Bact E2+ E3 Extra
A 73-year-old woman is admitted to the hospital for intravenous treatment of an abscess caused by Staphylococcus aureus. Subsequent to her treatment and discharge from the hospital, it is necessary to disinfect the hospital room. One thousand of the S. aureus cells are exposed to a disinfectant. After 10 minutes, 90% of the cells are killed. How many cells remain viable after 20 minutes? A. 500 B. 100 C. 10 D. 1 E. 0
C. 10
The action of which of the following agents or processes on non-spore forming bacteria can be reversed? A. A disinfectant B. A bactericidal agent C. A bacteriostatic agent D. Autoclaving at 121°C for 15 minutes E. Dry heat at 160-170°C for 1 hour
C. A bacteriostatic agent
Tigecycline, a new glycylcycline antibiotic with good activity against a variety of pathogens, is best used for treatment of which of the following infections? (A) Meningitis (B) Intra-abdominal infections caused by mixed aerobic and anaerobic bacteria (C) Neonatal sepsis (D) Urethritis caused by Chlamydia trachomatis (E) As monotherapy for bacteremia caused by Acinetobacter baumannii
(B) Intra-abdominal infections caused by mixed aerobic and anaerobic bacteria
An 8-year-old boy develops a severe sore throat. On examination, a grayish-white exudate is seen on the tonsils and pharynx. The differential diagnosis includes group A streptococcal infection, Epstein-Barr virus (EBV] infection, severe adenovirus infection, and diphtheria. [Neisseria gonorrhoeae pharyngitis would be included also, but the patient has not been sexually abused.] The cause of the boy's pharyngitis is most likely (A) A catalase-negative gram-positive coccus that grows in chains (B) A single-stranded positive-sense RNA virus (C) A catalase-positive gram-positive coccus that grows in clusters (D) A catalase-negative gram-positive bacillus (E) A double-stranded RNA virus
(A) A catalase-negative gram-positive coccus that grows in chains
A 19-year-old man presented to the clinic with a urethral discharge for the past 24 hours. Neisseria gonorrhoeae was cultured from the specimen and found to be beta- lactamasepositive and resistant to high levels (> 32 pg/mL] of tetracycline. Which of the following statements about these antimicrobial resistance factors is correct? (A) Beta-lactamase production and high-level resistance to tetracycline are both mediated by genes on plasmids (B) Beta-lactamase production is mediated by a gene on the bacterial chromosome while high-level tetracycline resistance is mediated by a gene on a plasmid (C) Beta-lactamase production is mediated by a gene on a plasmid while high-level tetracycline resistance is mediated by a gene on the bacterial chromosome (D) Beta-lactamase production and high-level resistance to tetracycline are both mediated by genes on the bacterial chromosome
(A) Beta-lactamase production and high-level resistance to tetracycline are both mediated by genes on plasmids
A 35-year-old man is a farmer in a tropical area of West Africa. He developed a persistent scaly papule on his leg. Ten months later a new crop of wart-like purplish scaly lesions appeared. These lesions slowly progressed to a cauliflower-like appearance. Chromoblastomycosis (chromomycosis) was diagnosed. Which statement regarding this disease is most correct? (A) In tissue, the organisms convert to spherical cells that reproduce by fission and exhibit transverse septations. (B) The etiologic agents are endogenous members of the mammalian flora and possess melanized cell walls. (C) The disease is caused by a single species. (D) Most infections are systemic. (E) Most infections are acute and clear spontaneously.
(A) In tissue, the organisms convert to spherical cells that reproduce by fission and exhibit transverse septations.
A 20-year-old Asian woman, a recent immigrant to the United States, develops fever and a cough productive of blood-streaked sputum. She has lost 6 kg of body weight in the past 6 weeks. Her chest radiograph shows bilateral upper lobe infiltrates with cavities. Given the history and chest radiography findings, which of the following drug regimens would be the best appropriate initial therapy while awaiting culture results? (A) Isoniazid, rifampin, pyrazinamide, and ethambutol (B) Penicillin G and rifampin (C) Cefotaxime, clindamycin, and trimethoprim-sulfamethoxazole (D) Ampicillin-sulbactam (E) Vancomycin, gentamicin, and clindamycin
(A) Isoniazid, rifampin, pyrazinamide, and ethambutol
A 36-year-old male patient has an abscess with a strain of Staphylococcus aureus that is betalactamase- positive. This indicates that the organism is resistant to which of the following antibiotics? (A) Penicillin G, ampicillin, and piperacillin (B) Trimethoprim-sulfamethoxazole (C) Erythromycin, clarithromycin, and azithromycin (D) Vancomycin (E) Cefazolin and ceftriaxone
(A) Penicillin G, ampicillin, and piperacillin
Susceptibility testing using an MIC method, as opposed to disk diffusion, is preferred for all of the following types of infections except: (A) Urinary tract infections (B) Endocarditis (C) Osteomyelitis (D) Bacteremia in a neutropenic patient (E) Bacterial meningitis
(A) Urinary tract infections
An uncommon serotype of Salmonella enterica subspecies enterica was found by laboratories in the health departments of adjacent states. The isolates were all from a small geographic area on either side of the border between the states, suggesting a common source for the isolates. (All the isolates were from otherwise healthy young adults who smoked marijuana; the same salmonella was isolated from a specimen of the marijuana.] By what method did the laboratories determine that these isolates were the same? (A) Capsular (K antigen] typing (B) 0 antigen and H antigen typing (C) DNA sequencing (D) Sugar fermentation pattern determination (E) Decarboxylase reaction pattern determination
(B) 0 antigen and H antigen typing
A primary mechanism responsible for the pathogenesis of the boy's disease [Question6] is (A) A net increase in intracellular cyclic adenosine monophosphate (B) Action of M protein (C) Action of IgAl protease (D) Action of enterotoxin A (E) Inactivation of elongation factor 2
(B) Action of M protein
Which statement regarding dermatophytosis is correct? (A) Chronic infections are associated with zoophilic dermatophytes, such as Microsporum canis. (B) Acute infections are associated with zoophilic dermatophytes, such as Microsporum canis. (C) Chronic infections are associated with anthropophilic dermatophytes, such as Microsporum canis. (D) Acute infections are associated with anthropophilic dermatophytes, such as Microsporum canis.
(B) Acute infections are associated with zoophilic dermatophytes,
Which statement regarding fungi is correct? (A) All fungi are able to grow as yeasts and molds. (B) Although fungi are eukaryotes, they lack mitochondria. (C) Fungi are photosynthetic. (D) Fungi have one or more nuclei and chromosomes. (E) Few fungi possess cell membranes.
(D) Fungi have one or more nuclei and chromosomes.
The most useful drug to treat ehrlichiosis is A Doxycycline B Penicillin G C Trimethoprim-sulfamethoxazole D Gentamicin E Nitrofurantoin
A. Doxycycline
Which one of the following pathogenic yeasts is not a common member of the normal human flora or microbiota? (A) Candida tropicalis (B) Malassezia globosa (C) Cryptococcus neoformans (D) Candida glabrata (E) Candida albicans
(C) Cryptococcus neoformans
Which of the following carbapenem antibiotics has no activity against Pseudomonas aeruginosa? (A) Imipenem (B) Meropenem (C) Doripenem (D) Ertapenem
(D) Ertapenem
A 54-year-old man developed a slowly worsening headache followed by gradual, progressive weakness in his right arm. A brain scan revealed a left cerebral lesion. At surgery an abscess surrounded by granulomatous material was found. Sections of the tissue and subsequent culture showed darkly pigmented septate hyphae indicating phaeohyphomycosis. This infection may be caused by species of which genus below? (A) Aspergillus (B) Cladophialophora (C) Coccidioides (D) Malassezia (E) Sporothrix
(B) Cladophialophora
Common contaminants of blood cultures include: (A) Gram-negative rods (B) Coagulase-negative staphylococci (C) Staphylococcus aureus (D) Anaerobes
(B) Coagulase-negative staphylococci
An 8-year-old boy develops a circular dry, scaly, and pruritic lesion on his leg. What is the diagnostic significance of observing branching, septate, nonpigmented hyphae in a potassium hydroxide/calcofluor white preparation of a scraping from this skin lesion? (A) Chromomycosis (B) Dermatophytosis (C) Phaeohyphomycosis (D) Sporotrichosis (E) No diagnostic significance
(B) Dermatophytosis
A mother states that she has observed her 4-year-old son scratching his anal area frequently. The most likely cause of this condition is (A) Trichomonas vaginalis (B) Enterobius vermicularis (C) Ascaris lumbricoides (D) Necator americanus (E) Entamoeba histolytica
(B) Enterobius vermicularis
Which statement regarding fungal growth and morphology is correct? (A) Pseudohyphae are produced by all yeasts. (B) Molds produce hyphae that may or may not be partitioned with cross-walls or septa. (C) Conidia are produced by sexual reproduction. (D) Most yeasts reproduce by budding and lack cell walls. (E) Most pathogenic dimorphic molds produce hyphae in the host and yeasts at 30°C.
(B) Molds produce hyphae that may or may not be partitioned with cross-walls or septa.
Your kidney transplant patient has developed nosocomial systemic candidiasis, but the patient's isolate of Candida glabrata is resistant to fluconazole. A reasonable alternative would be oral administration of: (A) Flucytosine (B) Posaconazole (C) Griseofulvin (D) Amphotericin
(B) Posaconazole
Which statement regarding the laboratory identification of fungi is correct? (A) Histoplasma capsulatum typically requires less than 48 hours of incubation to yield positive cultures from clinical specimens. (B) Since many saprobic (nonpathogenic) molds resemble dimorphic mycotic agents in culture at 30°C, the identification of putative dimorphic pathogenic fungi must be confirmed by conversion to the tissue form in vitro or by the detection of species-specific antigens or DNA sequence analysis. (C) Molds are routinely speciated by a battery of physiologic tests, such as the ability to assimilate various sugars. (D) A positive germ tube test provides a rapid presumptive identification of Candida glabrata. (E) Budding yeast cells and abundant pseudohyphae are typical of Pneumocystis jiroveci.
(B) Since many saprobic (nonpathogenic) molds resemble dimorphic mycotic agents in culture at 30°C, the identification of putative dimorphic pathogenic fungi must be confirmed by conversion to the tissue form in vitro or by the detection of species-specific antigens or DNA sequence analysis.
A 45-year-old man presents to the emergency room with a 3-day history of cough productive of blood-tinged sputum and a fever. The Gram stain of the sputum has many white blood cells and gram-positive diplococci. The most likely causative organism is (A) Staphylococcus aureus (B) Streptococcus pneumoniae (C) Mycoplasma pneumoniae (D) Klebsiella pneumonia
(B) Streptococcus pneumoniae
Which statement regarding sporotrichosis is correct? (A) The most common etiologic agent is Pseudallescheria boydii (Scedosporium apiospermum). (B) The etiologic agent is a dimorphic fungus. (C) The ecology of the etiologic agent is unknown. (D) Most cases are subcutaneous and nonlymphangitic. (E) Most patients are immunocompromised.
(B) The etiologic agent is a dimorphic fungus.
Blood cultures from the patient in Question 2 grow a non-lactose-fermenting gram- negative bacillus. Which of the following is likely to be a constituent of this organism? (A) 0 antigen 157, H antigen 7 (0157:H7] (B) Vi antigen (capsule; virulence antigen] (C) 0 antigen 139 (0139] (D) Urease (E) K1 (capsular type 1]
(B) Vi antigen (capsule; virulence antigen]
Modified Thayer-Martin medium was developed to increase the recovery of Neisseria gonorrhoeae from genital tract specimens. This medium can also be used for throat cultures for neisseriae. The ingredients that make this medium selective for neisseriae are (A) Agar (B) A source of amino acids (C) Antibiotics (D) Glucose (E) Vitamins
(C) Antibiotics
An 8-year-old girl develops Sydenham's chorea ("St. Vitus' dance") with rapid uncoordinated facial tics and involuntary purposeless movements of her extremities, strongly suggestive of acute rheumatic fever. She has no other major manifestations of rheumatic fever (carditis, arthritis, subcutaneous nodules, skin rash). The patient's throat culture is negative for Streptococcus pyogenes (group A streptococci). However, she, her brother, and her mother all had sore throats 2 months ago. A test that if positive would indicate recent Streptococcus pyogenes infections is (A) Antistreptolysin S antibody titer (B) Polymerase chain reaction for antibodies against M protein (C) Antistreptolysin 0 antibody titer (D) Esculin hydrolysis (E) Antihyaluronic acid antibody titer
(C) Antistreptolysin 0 antibody titer
All of the following agents have good activity against grampositive organisms except (A) Daptomycin (B) Vancomycin (C) Aztreonam (D) Quinupristin-dalfopristin (E) Tigecycline
(C) Aztreonam
Which of the following specimens does not usually contain anaerobes? (A) Aspiration from an infected maxillary sinus (B) Throat swab from a patient with a sore throat (C) Cerebrospinal fluid from a patient with meningitis (D) Expectorated sputum from a patient with communityacquired pneumonia
(C) Cerebrospinal fluid from a patient with meningitis
Which statement regarding dermatophytosis is correct? (A) Chronic infections are associated with zoophilic dermatophytes, such as Trichophyton rubrum. (B) Acute infections are associated with zoophilic dermatophytes, such as Trichophyton rubrum. (C) Chronic infections are associated with anthropophilic dermatophytes, such as Trichophyton rubrum. (D) Acute infections are associated with anthropophilic dermatophytes, such as Trichophyton rubrum.
(C) Chronic infections are associated with anthropophilic dermatophytes, such as Trichophyton rubrum.
An 18-year-old student has abdominal cramps and diarrhea. A plate of MacConkey's agar is inoculated and grows gram-negative rods. Triple sugar iron (TSI] agar is used to screen the isolates for salmonellae and shigellae. A result suggesting one of these two pathogens would be (A) Production of urease (B) Motility in the medium (C) Inability to ferment lactose and sucrose (D) Fermentation of glucose (E) Production of gas in the medium
(C) Inability to ferment lactose and sucrose
Which statement regarding fungal cell walls is correct? (A) The major components of fungal cell walls are proteins such as chitin, glucans, and mannans. (B) The cell wall is not essential for fungal viability or survival. (C) Ligands associated with the cell walls of certain fungi mediate attachment to host cells. (D) Fungal cell wall components are the targets for the major classes of antifungal antibiotics, such as the polyenes and azoles. (E) Fungal cell wall components rarely stimulate an immune response.
(C) Ligands associated with the cell walls of certain fungi mediate attachment to host cells.
A 28-year-old female sex worker from southern California complained of headaches, dizziness, and occasional episodes of "spacing out" during the past 2 weeks. A lumbar puncture revealed reduced sugar, elevated protein, and 450 mononuclear leukocytes per milliliter. She was seropositive for HIV. Her history is compatible with fungal meningitis due to Cryptococcus neoformans, Coccidioides posadasii, or a species of Candida. Which one of the following tests is confirmatory? (A) Meningitis due to Coccidioides posadasii would be confirmed by a positive test of the CSF for cryptococcal capsular antigen. (B) Meningitis due to Cryptococcus neoformans would be confirmed by a positive test of the CSF for complement fixation antibodies to coccidioidin. (C) Meningitis due to a species of Candida would be confirmed by the microscopic observation of oval yeast cells and pseudohyphae in the CSF. (D) Meningitis due to Coccidioides posadasii would be confirmed by a positive skin test to coccidioidin.
(C) Meningitis due to a species of Candida would be confirmed by the microscopic observation of oval yeast cells and pseudohyphae in the CSF.
A 32-year-old male tourist traveled to Senegal for 1 month. During the trip, he swam in the Gambia river. Two months after his return, he began complaining of intermittent lower abdominal pain with dysuria. Laboratory results of ova and parasites revealed eggs with a terminal spine. Which of the following parasites is the cause of the patient's symptoms? (A) Toxoplasma gondii (B) Schistosoma mansoni (C) Schistosoma haematobium (D) Ascaris lumbricoides (E) Taenia solium
(C) Schistosoma haematobium
Four members of a migrant farmworker family — mother, father, and two young children — come to the emergency room because of diarrhea and fever of 6- 1 2 hours' duration. Their stools have been frequent and flecked with blood. Several other people in the workers' camp have been ill with a similar diarrheal disease. This included the person who prepared the evening meal the previous day. The parents had normal physical examinations. The children showed signs of excessive fluid and electrolyte loss. The likely cause of this outbreak is (A) Salmonella enterica subspecies enterica serotype Typhimurium ( Salmonella Typhimurium] (B) Salmonella enterica subspecies enterica serotype Typhi [Salmonella Typhi] (C) Shigella flexneri (D) Rotavirus (E) Enterotoxigenic Escherichia coli (ETEC]
(C) Shigella flexneri
A group of six children under 8 years of age live in a semitropical country. Each of the children has several crusted weeping skin lesions of impetigo [pyoderma]. The lesions are predominantly on the arms and faces. Which of the following microorganisms is a likely cause of the lesions? (A) Escherichia coli (B) Chlamydia trachomatis (C) Staphylococcus aureus (D) Streptococcus pneumoniae (E) Bacillus anthracis
(C) Staphylococcus aureus
Aminoglycoside antibiotics typically cause which of the following adverse events? (A) They cause aplastic anemia. (B) They cause nonspecific stimulation of B cells. (C) They cause ototoxicity and nephrotoxicity. (D) They cause photosensitivity.
(C) They cause ototoxicity and nephrotoxicity.
A 38-year-old vice squad police officer comes to the emergency room with a chief complaint expressed as follows: "I have disseminated gonococcal infection again." He is correct. Cultures of his urethra and knee fluid yield Neisseria gonorrhoeae. He has previously had five episodes of disseminated gonococcal infection. The patient should be evaluated for (A) Selective IgA deficiency (B) A polymorphonuclear cell chemotactic defect (C) Deficiency of a late-acting complement component C5, C6, C7, or C8 (D) Absent lymphocyte adenosine deaminase activity (E) Myeloperoxidase deficiency
(D) Absent lymphocyte adenosine deaminase activity
Which of the following agents would not be expected to demonstrate postantibiotic affect against gram-negative bacilli? (A) Imipenem (B) Ciprofloxacin (C) Gentamicin (D) Ampicillin
(D) Ampicillin
A middle-aged male resident of southern California received a liver transplant. During the following months, he gradually developed fatigue, weight loss, cough, night sweats, dyspnea, and a nonhealing subcutaneous nodule on his nose. The chest radiograph revealed hilar lymphadenopathy and diffuse infiltrates. Direct examination and culture of a respiratory specimen were negative. Skin tests with PPD, blastomycin, coccidioidin, and histoplasmin were negative. Serologic test results were as follows: Negative serum test for cryptococcal capsular antigen in blood, positive immunodiffusion test for serum precipitins to fungal antigen F, and negative immunodiffusion tests for precipitins to antigens h, m, and A. Serum tests for fungal complement fixation antibodies were negative for Blastomyces dermatitidis, as well as both the mycelial and yeast antigens of Histoplasma capsulatum but yielded a titer of 1:32 to coccidioidin. Which interpretation of these data is the most tenable? (A) Clinical and serologic findings are inconclusive. (B) Clinical and serologic findings are most consistent with active disseminated histoplasmosis. (C) Clinical and serologic findings are most consistent with active disseminated blastomycosis. (D) Clinical and serologic findings are consistent with active disseminated coccidioidomycosis. (E) Clinical and serologic findings exclude a diagnosis of blastomycosis, histoplasmosis, and coccidioidomycosis.
(D) Clinical and serologic findings are consistent with active disseminated coccidioidomycosis.
A 42-year-old HIV-positive male, originally from Vietnam but now residing in Tucson, Arizona, presents with a painful ulcerative lesion on his upper lip (cheilitis). A biopsy was obtained, and the histopathologic slide (hematoxylin and eosin stain) revealed spherical structures (20-50 μm in diameter) with thick refractory cell walls. What is the likely disease consistent with this finding? (A) Infection with Penicillium marneffei (B) Cryptococcosis (C) Blastomycosis (D) Coccidioidomycosis (E) No diagnostic significance
(D) Coccidioidomycosis
A 37-year-old man with AIDS, currently living in Indianapolis, Indiana, presented with osteomyelitis of the left hip. A needle biopsy of the bone marrow was obtained, and the calcofluor white smear revealed a variety of myelogenous cells, monocytes, and macrophages containing numerous intracellular yeast cells that were elliptical and approximately 2 × 4 μm. What is the most likely diagnosis? (A) Blastomycosis (B) Candidiasis (C) Cryptococcosis (D) Histoplasmosis (E) No diagnostic significance
(D) Histoplasmosis
You are working in a rural medical clinic in China and a 3-yearold girl is brought in by her mother. The child appears emaciated and, upon testing, is found to have a hemoglobin level of 5 g/dL. Her feet and ankles are swollen, and there is an extensive rash on her feet, ankles, and knees. The most likely parasitic infection that causes the child's condition is (A) Schistosomiasis (B) Cercarial dermatitis (C) Cyclosporiasis (D) Hookworm infection (E) Trichuriasis (F) Ascariasis
(D) Hookworm infection
Which statement about blastomycosis is correct? (A) Similar to other endemic mycoses, this infection occurs equally in men and women. (B) Infection starts in the skin, and the organisms commonly disseminate to the lungs, bone, genitourinary tract, or other sites. (C) The disease is endemic to certain areas of South America. (D) In tissue, one finds large, thick-walled, single budding yeast cells with broad connections between the parent yeast and bud. (E) All cases require treatment with amphotericin B.
(D) In tissue, one finds large, thick-walled, single budding yeast cells with broad connections between the parent yeast and bud.
An 18-year-old woman who reports unprotected sex with a new partner 2 weeks previously develops fever and left lower quadrant abdominal pain with onset in association with her menstrual period. On pelvic examination in the emergency room there is bilateral tenderness when the uterus is palpated. A mass 2-3 cm in diameter is felt on the left, suggestive of tubo-ovarian abscess. Subsequently, Neisseria gonorrhoeae is cultured from her endocervix. The diagnosis is gonococcal pelvic inflammatory disease. A common sequela of this infection is (A) Cancer if the cervix (B) Urethral stricture (C) Uterine fibroid tumors (D) Infertility (E) Vaginal-rectal fistula
(D) Infertility
The exfoliative toxins, toxic shock toxin 1 (TSST- 1], and the enterotoxins are all superantigens. The genes for these toxins are (A) Present in all strains of Staphylococcus aureus (B) Widely distributed on the staphylococcal chromosome (C) On both the staphylococcal chromosome (TSST-1 and exfoliative toxins] and on plasmids (enterotoxins] (D) On the staphylococcal chromosome in a pathogenicity island (E) On plasmids
(D) On the staphylococcal chromosome in a pathogenicity island
A 47-year-old woman had a bone marrow transplant as part of her treatment for chronic myelogenous leukemia. While in the hospital she had a central venous catheter in place for administration of fluids. In the time following the transplant, but before it had engrafted, the patient had a very low white blood cell count. She developed a fever, and blood cultures were done. Which of the following scenarios suggests that the positive blood cultures resulted from a contaminant? (A) Two positive peripheral vein blood cultures with Staphylococcus aureus (B) Two positive peripheral vein blood cultures with Staphylococcus epidermidis along with two positive central line blood cultures with Staphylococcus epidermidis (C) One positive peripheral vein blood culture and one positive central line blood culture with Escherichia coli (D) One positive central venous line blood culture with a Corynebacterium species and two negative peripheral vein blood cultures (E) Two positive central line blood cultures with Candida albicans
(D) One positive central venous line blood culture with a Corynebacterium species and two negative peripheral vein blood cultures
Which statement regarding the epidemiology of candidiasis is correct? (A) Patients receiving bone marrow transplants are not at risk for systemic candidiasis. (B) Patients with impaired or low numbers of neutrophils and monocytes are not at risk for systemic candidiasis. (C) Patients with any form of diabetes have enhanced resistance to candidiasis. (D) Patients with AIDS frequently develop mucocutaneous candidiasis, such as thrush. (E) Pregnancy lowers the risk of candidal vaginitis.
(D) Patients with AIDS frequently develop mucocutaneous candidiasis, such as thrush.
A 27 -year-old woman is admitted to the hospital because of fever, with increasing anorexia, headache, weakness, and altered mental status of 2 days' duration. She works for an airline as a cabin attendant, flying between the Indian subcontinent and other places in Southeast Asia and the West Coast of the United States. Ten days prior to admission she had a diarrheal illness that lasted for about 36 hours. She has been constipated for the last 3 days. Her temperature is 39 °C, heart rate 68/min, blood pressure 120/80 mm Hg, and respirations 18/min. She knows who she is and where she is but does not know the date. She is picking at the bedclothes. Rose spots are seen on the trunk. The remainder of the physical examination is normal. Blood cultures are done and an intravenous line is placed. The most likely cause of her illness is (A) Enterotoxigenic Escherichia coli (ETEC) (B) Shigella sonnei (C) Salmonella enterica subspecies enterica serotype Typhimurium ( Salmonella Typhimurium] (D) Salmonella enterica subspecies enterica serotype Typhi ( Salmonella Typhi] (E) Enteroinvasive Escherichia coli (EIEC)
(D) Salmonella enterica subspecies enterica serotype Typhi ( Salmonella Typhi]
Two days ago, a 22-year-old man returned from a 2-week trip to Mexico. Within 24 hours, he developed diarrhea. Which of the following will not establish the etiology of his diarrhea? (A) Stool culture for Salmonella, Shigella, and Campylobacter (B) Stool culture for rotavirus and Norwalk-like virus (C) Stool enzyme immunoassay for Giardia lamblia antigen (D) Stool examination for Entamoeba histolytica
(D) Stool examination for Entamoeba histolytica
Which statement regarding aspergillosis is correct? (A) Patients with allergic bronchopulmonary aspergillosis rarely have eosinophilia. (B) Patients receiving parenteral corticosteroids are not at risk for invasive aspergillosis. (C) The diagnosis of pulmonary aspergillosis is frequently established by culturing Aspergillus from the sputum and blood. (D) The clinical manifestations of aspergillosis include local infections of the ear, cornea, nails, and sinuses. (E) Bone marrow transplant recipients are not at risk for invasive aspergillosis.
(D) The clinical manifestations of aspergillosis include local infections of the ear, cornea, nails, and sinuses.
A 65 -year-old man develops an abscess on the back of his neck. Culture yields Staphylococcus aureus. The isolate is tested and found to be positive for the mecA gene, which means that (A) The isolate is susceptible to vancomycin (B) The isolate is resistant to vancomycin (C) The isolate is susceptible to nafcillin (D) The isolate is resistant to nafcillin (E) The isolate is susceptible to penicillin G (F) The isolate is resistant to penicillin G
(D) The isolate is resistant to nafcillin
A 6-year-old boy develops fever and headache. He is taken to the emergency room where he is noted to have a stiff neck, suggesting meningeal irritation. A lumbar puncture is done and culture of the cerebrospinal fluid grows Neisseria meningitidis serogroup B. Which of the following should be considered for his family (household) members? (A) No prophylaxis or other steps are necessary (B) They should be given Neisseria meningitides pilin vaccine (C) They should be given Neisseria meningitides serogroup B polysaccharide capsule vaccine (D) They should be given rifampin prophylaxis (E) They should be given sulfonamide prophylaxis
(D) They should be given rifampin prophylaxis
Antimicrobial resistance has become a significant problem. Which one of the following is of major concern worldwide? (A) Nafcillin resistance in Staphylococcus aureus (B) Penicillin resistance in Streptococcus pneumoniae (C) Penicillin resistance in Neisseria gonorrhoeae (D) Vancomycin resistance in Staphylococcus aureus (E) Tobramycin resistance in Escherichia coli
(D) Vancomycin resistance in Staphylococcus aureus
An 1 1-year-old boy develops a mild fever and pain in his upper arm. An x-ray film of his arm shows a lytic lesion (dissolution] in the upper part of the humerus with periosteal elevation over the lesion. The patient is taken to surgery, where the lesion is debrided (dead bone and pus removed]. Culture from the lesion yields gram-positive cocci. A test shows that the organism is a staphylococcus and not a streptococcus. Based on this information, you know the organism is (A) Susceptible to nafcillin (B) Beta-lactamase-positive (C) A producer of protein A (D) Encapsulated (E) Catalase-positive
(E) Catalase-positive
Over a period of 3 weeks, a total of five newborns in the hospital nursery developed Staphylococcus aureus infections with S aureus bacteremia. The isolates all had the same colony morphology and hemolytic properties and identical antimicrobial susceptibility patterns, suggesting that they were the same. (Later molecular methods showed the isolates were identical.] Which of the following should be done now? (A) Prophylactic treatment of all newborns with intravenous vancomycin (B) Protective isolation of all newborns (C) Closing the nursery and referring pregnant women to another hospital (D) Hiring all new staff for the hospital nursery (E) Culture using mannitol salt agar of the anterior nares of the physicians, nurses, and others who cared for the infected babies
(E) Culture using mannitol salt agar of the anterior nares of the physicians, nurses, and others who cared for the infected babies
A 20 -year-old college student goes to the student health center because of dysuria, frequency, and urgency on urination for 24 hours. She has recently become sexually active. On urinalysis, many polymorphonuclear cells are seen. The most likely organism responsible for these symptoms and signs is (A) Staphylococcus aureus (B) Streptococcus agalactiae (C) Gardnerella vaginalis (D) Lactobacillus species (E) Escherichia coli
(E) Escherichia coli
All of the following are common mechanisms of resistance to the penicillins except (A) Production of β-lactamases (B) Alterations in target receptors (PBPs) (C) Inability to activate autolytic enzymes (D) Failure to synthesize peptidoglycans (E) Methylation of ribosomal RNA
(E) Methylation of ribosomal RNA
Which one of the following antifungal drugs does not target the biosynthesis of ergosterol in the fungal membrane? (A) Voriconazole (B) Itraconazole (C) Terbinafine (D) Fluconazole (E) Micafungin
(E) Micafungin
A previously healthy 23-year-old woman recently returned from her vacation after visiting friends in Arizona. She complained of severe headaches, saw "flashing lights," and had a purulent nasal discharge. She was admitted into the hospital with a diagnosis of bacterial meningitis and died 5 days later. Which of the following parasites should have been considered in the diagnosis? She had no prior history of travel outside of the United States. (A) Plasmodium falciparum (B) Toxoplasma gondii (C) Strongyloides stercoralis (D) Entamoeba histolytica (E) Naegleria fowleri
(E) Naegleria fowleri --> acquired via hot spring
The potassium hydroxide examination of sputum from a heart transplant patient with fever and pulmonary infiltrates contains oval budding yeast cells and pseudohyphae. What is the diagnostic significance? (A) Aspergillosis (B) Candidiasis (C) Hyalohyphomycosis (D) Phaeohyphomycosis (E) No diagnostic significance
(E) No diagnostic significance
A 24-year-old, HIV-negative migrant worker from Colombia presented with a painful ulcerative lesion on the tongue. The edge of the lesion was gently scraped and a calcofluor white-potassium hydroxide smear revealed tissue cells, debris, and several large, spherical, multiply budding yeast cells. Based on this observation, what is the most likely diagnosis? (A) Blastomycosis (B) Candidiasis (C) Coccidioidomycosis (D) Histoplasmosis (E) Paracoccidioidomycosis
(E) Paracoccidioidomycosis
Several Papua New Guinea villagers known to eat pork during celebrations were reported to be suffering from an outbreak of epileptiform seizures. One of the first things you should investigate is (A) The prevalence of Ascaris infections in the population (B) The prevalence of schistosomiasis in the population (C) The presence of Trypanosoma brucei gambiense in the villagers (D) The presence of Giardia cysts in the drinking water (E) The presence of Taenia solium in the pigs
(E) The presence of Taenia solium in the pigs
A specimen of pasteurized goat's milk is cultured for the presence of Brucella melitensis, an organism known to infect animals on an adjacent farm. The milk is declared safe to consume; however, some of those who consume it develop brucellosis. Which one of the following would best explain the disparity between the culture results and the patients' illnesses? A. Bacteria in the milk were viable but not cultivatable B. Incomplete pasteurization of the milk C. The organisms in the milk were in the lag phase when tested D. The milk contained a high concentration of a bactericidal antibiotic when tested E. There was post-test contamination of the milk
A. Bacteria in the milk were viable but not cultivatable
The growth rate of bacteria during the maximum stationary phase of growth is A. Zero B. Increasing C. Constant D. Decreasing E. Negative
A. Zero
A sexually active 24-year-old woman complains of vaginal itching and vaginal discharge. To verify your tentative diagnosis of trichomoniasis, you should include which of the following in your workup? (A) Specific serologic test (B) Ova and parasite fecal smear (C) Wet mount of vaginal fluid (D) Enzyme-linked immunoassay (ELISA) test of serum (E) Stool culture
C) Wet mount of vaginal fluid
A 37-year-old woman with a history of urinary tract infections comes to the emergency department with burning on urination along with frequency and urgency. She says her urine smells like ammonia. The cause of her urinary tract infection is likely to be A E. aerogenes B Proteus mirabilis C Citrobacter freundii D E. coli E S. marcescens
B Proteus mirabilis
A 4-year-old boy develops bloody diarrhea. Hemorrhagic colitis due to Escherichia coli O157:H7 is suspected. What medium should be inoculated to help the laboratory staff make the diagnosis of this infection? (A) Blood agar (B) Sorbitol MacConkey agar (C) Hektoen enteric agar (D) CIN (cefsulodin, irgasan, novobiocin) agar (E) Thiosulfate citrate bile salts sucrose agar
B) Sorbitol MacConkey agar
Methods of microbial control called ________ arrest the growth of microbes. A) germicidal B) germistatic C) sanitizing D) disinfection
B) germistatic
An instrument that will come into contact with only the skin of a patient should be disinfected with a(n) A) high-level germicide. B) low-level germicide. C) intermediate-level germicide. D) degerming agent only. E) germistatic agent only.
B) low-level germicide.
Chemical agents can interfere with the normal reaction between a specific enzyme and its substrate (chemical antagonism). Which one of the following inhibits energy-yielding cellular processes? A. 5-Methyltryptophan B. Cyanide C. Hydrogen peroxide D. Ethanol E. Lysozyme
B. Cyanide
Which of the following terms best describes a microorganism that grows at 20°C? A. Neutralophile B. Psychrotroph C. Mesophile D. Osmophile E. Thermophile
B. Psychrotroph
A 37-year-old man traveled to Peru during the time of the cholera epidemic. One day after returning home, he developed severe watery diarrhea. To enhance the isolation of Vibrio cholerae from his stool, the laboratory needs to include: (A) MacConkey agar (B) Campylobacter blood agar (C) Thiosulfate citrate bile salts sucrose agar (D) Bismuth sulfite agar (E) Hektoen agar
C) Thiosulfate citrate bile salts sucrose agar
All of the following cause zoonotic infections except A F. tularensis B B. melitensis C B. pertussis D Bacillus anthracis E Leptospira interrogans
C B. pertussis
4-year-old boy from Kansas City who recently started attending preschool and after-school daycare is brought to his pediatrician for a diarrheal illness characterized by fever to 38.2°C, severe lower abdominal pain, and initially watery diarrhea. His mother became concerned because the stools are now blood tinged 24 hours into the illness, and the child appears quite ill. The mother reports that two other children who attend the same after-school daycare have recently had diarrheal disease, one of whom likewise had bloody stools. Which of the following is the most likely pathogen causing the illness in these children? A An enterotoxigenic strain of E. coli B S. enterica subspecies enterica serotype Typhi (Salmonella Typhi) C S. sonnei D Edwardsiella tarda E Klebsiella oxytoca
C S. sonnei
Which of the following is an example of pasteurization? A) A public toilet is treated with disinfectants. B) A surgeon washes her hands before surgery. C) Heat is used to kill potential pathogens in apple juice. D) An autoclave is used to prepare nutrient agar. E) A nurse prepares an injection site with an alcohol swab.
C) Heat is used to kill potential pathogens in apple juice.
A physician obtains a sputum specimen from a patient suffering from tuberculosis. This sputum sample contains one viable Mycobacterium tuberculosis, an organism with a slow doubling time in vitro of 48 hours, which corresponds to a growth rate constant (k) in vitro of 0.04 h-1. Estimating that the biomass of this single mycobacterial organism is 2.3 × 10−13 g and assuming that this organism is immediately going to enter log phase growth, how many hours will it take to produce 10−6 g of biomass? A. 4 hours B. 40 hours C. 400 hours D. 4000 hours E. 40,000 hours
C. 400 hours
The growth rate of bacteria during the exponential phase of growth is A. Zero B. Increasing C. Constant D. Decreasing E. Negative
C. Constant
Your superior requests that you sterilize some surgical instruments. Which one of the following agents would you use? A. Benzoic acid (2%) B. Isopropyl alcohol (2%) C. Glutaraldehyde (2%) D. Hydrogen peroxide (2%) E. Quaternary ammonium compound (2%)
C. Glutaraldehyde (2%)
Eubacteria that lack cell walls and do not synthesize the precursors of peptidoglycan are called A. Gram-negative bacteria B. Viruses C. Mycoplasmas D. Serovar E. Bacilli
C. Mycoplasmas
The steps leading to the synthesis of peptidoglycan occur in the cytoplasm, on the cytoplasmic membrane, and extracellularly. Which antibiotic inhibits an extracellular step in peptidoglycan biosynthesis? A. Cycloserine B. Rifampin C. Penicillin D. Bacitracin E. Streptomycin
C. Penicillin
Which statement about phaeohyphomycosis is correct? (A) The infection only occurs in immunocompetent patients. (B) Infected tissue reveals branching, septate nonpigmented hyphae. (C) The causative agents are members of the normal microbial flora and can be isolated readily from the skin and mucosa of healthy persons. (D) Phaeohyphomycosis may exhibit several clinical manifestations, including subcutaneous or systemic disease, as well as sinusitis. (E) Cases rarely respond to treatment with itraconazole.
D) Phaeohyphomycosis may exhibit several clinical manifestations, including subcutaneous or systemic disease, as well as sinusitis.
Which of the following statements is TRUE of disinfectants? A) They are effective in destroying endospores. B) They are used on living tissue. C) They are used for sterilization. D) They are used on inanimate surfaces. E) They are only effective for short periods of time (seconds to minutes).
D) They are used on inanimate surfaces.
You notice a sign in a public restroom that states "Sanitized for your safety." This means A) sterilizing chemicals have been used in cleaning. B) antiseptics have been used to clean the area. C) degerming methods only have been used to clean the restroom. D) methods of disinfection that meet minimum standards of microbial removal have been used. E) only "organic" chemicals were used in the cleaning process to reduce microbial numbers.
D) methods of disinfection that meet minimum standards of microbial removal have been used.
The peptidoglycan biosynthetic pathway is of particular importance in medicine because it provides a basis for selective antibacterial action of several chemotherapeutic agents. All of the following antibiotics inhibit steps in peptidoglycan biosynthesis EXCEPT A. Cycloserine B. Vancomycin C. Bacitracin D. Streptomycin E. Penicillin
D. Streptomycin
A 54-year-old woman develops a right shoulder abscess with a strain of Staphylococcus aureus that is resistant to nafcillin. She was treated with a 2 -week course of intravenous vancomycin and improved. Three weeks later (week 5], the infection recurred and she was given 2 more weeks of intravenous vancomycin and again improved. Four weeks later (week 11], the infection recurred and the patient was again started on intravenous vancomycin. The minimum inhibitory concentrations (MICs] for vancomycin for the S aureus isolates were as follows: initial isolate (day 1], 1 pg/mL; week 5, 2 pg/mL; and week 11, 8 pg/mL. The patient failed to improve with the third course of vancomycin, and alternative therapy was used. The mechanism that best explains the relative resistance of the patient's strain of 5 aureus to vancomycin is (A) Acquisition of the vanAgene from another microorganism (B) Active transport of vancomycin out of the S aureus cell (C) Action of beta-lactamase (D) Increased cell wall synthesis and alterations in the cell wall structure (E) Phosphorylation and resultant inactivation of the vancomycin
D.Increased cell wall synthesis and alterations in the cell wall structure
Antimicrobial agents that damage nucleic acids also affect A) the cell wall. B) the cell membrane. C) the viral envelope. D) endospores. E) protein synthesis.
E) protein synthesis.
A 19-year-old man develops cough and fever. A chest radiograph shows consolidation of the left lower lobe. A diagnosis of pneumonia is made. Which of the following bacteria is a frequent cause of community-acquired pneumonia A. L. pneumophila B C. pneumoniae C S. pneumoniae D Mycoplasma pneumoniae E Klebsiella pneumoniae
E Klebsiella pneumoniae
A 24-year-old, HIV-negative migrant worker from Colombia presented with a painful ulcerative lesion on the tongue. The edge of the lesion was gently scraped and a calcofluor white-potassium hydroxide smear revealed tissue cells, debris, and several large, spherical, multiply budding yeast cells. Based on this observation, what is the most likely diagnosis? A Blastomycosis B Candidiasis C Coccidioidomycosis D Histoplasmosis E Paracoccidioidomycosis
E Paracoccidioidomycosis
The drug of choice for treatment of infections caused by Actinomyces species is A Tigecycline B Cefoxitin C Metronidazole D Imipenem E Penicillin
E Penicillin
A 60-year-old man was admitted to the hospital 2 weeks previously because of head trauma and other injuries that resulted from an automobile accident. A urinary tract catheter was inserted at admission and remains in place. The man develops a urinary tract infection with a gram-negative bacillus. The probable cause of this patient's infection is (A) Pseudomonas aeruginosa (B) Providencia rettgeri (C) Escherichia coli (D) Morganella morganii (E) Indeterminable without culture and identification Testing
E) Indeterminable without culture and identification Testing
A chemical agent that dissolves lipids can damage A) cells. B) bacterial endospores. C) enveloped viruses. D) non-enveloped and enveloped viruses. E) cells and enveloped viruses.
E) cells and enveloped viruses.
Washing dishes in the dishwasher with detergent and hot water is a ________ process. A) degerming B) disinfecting C) sterilizing D) sanitizing E) degerming and disinfecting
E) degerming and disinfecting
Aseptic means A) sterile. B) free of all microbes. C) clean. D) sanitized. E) free of pathogens
E) free of pathogens
Bacteria that are obligate intracellular pathogens of humans (eg, Chlamydia trachomatis) are considered to be A. Autotrophs B. Photosynthetic C. Chemolithotrophs D. Hyperthermophiles E. Heterotrophs
E. Heterotrophs
A 16-year-old cystic fibrosis patient is admitted to the hospital. A sputum culture yields Burkholderia cepacia. Subsequently, there are two other patients with B. cepacia bacteremia, and the organism is cultured from the sputum of four additional patients. During this nosocomial outbreak of B. cepacia, 50 environmental and 7 patient isolates are being subtyped to identify the source of the outbreak. Which of the following techniques would be most useful in this endeavor? A. Culture B. Ribotyping C. 16S rRNA sequencing D. Antimicrobial susceptibility testing E. Nucleic acid sequencing
E. Nucleic acid sequencing
Working as a medical missionary in rural India, you spray the umbilicus of a newly born infant with a solution containing the chemical structure in the associated figure to prevent a tetanus infection. Which class of chemical agent does this structure belong? A. Alcohol class B. Aldehyde class C. Bisphenol class D. Peroxygen class E. Quaternary ammonium class
E. Quaternary ammonium class
Which of the following is the most resistant to destruction by chemicals and heat? A. Spores of Aspergillus fumigatus B. Mycobacterium tuberculosis C. Ebola virus D. E. coli E. Spores of Bacillus anthracis
E. Spores of Bacillus anthracis
A bacterium with a genome having a G + C content of 45% harbors a plasmid encoding a gene with a G + C content of 55%. Which one of the following conclusions could be drawn? A. This gene codes for a cell wall peptidyl transferase. B. This gene codes for a critical bacterial cytochrome. C. This gene codes for a unique transfer RNA. D. This gene codes for a plasmid RNA-dependent DNA-polymerase. E. This gene codes for an antigenically diverse capsular polysaccharide.
E. This gene codes for an antigenically diverse capsular polysaccharide.
