter jejuni

A 48-year-old-woman complained to her physician of fever (103.5°F, 39.7°C), nausea, vomiting, and bloody diarrhea for the past 3 days. Further exams identified the most likely offending pathogen, and a therapy with azithromycin was able to eliminate the diarrhea. Which of the following bacteria most likely caused the patient's disease?

Isoniazid

A 49-year-old Asian woman recently diagnosed with tuberculosis started an appropriate multidrug therapy. Which of the drugs she was taking is inactivated by hepatic acetylation, the rate of which depends on genetic background?

Vancomycin and gentamicin

A 49-year-old man hospitalized for bacterial endocarditis had been receiving a treatment with two drugs given intravenously. One week into therapy, a routine urinalysis showed albuminuria, microscopic hematuria, and hyaline casts. Which of the following pairs of drugs most likely caused these findings?

Blockade of binding of aminoacyl-transfer RNA (tRNA) to bacterial ribosomes

A 49-year-old woman on vacation in the south of Italy presented with fever, headache, and a small, button-like skin ulcer, 5 mm (about 0.2 inch) in diameter, with a black center. The diagnosis of Mediterranean spotted fever was made,and the woman was prescribed doxycycline. Which of the following molecular actions most likely mediated the therapeutic effect of the drug in the patient's disease?

Fosfomycin

A 49-year-old woman recently diagnosed with an uncomplicated urinary tract infection started a treatment with an antibiotic that impairs cell wall synthesis by inhibiting enolpyruvate transferase. Which of the following drugs has this mechanism of action?

To obtain a bactericidal effect that is unlikely with either drug given alone

A 49-year-old woman recently diagnosed with urinary tract infection started treatment with combined trimethoprim- sulfamethoxazole. Which of the following best explains the main reason for combining these two drugs?

Pasteurella multocida: penicillin G

A 5-year-old boy was brought to the clinic by his mother because of a localized,crusted lesion on his left leg.The mother reported that 3 days earlier, the boy had been bitten by his pet dog. A purulent discharge from the lesion was found to contain many small gram-negative coccobacilli. Which of the following correctly pairs the most likely offending pathogen with the appropriate treatment?

Ciprofloxacin

A 50-year-old obese man complained to his physician of a sharp pain in his left calf. Medical history indicated that 1 week ago he had started an antibiotic treatment for acute prostatitis. Further exams led to the diagnosis of Achilles tendon rupture. Which of the following drugs most likely led to the patient's leg pain?

Escherichia coli

A 50-year-old woman recently diagnosed with a urinary tract infection started treatment with trimethoprim-sulfame-thoxazole. All symptoms disappeared after 1 week. Which of the following bacteria was most likely the cause of the patient's infection?

Increased activity of the multidrug efflux pump

A 50-year-old woman recently diagnosed with gastric ulcer started a triple treatment for Helicobacter pylori infection that included tetracycline. Two weeks later, the H. pylori test was still positive, and the physician suspected the development of resistance to tetracycline. Which of the following mechanisms could account for the bacterial resistance to tetracyclines?

Cephalexin

A 51-year-old woman recently diagnosed with acute bacterial cystitis started an appropriate antibiotic treatment. The ad- ministered drug achieves therapeutic concentration in the urine because it is primarily eliminated by the kidney through active secretion in the proximal tubule. Which of the follow- ing drugs did the patient most likely take?

Piperacillin and tobramycin

A 51-year-old woman was admitted to the hospital with fever (102.7°F, 39.3°C), shaking chills, nausea and vomiting, flank pain, and hematuria. She had been suffering from chronic urinary tract infections for 1 year and from type II diabetes for 10 years. Further tests led to the diagnosis of acute pyelonephritis due to Pseudomonas aeruginosa. Which of the fol- lowing pairs of drugs would be appropriate for this patient?

Amoxicillin

A 52-year-old man presented to his physician with an extensive skin rash on his trunk and limbs. The man had been suffering from non-Hodgkin lymphoma for 2 years. A few days earlier, he was diagnosed with acute bacterial pharyngitis and started on an antibiotic. The physician said the rash was most likely an allergic reaction to the antibiotic. Which of the following drugs most likely caused this reaction?

Metronidazole and tetracycline

A 52-year-old woman complained to her physician of recurrent epigastric pain. Endoscopy revealed a gastric ulcer, and biopsy results were positive for Helicobacter pylori. To eradicate H. pylori, the physician prescribed a therapy that included omeprazole and two antibiotics. Which of the following pairs of antibiotics would be appropriate for this patient?

Cefoxitin and tobramycin

A 53-year-old woman hospitalized for resection of breast carcinoma presented with fever (103.8°F, 39.4°C), cough, dyspnea, and viscid, currant jelly−like sputum 3 days after surgery. A Gram stain showed numerous gram-negative bacilli with large capsules. A chest radiograph showed dense right upper field infiltrates. A diagnosis of nosocomial pneumonia was made. Which of the following pairs of antibiotics would be most appropriate for the emergency therapy of this patient?

Bacteroides fragilis: imipenem

A 53-year-old woman presented to the clinic complaining of 3 weeks of night sweats, cough productive of foul-smelling sputum, and about 10 lb (4.5 kg) of weight loss. Physical examination showed fever (101.3°F, 38.5°C), clear lung fields, and mild clubbing.Chest radiography showed a thick-walled abscess in the left lobe. Gram stain of the sputum revealed gram-negative rods, and aerobic cultures were negative. Which of the following correctly pairs the most likely causative pathogen with the appropriate treatment?

Increased production of para-aminobenzoic acid

A 53-year-old woman suffering from a urinary tract infection started a treatment with trimethoprim-sulfamethoxazole. One week later, burning upon urination was still pronounced, and the physician suspected that resistance to sulfamethoxazole had occurred. This resistance was most likely due to which of the following mechanisms?

Trimethoprim

A 54-year-old alcoholic woman complained to her physician of weakness, drowsiness, and dyspnea on exertion. Medical history indicated she was diagnosed with acute cystitis 10 days earlier and started an antibacterial therapy. Pertinent results of blood tests were red blood cell count 3.2 × 106/ mm3 (normal, female 3.5−5.5 × 106/mm3), mean corpuscular volume 115 fL (normal 80−100 fL). Which of the following drugs most likely caused these lab results?

50

A 54-year-old man suffering from chronic renal insuficiency was about to receive gentamicin and piperacillin for sepsis, apparently due to gram-negative bacteria. The patient's creatinine clearance was about one half the normal value. The physician chose to change the dosage of gentamicin and maintain the normal dosing interval. Assuming that the usual gentamicindoseforsepsisis100mgevery8hours,which of the following (in milligrams) would be an appropriate initial dose of gentamicin for this patient?

Penicillin G and gentamicin

A 54-year-old man was admitted to the hospital with fever (100.6°F, 38.1°C), night sweats, arthralgias, and 15 lb (6.8 kg) of unintentional weight loss. Past history was significant for rheumatic fever at the age of 9 and for dental surgery 1 month ago. The symptoms started about 2 weeks after the dental procedure. Physical examination was significant for mitral regurgitation, subungual splinter hemorrhages, and hemorrhagic plaques on the soles of both feet. Three blood cultures were ordered, and an empiric therapy was started. Which of the following should be an appropriate treatment for the patient at this time?

Impairment of normal microflora of the host

A 54-year-old woman presented to her physician complaining of vaginal itching and a thick, white vaginal discharge. One week earlier, the woman had started treatment with amoxicillin because of a skin infection. Subsequent exams led to the diagnosis of candida vaginitis that the physician thought was a superinfection related to the amoxicillin treatment. Which of the following best explains why broad-spectrum penicillins can cause superinfections?

Trimethoprim-sulfamethoxazole

A 55-year-old woman complained to her physician of burn- ing on urination, frequent urination, and bladder pain. A urine culture and susceptibility test showed that Escherichia coli was the main infecting organism and that it was resistant to ampicillin, cefotaxime, ciprofloxacin, and amikacin. Which of the following antibiotics would be most appropriate to treat the patient's infection?

Cefepime

A 55-year-old woman recently diagnosed with bacterial pyelonephritis started a treatment with a β-lactam antibiotic that is resistant to most β-lactamases. Which of the following drugs was most likely administered?

Sulfamethoxazole

A 56-year-old Black woman complained to her physician of tiredness and fatigue. She also noticed that her urine had be- come dark. Medical history was significant for glucose-6- phosphate dehydrogenase deficiency and recurrent urinary tract infection. Five days earlier, the patient complained of burning sensation upon urination and started the prescribed antibiotic therapy. Urinalysis revealed bilirubin and uro-bilinogen. Which of the following drugs could have caused the patient's signs and symptoms?

Catalase-peroxidase

A 56-year-old Hispanic man diagnosed with bone tuberculosis started a multidrug treatment, but 4 months later, the disease was minimally improved, and susceptibility testing showed a complete resistance to isoniazid. A high level of resistance of tubercle bacilli to isoniazid involves a decrease in the activity of which of the following enzymes?

Penicillin G

A 56-year-old farmer presented to the clinic with a small, at, hard swelling under the oral mucosa that formed a fistula discharging yellow granules. One month earlier, he had several teeth extracted because of paradental abscesses. Anaerobic cultures of the biopsy material showed small, spidery colonies containing gram-positive, non-acid-fast rods and branching filaments.A diagnosis was made,and an antibiotic therapy was prescribed. Which of the following drugs would be most appropriate for this patient?

Start on oral metronidazole.

A 56-year-old man was admitted to the hospital with fever (101.7°F, 38.7°C), severe abdominal pain, and loose, bloody stools. Further exams led to the diagnosis of Clostridium difficile−associated colitis. Therapy with oral vancomycin was started, but 2 days later, the diarrhea was not improved. Which of the following changes in the therapy would be appropriate at this time?

Pyridoxine

A 57-year-old man complained of a tingling sensation in his limbs and that his arms sometimes felt heavy. The man, who had been suffering from type II diabetes for 10 years, had been recently diagnosed with pulmonary tuberculosis and had been receiving isoniazid and rifampin for 1 month. The concomitant use of which of the following drugs would have most likely prevented the patient's neurologic symptoms?

Cefoperazone

A 57-year-old woman consulted her physician because of fever (101°F, 38.3°C), chills, nausea and vomiting, and pain in the upper right quadrant. Subsequent exams led to the diagnosis of acute cholecystitis. An appropriate therapy was started, including a cephalosporin that is primarily eliminated in the bile. Which of the following drugs was most likely administered?

Inhibition of bacterial inactivation of amoxicillin

A 6-year-old boy presented to his pediatrician with fever (101.3°F, 38.5°C) and sharp pain in his left ear. On physical examination, the left tympanic membrane was red, opaque, and bulging. Amoxicillin was prescribed, but 3 days later, the symptoms were not reduced.The pediatrician decided to modify the therapy and prescribed amoxicillin/potassium clavulanate. Which of the following best explains the advantage of adding potassium clavulanate to amoxicillin?

Neomycin

A 60-year-old man recently diagnosed with carcinoma of the colon was admitted to the hospital for colectomy. Which of the following drugs would be appropriate to be included in the oral prophylactic treatment of this patient to prevent surgical infection?

Amoxicillin

A 61-year-old woman with poor dentition was scheduled to have all of her remaining teeth extracted for subsequent fitting of dentures. Past medical history was signicant for numerous infections of the oral cavity. The woman had been suffering from mitral stenosis with mild cardiac insufficiency for 5 years. Which of the following drugs would be the most appropriate agent to prescribe to this woman before and after the extraction?

Amikacin

A 62-year-old man complained to his physician of burning on urination and bladder pain. The man was wearing a per- manent urinary catheter because of inoperable prostate hy- perplasia. A urine culture was ordered, and a susceptibility test gave the following results: (Abbreviations: I = intermediate; R = resistant; S = susceptible; TMP-SMX = trimethoprim-sulfametoxazole) Escheridia coli - Ticaricillin (S), Amikacin (S), Ceftazidime (I), Ciprofloxacin (S), TMP-SMX (S) Klebsiella pneumoniae - Ticaricillin (R), Amikacin (S), Ceftazidime (S), Ciprofloxacin (I), TMP-SMX (S) Pseudomonas aeruginosa - Ticaricillin (S), Amikacin (S), Ceftazidime (S), Ciprofloxacin (S), TMP-SMX (R) Proteus vulgaris - Ticaricillin (S), Amikacin (I), Ceftazidime (I), Ciprofloxacin (I), TMP-SMX (R) Which of the following drugs would be most appropriate for this patient?

Pyrazinamide

A 62-year-old man presented to the hospital complaining of anorexia, nausea and vomiting, and abdominal discomfort. He also had pain on motion and stiffness in several joints. The man, recently diagnosed with renal tuberculosis,started a four-drug combination regimen 1 month ago. Lab results showed serum aspartate aminotransferase of 280 U/L(nor- mal 8−20 U/L) and serum uric acid of 25 mg /dL (normal 3.0−8.2 mg/dL). Which of the following drugs most likely caused the patient symptoms and signs?

Azithromycin

A 63-year-old alcoholic man presented to the emergency department with fever (102.2°F, 39°C), chest pain, and a cough producing mucoid sputum. Physical examination revealed a man in obvious distress with the following vital signs: blood pressure 140/85 mm Hg, pulse 55 bpm, respirations 22/min. Sputum culture showed gram-negative rods able to grow only on charcoal yeast extract agar. Which of the following antibiotics would be most appropriate for this patient?

Transpeptidase

A 63-year-old homeless man was admitted to the hospital with fever, general malaise, and a swollen, painful leg. Physical examination showed a man in obvious distress with the following vital signs: blood pressure 88/50 mm Hg, heart rate 115 bpm, respirations 22/min,temperature 103.1°F(39.5°C). His right leg had a large wound and appeared swollen with a "bronze" discoloration and crepitation of the tissue. A presumptive diagnosis was made. An empiric therapy was started that included extensive debridement of the wound and administration of a drug that was able to cure the infection. The mechanism of action of the given drug most likely involved the inhibition of which of the following bacterial enzymes?

Arabinosyl transferase

A 63-year-old man recently diagnosed with pulmonary tuberculosis started a multidrug treatment that included ethambutol. Inhibition of which of the following enzymes most likely mediated the therapeutic efficacy of the drug in the patient's disease?

Isoniazid-induced hepatitis

A 64-year-old alcoholic woman su ering from pulmonary tuberculosis complained of anorexia, nausea, and abdominal discomfort. She had been receiving isoniazid, ethambutol, and rifampin for 2months. Lab results revealed anaspartate aminotransferase level of 330 U/L(normal 8−20 U/L). Which of the following best explains the reason for the patient's signs and symptoms?

Daptomycin

A 64-year-old homeless man was taken to the emergency department because of chills, fever, nausea and vomiting, and a laceration in his left harm. Vital signs on admission were blood pressure 100/52 mm Hg,pulse 124 bpm, respirations 32/min, temperature (102.2°F, 39°C). Physical examination showed a critically ill patient with an infected wound, and microbiological tests from a wound specimen showed vancomycin-resistant Staphylococcus aureus. Emergency therapy was started. Which of the following drugs would be appropriate for this patient?

Ciprofloxacin

A 64-year-old man was admitted to the hospital because of a 3-day history of fever, chest pain, cough, nausea, vomiting, and diarrhea.His past medical history was relevant for heavy cigarette smoking, surgery for prostatic hyperplasia, and intolerance to macrolide antibiotics. Vital signs were blood pressure 135/80 mm Hg, pulse 50 bpm, respirations 16/min, body temperature 102°F (38.8°C). A chest x-ray revealed a patchy infiltrate in the lower left lobe, and urinalysis showed microhematuria. Which of the following drugs would be appropriate for the therapy of the patient's disease?

Erythromycin

A 65-year-old man complained to his physician of nervousness, insomnia, and palpitations. The man had been suffering from chronic obstructive pulmonary disease for several years and had been receiving therapy that included theophylline. A few days earlier,he had been diagnosed with streptococcal pharyngitis and started an appropriate treatment. The physician thought that the patient's symptoms were most likely due to an antibiotic−theophylline interaction. Which of the following antibiotics was most likely responsible for this interaction?

Inhibition of peptidoglycan synthesis

A 65-year-old woman was admitted to the emergency department with altered consciousness,fever,nausea,and vomiting. Vital signs on admission were blood pressure 90/50 mm Hg, pulse 115 bpm, respirations 20/min, temperature 103.6°F (39.8°C). Physical examination showed a patient in obvious distress with a stiff neck and positive Brudzinski sign. Pupils were equal, poorly reactive to light, and papill- edema was present. An empirical intravenous therapy was started with ampicillin, ceftriaxone, and vancomycin. Which of the following best explains the mechanism of action com- mon to all of the given drugs?

Increase the dose of warfarin.

A 66-year-old man recently diagnosed with pulmonary tuberculosis started a three-drug treatment with isoniazid, rifampin, and ethambutol. The man, who had been suffering from atrial brillation for 4 years, was currently being treated with propranolol and warfarin. At this point, which of the following changes in the patient's therapeutic regimen would be appropriate?

Plasmid-mediated production of bacterial transferases

A 66-year-old woman complained to her physician of urinary urgency and burning pain during urination. A urine culture revealed that Escherichia coli was the o ending organism, and a susceptibility test showed that the bacterium was resistant to aminoglycoside antibiotics. Which of the following mechanisms can account for the bacterial resistance to aminoglycosides?

Connection of two amino sugar chains by peptide bridges

A 68-year-old man diagnosed with streptococcal pneumonia started treatment with a third-generation cephalosporin. Which of the following steps in the turnover of bacterial cell walls is specifically inhibited by this antibiotic?

Amikacin

A 68-year-old man hospitalized because of advanced renal insufficiency was found to have pneumonia due to Pseudomonas aeruginosa. An appropriate antibiotic treatment was planned, but the dose of the drug was reduced because its half-life can be 20 to 40 times longer in patients with kidney failure. Which of the following drugs was most likely prescribed?

Concentration-dependent killing and long post-antibiotic effect

A 69-year-old man recently diagnosed with a Proteus mirabilis infection started treatment with a daily intramuscular injection of gentamicin. Which of the following pairs of properties best explains why the drug is usually administered once daily despite the short half-life of gentamicin (about 2 hours)?

Penicillin G and naproxen

A 7-year-old boy was admitted to the hospital with fever (102°F,38.8°C) and joint pain in his knees and wrists. He had a history of a severe sore throat for 3 weeks. Vital signs on admission were blood pressure 122/80 mm Hg, heart rate 110 bpm, respirations 24/min. Physical examination showed red, hot, and painful knees and a nonpruritic rash with distinct disk like borders on his thighs and stomach. Subcutaneous, painless nodules were present over the bone surface of his elbows and knees. Heart auscultation revealed a mitral valve regurgitation murmur. Pertinent lab results on ad- mission were erythrocyte sedimentation rate 80/h (normal < 10/h for children), antistreptolysin-O titer 410 IU (normal <200 IU). A diagnosis was made,and a suitable therapy was prescribed. Which of the following pairs of drugs would be most appropriate for the initial treatment of this patient?

Piperacillin

A 7-year-old girl was admitted to the emergency department with fever (101.8°F, 38.8°C) and a productive cough of thick, greenish sputum. Her medical history was significant for cystic fibrosis and several episodes of pneumonia over the past 3 years. Gram stain of the sputum revealed gram- negative rods.Growth of bacteria on agar culture exhibited a blue-green pigment. Which of the following β-lactam drugs would be appropriate to include in the therapeutic regimen of this patient?

Ampicillin

A 70-year-old female resident in a nursing facility was admitted to the hospital because of fever (101.4°F 38.6°C), diarrhea, and severe abdominal pain. Four days earlier, the patient had started antibiotic treatment because of acute tonsillitis due to β-hemolytic streptococci. Physical examination showed a critically ill patient with abdominal distention and absent bowel sounds. Colonoscopy revealed diffuse ulcerations and exudative plaques lining the colonic mucosa. Which of the following antibiotics most likely caused the patient's disease?

Aminoglycosides

A 70-year-old woman complained to her physician of head- ache, nausea and vomiting, vertigo, tinnitus, and progressive loss of hearing. The woman had been receiving an antibiotic for 2 weeks to treat a urinary tract infection apparently due to Serratia marcescens. The drug used was most likely a member of which of the following antibiotic classes?

Amoxicillin/clavulanate

A 71-year-old diabetic man was admitted to the hospital with fever (101.2°F, 38.4°C) and a throbbing foot pain for the past 10 hours. Physical examination revealed a putrid smelling,pus-filled ulcer on the right foot. A metal probe inserted into the wound detected bone and a deep cavity. A Gram stain of the pus showed gram-positive cocci in chains,gram- negative diplococci, and gram-positive and -negative rods. Which of the following antibiotics would be most appropriate to give while blood and drainage cultures were processed?

Tobramycin

A 72-year-old female resident of a nursing facility was ad- mitted to the hospital because of steadily declining urine output over the past 3 days. The woman had been receiving an antibiotic for 2 weeks to treat a urinary tract infection apparently due to Pseudomonas aeruginosa. A urinalysis showed albuminuria, hematuria, and hyaline casts. Which of the following drugs most likely caused the patient's disorder?

Decreased permeability of the bacterial cell membrane to the drug

A 73-year-old man diagnosed with pneumonia due to Pseu- domonas aeruginosa was started on piperacillin, but 2 days later, the disease was not improved, and the physician suspected that the infective organism was resistant to the drug. Which of the following was most likely the mechanism of bacterial resistance to this antibiotic?

Bacteroides fragilis

A 73-year-old man presented with fever (101.9°F, 38.8°C) and pain in the perineum and left buttock. Four days earlier, the man had undergone bowel surgery for colon cancer, which was complicated by escape of bowel contents into the peritoneal cavity. Medical history of the patient was significant for allergic reactions to several antibiotics, including penicillins and metronidazole. Further exams led to the diagnosis of acute peritonitis. The patient's illness responded to an empiric emergency treatment that included parenteral administration of clindamycin. Which of the following micro-organisms was most likely the main cause of the patient's infection?

Aztreonam

A 74-year-old man was recently diagnosed with pneumonia due to Pseudomonas aeruginosa. Past history of the patient was signifcant for a severe allergic reaction to ampicillin. A treatment was started with a β-lactam antibiotic that is highly resistant to β-lactamases and is active only against most gram-negative aerobic bacteria. Which of the following drugs was most likely given?

Cefazolin

A 75-year-old man was admitted to the hospital for hip re- placement. Which of the following antibiotics would be an appropriate prophylactic agent to be given before surgery?

Metronidazole

A 75-year-old woman was admitted to the hospital with fever (102.6°F, 39.2°C), abdominal cramping, and foul-smelling, watery stools. A colonoscopy revealed exudative plaques attached to the surface of the inflamed colonic mucosa. The woman had been receiving high doses of ampicillin for 2 weeks to treat a urinary tract infection. Which of the fol- lowing drugs would be most appropriate for this patient?

Cefotetan

A 76-year-old man complained to his physician of a foul- smelling secretion from his left ear for the past 2 weeks.Further exams led to the diagnosis of chronic otitis media, and cultures from fluid secretions indicated Bacteroides fragilis as the main causative agent. An appropriate antibiotic treatment was started. Four days later, blood results indicated a prothrombin time of 25 seconds (normal 10−14 seconds). Which of the following drugs most likely caused this lab result?

Quinupristin/dalfopristin

A 76-year-old woman was admitted to the hospital because of fever (102.6°F, 39.2°C), shortness of breath, and cough productive of purulent sputum. X ray of the chest showed several areas of infiltration with possible abscess formation. A blood culture indicated the infection was due to staphylococci, and a susceptibility test showed that they were resistant to methicillin and vancomycin. Which of the following antibiotic therapies would be most appropriate for this patient?

Ampicillin and tobramycin

A 79-year old female resident of a nursing facility complained of burning on urination and bladder pain. Microscopic examination of urine sediment revealed many gram-positive bacteria, and a urine culture indicated Enterococcus faecalis as the sole causative agent. Which of the following pairs of drugs would be most appropriate for the treatment of this patient?

Tigecycline

A glycylcycline antibiotic active against vancomycin-resistant staphylococci

Azithromycin

A macrolide antibiotic with a very long half-life (about 40 hours)

Piperacillin

A penicillin active against Klebsiella species

Cloxacillin

A penicillinase-resistant penicillin

Ceftriaxone

A previously healthy 3-year-old child was admitted to the hospital with sore throat, fever, chills, painful swallowing, and dyspnea for the past 10 hours. Physical examination revealed a seriously ill patient with edematous erythema over the anterior neck, cervical lymph node enlargement, crackles in the left lung base, and diffuse wheezing best heard as stridor over the neck.Sputum Gram stain showed numerous gram-negative coccobacilli. A diagnosis of acute supraglottitis was made,and an emergency therapy was started.Which of the following drugs would be most appropriate for the patient's disease?

Metronidazole

A prodrug that requires bacterial activation

Demeclocycline

A tetracycline antibiotic sometimes used in syndrome of in-appropriate antidiuretic hormone secretion (SIADH)

Ceftazidime

A third-generation cephalosporin active against Pseudomonas aeruginosa

Pneumocystis jiroveci

A36-year-old man presented to the clinic with fever (100.4°F, 38.6°C), nonproductive cough, mild dyspnea, and facial seborrheic dermatitis. The man was HIV seropositive, and his CD4 lymphocyte count was 100/mm3. A silver-stained preparation from bronchial lavage revealed a large number of cysts containing sporozoites. A diagnosis of pneumonia was made, and a treatment with trimethoprim-sulfamethoxazole for 14 days was able to cure the infection. Which of the fol- lowing bacteria was most likely the cause of the patient's infection?

Ototoxicity

A60-year-old man presented with fever (102°F,38.9°C), general malaise, and tachypnea. The man had been hospitalized for the past 4 days for evaluation of stage C cardiac failure. Medical therapy on admission included furosemide, losartan, aspirin, and atenolol. Further tests led to the diagnosis of nosocomial pneumonia due to Pseudomonas aeruginosa, and a therapy with ceftazidime and amikacin was started. Because of his current cardiac therapy, the patient was at increased risk of which of the following adverse effects of amikacin?

Elongation of peptidoglycan

An 11-year-old girl was taken to the clinic because of fever (102°F, 38.8°C), shortness of breath, and cough productive of purulent sputum. A chest radiograph showed several areas of infiltration with possible abscess formation. Coagulase-positive bacteria were cultured from the blood, and a susceptibility test showed that they were methicillin-resistant. Treatment with vancomycin was started. Inhibition of which of the following molecular actions most likely mediated the therapeutic effect of the drug in the patient's disease?

Gentamicin

An 1168-g (2.57-lb) preterm male born to a febrile mother presented with respiratory distress a few hours after the delivery. Physical examination and lab results suggested neonatal sepsis, and an empirical antibiotic therapy was instituted. Later, blood cultures indicated Listeria monocytogenes as the offending organism. Which of the following drugs would be most appropriate to administer in combination with ampicillin for the treatment of his infection?

Dicloxacillin

An 8-year-old girl was brought to the clinic because of fever (101.5°F, 38.6°C) and extensive skin abrasions on the right leg. Her mother explained that the girl had fallen off her bicycle a few days earlier and su ffered several abrasions. Physical examination showed the skin of the right leg was hot, red, and edematous with a surface "peau d'orange" appearance. Regional lymphadenopathy was also present. A Gram stain from scrapings of the lesions showed the presence of a large number of gram-positive cocci. Which of the following drugs would be appropriate for the treatment of this patient?

Ciprofloxacin

An 83-year-old female resident in a nursing facility presented with fever (100.5°F, 38°C), dry cough, and general malaise. Further exams led to the diagnosis of hospital-acquired pneumonia due to Pseudomonas aeruginosa. Treatment was started with a drug that is effective against most gram-negative bacteria, as well as against some mycobacteria, mycoplasmas, chlamydiae, and rickettsiae. Which of the following drugs was most likely given?

Streptomycin

An aminoglycoside antibiotic active against amebiasis and giardiasis

Neomycin

An aminoglycoside antibiotic sometimes used in hepatic encephalopathy

Ciprofloxacin

Resistance to this drug may be due to a change in DNA gyrase

Trimethoprim

This drug blocks the last two steps in bacterial tetrahydro-folate biosynthesis

Rifampin

This drug imparts a harmless orange color to urine, sweat, and tears.

Clarithromycin

This drug is effective against some atypical mycobacteria but not against Mycobacterium tuberculosis.

Aztreonam

This drug shows no cross-allergenicity with other β-lactam antibiotics.