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MLT MICROBIOLOGY
BOC MLT MICROBIOLOGY #2
| Question | Answer |
|---|---|
| 167) A gastroenterologist submits a gastric biopsy from a patient with a peptic ulcer. To obtain presumptive evidence of Helicobacter pylori, a portion of the specimen should be added to which media? a. urea broth b. tetrathionate c. selenite d. trypt | a. urea broth a (Helicobacter pylori produces large amounts of extracellular urease and is positive for urea within 2 hours.) |
| 168) A 4 yr. old boy is admitted to the hospital with suspected meningitis. He has not had most of the childhood vaccines. The suspected pathogen is: a. Listeria monocytogenes b. Haemophilus influenzae c. Streptococcus agalactiae d. Neisseria meningit | b. Haemophilus influenzae b (Haemophilus influenzae was previously the most common cause of bacterial meningitis in young children. |
| 171) A gram stain of a touch prep from a gastric biopsy shows gram-negative bacilli that are slender and curved. The most likely pathogen is: a. Burkholderia cepacia b. Corynebacterium urealyticum c. Helicobacter pylori d. Pasteurella multocida | c. Helicobacter pylori c (Helicobacter pylori is known to cause gastritis and is a gram-negative, curved bacillus.) |
| 172) A CSF has been inoculated onto SBA and choc agar plates and into a tube of trypticase soy broth. All media were incubated in an atmosphere of 5% CO2. Which of the following organisms would usually be isolated by this procedure? a. Francisella tulare | b. Haemophilus influenzae b (Haemophilus influenzae is recovered on chocolate agar. |
| 173) If present, a characteristic that is helpful in separating Pseudomonas aeruginosa from other members of the Pseudomonas family is: a. positive test for cytochrome oxidase b. oxidative metabolism in the OF test d. growth at 42 C | d. growth at 42 C (Pseudomonas aeruginosa grows at 42 C, but this temperature is inhibitory for other Pseudomonas species.) |
| 175) Which of the following results is typical of Campylobacter jejuni? a. optimal growth at 42 C b. oxidase negative c. catalase negative d. nonmotile | a. optimal growth at 42 C a (Campylobacter jejuni will grow at 37 C, but prefers 42 C. It is oxidase and catalase positive and motile.) |
| 176) Optimum growth of Campylobacter jejuni is obtained on suitable media incubated at 42 C in an atmosphere containing: a. 6% O2, 10%-15% CO2, 85%-90% nitrogen b. 10% H2, 5% CO2, 85% nitrogen c. 10% H2, 10% CO2, 80% nitrogen d. 25% O2, 5% CO2, 70% ni | a. 6% O2, 10%-15% CO2, 85%-90% nitrogen a (Campylobacter is microaerophilic, and requires a decreased oxygen and increased carbon dioxide atmosphere for growth.) |
| 178) Haemophilus influenzae is most likely considered normal indigenous flora in the: a. oropharynx b. female genital tract c. large intestine d. small intestine | a. oropharynx a (Haemophilus influenzae is indigenous flora of the upper respiratory tract.) |
| 179) Haemophilus influenzae becomes resistant to ampicillin when the organism produces a: a. capsule of polysaccharide material b. affinity for the beta-lactam ring of the ampicillin c. porphobilinogen d. beta-lactamase enzyme | d. beta-lactamase enzyme (The beta-lactamase enzyme produced by Haemophilus influenzae inactivates the antibiotics that have a beta-lactam ring in their structure, such as penicillins and cephalosporins.) |
| 180) An isolate on chocolate agar from a patient with epiglottitis was suggestive of Haemophilus species. Additional testing showed that the isolate required NAD for growth and was nonhemolytic. The organism is most likely Haemophilus: | . parainfluenzae d (Haemophilus parainfluenzae requires NAD for growth but not hemin. This distinguishes it from H influenzae. H haemolyticus is hemolytic, and H ducreyi does not cause epiglotittis.) |
| 181) Which of the following specimens is considered to be the most sensitive for the recovery of Brucella in cases of chronic infection? a. blood b. urine c. bone marrow d. lymph node | c. bone marrow c (Bone marrow is considered the most sensitive specimen for the recovery of Brucella.) |
| 185) A gram negative bacillus with bipolar staining was isolated from a wound infection caused by a bite from a pet cat | b. Pasteurella multocida b (Pasteurella multocida does not grow on MacConkey agar, and is associated with wounds resulting from dog and cat bites. Vibrio cholerae is motile and Pseudomonas and Aeromonas grow on MacConkey.) |
| 187) While swimming in a lake near his home, a young boy cut his foot, and an infection developed. The culture grew a nonfastidious gram-negative, oxidase positive, beta-hemolytic, motile bacilli that produced deoxyribonuclease. | . Aeromonas hydrophila (Enterobacteriaceae, such as E coli, Serratia and Enterobacter, are oxidase negative. The only selection that is oxidase positive is Aeromonas. It is associated with wounds contaminated with water.) |
| 190) Serum samples collected from a patient with pneumonia demonstrate a rising antibody titer to Legionella. A bronchoalveolar lavage (BAL) specimen from this patient had a positive antigen test for legionella but no organisms were recovered on buffered | d. culture was not incubated long enough d (Media for isolation of Legionella should be incubated at 35 - 37 C for at least 7 days.) |
| 191) Which characteristic best differentiates Acinetobacter species from Moraxella species? a. production of indophenol oxidase b. growth on MacConkey agar c. motility d. susceptibility to penicillin | a. production of indophenol oxidase a (Both Acinetobacter and Moraxella display resistance to penicillin, and some species grow on MacConkey agar. Acinetobacter are oxidase negative, and Moraxella are oxidase positive.) |
| 192) An organism has been identified as a member of the fluorescent group of Pseudomonas. Which of the following sets of tests should be used to determine the species of the organism? | a. growth at 42 C, pyocyanin production, gelatinase production a (Growth at 42 C and pyocyanin production are classic tests for the identification of Pseudomonas aeruginosa. Gelatin hydrolysis separates Pseudomonas putida [negative] from Pseudomonas fluo |
| 193) Appropriate culture requirements for a specimen from a patient suspected of having tularemia include: a. a media with cysteine such as BYCA b. colistin nalidixic acid agar c. Mueller-Hinton agar with 5% sheep blood agar d. Regan-Lowe media | a. a media with cysteine such as BYCA a (Francisella tularensis is the causative agent of tularemia. It has a specific growth requirement for cysteine.) |
| 196) A laboratory aid receives a bronchoscopy sample with the request to culture for Legionella. The assistant asks a microbiologist for direction of plating protocol. | d (Buffered charcoal yeast extract agar is recommended for culture of specimens for Legionella.) |
| 197) A community hospital microbiology lab is processing significant numbers of stool cultures because of an outbreak of diarrhea following heavy rains and flooding in the country. A media that should be incorporated in the plating protocol is: | d. thiosulfate citrate bile salts sucrose for Vibrio species d (Thiosulfate citrate bile salt agar is a selective media for Vibrio, and it also differentiates sucrose-fermenting species, such as V cholerae and V alginolyticus) |
| 199) Differentiating tests that will separate Burkholderia from Stenotrophomonas include: a. Gram stain reaction b. growth on MacConkey c. glucose fermentation d. oxidase | d. oxidase d (Both organisms are gram-negative bacilli and grow on MacConkey agar. Neither ferments glucose. Stenotrophomonas is oxidase negative, while most other nonfermenters are oxidase positive.) |
| 202) The lab receives a blood culture from a veterinarian who has been ill for many weeks with fevers in the afternoon and evenings, arthritis, and fatigue. The blood culture is positive after 5 days, and the organism has the following characteristics: | d. take extra safety precautions for possible Brucella d (Brucella causes undulant fever and is a cause of fever of unknown origin. It is slow growing, and is associated with laboratory-acquired infections. It is also a potential agent of bioterrorism. S |
| 203) The primary isolation of Neisseria gonorrhoeae requires: a. anaerobic conditions b. starch media c. carbon dioxide d. blood agar | c. carbon dioxide c (Neisseria gonorrhoeae requires an enhanced CO2 atmosphere for optimal growth.) |
| 204) Assuming the agent isolated from a patient's spinal fluid produces a positive oxidase test, the most likely diagnosis is: a. tuberculosis meningitis b. meningococcal meningitis c. viral meningitis d. pneumococcal meningitis | b. meningococcal meningitis b (Of the possible types of meningitis listed, only Neisseria meningitidis is oxidase positive.) |
| Gram Stain: gram-negative diplococci indophenol oxidase - positive glucose - positive maltose - negative sucrose - negative | c. genitourinary tract c (Based on the biochemicals listed the most likely identification of the organism is Neisseria gonorrhoeae. N gonorrhoeae is most commonly isolated from the genitourinary tract.) |
| 206) An urethral swab obtained from a man with a urethral exudate was plated directly on chocolate agar and modified Thayer-Martin agar. A Gram stain was made. The gram stain showed gram-negative diplococci. The culture plates were incubated at 35 C, but | d. organism requires CO2 for growth d (Neisseria gonorrhoeae requires an enhanced carbon dioxide atmosphere for optimal growth.) |
| 207) A gram stain performed on a sputum specimen revealed gram-neg diplococci within PMN's. Oxidase testing is positive and carbohydrate degradation tests are inert. The organism is: | . Moraxella catarrhalis b (The Neisseria species listed all ferment several carbohydrates, Moraxella catarrhalis is biochemically inert and does not ferment carbohydrates.) |
| 208) Coagglutination is associated with: a. Chlamydia trachomatis b. Neisseria gonorrhoeae c. Streptococcus pneumoniae d. Klebsiella pneumonia | b. Neisseria gonorrhoeae b (One of the less commonly used methods for identification of Neisseria gonorrhoeae grown in culture is coagglutination.) |
| 209) Clinical resistance to penicillin correlates most frequently with beta-lactamase production in: a. Neisseria gonorrhoeae b. Neisseria meningitidis c. Streptococcus agalactiae d. Streptococcus pyogenes | a. Neisseria gonorrhoeae The primary mechanism of penicillin resistance in N gonorrhoeae is beta-lactamase.) |
| 210) All species of the genus Neisseria have the enzyme to oxidize: a. naphthylamine b. dimethylaminobenzaldehyde c. glucopyranoside d. tetramethyl-phenylenediamine | d. tetramethyl-phenylenediamine d (Since all Neisseria species are oxidase positive, they possess the enzyme to oxidize tetramethyl-phenylenediamine.) |
| 211) The diagnosis of Neisseria gonorrhoeae in females is best made from: a. clinical history b. an endocervical culture c. a gram stain of cervical secretions d. examination for clue cells | b. an endocervical culture |
| 213) Which of the following is the most reliable test to differentiate Neisseria lactamica from Neisseria meningitidis? a. acid from maltose b. growth on modified Thayer-Martin agar c. lactose degradation d. nitrite reduction to nitrogen gas | c. lactose degradation c (Both Neisseria meningitidis and N lactamica produce acid from maltose and grow on modified Thayer martin agar. N lactamica ferments lactose, N meningitidis does not.) |
| 214) Definitive identification of Neisseria gonorrhoeae is made with the: a. gram stain b. oxidase test c. degradation of amino acid d. hydrolysis of carbohydrates | d. hydrolysis of carbohydrates d (Of the choices provided, only fermentation of carbohydrates provides definitive identification of Neisseria gonorrhoeae.) |
| 215) A gram-negative diplococcus that grows on modified Thayer-Martin medium can be further confirmed as Neisseria gonorrhoeae if it is: | b. oxidase positive and glucose positive, maltose negative b (Neisseria gonorrhoeae is oxidase positive and ferments glucose but not maltose.) |
| 216) An organism previously thought to be nonpathogenic, Moraxella catarrhalis, is now known to be associated with opportunistic respiratory infection and nosocomial transmission. | b. carbohydrate negative (asaccharolytic) b (Moraxella catarrhalis is an oxidase- positive gram-negative diplococcus that is usually beta-lactamase positive. It does not ferment carbohydrates.) |
| 217) An autopsy performed on an 8 yr. old child revealed Waterhouse-Friederichsen syndrome. Blood and throat cultures taken just prior to death were positive for which organism? | b. Neisseria meningitidis b (Waterhouse-Friederichsen syndrome is a known complication of severe Neisseria meningitidis infection.) |
| 219) A gram stain of organisms on Loeffler agar showed pleomorphic gram-positive bacilli. The organism should be subcultured to: a. blood b. chocolate c. MacConkey d. potassium tellurite | . potassium tellurite d (Media containing potassium tellurite is used for the recovery of Corynebacterium diphtheriae.) |
| 220) Which organism commonly causes food poisoning by consumption of foods containing excessive populations of organisms or preformed enterotoxin? | c. Bacillus cereus (Bacillus cereus is the etiologic agent of 2 distinct types of food poisoning syndromes. Spores can survive cooking and germinate. Vegetative cells multiply and produce toxin. |
| 222) The best procedure to differentiate Listeria monocytogenes from Corynebacterium species is: a. catalase b. motility at 25 C c. motility at 35 C d. Gram stain | b. motility at 25 C -both are catalase-positive and gram-positive bacilli -LISTERIA tumbling following growth at 25C -Corynebacterium species are motile when grown at 35 C.) |
| 223) Establishing the pathogenicity of a microorganism isolated from a child's throat and identified as Corynebacterium diphtheria would depend upon | c. a positive toxigenicity test (In order to determine if an isolate of Corynebacterium diphtheriae produces toxin, testing for the presence of diphtheria toxin must be performed using methods such as the Elek test or PCR.) |
| 224) Which feature distinguishes Erysipelothrix rhusiopathiae from other clinically significant non-spore-forming, gram-positive, facultatively anaerobic bacilli? a. "tumbling" motility b. beta-hemolysis d. H2S production | d. H2S production d (Erysipelothrix rhusipathiae is the only gram-positive bacillus that produces hydrogen sulfide when inoculated into triple sugar iron agar.) |
| 225) Listeria can be confused with some streptococci because of its hemolysis and because it is: a. nonmotile b. catalase negative c. oxidase positive d. esculin positive | d. esculin positive d (Listeria may be confused with some streptococci because Listeria is beta- hemolytic and is capable of hydrolyzing esculin.) |
| 227) A branching gram-positive, partially acid-fact organism is isolated from a bronchial washing on a 63 yr. old woman receiving chemotherapy. The organism does not hydrolyze casein, tyrosine or xanthine. The most likely identification is: | . Nocardia asteroides d (Nocardia asteroides are partially acid fast, and do not hydrolyze the substrates casein, tyrosine, or xanthine.) |
| 228) The characteristic that is most commonly associated with the presence of strict anaerobic bacteria and can be taken as presumptive evidence of their presence in a clinical specimen is the: | d. presence of a foul, putrid odor from tissue specimens and cultures (Anaerobic bacteria characteristically produce foul-smelling metabolic end products.) |
| 230) An aspirate of a deep wound was plated on blood agar plates aerobically and anaerobically. At 24 hrs. there was growth on the anaerobic plate only. The next step in the evaluation of this culture is to: | b. begin organism identification b (A probable anaerobe is the only organism growing so the microbiologist can proceed with identification.) |
| 231) Anaerobic infections differ from aerobic infections in which of the following? a. they usually respond favorably with aminoglycoside therapy b. they usually arise from exogenous sources c. they are usually polymicrobic d. Gram stains of specimens | c. they are usually polymicrobic c (Most infections involving anaerobes are polymicrobic and can include obligate aerobes, facultative anaerobes, microaerophilic bacteria in addition to anaerobic bacteria.) |
| 4) Which of the following clean catch urine culture colony counts indicates the patient likely has a urinary tract infection? a. 10^1 CFU/mL b. 10^3 CFU/mL c. 10^5 CFU/mL d. no growth | b. 10^3 CFU/mL The Infectious Disease Society of America consensus definition of cystitis is greater than or equal to 1,000 CFU/mL of a uropathogen.) |
| squamous epithelial cells (>25/Ipf) and neutrophils - moderate gram-positive cocci in chains and diplococci - moderate gram-negative diplococci - moderate palisading gram-positive bacilli all in moderate amounts | d. oropharyngeal flora In this specimen, >25 epithelial cells per low power field is an indicator of poor specimen quality, and the bacteria present are representative of oropharyngeal flora.) |
| A diabetic foot swab from a 82-year-old woman - neutrophils, no squamous epithelial cells - gram-negative bacilli - gram-positive cocci in chains sheep blood/ agar plates routinely used for wound cultures, the technologist might also process a(n): | a. CNA agar plate (CNA agar is a selective medium commonly used in the isolation of gram-positive aerobic and anaerobic organisms. Since the Gram stain indicates a mixture of gram-positive and gram-negative organisms, use of CNA will aid in the recove |
| 33) A Gram stain from a swab of a hand wound reveals: - moderate neutrophils - no squamous epithelial cells - moderate gram-positive cocci in chains - moderate large gram-negative bacilli | d. Columbia CNA, MacConkey d (Columbia CNA agar is a selective medium used for the isolation of gram- positive organisms. MacConkey agar is a selective and differential medium used for the isolation of gram-negative organisms |
| 44) Which of the following factors would make an organism appear to be more resistant on a disk diffusion susceptibility test? | b. too many organisms in the inoculum b (To ensure the reproducibility of disk diffusion testing, the inoculum must be standardized. [too many organisms], zone sizes would be smaller than expected and appear falsely resistant.) |
| 48) Which of the following antibiotics would routinely be tested and reported for isolates of Pseudomonas aeruginosa? a. penicillin b. erythromycin c. clindamycin d. gentamicin | d. gentamicin d (Aminoglycoside antibiotics such as gentamicin are active against Pseudomonas and routinely tested and reported on these isolates. |
| 65) A sputum specimen is received for culture and Gram stain. The Gram stained smear from this specimen is seen in the image (total magnification 100x): The technologist's best course of action would be to: | d. call the patient care area and request a new specimen neutrophils =positive quality, squamous epithelial cells negative indicator of quality, suggesting oropharyngeal contamination[> 10/low power field], and would be unacceptable for culture.) |
| 67) Examine the broth microdilution susceptibility test shown above and determine the MIC for gentamicin. a. >64 mg/mL b. 32 mg/mL c. 16 mg/mL d. <2 mg/mL | d. <2 mg/mL GENTAMICIN:64,32,16,8,4,2 The well with the lowest concentration of antibiotic displaying no growth is read as the minimum inhibitory concentration [MIC].) |
| 73) A 73-year-old man diagnosed as having pneumococcal meningitis is not responding to his penicillin therapy. Which of the following tests should be performed on the isolate to best determine this organism's susceptibility to penicillin? | b. oxacillin disk diffusion |
| 234) Acceptable specimens for the culture of anaerobic bacteria that cause disease include: a. abscesses b. gingival swabs c. skin swabs d. vaginal swabs | a. abscesses |
| 235) Propionibacterium acnes is most often associated with: a. normal oral flora b. post-antibiotic diarrhea c. tooth decay d. blood culture contamination | d. blood culture contamination d (Propionibacterium acnes is part of the normal flora of the skin, so it is frequently isolated from improperly collected blood cultures.) |
| 236 The etiologic agent of botulism is: a. highly motile b. non-spore-forming c. Clostridium perfringens d. an exotoxin producer | d. an exotoxin producer d (The toxin produced by Clostridium botulinum is a neurotoxin that is excreted by the organism in food materials, and is then ingested.) |
| 237) A strict anaerobe that produces terminal spores is: a. Clostridium tetanus b. Corynebacterium diphtheriae c. Bacillus anthracis d. Propionibacterium acnes | a. Clostridium tetanus a (Corynebacterium species and Propionibacterium species do not produce spores, and Bacillus is an aerobic organism.) |
| 238) An anaerobic, spore-forming, nonmotile, gram-positive bacillus isolated from a foot wound is most likely: a. Actinomyces israelii b. Clostridium perfringens c. Bacillus subtilis d. Eubacterium lentum | b. Clostridium perfringens Clostridium perfringens is a spore-forming anaerobe organism.) |
| 240) The reverse CAMP test, lecithinase production, double zone hemolysis, and Gram stain morphology are all useful criteria in the identification of: a. Clostridium perfringens b. Streptococcus agalactiae c. Propionibacterium acnes d. Bacillus anthra | a. Clostridium perfringens a (The reverse CAMP test, production of lecithinase, and demonstration of double zone hemolysis are tests and characteristics used for the identification of Clostridium perfingens,) |
| 243) An anaerobic gram-positive bacilli with subterminal spores was isolated from a peritoneal abscess. The most likely identification of this organism is: a. Bacillus cereus b. Clostridium septicum c. Eubacterium lentum d. Bifidobacterium dentium | b. Clostridium septicum Clostridium septicum forms subterminal spores.) |
| 244) The most meaningful laboratory procedure in confirming the diagnosis of clinical botulism is: a. demonstration of toxin in the patient's serum b. recovery of Clostridium botulinum from suspected food c. recovery of Clostridium botulinum from the p | . demonstration of toxin in the patient's serum a (Botulism infection is confirmed by reference laboratories such as the CDC by demonstrating toxin in serum, feces, gastric contents or vomitus.) |
| 245) A stool sample is sent to the laboratory for culture to rule out Clostridium difficile. What media should the microbiologist use and what is the appearance of the organisms on this media? | c. CCFA: yellow, ground glass colonies CCFA is also differential-fermentation of lactose produces classic colony morphology for this organism.) |
| 246) A Gram stain of a necrotic wound specimen showed large gram-positive bacilli. There was 3+ growth on anaerobic media only, with colonies producing a double zone of hemolysis. To identify the organism, the microbiologist should: | c. set up egg yolk agar plate (The Gram stain and double zone of hemolysis are characteristics of Clostridium perfingens. C perfingens is lecithinase positive on the egg yolk agar test for lecithinase and lipase.) |
| 250) Which of the following genera include anaerobic gram-negative non-sporulating bacilli? a. Brucella b. Pasteurella c. Actinomyces d. Bacteroides | d. Bacteroides Bacteroides species are anaerobic, gram-negative bacilli.) |
| 257) A control strain of Clostridium should be used in an anaerobe jar to assure: a. that plate media is working b. that an anaerobic environment is achieved c. that the jar is filled with a sufficient number of plates d. that the indicator strip is c | b. that an anaerobic environment is achieved The growth of one of these Clostridium species would confirm that an anaerobic environment has been achieved in the anaerobic jar.) |
| 259) The major features by which molds are routinely identified are: a. macroscopic characteristics and microscopic morphology b. biochemical reactions and microscopic morphology c. macroscopic characteristics and selective media d. specialized sexual | a. macroscopic characteristics and microscopic morphology |
| 260) A sputum specimen from a patient with a known Klebsiella pneumoniae infection is received in the laboratory for fungus culture. The proper procedure for handling this specimen is to | c. include media that have cycloheximide and chloramphenicol added to inhibit bacterial organisms and saprophytic fungi |
| 261) Many fungal infections are transmitted to man via inhalation of infectious structures. Which of the following is usual]y contracted in this manner? a. Sporothrix schenckii b. Trichophyton rubrum c. Malassezia furfur d. Histoplasma capsulatum | d. Histoplasma capsulatum d (Histoplasma capsulatum is most frequently transmitted by inhalation.) |
| 262) A smear of skin tissue reveals fluorescent septate hyphae. The smear was prepared using: a. acridine orange b. calcofluor white c. auramine rhodamine d. periodic acid-Schiff | b. calcofluor white |
| 265) An organism that demonstrates budding yeast cells with wide capsules in an India ink preparation of spinal fluid is probably: a. Cryptococcus neoformans b. Histoplasma capsulatum c. Blastomyces dermatitidis d. Candida albicans | a. Cryptococcus neoformans a (Cryptococcus neoformans is a cause of meningitis in immunocompromised patients, and produces a polysaccharide capsule.) |
| 266) The formation of germ tubes presumptively identifies: a. Candida tropicalis b. Candida parapsilosis c. Candida glabrata d. Candida albicans | d. Candida albicans (Candida albicans produces germ tubes.) |
| 267) An HIV-positive patient began to show signs of meningitis. A spinal fluid was collected and cultured for bacteria and fungus. A budding, encapsulated yeast was recovered. Which organism is consistent with this information? | a. Cryptococcus neoformans (Cryptococcus neoformans is a cause of meningitis in immunocompromised patients, and produces a polysaccharide capsule.) |
| 269) Gram stain examination of a CSF specimen indicates the presence of yeast-like cells with gram-positive granular inclusions. Which of the following techniques should be used next to assist in the identification of this organism? | c. India ink (Cryptococcus may not stain well on Gram stain. Rapid identification is important when yeast is detected in CSF, the presence of capsules seen in an India ink preparation would be presumptive for C neoformans.) |
| India ink: no encapsulated yeast cells - cryptococcal antigen: negative - urea: negative - germ tube: negative What should the technologist do next to identify | d. carbohydrate assimilation |
| 273) The recovery of some Cryptococcus species may be compromised if the isolation media contains: a. cycloheximide b. gentamicin c. chloramphenicol d. penicillin | a. cycloheximide |
| 278) The most sensitive test for the initial diagnosis of cryptococcal disease is: a. India ink b. Gram stain c. cryptococcal antigen d. Giemsa stain | c. cryptococcal antigen |
| 279) Which of the following statements concerning the germ tube test is true? | c. Candida albicans and Candida tropicalis can be used as positive and negative controls, respectively c (Candida albicans [positive] and C tropicalis [negative] |
| 280) Which of the following procedures should be performed to confirm that an unknown mold is one of the pathogenic dimorphic fungi: | b. culture conversion to yeast form |
| 281) Lab workers should always work under a biological safety hood when working with cultures of: a. Streptococcus pyogenes b. Staphylococcus aureus c. Candida albicans d. Coccidioides immitis | d. Coccidioides immitis (The arthroconidia of Coccidioides immitis are highly infectious; cultures must be handled with care to minimize aerosols.) |
| 285) Which of the following is a dimorphic fungus? a. Sporothrix schenckii b. Candida albicans c. Cryptococcus neoformans d. Aspergillus fumigatus | a. Sporothrix schenckii |
| 291) Which of the following is most often used to prepare a slide from a plate culture of a dermatophyte for microscopic observation? a. lactophenol cotton blue b. potassium hydroxide c. iodine solution d. Gram stain | a. lactophenol cotton blue |
| 295) On day 3 of a fungal culture, grayish cottony growth is observed that is filling the container. The most likely mold isolated is a: a. dermatophyte b. dimorphic mold c. zygomycete d. dematiaceous mold | c. zygomycete c (Zygomycetes grow rapidly and fill the dish with cotton candy-like growth.) |
| 296) The appropriate specimen for the diagnosis of mucormycosis is: a. nasal swab b. sputum c. sinus washing d. eschar biopsy | d. eschar biopsy d (Mucormycosis is an aggressive infection where biopsy, curettage or fine-needle aspiration is essential for diagnosis.) |
| 303) In processing clinical specimens and fungal isolates, laboratory workers may contract systemic fungal infections through: a. inhalation b. ingestion c. skin contact d. insect vector | a. inhalation a (Inhalation is a common mode of transmission for fungal spores. Specimens for fungal culture should be processed in a biological safety cabinet to minimize the potential for aerosol spread.) |
| 304) A sputum specimen received at 8 AM for an Acid Fast smear reveals acid-fast bacilli. This specimen was concentrated by the NALC-sodium hydroxide method and inoculated on 2 Lowenstein-Jensen slants and held for 8 weeks at 35C in 5%-10% CO2. No growth. | b. an improper specimen was submitted for culture b (Early-morning sputum specimens are optimal for AFB culture.) |
| 305) The preferred carbon source for mycobacteria is: a. glycerol b. glucose c. fatty acids d. casein hydrolysate | a. glycerol a (Mycobacteria use glycerol as a carbon source in the presence of mineral salts.) |
| 310) Which of the following combinations of media provides an egg base, agar base, and a selective egg or agar base media? | b. Lowenstein-Jensen, Middlebrook 7H11, Lowenstein-Jensen Gruft b (Lowenstein-Jensen is an egg-based medium, 7811 is an agar-based medium, and Lowenstein-Jensen Gruft is a selective egg-based medium.) |
| 311) Which of the following reagents should be used as a mucolytic, alkaline reagent for digestion and decontamination of a sputum for mycobacterial culture? a. N-acetyl-L-cystine and NaOH b. NaOH alone c. zephiran-trisodium phosphate d. oxalic acid | a. N-acetyl-L-cystine and NaOH a (The most widely used digestion decontamination method is the N-acetyl-L-cysteine-2% NaOH method.) |
| 312) The function of N-acetyl-L-cysteine in the reagent for acid-fast digestion-decontamination procedure is to: a. inhibit growth of normal respiratory flora b. inhibit growth of fungi c. neutralize the sodium hydroxide d. liquefy the mucus | d. liquefy the mucus d (N-acetyl-L-cysteine [NALC] is a mucolytic agent; the concentration of NALC may be increased to digest thick, mucoid specimens. |
| 313) When staining acid-fast bacilli with Truant auramine-rhodamine stain, potassium permanganate is used as a: a. decolorizing agent b. quenching agent c. mordant d. dye | b. quenching agent b (The counterstain acts as a quenching agent and reduces the background fluorescence of cellular debris.) |
| 314) Middlebrook 7H10 and 7H11 media must be refrigerated in the dark, and incubated in the dark as well. If these conditions are not met, the media may prove toxic for mycobacteria because: | d (If exposed to light, agar-based media such as 7H11 may release formaldehyde, which is toxic to mycobacteria.) |
| 315) The method used for processing specimens for mycobacterial culture contaminated with Pseudomonas is: a. N-acetyl-L-cystine and NaOH b. NaOH c. zephiran-trisodium phosphate d. oxalic acid | d. oxalic acid d (The oxalic acid method is superior to alkali methods for processing specimens contaminated with Pseudomonas.) |
| 316) An AFB broth culture is positive for acid-fast bacilli at 1 week while the agar slant shows no growth. The most likely explanation for this is: | b. AFB grow more rapidly in liquid media |
| 317) A bronchial washing is processed for acid-fast bacilli. Which of the following precautions should be taken in order to prevent infection of laboratory personnel? | d. process all specimens in a biological safety hood (Specimens processed for mycobacterial culture must be processed in a biological safety cabinet to minimize aerosol transmission of the organism.) |
| 318) Tubercle bacilli are specifically stained by: a. crystal violet b. 1% acid fuchsin c. methylene blue d. carbol fuchsin | d. carbol fuchsin d (Mycobacteria form stable complexes with Kinyoun carbol fuchsin.) |
| 402) A stool specimen for ova and parasite examination contained numerous rhabditiform larvae Which factor does not aid in the identification of larvae? | b. type of water vegetation consumed |
| 400) The scolex of Taenia saginata has: a. 4 suckers b. no suckers and 14 hooklets c. 24 hooklets d. 26 - 28 sucking discs | a. 4 suckers (The scolex of Taenia saginata is square with 4 suckers and no hooks.) |
| 399) Organisms that can be easily identified to the species level from the ova in fecal specimens include: a. Metagonimus yokogawai, Heterophyes heterophyes b. Taenia solium, Taenia saginata d. Paragonimus westermani, Hymenolepis nana | d. Paragonimus westermani, Hymenolepis nana |
| 398) The causative agent of cysticercosis is: a. Taenia solium b. Taenia saginata c. Ascaris lumbricoides d. Trichuris trichiura | a. Taenia solium a (Humans may become infected with Taenia solium by either ingesting the larval form or ova. If ova are ingested the parasite cannot complete the life cycle, and cysticerci encyst in various tissues including the brain.) |
| 393) Proper collection of a sample for recovery of Enterobius vermicularis includes collecting: a. a 24-hour urine collection b. a first morning stool collection with proper preservative c. a scotch tape preparation from the perianal region | c. a scotch tape preparation from the perianal region |
| 392) The best method to demonstrate the ova of Enterobius vermicularis is: a. acid-ether concentration b. cellophane tape preparation c. formalin-ether concentration d. zinc sulfate flotation | b. cellophane tape preparation |
| 380) Multifocal brain lesion in AIDS patients is commonly caused by: a. Toxoplasma gondii b. Pneumocystis jiroveci c. Cryptosporidium parvum d. Giardia lamblia | a. Toxoplasma gondii a (The most common cause of ring- enhancing brain lesions in a patient with HIV/AIDS is Toxoplasma gondii.) |
| 373) Artifacts found in a stool specimen that can be confused with ova or cysts are: a. partially digested meat fibers b. degenerated cells from the gastrointestinal mucosa c. dried chemical crystals d. pollen grains | d. pollen grains (Pollen grains are common artifacts in stool specimens submitted for ova and parasite examination. Their appearance is similar to protozoan cysts.) |
| 371) A cell culture line used for the recovery of Chlamydia trachomatis from clinical specimens is: a. HeLa 229 b. Hep- 2 c. BHK-21 d. McCoy | d. McCoy (McCoy cells, in addition to buffalo green monkey kidney cells, are susceptible to infection with Chlamydia trachomatis and are used routinely for the recovery of C trachomatis in culture.) |
| 363) Mycoplasmas differ from other bacteria in that they: a. do not cause disease in humans b. cannot grow in artificial inanimate media c. lack cell walls d. are not serologically antigenic | c. lack cell walls c (Mycoplasma are smaller than other bacteria and lack a cell wall. Instead, they possess a trilaminar cell membrane. Because they lack a cell wall, they cannot be stained with Gram stain.) |
| 362) Chlamydial infections have been implicated in: a. urethritis and conjunctivitis b. gastroenteritis and urethritis c. neonatal pneumonia and gastroenteritis d. neonatal meningitis and conjunctivitis | a. urethritis and conjunctivitis a (Chlamydia trachomatis is a well-known cause of sexually transmitted infections, including urethritis and cervicitis, as well as inclusion conjunctivitis and pneumonia in neonates. It also causes trachoma and lymphogr |
| 361) Psittacosis is transmissible to man via contact with: a. insects b. birds c. cattle d. dogs | b. birds b (Chlamydophila psittaci, the agent of psittacosis, is transmitted to humans via inhalation of nasal secretions, as well as infected fecal or feather dust, of psittacine birds [parrot family].) |
| 360) Relapsing fever in humans is caused by: a. Borrelia recurrentis b. Brucella abortus c. Leptospira interrogans d. Spirillum minus | a. Borrelia recurrentis a (Relapsing fever is caused by Borrelia recurrentis and is transmitted by the human body louse. Relapsing fever is characterized by the acute onset of high fever lasting 3 - 7 days, interspersed with periods of no fever lasting |
| 352) Colds and other acute respiratory diseases are most often associated with: a. Epstein-Barr virus b. adenovirus c. coxsackie B d. reovirus | b. adenovirus b (Adenovirus infections are common. It causes up to 5% of all respiratory infections, and the prevalence of infection is higher [up to 14%].) |
| 351) Encephalitis is most commonly associated with which of the following viruses? a. Epstein-Barr b. herpes simplex c. coxsackie B d. varicella zoster | b. herpes simplex b (Herpes simplex virus is the most common cause of fatal sporadic encephalitis in the United States.) |
| 350) The genus of virus associated with anogenital warts, cervical dysplasia and neoplasia is: a. herpes simplex virus b. papillomavirus c. cytomegalovirus d. coxsackierus | b. papillomavirus |
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