pharm exam 5 practice questions
Aluminum and calcium ions in the gut interfere with the absorption of which of the following drugs? A. Chloramphenicol B. Penicillin V C. Doxycycline D. Ampicillin E. Sulfisoxazole
C
An eleven-month-old boy has bacterial meningitis. Which of the following drugs should you use to start the initial therapy? A. Doxycycline B. Sulfamethoxazole/trimethoprim C. Cefotaxime D. Gentamicin E. Bacitracin
C
J.C., a 23 year old male naval officer, recently stationed in the Philippines, has contracted gonorrhea (Neisseria gonorrhoeae). His medical record indicates that he is allergic to penicillin. Which of the following is the drug of choice to treat this infection? Amoxicillin. Ceftriaxone Fluoroquinolone. D. Sulfamethoxazole/trimethoprim E. Doxycycline.
C
Serious side effects such as renal tubular necrosis and renal failure, deafness due to cochlear toxicity, vertigo, and neuromuscular blockade are associated with which of the following drugs? A. Doxycycline B. Amoxicillin C. Gentamicin D. Chloramphenicol E. Erythromycin
C
Which of the following antibiotics can only be used topically? A. Streptomycin B. Gentamicin C. Neomycin D. Tobramycin E. Netilmicin
C
Which of the following drugs increases the motility of the gastrointestinal tract? A. ciprofloxacin B. tetracycline C. erythromycin D. penicillin G E. vancomycin
C
1. Which of the following drugs is LEAST likely to be effective in the treatment of an infection caused by beta lactamase-producing Staphylococcus. aureus? Amoxicillin Nafcillin Methicillin Oxacillin Cefazolin
A
2. An antibiotic that arrests the growth and replication of bacteria, thus limiting the spread of infection while the immune system attacks, immobilizes, and eliminates the pathogens is called: A. bacteriostatic B. synergistic C. broad spectrum D. bactericidal E. selective
A
An AIDS patient develops septic arthritis due to Pseudomonas aeruginosa. Treatment with an antipseudomonal penicillin, ticarcillin, alone is ineffective in halting the infection. An additional antibiotic effective against P. aeruginosa that could be added to the regiment is: A. Tetracycline B. Gentamicin C. Neomycin D. Chloramphenicol E. Minocycline
B
. Which of the followings is the appropriate mechanism of action of oseltamivir (Tamiflu)? A. Inhibition of neuraminidase of influenza A or B virus. B. Inhibition of viral protein synthesis. C. Inhibition of viral RNA synthesis. D. Inhibition of viral DNA synthesis E. Inhibition of viral assembly inside the host cells.
A
1. A 70-year-old alcoholic male with poor dental hygiene is to have his remaining teeth extracted for subsequent dentures. He has mitral valve stenosis with mild cardiac insufficiency and is being treated with captopril, digoxin, and furosemide. The dentist decides that his medical history warrants prophylactic antibiotic therapy prior to the procedure. Which of the following drugs can be prescribed? Amoxicillin Sulfamethoxazole/trimethoprim Ketoconazole Metronidazole Flucytosine
A
1. Appropriate clinical indications (DOC) for use of Sulfonamide + trimethoprim (sulfamethoxazole/trimethoprim) include: Pneumocystis carinii pneumonia. Sepsis due to Serratia marcescens A hospital-acquired staphylococcal osteomyelitis Internal abscess caused by B. fragilis infection Syphilis
A
1. Penicillins and cephalosporins are: A. bactericidal only for bacteria that are actively growing and synthesizing cell walls. B. bacteriostatic unless administered in high doses. C. bacteriostatic unless combined with an aminoglycoside. D. only bactericidal for gram negative organisms. E. only bactericidal for gram positive organisms.
A
2. Metronidazole is clinically effective in treating amebiasis, giardiasis, and trichomoniasis. Which of the following is the mechanism of action of metronidazole? A. It produces free radical that damages parasite DNA, proteins, and membranes B. It inhibits parasite DNA synthesis C. It inhibits parasite RNA synthesis D. It inhibits parasite protein synthesis E. It inhibits parasite cell wall synthesis.
A
3. Penicillin G plus gentamicin are used in combination to treat enterococcal endocarditis. Which of the following is the appropriate mechanism to cause synergistic action of the two drugs? A. Inhibition of cell wall synthesis by penicillin G allows passage of gentamicin to its target in the cell. B. Inhibition of cell wall synthesis by penicillin G prevents passage of gentamycin to its target cells because cell growth is arrested. C. Presence of gentamicin enhances passage of penicillin G to its target in the cell. D. Presence of gentamicin enhances the interaction of penicillin G with penicillin binding protein (PBP). E. Presence of gentamicin increases the effective concentration of penicillin G inside bacterial cells.
A
4. Which of the following drugs is appropriate to treat chloroquine resistant malaria? A. Mafloquine B. Suramin C. Penicillin G D. Nifurtimox E. Acyclovir
A
9. Which of the following drugs is a drug of choice for treating enteric protozoa infections (Entamoeba histolytica, Giardia lamblia) and pseudomembranous colitis due to Clostridium difficile? A. metronidazole B. ciprofloxacin C. erythromycin D. sulfamethoxazole/trimethoprim E. tetracycline
A
An eight-month old pregnant student complains of lower abdominal pain and a 48-hour history of dysuria. She does not have any fever; an analysis of her urine shows protein, but no blood or glucose. A culture of her urine shows the presence of E. coli. Which of the following is useful for treating urinary tract infection orally without causing risks to the fetus? A. Cephalexin B. Sulfonamide+ Trimethoprim = sulfamethoxazole/trimethoprim—(Bactrim) C. Penicillin V D. Tetracycline E. Penicillin G
A
Indicated for serious staph infection A - Nafcillin. B - Sulbactam. C - Ticarcillin. D- Clavulanic Acid E - Probenecid F -Sulfamethoxazole/trimethoprim
A
Second and third generation cephalosporins are more effective against ____________ and are less effective against ____________________ compared to the first generation cephalosporins. gram (-) bacteria; gram (+) bacteria gram (+) bacteria; gram (-) bacteria gram (+) bacteria; obligate anaerobic bacteria E. coli; Klebsiella sp. Treponema pallidum; gram (-) cocci
A
Which of the followings is the most serious adverse effect of Ethambutol? A. Optic neuritis B. Hearing loss C. Drug induced hepatitis D. Methemoglobinemia E. Skin decoloration
A
A 24-year-old woman comes to a clinic with complaints of dry cough, headache, fever, and malaise, which have lasted 3 or 4 d. She appears to have some respiratory difficulty, and chest examination reveals rales but no other obvious signs of pulmonary involvement. However, extensive patchy infiltrates are seen on chest x-ray film. Gram stain of expectorated sputum fails to reveal any bacterial pathogens. The patient mentions that a colleague at work had similar symptoms to those she is experiencing. The patient has no history of serious medical problems. She takes loratadine for allergies and supplementary iron tablets, and she drinks at least 6 cups of caffeinated coffee per day. The physician makes an initial diagnosis of community-acquired pneumonia. A 5-d course of treatment for community-acquired pneumonia would be effective in this patient with little risk of drug interactions if the drug prescribed were (A) Azithromycin (B) Clindamycin (C) Doxycycline (D) Erythromycin (E) Vancomycin
Azithromycin has a half-life of more than 70 h, which allows for once-daily dosing and a 5-d course of treatment for community-acquired pneumonia. Unlike other macrolides, azithromycin does not inhibit cytochrome P450 enzymes involved in drug metabolism. The answer is A.
1. A 23-year-old presents with vulvovaginal itching, vaginal soreness, and vulvar burning accompanied by a thick, white discharge that has the consistency of cottage cheese. Her current medications include oral tetracycline for acne and Ortho-Novum 1/35 for birth control. She has regular menstrual cycles and her last menstrual period was four days ago. Which of the following is the most appropriate topical treatment? A. Flucytosine B. Clotrimazole C. Griseofulvin D. Amphotericin B E. Tolnaftate
B
1. J.C., a 23 year old male naval officer, recently stationed in the Philippines, has contracted syphilis (Treponema, a spirochete). Which of the following is the drug of choice to treat this infection? Chloramphenicol Penicillin G An aminoglycoside Vancomycin A sulfonamide
B
1. Sulfonamides are mostly frequently indicated for the treatment of which of the following? A. Gonorrhea B. Chronic urinary tract infections C. Influenza D. Most streptococcal infections E. Meningococcal infections
B
1. Which of the following antifungal agents disrupts mitotic spindle formation? A. Ketoconazole B. Griseofulvin C. Nystatin D. Amphotericin B E. Flucytosine
B
1. Which of the following drugs may cause cyanosis, abdominal distention, and cardiovascular collapse in neonates? A. Doxycycline B. Chloramphenicol C. Minocycline. D. Tetracycline. E. Streptomycin.
B
1. Which of the following statements concerning fluoroquinolones is correct? A. They are seldom effective in the treatment of urogenital infections caused by multi-drug resistant organisms. B. Resistance may involve changes in penicillin binding proteins. C. They can be administered orally as a result of their high oral bioavailability. D. These drugs are ineffective against most strains of Enterobacter, Neisseria, Pseudomonas, and Salmonella spp. E. No dosage adjustment is usually required for patients with renal insufficiency.
B
1. Your son loves to roam the woods behind your home in Georgia with just a pair of shorts on, barefooted. Lately, he has stayed in more and appears tired. You take him to your family physician. He indicates the boy has iron deficiency anemia and eosinophilia. He asks if your son is frequently outdoors barefooted. An invasive organism that directly invades intact skin is suspected. Which of the following is the suggested drug treatment? A. Chloroquine B. Mebendazole C. Tetracycline D. Praziquantel E. Sulfamethoxazole/Trimethoprim
B
1. rimethoprim and sulfamethoxazole are often used in combination because: A. they act on the same step in the same pathway B. they act on sequential steps in the same pathway C. they act on different pathways D. trimethoprim activates sulfamethoxazole E. trimethoprim increases the permeability of the bacterial cell wall to sulfamethoxazole
B
3. You are planning to participate in a humanitarian medical trip to rural and medically-underserved areas of West Africa. Which of the following drugs could be utilized prophylactically to prevent infection with Plasmodium falciparum? A. Chloramphenicol B. Chloroquine C. Acyclovir D. Idoxuridine E. Metronidazole
B
An eight-month old pregnant student complains of lower abdominal pain and a 48-hour history of dysuria. She does not have any fever; an analysis of her urine shows protein, but no blood or glucose. A culture of her urine shows the presence of E. coli. Which of the following is useful for treating urinary tract infection orally without causing risks to the fetus? A. Cephalexin B. Sulfonamide+ Trimethoprim = sulfamethoxazole/trimethoprim—(Bactrim) C. Penicillin V D. Tetracycline E. Penicillin G
B
T. K., a 26 year old, sexually active male, complains of mild dysuria and a mucoid-like urethral discharge which started about 15 days after his last intercourse. There was no fever, lymphadenopathy, penile lesions, or hematuria. A Gram's stain smear of an anterior urethral specimen showed 20 PMNs per oil immersion (1000X) field and no intracellular gram-negative diplococci. The pathogen was identified to be Chlamydial trachomatis. The DOC to treat this infection is: A. Penicillin G B. Doxycycline C. A sulfonamide D. An aminoglycoside E. Ketoconazole
B
Which of the following would be a drug of choice (DOC) for the treatment of Vibrio cholerae infection? A. Penicillin G B. Doxycycline C. Ampicillin. D. Gentamicin E. Erythromycin.
B
1. Has low antibacterial activity but is a strong inhibitor of penicillinases. A - Nafcillin. B - Sulbactam. C - Ticarcillin. D- Clavulanic Acid E - Probenecid F -Sulfamethoxazole/trimethoprim
B & D
1. A 25-year-old male AIDS patient has a fever of 102 o F and complains of severe headaches during the past week. Staining of his cerebrospinal fluid sample with India ink reveals Cryptococcus neoformans. Which of the followings is the drug of choice to treat this patient? Oral amphotericin B Intravenous ketoconazole Intrathecal amphotericin B Oral griseofulvin Intravenous amphotericin B plus ketoconazole
C
1. Active against Pseudomonas and susceptible to beta-lactamases. A - Nafcillin. B - Sulbactam. C - Ticarcillin. D- Clavulanic Acid E - Probenecid F -Sulfamethoxazole/trimethoprim
C
1. The mechanism of action of fluoroquinolones is due to the inhibition of: A. protein synthesis. B. cell wall synthesis. C. DNA gyrase. D. spindle formation. E. microtubule formation.
C
1. Which of the following drugs is a peptide that prevents the attachment and fusion of the HIV-1 virus to the mammalian cell membrane? A. Dapsone B. Efavirenz C. Enfuvirtide D. Ethambutol E. Foscarnet
C
1. Which of the following drugs is poorly absorbed orally but can be used topically to treat eye and skin staphylococcal infections? Vancomycin Imipenem Bacitracin Erythromycin. Chloramphenicol
C
1. Which of the following is an adverse effect of sulfamethoxazole? Transient inhibition of bone growth. Ototoxicity and renal toxicity. Stevens-Johnson syndrome. Neuromuscular blockade. Thrombocytopenia (reduction of platelet number).
C
2. Which of the following drugs would the World Health Organization (WHO) consider for the treatment of a pandemic of a new strain bird flu in East Asia. A. Acyclovir B. Interferon 2b C. Oseltamivir D. Ribavirin E. Zidovudine (AZT)
C
A 26-year-old woman was treated for a suspected chlamydial infection at a neighborhood clinic. She was given a prescription for oral doxycycline to be taken for 14 d. Three weeks later, she returned to the clinic with a mucopurulent cervicitis. On questioning she admitted not having the prescription filled. The best course of action at this point would be to (A) Delay drug treatment until the infecting organism is identified (B) Rewrite the original prescription for oral doxycycline (C) Treat her in the clinic with a single oral dose of azithromycin (D) Treat her in the clinic with an intravenous dose of amoxicillin (E) Write a prescription for oral erythromycin for 10 d
Cervicitis or urethritis is often caused by C trachomatis. Such infections may develop slowly because of the long incubation period of chlamydial infection. Treatment with oral doxycycline for 14 d (as originally prescribed) would have eradicated C trachomatis and most other organisms commonly associated with nongonococcal cervicitis or urethritis. Given the limited compliance of this patient, the best course of action would be the administration (in the clinic) of a single oral dose of azithromycin. The answer is C
A 4-year-old child is brought to the hospital after ingesting pills that a parent had used for bacterial dysentery when traveling outside the United States. The child has been vomiting for more than 24 h and has had diarrhea with green stools. She is now lethargic with an ashen color. Other signs and symptoms include hypothermia, hypotension, and abdominal distention. The drug most likely to be the cause of this problem is (A) Ampicillin (B) Azithromycin (C) Chloramphenicol (D) Doxycycline (E) Erythromycin
Chloramphenicol is commonly used outside the United States for treatment of bacillary dysentery. The drug causes a dose-dependent (reversible) suppression of erythropoiesis. Although the gray baby syndrome was initially described in neonates, a similar syndrome has occurred with overdosage of chloramphenicol in older children and adults, especially those with hepatic dysfunction. The answer is C.
Clarithromycin and erythromycin have very similar spectra of antimicrobial activity. The major advantage of clarithromycin is that it (A) Does not inhibit hepatic drug-metabolizing enzymes (B) Eradicates mycoplasmal infections in a single dose (C) Has greater activity against H pylori (D) Is active against methicillin-resistant strains of staphylococci (E) Is active against strains of streptococci that are resistant to erythromycin
Clarithromycin can be administered less frequently than erythromycin, but it is not effective in single doses against susceptible organisms. Organisms resistant to erythromycin, including pneumococci and methicillin-resistant staphylococci, are also resistant to other macrolides. Drug interactions have occurred with clarithromycin through its ability to inhibit cytochrome P450. Clarithromycin is more active than erythromycin against M avium complex, T gondii, and H pylori. The answer is C
1. A 25-year-old patient is diagnosed with pneumonia due to Mycoplasma pneumoniae. What is the drug of choice for treating this condition? A. Oral penicillin V B. IM penicillin G C. sulfamethoxazole/trimethoprim D. Erythromycin. E. Chloramphenicol
D
1. A patient complains of diarrhea. Initial treatment with tetracycline leads to pseudomembranous colitis due to overgrowth of Clostridium difficile. Which of the following drugs should be used to treat this condition? Penicillin G Spectinomycin Polymyxin Vancomycin. Bacitracin
D
1. The mechanism of action of sulfamethoxazole is the inhibition of synthesis of bacterial: protein synthesis DNA uncoiling cell wall synthesis purines and pyrimidines RNA translation
D
1. Which one of the following is effective by oral administration and could be used for an infection caused by a beta-lactamase producing strain of gram-negative bacteria? Methicillin Ticarcillin Penicillin V Amoxicillin plus clavulanic acid Piperacillin
D
3. A 45-year-old male has biopsy-proven hepatic cirrhosis with elevated serum transaminases currently. Additional testing also indicates elevated titers of anti-HBV antibodies. Interferon alpha-2b in combination with ribavirin is indicated for his treatment. Which of the followings is the mechanism of action of this drug combination? A. Inhibition of viral RNA and DNA synthesis. B. Inhibition of assembly of viral particles. C. Inhibition of viral entry into host cells. D. Inhibition of viral protein synthesis and viral DNA synthesis. E. Inhibition of viral reverse transcriptase.
D
A 34-year-old female presents with lymphadenopathy, migratory joint and muscle pain, fever, headache, stiff neck, and lethargy of one week's duration. She reports noticing a "Bullseye" looking red spot with a pale center on her right side while she was camping in New England two weeks ago. An appropriate treatment for her condition would be: A. Erythromycin B. Gentamicin C. Neomycin D. Doxycycline E. Ampicillin
D
A 52-year-old man (weight 70 kg) is brought to the hospital emergency department in a confused and delirious state. He has had an elevated temperature for more than 24 h, during which time he had complained of a severe headache and had suffered from nausea and vomiting. Lumbar puncture reveals an elevated opening pressure, and cerebrospinal fluid findings include elevated protein, decreased glucose, and increased neutrophils. Gram stain of a smear of cerebrospinal fluid reveals gram-positive diplococci, and a preliminary diagnosis is made of purulent meningitis. The microbiology report informs you that for approximately 15% of S pneumoniae isolates in the community, the minimal inhibitory concentration for penicillin G is 20 mcg/mL. If this patient had been 82-years-old and the Gram stain of the smear of cerebrospinal fluid had revealed gram-positive rods resembling diphtheroids, the antibiotic regimen for empiric treatment would include (A) Ampicillin (B) Cefoxitin (C) Ceftriaxone (D) Fosfomycin (E) Vancomycin
Diphtheroid-like gram-positive rods in the cerebrospinal fluid smear of an elderly patient are indicative of L monocytogenes. Listeria infections are more common in neonates, elderly patients, and those who have been treated with immunosuppressive agents. Treatment consists of ampicillin with or without an aminoglycoside such as gentamicin. Trimethoprim-sulfamethoxazole can also be used (see Chapter 46). The answer is A.
. Which of the following drugs is a recommended treatment for eradication of Helicobacter pylori in patients with peptic ulcers? A. penicillin G B. vancomycin C. ciprofloxacin D. clindamycin E. clarithromycin
E
1. A 25-year-old patient is diagnosed with active tuberculosis. What is the drug of choice for treating this condition? A. Isoniazid B. Rifampin C. Ethambutol D. Pyrazinamide E. All of the above
E
1. All of the following statements about penicillin G are correct EXCEPT: Levels in the blood can be increased by co-administration of probenecid. If administered orally, it is variably absorbed because of its degradation by stomach acid. It is more effective in killing growing bacteria than microorganisms in the stationary phase. It can act synergistically with aminoglycosides. It is excreted from the body primarily via the liver into the bile
E
1. Which of the following could be used to treat an AIDS patient who has developed fungal meningitis? A. IV Miconazole B. IM Clotrimazole C. Oral Griseofulvin D. Oral Tolnaftate E. Intrathecal Amphotericin B
E
1. Which of the following drugs is indicated for serious infections caused by drug-resistant, gram (+) organisms, including beta-lactamase producing staphylococci? Metronidazole Sulfamethoxazole/trimethoprim Ampicillin Cephazolin Vancomycin
E
Prevents renal excretion of penicillin A - Nafcillin. B - Sulbactam. C - Ticarcillin. D- Clavulanic Acid E - Probenecid F -Sulfamethoxazole/trimethoprim
E
Which of the following would be most appropriate for the treatment for pneumonia caused by Klebsiella pneumoniae? A. Penicillin G B. Nafcillin C. Amoxicillin D. Cephalexin E. Ceftriaxone
E
A 36-year-old woman recently treated for leukemia is admitted to the hospital with malaise, chills, and high fever. Gram stain of blood reveals the presence of gram-negative bacilli. The initial diagnosis is bacteremia, and parenteral antibiotics are indicated. The records of the patient reveal that she had a severe urticarial rash, hypotension, and respiratory difficulty after oral penicillin V about 6 mo ago. The most appropriate drug regimen for empiric treatment is (A) Aztreonam (B) Ceftriaxone (C) Meropenem (D) Oxacillin (E) Ticarcillin plus clavulanic acid
Each of the drugs listed has activity against some gram-negative bacilli. All penicillins should be avoided in patients with a history of allergic reactions to any individual penicillin drug. Cephalosporins should also be avoided in patients who have had anaphylaxis or other severe hypersensitivity reactions after use of a penicillin. There is partial cross-reactivity between penicillins and the carbapenems such as imipenem and meropenem, but no cross-reactivity between the penicillins and aztreonam. The answer is A.
Which of the following statements about beta-lactam antibiotics is false? (A) Cephalexin and other first-generation cephalosporins do not cross the blood-brain barrier (B) Ceftriaxone and nafcillin are both eliminated mainly via biliary secretion (C) Instability of penicillins in gastric acid can limit their oral absorption (D) Renal tubular reabsorption of amoxicillin is inhibited by probenecid (E) Ticarcillin has activity against several gram negative rods
First- and second-generation cephalosporins are not effective in meningitis because they do not readily enter the cerebrospinal fluid. The elimination half-lives of many beta-lactam antibiotics are prolonged by probenecid, which inhibits their proximal tubular secretion. The answer is D.
A patient needs antibiotic treatment for native valve, culture-positive infective enterococcal endocarditis. His medical history includes a severe anaphylactic reaction to penicillin G during the last year. The best approach would be treatment with (A) Amoxicillin-clavulanate (B) Aztreonam (C) Ceftriaxone (D) Ticarcillin (E) Vancomycin
In patients who have had a severe reaction to a penicillin, it is inadvisable to administer a cephalosporin or a carbapenem such as meropenem. Aztreonam has no significant activity against gram-positive cocci, so the logical treatment in this case is vancomycin, often with an aminoglycoside (eg, gentamicin) for synergistic activity against enterococci. The answer is E.
A 24-year-old woman comes to a clinic with complaints of dry cough, headache, fever, and malaise, which have lasted 3 or 4 d. She appears to have some respiratory difficulty, and chest examination reveals rales but no other obvious signs of pulmonary involvement. However, extensive patchy infiltrates are seen on chest x-ray film. Gram stain of expectorated sputum fails to reveal any bacterial pathogens. The patient mentions that a colleague at work had similar symptoms to those she is experiencing. The patient has no history of serious medical problems. She takes loratadine for allergies and supplementary iron tablets, and she drinks at least 6 cups of caffeinated coffee per day. The physician makes an initial diagnosis of community-acquired pneumonia. Regarding the treatment of this patient, which of the following drugs is most suitable? (A) Ampicillin (B) Clindamycin (C) Doxycycline (D) Linezolid (E) Vancomycin
It is often difficult to establish a definite cause of community-acquired pneumonia (CAP). More than 80% of cases are caused by typical pathogens such as S pneumoniae, H influenzae, or M catarrhalis, and 15% are due to the nonzoonotic atypial pathogens such as Legionella species, Mycoplasma species, or C pneumoniae. Currently, monotherapy coverage of both typical and atypical pathogens in CAP is preferred to double-drug therapy. Preferred initial therapy includes a macrolide, doxycycline, or a quinolone active against respiratory pathogens (Chapter 46). Ampicillin, clindamycin, and vancomycin have low activity against atypical pathogens in CAP. The answer is C.
The primary mechanism of resistance of gram-positive organisms to macrolide antibiotics including erythromycin is (A) Changes in the 30S ribosomal subunit (B) Decreased drug permeability of the cytoplasmic membrane (C) Formation of drug-inactivating acetyltransferases (D) Formation of esterases that hydrolyze the lactone ring (E) Methylation of binding sites on the 50S ribosomal subunit
Methylase production and methylation of the receptor site are established mechanisms of resistance of gram-positive organisms to macrolide antibiotics. Such enzymes may be inducible by macrolides or constitutive; in the latter case, cross-resistance occurs between macrolides and clindamycin. Increased expression of efflux pumps is also a mechanism of macrolide resistance. Esterase formation is a mechanism of macrolide resistance seen in coliforms. The answer is E.
The primary mechanism of antibacterial action of the penicillins involves inhibition of (A) Beta-lactamases (B) Cell membrane synthesis (C) N-acetylmuramic acid synthesis (D) Peptidoglycan cross-linking (E) Transglycosylation
Penicillins (and cephalosporins) bind to PBPs acting at the transpeptidation stage of cell wall synthesis (the final step) to inhibit peptidoglycan cross-linking. The beta-lactam antibiotics also activate autolysins, which break down the bacterial cell wall. Synthesis of N-acetylmuramic acid is inhibited by fosfomycin. Vancomycin inhibits transglycolase, preventing elongation of peptidoglycan chains. The answer is D.
A 52-year-old man (weight 70 kg) is brought to the hospital emergency department in a confused and delirious state. He has had an elevated temperature for more than 24 h, during which time he had complained of a severe headache and had suffered from nausea and vomiting. Lumbar puncture reveals an elevated opening pressure, and cerebrospinal fluid findings include elevated protein, decreased glucose, and increased neutrophils. Gram stain of a smear of cerebrospinal fluid reveals gram-positive diplococci, and a preliminary diagnosis is made of purulent meningitis. The microbiology report informs you that for approximately 15% of S pneumoniae isolates in the community, the minimal inhibitory concentration for penicillin G is 20 mcg/mL. Treatment of this patient should be initiated immediately with intravenous administration of (A) Amoxicillin (B) Cephalexin (C) Ceftriaxone plus vancomycin (D) Nafcillin (E) Piperacillin
Pneumococcal isolates with a minimal inhibitory concentration for penicillin G of greater than 2 mcg/mL are highly resistant. Such strains are not killed by the concentrations of penicillin G or ampicillin that can be achieved in the cerebrospinal fluid. Nafcillin has minimal activity against penicillin-resistant pneumococci and piperacillin is mainly used for infections caused by gram-negative rods. Cefotaxime and ceftriaxone are the most active cephalosporins against penicillin-resistant pneumococci, and the addition of vancomycin is recommended in the case of highly resistant strains. The answer is C.
A 52-year-old man (weight 70 kg) is brought to the hospital emergency department in a confused and delirious state. He has had an elevated temperature for more than 24 h, during which time he had complained of a severe headache and had suffered from nausea and vomiting. Lumbar puncture reveals an elevated opening pressure, and cerebrospinal fluid findings include elevated protein, decreased glucose, and increased neutrophils. Gram stain of a smear of cerebrospinal fluid reveals gram-positive diplococci, and a preliminary diagnosis is made of purulent meningitis. The microbiology report informs you that for approximately 15% of S pneumoniae isolates in the community, the minimal inhibitory concentration for penicillin G is 20 mcg/mL. Resistance of pneumococci to penicillin G is due to (A) Alterations in porin structure (B) Beta-lactamase production (C) Changes in chemical structure of target penicillin-binding proteins (D) Changes in the d-Ala-d-Ala building block of peptidoglycan precursor (E) Decreased intracellular accumulation of penicillin G
Pneumococcal resistance to penicillins is due to changes in the chemical structures of the target penicillin-binding proteins located in the bacterial cytoplasmic membrane. A similar mechanism underlies the resistance of staphylococci to methicillin (MRSA strains). A structural alteration in the d-Ala-d-Ala component of the pentapeptide side chains of peptidoglycans is the basis for a mechanism of resistance to vancomycin. The answer is C.
Concerning quinupristin-dalfopristin, which statement is accurate? (A) Active in treatment of infections caused by E faecalis (B) An effective drug in treatment of multidrug-resistant streptococcal infections (C) Bacteriostatic (D) Hepatotoxicity has led to FDA drug alerts (E) Increase the activity of hepatic drug-metabolizing enzymes
Quinupristin-dalfopristin is bactericidal against many drug-resistant gram-positive cocci, including multidrug-resistant streptococci, MRSA, and vancomycin-resistant enterococci. The streptogramins have activity against E faecium (not E faecalis). The drugs are potent inhibitors of CYP3A4 and interfere with the metabolism of many other drugs. The streptogramins are not hepatotoxic. The answer is B.
The mechanism of antibacterial action of tetracycline involves (A) Antagonism of bacterial translocase activity (B) Binding to a component of the 50S ribosomal subunit (C) Inhibition of DNA-dependent RNA polymerase (D) Interference with binding of aminoacyl-tRNA to bacterial ribosomes (E) Selective inhibition of ribosomal peptidyl transferases
Tetracyclines inhibit bacterial protein synthesis by interfering with the binding of aminoacyl-tRNA molecules to bacterial ribosomes. Peptidyl transferase is inhibited by chloramphenicol. The answer is D.
A 24-year-old woman comes to a clinic with complaints of dry cough, headache, fever, and malaise, which have lasted 3 or 4 d. She appears to have some respiratory difficulty, and chest examination reveals rales but no other obvious signs of pulmonary involvement. However, extensive patchy infiltrates are seen on chest x-ray film. Gram stain of expectorated sputum fails to reveal any bacterial pathogens. The patient mentions that a colleague at work had similar symptoms to those she is experiencing. The patient has no history of serious medical problems. She takes loratadine for allergies and supplementary iron tablets, and she drinks at least 6 cups of caffeinated coffee per day. The physician makes an initial diagnosis of community-acquired pneumonia. If this patient were to be treated with erythromycin, she should (A) Avoid exposure to sunlight (B) Avoid taking supplementary iron tablets (C) Decrease her intake of caffeinated beverages (D) Have her plasma urea nitrogen or creatinine checked before treatment (E) Temporarily stop taking loratadine
The inhibition of liver cytochrome P450 by erythromycin has led to serious drug interactions. Although erythromycin does not inhibit loratadine metabolism, it does inhibit the CYP1A2 form of cytochrome P450, which metabolizes methylxanthines. Consequently, cardiac and/or CNS toxicity may occur with excessive ingestion of caffeine. Unlike the tetracyclines, the oral absorption of erythromycin is not affected by cations and the drug does not cause photosensitivity. Because erythromycin undergoes biliary excretion, there is little reason to assess renal function before treatment. The answer is C.
A 55-year-old patient with a prosthetic heart valve is to undergo a periodontal procedure involving scaling and root planing. Several years ago, the patient had a severe allergic reaction to procaine penicillin G. Regarding prophylaxis against bacterial endocarditis, which one of the following drugs taken orally is most appropriate? (A) Amoxicillin 10 min before the procedure (B) Clindamycin 1 h before the procedure (C) Erythromycin 1 h before the procedure and 4 h after the procedure (D) Vancomycin 15 min before the procedure (E) No prophylaxis is needed because this patient is in the negligible risk category
This patient is in the high-risk category for bacterial endocarditis and should receive prophylactic antibiotics before many dental procedures. The American Heart Association recommends that clindamycin be used in patients allergic to penicillins. Oral erythromycin is not recommended because it is no more effective than clindamycin and causes more gastrointestinal side effects. Intravenous vancomycin (not oral), sometimes with gentamicin, is recommended for prophylaxis in high-risk penicillin-allergic patients undergoing genitourinary and lower gastrointestinal surgical procedures. Complete cross-allergenicity must be assumed between individual penicillins. The answer is B.
A 33-year-old man was seen in a clinic with a complaint of dysuria and urethral discharge of yellow pus. He had a painless clean-based ulcer on the penis and nontender enlargement of the regional lymph nodes. Gram stain of the urethral exudate showed gram-negative diplococci within polymorphonucleocytes. The patient informed the clinic staff that he was unemployed and had not eaten a meal for 2 d. Immunofluorescent microscopic examination of fluid expressed from the penile chancre of this patient revealed treponemes. Because he appears to be infected with Treponema pallidum, the best course of action would be to (A) Administer a single oral dose of fosfomycin (B) Give no other antibiotics because drug treatment of gonorrhea provides coverage for incubating syphilis (C) Inject intramuscular benzathine penicillin G (D) Treat with oral tetracycline for 7 d (E) Treat with vancomycin
This patient with gonorrhea also has primary syphilis. The penile chancre, the enlarged nontender lymph nodes, and the microscopic identification of treponemes in fluid expressed from the lesion are essentials of diagnosis. Although a single dose of ceftriaxone may cure incubating syphilis, it cannot be relied on for treating primary syphilis. The most appropriate course of action in this patient is to administer a single intramuscular injection of 2.4 million units of benzathine penicillin G. For penicillin-allergic patients, oral doxycycline or tetracycline for 15 d (not 7 d) is effective in most cases (see Chapter 44). However, lack of compliance may be a problem with oral therapy. Fosfomycin and vancomycin have no significant activity against spirochetes. The answer is C.
A 33-year-old man was seen in a clinic with a complaint of dysuria and urethral discharge of yellow pus. He had a painless clean-based ulcer on the penis and nontender enlargement of the regional lymph nodes. Gram stain of the urethral exudate showed gram-negative diplococci within polymorphonucleocytes. The patient informed the clinic staff that he was unemployed and had not eaten a meal for 2 d. The most appropriate treatment of gonorrhea in this patient is (A) A single intramuscular dose of ceftriaxone (B) Amoxicillin orally for 7 d (C) Procaine penicillin G intramuscularly as a single dose plus oral probenecid (D) Meropenem orally for 7 d (E) Vancomycin intramuscularly as a single dose
Treatments of choice for gonorrhea include a single dose of ceftriaxone (intramuscularly). Because of the high incidence of beta-lactamase-producing gonococci, the use of penicillin G or amoxicillin is no longer appropriate for gonorrhea. Similarly, many strains of gonococci are resistant to tetracyclines. Alternative drugs (not listed) for gonorrhea include cefixime, azithromycin (see Chapter 44) or spectinomycin (see Chapter 45). The answer is A.
Which statement about vancomycin is accurate? (A) Active against methicillin-resistant staphylococci (B) Bacteriostatic (C) Binds to PBPs (D) Hepatic metabolism (E) Oral bioavailability
Vancomycin is a bactericidal glycoprotein. It inhibits cell wall synthesis but does not bind to PBPs and is not susceptible to beta-lactamases. Vancomycin is not absorbed after oral administration and is used by this route in the treatment of colitis caused by C difficile and staphylococci. It undergoes renal elimination. Vancomycin is commonly considered the drug of first choice for parenteral use against methicillin-resistant staphylococci. The answer is A.
