Microbiology Review
Sodium polyanetholsulfonate (SPS) is used as an anticoagulant for blood cultures because it: (a) inactivates penicillin and cephalosporins (b) prevents clumping of red blood cells (c) inactivates neutrophils and components of serum complement (d) facilitates growth of anaerobes
(c) inactivates neutrophils and components of serum complement
Which of the following groups of specimens would be acceptable for anaerobic culture? (a) vaginal swab, eye swab (b) intraoral surface swab, leg tissue (c) pleural fluid, brain abscess fluid (d) urine, sputum
(c) pleural fluid, brain abscess fluid
49) During the previous month, Staphylococcus epidermidis has been isolated from blood cultures at 2-3 times the rate from the previous year. The most logical explanation for the increase in these isolates is that: (a) the blood culture media are contaminated with this organism (b) the hospital ventilation system is contaminated with the organism (c) there has been a break in proper skin preparation before drawing blood for culture (d) a relatively virulent isolate is being spread from patient to patient
(c) there has been a break in proper skin preparation before drawing blood for culture
The proper blood-to-broth ratio for blood culture to reduce the antibacterial effect of serum in adults is: a) 1:2 b) 1:3 (c) 1:10 (d) 1:30
(c) 1:10
43) The Gram stain from a blood culture shows gram-positive cocci in chains. The subcultured plates from the blood culture show no growth. Additional testing should be done to detect the presence of: (a) Staphylococcus saprophyticus (b) Aerococcus urinae (c) Abitrophia defectiva (d) Streptococcus pneumoniae
(c) Abitrophia defectiva Nutritionally deficient streptococci such as (c) do not grow on SBA without certain additives
54) Which of the following specimens is considered to be the most sensitive for the recovery of Brucella (zoonotic) in cases of chronic infection? (a) Blood (b) Urine (c) Bone marrow (d) Lymph node
(c) Bone marrow
The primary isolation of Neisseria gonorrhoaea requires: (a) Anaerobic conditions (b) Starch media (c) Carbon dioxide (d) Blood agar
(c) Carbon dioxide
58) Which one of the following anaerobes is inhibited by sodium polyanethol sulfonate (SPS)? (a) Bacteroides fragilis (b) Propionibacterium acnes (c) Peptostreptococcus anaerobius (d) Veillonella parvula
(c) Peptostreptococcus anaerobius
The steam autoclave method of sterilization requires: (a) 15 lb of pressure for 15 minutes (b) dry heat for 20 minutes (c) a maximum temperature of 100°C (d) a source of ethylene oxide
(a) 15 lb of pressure for 15 minutes
41) Relapsing fever in humans is caused by: (a) Borrelia recurrentis (b) Brucella abortus (c) Leptospira interrogans (d) Spirillium minus
(a) Borrelia recurrentis
76) A 17-year-old female with cystic fibrosis is diagnosed with pneumonia. A sputum sample grew gram-negative bacilli with yellow, smooth colonies that have the following biochemical reactions: Oxidase - pos TSI - K/K Glucose - oxidized Fluorescence - neg Lysine decarboxylase - pos The organism is most likely: (a) Burkholderia cepacia (b) Klebsiella pneumoniae (c) Shewanella putrefaciens (d) Stenotrophomonas maltophilia
(a) Burkholderia cepacia Burkholderia cepacia is associated with respiratory infections in cystic fibrosis patients.
An organism that must be incubated in a microaerophilic environment for optimal recovery is: (a) Campylobacter jejuni (b) E. coli (c) Pseudomonas aeruginosa (d) Proteus mirabilis
(a) Campylobacter jejuni
57) Propionibacterium acnes is most often associated with: (a) food poisoning (b) post-antibiotic diarrhea (c) tooth decay (d) blood culture contamination
(d) blood culture contamination
62) The organism most commonly associated with neonatal purulent meningitis is: (a) Neisseria meningitidis (b) Streptococcus pneumoniae (c) group B streptococci (d) Haemophilus influenzae
(c) group B streptococci All of these organisms are causes of meningitis. GBS, S. agalactiae, is the cause of neonatal meningitis.
Which selective medium is used for the isolation of gram-positive microorganisms? (a) Columbia CNA with 5% sheep blood (b) Trypticase soy agar with 5% sheep blood (c) Eosin methylene blue (d) Modified Thayer-Martin
(a) Columbia CNA with 5% sheep blood
45) Gram positive cocci in chains are seen on a Gram stain from a blood culture. The organism grows as a beta-hemolytic colony. Further tests that could be performed include: (a) PYR, bacitracin, and hippurate hydrolysis (b) Catalase and agglutination test for Protein A (c) Oxidase and mass spectrometry (d) Voges-Proskauer and methyl red
(a) PYR, bacitracin, and hippurate hydrolysis
52) A blood culture from a 64-year-old male with lymphoma was positive blood culture at 18 hours incubation. The organisms are non-lactose fermenting gram-negative bacilli on MacConkey agar. Further testing gives the following reactions: Oxidase - neg TSI - K/A (no gas) Motility - pos Indole - pos Citrate - pos Ornithine decarboxylase - neg Urea - pos Phenylalanine deaminase - pos VP - neg The genus is: (a) Morganella (b) Proteus (c) Providencia (d) Serratia
(a) Providencia The first result that sticks out is a positive Phenylalanine deaminase, which rules out Serratia. The TSI result rules out Proteus because it produces H2S gas A negative ornithine and positive citrate distinguishes Providencia from Morganella
50) A 55-year-old man presents to the ER with chest pain and is found to have suffered a heart attack. He has a past history of hypertension and high cholesterol. The patient is admitted and scheduled for a triple bypass procedure. During recovery, he becomes septic, developing a high grade fever and pneumonia. Gram-positive cocci in clusters, isolated from both his lungs via induced sputum specimen and the surgical incision, produce beta hemolytic, catalase-positive colonies on SBA. Identify the organism most likely isolated and the biochemical test performed to confirm the identification. (a) Staphylococcus aureus and latex agglutination (b) Streptococcus pyogenes and PYR (c) Streptococcus agalactiae and latex agglutination (d) Enterococcus faecium and PYR
(a) Staphylococcus aureus and latex agglutination
53) A blood culture bottle with macroscopic signs of growth is Gram stained and the technician notes small, curved gram-negative bacilli resembling "gull wings". It is subcultured to blood and chocolate agar, and incubated aerobically and anaerobically. After 24 hours, no growth is apparent. The next step should be to: (a) Subculture the bottle and incubate in microaerophilic conditions (b) Assume the organism is nonviable and ask for a repeat specimen (c) Utilize the oxidase and indole test to detect Aeromonas (d) Subculture the bottle to a medium containing X and V factors
(a) Subculture the bottle and incubate in microaerophilic conditions
Appropriate culture requirements for a specimen from a patient suspected of having tularemia include: (a) a media with cysteine such as buffered charcoal yeast extract agar (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 buffered charcoal yeast extract agar
Acceptable specimen sources for culture of anaerobic bacteria includes: (a) abscess (b) stool (c) clean catch urine (d) vaginal
(a) abscess
44) Gram stain examination from a blood culture bottle shows dark blue, spherical organisms in clusters. Growth on sheep blood agar shows small, round, pale yellow colonies. Further tests should include: (a) catalase production and coagulase test (b) bacitracin susceptibility and serological typing (c) oxidase and deoxyribonuclease reactions (d) Voges-Proskauer and methyl red reactions
(a) catalase production and coagulase test The gram stain and culture growth describe a Staphylococcus species. A positive catalase indicates that the organism is most likely a member of the Staph genus. Latex agglutination is used to differentiate S. aureus from coagulase-negative staph.
Campylobacter jejuni isolation requires the fecal specimen be: (a) inoculated onto selective plating media and incubated in reduced oxygen with added CO2 at 42°C (b) stored in trypticase soy broth before plating to ensure growth of the organism (c) inoculated onto selective plating media and incubated at both 35°C and at room temperature (d) incubated at 35°C for 2 hours in Cary-Blair media for inoculating onto selective plating media
(a) inoculated onto selective plating media and incubated in reduced oxygen with added CO2 at 42°C
Upon review of a sputum Gram stain, the technician notes that the nuclei of all of the neutrophils present in the smear are staining dark blue. The best explanation for this finding is: (a) the slide was inadequately decolorized with acetone/alcohol (b) the sputum smear was prepared too thin (c) the cellular components have stained as expected (d) the iodine was omitted from the staining procedure
(a) the slide was inadequately decolorized with acetone/alcohol
70) An organism from a peritoneal abscess is isolated on kanamycin-vancomycin laked blood agar and grows black colonies on BBE agar. It is nonpigmented, catalase positive, and indole negative. The genus of this organism is: (a) Acidominococcus (b) Bacteroides (c) Porphyromonas (d) Prevotella
(b) Bacteroides Bacteroides fragilis grows on BBE agar because it can hydrolyze esculin and it produces black colonies. Prevotella and Porphyromonas are pigmented, bile-sensitive organisms.
A medium that can be used to recover Francisella tularensis is: (a) Bordet-Gengou agar (b) Buffered charcoal yeast extract (BCYE) agar (c) Loeffler agar (d) MacConkey agar
(b) Buffered charcoal yeast extract (BCYE) agar F. tularensis is fastidious and requires cysteine or cystine for growth (BCYE).
77) A college student who recently studied a semester abroad in Southeast Asia is admitted to the hospital with a diagnosis of "glanders-like" infection (melioidosis). A sputum specimen grows small, gram-negative bacilli that are oxidase positive, reduce nitrate to gas, and oxidize glucose, lactose, and mannitol. What is the most likely organism? (a) Stenotrophomonas maltophilia (b) Burkholderia pseudomallei (c) Pseudomonas aeruginosa (d) Acinetobacter baumannii
(b) Burkholderia pseudomallei (b) is an organism commonly found in the soil of Southeastern Asian countries and parts of northern Australia. Infection with the organism causes melioidosis which is also referred to as "glanders-like" disease.
59) A patient has a suspected diagnosis of subacute bacterial endocarditis. His blood cultures grow non-spore-forming pleomorphic gram positive bacilli only in the anaerobic bottle. What test(s) will give a presumptive identification of this microorganism? (a) Beta-hemolysis and oxidase (b) Catalase and spot indole (c) Esculin hydrolysis (d) Hydrolysis of gelatin
(b) Catalase and spot indole Propionibacterium acnes is part of the normal flora on the skin and is a common blood culture contaminant. The Gram stain given is typical for P. acnes, and it is catalase and indole positive
Anaerobic gram-positive bacilli with subterminal spores were isolated from a peritoneal abscess. The colony has a swarming appearance. The most likely identification of this organism is: (a) Bacillus cerus (b) Clostridium septicum (c) Eubacterium lentum (d) Bifidobacterium dentium
(b) Clostridium septicum Bacillus species are not anaerobic. Eubacterium and Bifidobacterium species are anaerobic gram-positive bacilli that do not form spores.
Which of the following is the most appropriate specimen source and primary media selection? (a) CSF: Columbia CNA, MacConkey (b) Endocervical: Chocolate, Martin Lewis (c) Sputum: SBA, KV-laked blood (d) Urine: SBA, Columbia CNA
(b) Endocervical: Chocolate, Martin Lewis
73) A sputum culture from an alcoholic seen in the ER grows gray, mucoid, stringy colonies on SBA. The isolate grows readily on MacConkey agar and forms mucoid, dark pink colonies. The colonies yield the following test results: ONPG - pos Indole - neg Glucose - pos Oxidase - neg Citrate - pos VP - pos The organism is most likely: (a) Edwardsiella tarda (b) Klebsiella pneumoniae (c) Escherichia coli (d) Proteus vulgaris
(b) Klebsiella pneumoniae Klebsiella pneumoniae is the only answer choice that is VP positive Edwardsiella tarda and E. coli are both indole positive Proteus vulgaris produces clear colonies on MacConkey
A vaginal/rectal swab is collected from a pregnant patient to screen for group B Streptococcus colonization. What is the best medium to use for specimen inoculation? (a) blood agar (b) LIM broth (c) CNA agar (d) thioglycollate broth
(b) LIM broth
The most important variable in the recovery of organisms in adult patients with bacteremia is: (a) Subculture of all bottles at day 5 of incubation (b) The recommended volume of blood cultured (c) Collection of daily blood culture sets for 3 consecutive days (d) Collection of multiple blood culture sets from a single venipuncture
(b) The recommended volume of blood cultured
78) An organism previously thought to be nonpathogenic, Moraxella catarrhalis, is now known to be associated with opportunistic respiratory infection and nosocomial transmission. Characteristic identification criteria include: (a) beta-lactamase negative (b) butyrate esterase positive (c) gram-negative bacilli (d) oxidase negative
(b) butyrate esterase positive Moraxella catarrhalis are oxidase-positive gram-negative diplococci that are usually beta-lactamase positive. Unlike Neisseria spp., it is butyrate esterase positive.
Virus transport medium should contain agents that: (a) enable rapid viral growth during the transport time (b) inhibit bacterial and fungal growth (c) destroy nonpathogenic viruses (d) inhibit complement-fixation antibodies
(b) inhibit bacterial and fungal growth
A 21-year old patient presents with pharyngitis. A throat swab is collected and submitted for anaerobic culture. This specimen should be: (a) set up immediately (b) rejected as unacceptable (c) inoculated into thioglycollate broth (d) sent to a reference laboratory
(b) rejected as unacceptable
42) Three sets of blood cultures were obtained from an adult patient with fever and suspected endocarditis. The aerobic bottle of one set had growth of Staphylococcus epidermidis at 5 days of incubation. This indicates that: (a) there was low-grade bacteremia (b) the organism is most likely a contaminant (c) the patient has a line infection (d) the blood culture bottles are defective
(b) the organism is most likely a contaminant
A diabetic foot swab from an 82-year-old woman with recurrent infections is submitted for culture. The Gram stain reveals: Many neutrophils, no squamous epithelial cells Many gram-negative bacilli Many gram-positive cocci in chains The physician requests that all pathogens be worked up. In addition to the SBA, chocolate, and MacConkey agar plates routinely used for wound cultured, the technologist might also process a(n): (a) anaerobic blood agar plate (b) Buffered Charcoal Yeast Extract (BCYE) agar plate (c) CNA agar plate (d) XLD agar plate
(c) CNA agar plate
71) thin, gram-negative bacillus with tapered ends isolated from an empyema specimen grew only on anaerobic sheep blood agar. It was found to be indole positive, lipase negative, and was inhibited by 20% bile. The most probable identification of this isolate would be: (a) Bacteroides distasonis (b) Prevotella melaninogenica (c) Fusobacterium nucleatum (d) Clostridium septicum
(c) Fusobacterium nucleatum Fusobacterium has characteristic tapered ends. Bacteroides is bile-resistant. Clostridium is a gram-positive bacilli and is lipase positive.
65) A technologist is reading a Gram stain from a CSF and observes many intracellular gram-negative diplococci. Which set of chemistry and hematology CSF results would most likely be seen in someone with this type of infection? (a) Increased WBCs, increased Glucose, increased Protein (b) Decreased WBCs, decreased Glucose, decreased Protein (c) Increased WBCs, decreased Glucose, increased Protein (d) Decreased WBCs, increased Glucose, decreased Protein
(c) Increased WBCs, decreased Glucose, increased Protein The classic CSF alterations associated with bacterial meningitis are a high WBC count with a neutrophil predominance as well as a low CSF glucose and high CSF protein.
Beta-hemolytic gram-positive cocci were isolate from the CSF of a 2-day-old infant with signs of meningitis. The isolate grew on SBA under aerobic conditions and was resistant to a bacitracin disk. Which of the following should be performed for the identification of the organism? (a) Oxidase production (b) Catalase formation (c) Latex antigen grouping (d) Esculin hydrolysis
(c) Latex antigen grouping The organism is most likely Streptococcus agalactiae. Polysaccharide latex agglutination will confirm the identification of S. agalactiae and differentiate it from other beta-hemolytic streptococci.
The best media for culture of Bordetella pertussis is: (a) Phenylethyl alcohol agar (PEA) (b) Potassium tellurite blood agar (c) Regan-Lowe agar (d) Tinsdale agar
(c) Regan-Lowe agar PEA is selective for gram-positive cocci Potassium tellurite blood agar and Tinsdale agar are selective/differential media useful in isolating Corynebacterium diptheriae.
69) A Gram-stain of peritoneal fluid showed large gram-positive bacilli. There was a 3+ growth on anaerobic media only, with colonies producing a double zone of hemolysis. To assist with the classic identification of the organism, a microbiology could: (a) Determine if the organism ferments glucose (b) Perform the oxidase test (c) Set up egg yolk agar plate (d) Test for bile tolerance
(c) Set up egg yolk agar plate The Gram stain and double zone of hemolysis are characteristic of Clostridium perfringes. C. perfringes is lecithinase positive on the egg yolk agar test for lecithinase and lipase.
32) Anticoagulants acceptable for use with blood, bone marrow, and synovial fluid specimens that are to be cultured include: (a) EDTA and sodium citrate (b) Heparin and sodium citrate (c) Sodium polyanethol sulfonate (SPS) and heparin (d) Sodium polyanethol sulfonate (SPS) and EDTA
(c) Sodium polyanethol sulfonate (SPS) and heparin SPS and heparin anticoagulants are acceptable to use with specimens that are not to be cultured.
51) A patient with a prosthetic heart valve visits the dentist for her yearly checkup. Two weeks later, she presents to her primary care physician with a high fever, chills, and shortness of breath, and receives a diagnosis of subacute endocarditis. Multiple blood culture sets were drawn on the patient and sent to the lab. Twenty-four hours later the bottles are positive for bacterial growth. Which organism would you expect to grow? (a) Staphylococcus lugdenensis (b) Staphylococcus saprophyticus (c) Streptococcus viridans (d) Streptococcus agalactiae
(c) Streptococcus viridans
The optimal collection of a wound specimen for culture of anaerobic organisms is a: (a) Swab of lesion obtained before antibiotic administration (b) Swab of lesion obtained after antibiotic administration (c) Syringe filled with pus, obtained before antibiotic administration (d) Syringe filled with pus, obtained after antibiotic administration
(c) Syringe filled with pus, obtained before antibiotic administration
36) In general, anaerobic infections differ from aerobic infections in which one of the following? (a) They usually respond favorably to aminoglycoside therapy (b) They usually arise from exogenous sources (c) They are usually polymicrobic (can include obligate aerobes, facultative anaerobes, microaerophilic bacteria in addition to anaerobic bacteria) (d) Gram stains of specimens are less helpful in diagnosis
(c) They are usually polymicrobic (can include obligate aerobes, facultative anaerobes, microaerophilic bacteria in addition to anaerobic bacteria)
64) A 4-year-old is admitted with symptoms of meningitis, and a gram stain of the CSF reveals small, pleomorphic, gram negative coccobacilli. After 24 hours incubation at 35°C, small, moist, gray colonies, which are oxidase variable, are found on the chocolate agar plate only. Which of the following biochemical data would be consistent with this isolate? (a) CTA dextrose: pos, CTA maltose: pos, ONPG: neg (b) Sodium hippurate hydrolysis: pos, A disk: neg, CAMP test: pos (c) X factor: NG, V factor: NG, XV factor: Growth, horse blood: No hemolysis (d) Catalase: pos, Esculin hydrolysis: pos, Methyl-red: pos, "umbrella" motility at room temperature
(c) X factor: NG, V factor: NG, XV factor: Growth, horse blood: No hemolysis These are classic Gram stain, growth, and biochemical characteristics of Haemophilus influenzae
Media used to support growth of Legionella pneumophila should contain which of the following additives? (a) X and V factors (b) hemin and Vitamin K (c) charcoal and yeast extract (d) dextrose and laked blood
(c) charcoal and yeast extract
A CSF specimen containing only 2 drops of CSF was collected by lumbar puncture from a febrile 25-year old male and was submitted for a stat gram stain and culture. The direct specimen Gram stain was reported as many neutrophils and no microorganism seen. The remain drop of CSF should be inoculated to: (a) blood agar (b) CNA agar (c) chocolate agar (d) Thayer-Martin agar
(c) chocolate agar Enriched media such as chocolate agar will grow everything plus Haemophilus and Neisseria species. Blood agar will grow only non-fastidious organisms that does not include Haemophilus and Neisseria species.
An antibiotic used to suppress or kill contaminating fungi in media is: (a) amphotericin B (b) chloramphenicol (c) cycloheximide (d) streptomycin
(c) cycloheximide Cycloheximide is added to inhibit faster-growing saprophytic (obtaining nourishment from organic material decay) organisms Chloramphenicol suppresses bacterial growth Streptomycin B does not inhibit fungi
74) A patient with nosocomial pneumonia has a sputum Gram stain that shows many neutrophils and numerous small gram-negative coccobacilli. The organism grew in 24 hours as a mucoid, hemolytic colony on blood agar and a colorless colony on MacConkey agar. What is the organism based on the following characteristics: Oxidase - neg Catalase - pos Nitrate - neg ONPG - neg Ornithine decarboxylase - neg Lysine decarboxylase - neg (a) Stenotrophomonas maltophilia (b) Alcaligenes faecalis (c) Moraxella lacunata (d) Acinetobacter baumannii
(d) Acinetobacter baumannii Moraxella and Alcaligenes are oxidase positive. Stenotrophomonas are gram-negative bacilli and are lysine and ONPG positive.
31) A differential medium that can be used as a primary isolation agar producing predictable colored colonies that can be distinguished from other organism colony types describes: (a) BCYE agar (b) Blood PEA (c) Campylobacter blood agar (d) Chromagar
(d) Chromagar
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 Select the appropriate media that will selectively isolate each organism. (a) KV-laked agar, Thayer-Martin (b) sheep blood, MacConkey (c) Columbia CNA, chocolate (d) Columbia CNA, MacConkey
(d) Columbia CNA, MacConkey
A bronchoscopy sample with the request for culture of Legionella is sent to the laboratory. The correct plating protocol is: (a) Culture on thiosulfate citrate bile salt media (b) Incubate the culture media anaerobically (c) Reject the specimen and request a sputum sample (d) Culture on buffered charcoal yeast extract agar with antibiotics
(d) Culture on buffered charcoal yeast extract agar with antibiotics
An 18-year-old boy is admitted to the hospital with suspected meningitis. He is lethargic and presents with a rigid neck. He has not had most of the recommended vaccines from childhood to now. Gram stain of his spinal fluid shows many PMNS with intra and extracellular gram-negative diplococci. The suspected pathogen is: (a) Listeria monocytogenes (b) Haemophilus influenzae (c) Streptococcus agalactiae (d) Neisseria meningitidis
(d) Neisseria meningitidis
47) The most frequent cause of prosthetic heart valve infections occurring within 2-3 months after surgery is: (a) Streptococcus pneumoniae (b) Streptococcus pyogenes (c) Staphylococcus aureus (d) Staphylococcus epidermidis
(d) Staphylococcus epidermidis
48) Gram-positive cocci isolated from a blood culture have the following characteristics: Optochin susceptibility - negative Bacitracin susceptibility - negative Bile esculin hydrolysis - negative Hippurate hydrolysis - positive Catalase - negative The organism is most likely: (a) Staphylococcus aureus (b) Streptococcus pneumoniae (c) Streptococcus pyogenes (GAS) (d) Streptococcus agalactiae (GBS)
(d) Streptococcus agalactiae (GBS) Catalase is negative, therefore S. aureus is ruled out. GBS is bacitracin and optochin resistant and bile-esculin negative
Vibrio parahaemolyticus is best isolated from feces on: (a) Eosin methylene blue (EMB) agar (b) Hektoen enteric (HE) agar (c) Salmonella Shigella (SS) agar (d) Thiosulfate citrate bile salts (TCBS) agar
(d) Thiosulfate citrate bile salts (TCBS) agar
A community hospital microbiology laboratory is processing significant numbers of stool cultures because an outbreak of diarrhea following heavy rains and flooding in the country. A media that should be incorporated in the plating protocol is: (a) Colistin nalidixic acid for Listeria (b) MacConkey agar with sorbitol for Campylobacter (c) Mannitol salt agar for Enterococcus species (d) Thiosulfate citrate bile salts sucrose for Vibrio species
(d) Thiosulfate citrate bile salts sucrose for Vibrio species
Which of the following sample requests is acceptable? (a) Feces submitted for anaerobic culture (b) Foley catheter tip submitted for aerobic culture (c) Rectal swab submitted for direct smear of gonococci (d) Urine for culture of acid-fast bacilli
(d) Urine for culture of acid-fast bacilli
40) The principle difference between the Ziehl-Neelsen acid-fast stain technique and the Kinyoun acid-fast stain technique is: (a) Types of dyes used (b) Type of microscope used to interpret stained smears (c) Strength of acid decolorizer (d) Use of heat to allow the dye to penetrate organism
(d) Use of heat to allow the dye to penetrate organism
55) A college student attended a beach party where raw oysters and other shellfish were consumed. The next day, he had symptoms of septicemia. The blood cultures grew gram-negative bacilli with the following characteristics: Oxidase- pos MacConkey agar- pink colonies O/129 - susceptible The most likely organism is: (a) Aeromonas hydrophilia (b) Pseudomonas putida (c) Serratia marcescens (d) Vibrio vulnificus
(d) Vibrio vulnificus
Which of the following is the most appropriate organism and media combination? (a) Vibrio species - Skirrow (b) Enterohemorrhagic E. coli - Phenylethyl alcohol (PEA) (c) Campylobacter species - Charcoal yeast extract (d) Yersinia enterocolitica - CIN
(d) Yersinia enterocolitica - CIN
67) A 25-year-old man who had recently worked as a steward on a transoceanic grain ship presented to the emergency room with high fever, diarrhea and prostration. Axillary lymph nodes were hemorrhagic and enlarged. A Wright-Giemsa stain of the aspirate showed bacilli that were bipolar, resembling safety pins. The most likely identification of this organism is: (a) Brucella melitensis (b) Streptobacillus monoliformis (c) Spirillum minus (d) Yersinia pestis
(d) Yersinia pestis Yersinia pestis has been described as having a "safety pin" shape on Wright-Giemsa stain. The patient's presentation is classic for bubonic plague.
The most appropriate method for collecting a urine specimen from a patient with an indwelling catheter is: (a) remove the catheter, cut the tip, and submit it for a culture (b) disconnected the catheter from the bag, and aseptically collect urine from the terminal end of the tube (c) aseptically collect urine directly from the drainage bag (d) aspirate urine aseptically from the catheter tubing
(d) aspirate urine aseptically from the catheter tubing
A male urethral discharge specimen submitted for culture should be inoculated to: (a) SBA and phenylethyl alcohol agars (b) Eosin-methylene blue and SBA (c) Thioglycolate broth and chocolate agar (d) chocolate and modified Thayer-Martin agar
(d) chocolate and modified Thayer-Martin agar
30) A wound specimen grew 2 colony types on SBA and a single, clear colony type on MacConkey agar. SBA growth was documented as: Colony type #1 swarming over entire plate, Gram stain: gram-negative bacilli Colony type #2 white colony, Gram stain: gram-positive cocci in clusters The best way to isolate colony type #2 from colony type #1 is to subculture: (a) colony type #1 to SBA and chocolate agars (b) colony type #1 to SBA and/or MacConkey agar (c) colony type #2 to SBA and chocolate agars (d) colony type #2 to CNA and/or PEA agar
(d) colony type #2 to CNA and/or PEA agar Colony #1 is a probable Proteus spp. To isolate colony #2 from the swarming colony, a medium selective for GPC must be used (CNA and PEA).
75) 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 charcoal yeast extract medium after 2 days of incubation. The best explanation is that the: (a) antibody titer represents an earlier infection (b) positive antigen test is a false positive (c) specimen was cultured on the wrong media (d) culture was not incubated long enough
(d) culture was not incubated long enough Colonies should grow within 3 to 4 days. Plates should be held for 2 weeks.
46) "Nutritionally variant" streptococci are: (a) Enterococci (b) Group D Enterococci (c) Beta hemolytic strep (d) in the genera Granulicatella and Abitrophilia
(d) in the genera Granulicatella and Abitrophilia
61) CBF test results that are most consistent with viral meningitis include: (a) decreased protein level (b) decreased glucose level (c) increased lactate level (d) increased mononuclear lymphocyte count
(d) increased mononuclear lymphocyte count Differential diagnosis of viral meningitis includes normal lactate levels (increased in bacterial, tubercular and fungal), normal glucose level, and increased protein level. Lymphocytes are normally present.
60) Microorganisms resembling Mycoplasma pneumoniae have been isolated from the blood of patients treated with antibiotics that: (a) complex with flagellar protein (b) interfere with cell membrane function (c) inhibit protein synthesis (d) interfere with cell wall synthesis
(d) interfere with cell wall synthesis Mycoplasma species do not have a cell wall, therefore antibiotics interfering with cell wall synthesis would be ineffective
29) When processing a patient specimen for Gram stain and culture, the proper use of a biological safety cabinet includes: (a) bringing into the cabinet all required media and equipment just prior to setting up each individual specimen (b) keeping the ultraviolet light on for the first 30 minutes of working in the cabinet (c) not using any heat generating equipment such as open flames or microburner/incinerators (d) not disrupting the air curtain barrier by keeping air flow and exhaust grills unobstructed
(d) not disrupting the air curtain barrier by keeping air flow and exhaust grills unobstructed
37) An expectorated sputum is sent to the laboratory for culture from a patient with respiratory distress. The Gram stain of the specimen shows many squamous epithelial cells (>25/lpf) and rare neutrophils. The microscopic appearance of the organisms present include: Moderate gram-positive cocci in chains and diplococci Moderate gram-negative diplococci Moderate palisading gram-positive bacilli all in moderate amounts This Gram stain is most indicative of: (a) a pneumococcal pneumonia (b) an anaerobic infection (c) an Haemophilus pneumonia (d) oropharyngeal flora
(d) oropharyngeal flora (contamination)
56) The laboratory 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: Gram stain: small, gram-negative coccobacilli Sheep blood agar: growth after 48 hours with small, smooth, raised colonies What should the microbiologist do next? (a) consider the growth contamination and perform another gram stain (b) perform biochemical identification for HACEK organisms (c) perform identification and susceptibility testing using an automated system (d) take extra safety precautions for possible Brucella
(d) take extra safety precautions for possible Brucella Brucella causes undulant fever and is a cause of fever of unknown origin. It's slow growing and associated with laboratory-acquired infections.