Microbiology Practice Questions & Ratio

MEDICAL LABORATORY SCIENCE • MICROBIOLOGY-PARASITOLOGY PRACTICE QUESTIONS + ANSWERS & RATIONALIZATIONS • • • • • • • • • Respiratory specimens are best collected with what type of swabs? a. Calcium alginate swabs b. Dacron or polyester-tipped swabs c. Swabs with cotton tips or wooden shafts d. All of the above are acceptable What is the safe volume of blood to be drawn for pediatric blood cultures? a. <1 mL b. 1 to 5 mL c. 5 to 10 mL d. 10 to 20 mL The optimal time to collect blood cultures is: a. Shortly before the fever spikes b. While the fever spikes c. Shortly after the fever spikes d. No more than one set daily → Highest concentration of bacteria in the blood occurs before the fever spikes Which of the following may impede detection of protozoa: a. Baby oil b. Cooking oil c. Hair oil d. Mineral oil When setting up a urine culture, a calibrated loop is used that delivers a specific amount of urine to the media plate. What is that amount? a. 0.01 or 0.001 mL of urine b. 0.10 or 0.01 mL of urine c. 0.001 or 0.0001 mL of urine d. None of the above is correct Quebec Colony Counter: a. Brightfield b. Darkfield Which one of the following organisms does not require susceptibility testing to the antimicrobial indicated when isolated from a clinically significant source? a. S. aureus: clindamycin b. P. mirabilis: gentamycin c. S. pyogenes: penicillin d. E. coli: levofloxacin Which method is most useful for confirmation that a culture isolate is Group B streptococcus a. Southern blotting b. PCR c. Direct hybridization d. Probe capture assay An organism isolated from a urine culture has the following reactions: Gram-negative rod TSI A/AG → EKE IMVIC + + - Motile Urease neg a. E. cloacae b. S. marcescens c. K. pneumoniae d. E. coli • • • • • • An organism isolated from a urine culture has the following reactions: Gram-negative rod TSI A/AG → EKE IMVIC - - + + Motile Lysine decarboxylase neg No capsule a. E. cloacae b. E. coli c. K. pneumoniae d. Serratia marcescens An organism isolated from a urine culture has the following reactions: Gram-negative rod Urease and phenylalanine deaminase pos TSI K/AG, H2S (-) Lysine decarboxylase neg Ornithine decarboxylase pos Motility pos or neg a. P. mirabilis b. Providencia c. Morganella d. P. vulgaris An organism isolated from a urine culture has the following reactions: Gram-negative rod Urease and phenylalanine deaminase nleg TSI K/A Lysine decarboxylase neg Motility neg Which of the following organism is it? a. Salmonella subgroup 3 (Arizona) b. P. mirabilis c. Shigella d. C. freundii Most of the pathology associated with parasitic infections results from which of the following? a. Symbiotic relationships with the host b. Elaborate parasitic life cycles c. Immune response to the offending organism d. Innate defense mechanisms of the host The chronic nature of parasitic infections is caused by the host’s: a. Inability to eliminate the infective agent b. Type I hypersensitivity response to the infection c. Ability to form a granuloma around the parasite d. Tendency to form circulating immune complexes Polyvinyl alcohol used in the preparation of permanently stained smears of fecal material: a. Concentrates eggs b. Dissolves artifacts c. Serve as an adhesive d. Enhances stain penetration Microsporidia Modified Trichrome specimen: (1) Fresh stool (2) Refrigerated stool (3) Ethanol-fixed (4) Formalin-fixed a. 1, 2 b. 1, 3 c. 1, 4 d. 1, 2, 3 1 • • • • • • • • • • • Which of the following microorganism is susceptible to changes in temperature? a. N. meningitidis b. Shigella c. Both A and B d. None of the above Which of the following specimens/s is stored at 4C? a. Stool b. Urine c. Viral specimens d. All of the above Critical or panic value, except: a. Positive blood cultures b. S. pyogenes is a surgical wound c. Negative malaria test d. Positive acid-fast stain Which of the following refers to the patient preparation in obtaining superficial abscess? a. Wiping the area with KH b. Wiping area with sterile saline or 70% alcohol c. Wiping area with iodine then 70% alcohol d. None of the above CSF for microbiologic examination should be transported to laboratory: a. <15 minutes b. <1 hour c. <2 hours Patient preparation in obtaining sputum specimen: a. Have patient gargle Listerine b. Have patient brush teeth and then rinse or gargle with water before collection c. Have patient gargle with alcohol d. Have patient brush teeth and then rinse or gargle with Listerine before collection The most important diagnostic tool in treating patients with clinical infections in the ER is the: a. Acid fast stain b. Gram stain c. Culture and sensitivity d. None of the above All of the following organisms contain cell wall with mycolic acid, except: a. Nocardia b. Rhodococcus c. Streptomyces d. Corynebacterium Which of the following refers to the reaction of gram positive organism after decolorization? a. Stain purple b. Remain purple c. Remain pink d. Become colorless Which of the following stains binds to cell walls of fungi? a. Calcofluor white b. Auramine-Rhodamine → mycolic acid c. FITC → w/ abs d. Acridine orange → nucleic acid FITC grading: Bright apple-green fluorescence: a. 1+ b. 2+ c. 3+ d. 4+ • • • • • • • • • • In acridine orange staining, bacteria and yeasts will fluoresce _____ against a green-fluorescing or dark background: a. Yellow b. Orange c. Red Colistin-nalidixic acid agar (CAN) is used primarily for the recovery of: a. Neisseria b. Enterobacteriaceae c. P. aeruginosa d. S. aureus Xylose lysine deoxycholate (XLD) agar is a highly selective medium used for the recovery of which bacteria? a. Staphylococcus spp. from normal flora b. Yersinia spp. that do not grow on Hektoen agar c. Enterobacteriaceae from GI specimens d. Streptococcus spp. from stool cultures Select the medium best suited for the recovery of Y. enterocolitica form a patient with gastroenteritis. a. Hektoen agar b. Cefsulodin-Irgasan-Novobiocin (CIN) agar c. Blood agar d. EMB agar Cycloserine-cefoxitin-fructose agar (CCFA) is used for the recovery of: a. Y. enterocolitica b. Y. intermedia c. C. perfringens d. C. difficile Incomplete or partial hemolysis; green or brown color surrounding the colony: a. Alpha hemolysis b. Beta hemolysis c. Gamma hemolysis d. Alpha prime hemolysis Which of the following grow in the bottom of the broth: a. Facultative anaerobic b. Strictly aerobic c. Strictly anaerobic d. None of the above Selective media: a. May be differential b. Allow the growth of all organism c. Are utilized for growth of fastidious organisms d. Contain dyes or antibiotics to suppress the growth of some organisms All of the following are differential media, except: a. Blood agar b. Chocolate agar c. MacConkey’s agar d. Eosin Methylene Blue Grayish white, transparent, matte, glossy, large zone of beta hemolysis: a. S. pyogenes b. S. agalactiae c. S. pneumoniae d. B. anthracis 2 • • • • • • • • Translucent to opaque; flat glossy with narrow zone of beta hemlysis; some strains nonhemolytic: a. S. pyogenes b. S. agalactiae c. S. pneumoniae d. B. anthracis SITUATION: A group of elementary students became ill after eating undercooked ground beef in the school cafeteria. The suspected pathogen, E. coli serotype O157:H7, I susually recovered using which of the following media? a. XLD agar b. MacConkey agar c. MacConkey agar with Sorbitol d. Hektoen agar The most sensitive method for the detection of βlactamase in bacteria is by the use of: a. Chromogenic cephalosporin b. Penicillin c. Oxidase d. Chloramphenicol acetyltransferase The breakpoint of an antimicrobial drug refers to: a. The amount needed to cause bacteriostasis b. A MIC of 16 ug/mL or greater c. A MIC of 64 ug/mL or greater d. The level of drug that is achievable in serum Which of the following variables may change the results of an MMIC? a. Inoculum size b. Incubation time c. Growth rate of the bacteria d. All of these options According to the Kirby-Bauer standard antimicrobial susceptibility testing method, what should be done when interpreting the zone size of a motile, swarming organism such as a Proteus species? a. The swarming area should be ignored b. The results of the disk diffusion method are invalid c. The swarming area should be measured as the growth boundary d. The isolate should be retested after diluting to a 0.5 McFarland standard The lowest concentration of antibiotic that inhibits growth of a test organism is the: a. Minimum inhibitory concentration b. Serum inhibitory concentration c. Minimum bactericidal titer d. Maximum inhibitory titer Susceptibility testing performed on QC organisms using a new media lot number yielded zone sites that were too large for all antibiotics testes. The testing was repeated using media from a previously used lot number, and all zone sizes were acceptable. Which of the following best explains the unacceptable zone sized? a. The antibiotic disks were not stored with the proper desiccant b. The depth of the media was too thick c. The depth of the media was too thin d. The antibiotic disks were not properly applied to the media • • • • • • • • After satisfactory performance of a daily disk diffusion susceptibility quality control is documented, the frequency of quality control can be reduced to: a. Twice a week b. Every week c. Every other week d. Every month Which class of antibiotics is used for the treatment of serious gram-negative infections as well as infections with Mycobacterium tuberculosis? a. Cephalosporins b. Penicillins c. Tetracyclines d. Aminoglycosides → Primary MTB Drugs (RIPE): Rifampin, Isoniazid, Pyrazinamide, Ethambutol Which of the following biosafety cabinets is completely enclosed with negative pressure, afford the most protection. Air coming into and going out of the cabinet is filter sterilized, and the infectious material within is handled with rubber gloves that are attached to cabinet? a. Class I cabinet b. Class II cabinet c. Class III cabinet d. None of the above Process mediated through viruses capable fo infecting bacteria (bacteriophage); viruses integrate their DNA into the bacterial cell’s chromosome where viral DNA replication and expression occur? a. Transformation b. Transduction c. Conjugation d. None of the abbove Which of the following B. stearothermophilus component/structure is used a quality control for autoclave? a. Cell wall b. Spores c. Nucleus d. Cell membrane Which atmospheric condition is needed to recover Campylobacter spp. from specimens inoculated onto a Campy-selective agar at 35-37C and 42C? a. 5% O2, 10% CO2, and 85% N2 b. 20% O2, 10% CO2, and 70% N2 c. 20% O2, 20% CO2, and 60% N2 d. 20% O2, 5% CO2, and 75% N2 Most spoilage bacteria grow best at ____ pH: a. Acid b. Alkaline c. Neutral d. None of the above Most common method of treating infectious waste: a. Filtration b. Incineration c. Dry heat d. Ionizing radiation 3 • • • • • • • • • • • • Exotic agents that are considered high risk and cause life threatening disease; including Marburg virus or CongoCrimean hemorrhagic fever are handled in: a. BSL 1 b. BSL 2 c. BSL 3 d. BSL 4 Positive result in acetamide, acetate, and citrate utilization test: a. Red b. Yellow c. Blue d. Green Zone of inhibition in bacitracin susceptibility test = 16 mm: a. Bacitracin susceptible; positive b. Bacitracin resistant; negative Positive control in the bile esculin test: a. E. faecalis b. E. coli c. S. pyogenes Positive result in CAMP test: a. Enhancement of hemolysis b. No enhancement of hemolysis Cetrimide agar is used to isolate: a. E. coli b. P. aeruginosa Preferred plasma in the coagulase test: a. Sheep plasma EDTA b. Sheep plasma citrate c. Rabbit plasma EDTA d. Rabbit plasma citrate Free coagulate test is detected by the: a. Slide test b. Tube test → Tube test results can be positive at 4 hours and then revert to negative after 24 hours pH indicator used in Moeller’s method for the detection of decarboxylase: a. Phenol red b. Bromothymol blue c. Bromocresol purple Positive result in DNA hydrolysis test: a. Media turns green b. Media turns colorless Positive result in esculin hydrolysis test: (1) Blackened medium (2) No blackening of medium (3) Loss of fluorescence under Wood’s lamp (4) No loss of fluorescence a. 1, 3 b. 1, 4 c. 2, 3 d. 2, 4 Fermentation media: BHI w/ bromocresol purple (1) Differentiates enteric bacteria from corynebacteria (2) Differentiate enterococci from streptococci (3) Pink color is the positive result (4) Yellow color is the positive result a. 1, 3 b. 1, 3 c. 2, 3 d. 2, 4 • • • • • • • • • • • Positive control in the Hippurate test: a. S. agalactiae b. S. pyogenes Reagent that is more sensitive for detecting small amounts of indole and the technique of choice to detect indole production for anaerobes: a. Kovac’s reagent b. Ehrlich’s reagent Study the picture: a. The organism is motile b. The organisms is nonmotile Which of the following colors indicates a positive acetamide utilization test? a. Yellow b. Blue c. Green d. Purple The slide coagulase tests detects: a. Bound coagulase b. Clumping factor c. Free coagulase d. A and B Which of the following can be used as positive control in control in the Hippurate hydrolysis test? a. S. agalactiae b. S. pyogenes Which of the following can be used as positive control in the Optochin susceptibility test? a. S. pneumoniae b. S. pyogenes The test used most often to separate the Micrococcaceae family from the Streptococcaceae family is: a. Bacitracin b. Catalase c. Hemolysis pattern d. All of these options Which of the following tests will rapidly differentiate micrococci from staphylococci? a. Catalase b. Coagulase c. Modified oxidase d. Novobiocin susceptibility The Vogues-Proskauer test detects which end product of glucose fermentation? a. Acetoin b. Nitrite c. Acetic acid d. Hydrogen sulfide A positive Simmons citrate test is seen as a: a. Blue color in the medium after 24 hours of incubation at 35C b. Red color in the medium after 18 hours of incubation at 35C c. Yellow color in the medium after 24 hours of incubation at 35C d. Green color in the medium after 18 hours of incubation at 35C 4 • • • • • • • • • Decarboxylation of the amino acids lysine, ornithine, and arginine results in the formation of: a. Ammonia b. Urea c. CO2 d. Amines Which genera are positive for phenylalanine deaminase? a. Eneterobacter, Eschericia, and Salmonella b. Morganella, Providencia, and Proteus c. Klebsiella and Enterobacter d. Proteus, Escherichia, and Shigella Cetrimide agar is used as a selective isolation agar for which organism? a. Acinetobacter spp. b. Pseudomonas aeruginosa c. Moraxella spp. d. Stenotrophomonas maltophilia Which reagents are used to develop the red color indicative of a positive reaction in the nitrate reduction test? a. Sulfanilic acid and α-naphthylamine b. Ehrlich’s and Kovac’s reagents c. o-Nitrophenyl-β-D-galactopyranoside d. Kovac’s reagent Toxic shock syndrome is attributed to infection with: a. Staphylococcus epidermidis b. S. hominis c. S. aureus d. S. saprophyticus Staphylococcus epidermidis is recovered from which of the following sources? a. Prosthetic heart valves b. Intravenous catheters c. Urinary tract d. All of these options S. aureus recovered from a wound culture gave the following antibiotic sensitivity pattern by the standardized Kirby-Bauer method: Penicillin = R Ampicillin = S Cephalothin = R Cefoxitin = R Vancomycin = S Methicillin = R Which is the drug of choice for treating this infection? a. Penicillin b. Ampicillin c. Cephalothin d. Vancomycin Urine cultured from the catheter of an 18-year-old femail patient produced more than 100,000 col/mL on a CAN plate. Colonies were catalase positive, coagulase negative by the latex agglutination slide method as well as the tube coagulase test. The best single test for identification is: a. Lactose fermentation b. Urease c. Catalase d. Novobiocin susceptibility The Quellung test is used to identify which Streptococcus species? a. S. pyogenes b. S. agalactiae c. S. sanguis d. S. pneumoniae • • • • • • • • A gram stain of a urethral discharge from a man showing extracellular and intracellular gram-negative diplococci within segmented neutrophils is a presumptive identification for: a. N. gonorrhoeae b. N. meningitidis c. M. catarrhalis d. N. lactamica Culture on MTM media of a vaginal swab produced several colonies of gram-negative diplococci that were catalase oxidase positive and Superoxol negative. Given the following carbohydrate reactions, select the most likely identification. Glucose (+) Sucrose (-) Lactose (+) Maltose (+) Fructose (-) a. N. gonorrhoeae b. N. sicca c. N. flavescens d. N. lactamica Which test is used for the determination of inducible clindamycin resistance in staphylococci and streptocci? a. E-test b. D-zone test c. A-test d. CAMP test B. anthracis and B. cereus can best be differentiated by which tests? a. Motility and β-hemolysis on a blood agar plate b. Oxidase and β-hemolysis on a blood agar plate c. Lecithinase and glucose d. Lecithinase and catalase Culture of a finger wound specimen from a meat packer produced short gram-positive bacilli on a blood agar plate with no hemolysis. Given the following test results at 48 hours, what is the most likely identification? Catalase = neg H2S/TSI = neg Motility, wet prep = neg Motility (media) = neg (bottle-brush growth in stab) a. B. cereus b. L. monocytogenes c. E. rhusiopathiae d. B. subtilis Kligler iron agar (KIA) differs from triple-sugar iron agar in the: a. Ratio of lactose to glucose b. Ability to detect H2S production c. Use of sucrose in the medium d. Color reaction denoting production of acid Which genera of Enterbacteriacea are usually nonmotile at 36C? a. Shigella, Klebsiella, and Yersinia b. Escherichia, Edwardsiella, and Enterobacter c. Proteus, Providencia, and Salmonella Cold enrichment of feces (incubation at 4C) in phosphatebuffered saline prior to subculture onto enteric media enhance the recover of: a. ETEC b. S. parathypi c. Hafnia alvei d. Y. enterocolitica 5 • • • • • • • • Which single test best separates Klebsiella oxytoca from K. pneumoniae? a. Urease b. Sucrose c. Citrate d. Indole The Shiga-like toxin (verotoxin) is produced mainly by which Enterobacteriaceae? a. K. pneumoniae b. E. coli → EHEC/STEC/VTEC c. S. typhimurium d. Enterobacter cloacae Three consecutive stool cultures form a 25 year old male patient produced scant normal fecal flora on MacConkey and Hektoen agars. However, colonies on CIN agar displayed “bulls-eye” colonies after 48 hours incubation. The patient had been suffering from enterocolitis with fever, diarrhea, and abdominal pain for 2 days. What is the most likely identification of this gram-negative rod? a. E. coli b. P. mirabilis c. Y. enterocolitica d. K. pneumoniae Which Pseudomonas is usually associated with a lung infection to cystic fibrosis? a. P. fluorescens b. P. aeruginosa c. P. putida d. B. pseudomallei Which organism is associated with immunodeficiency syndromes and melioidosis (glanders-like disease in Southeast Asia and norther Australia) a. P. aeruginosa b. P. stutzeri c. P. putida d. B. pseudomallei Alcaligenes faecalis (formerly A. odorans) is distinguished from B. bronchiseptica with which test? a. Urease (rapid) b. Oxidase c. Growth on MacConkey agar d. Motility A 20-year-old horse groomer exhibited a “glanders-like” infection. His history indicated he had suffered several open wounds on his hands 2 weeks before the selling of his lymph nodes. A gram negative rod was recovered from ablood culture that grew well on blood and MacConkey agars. Most of the biochemical tests were negative, including the cytochrome oxidase test. What is the most likely identification? a. B. mallei b. P. aeruginosa c. P. stutzeri d. B. pseudomallei A visitor to South America who returned with diarrhea is suspected of being infected with V. cholerae. Select the best medium for recovery and identification of this organism. a. MacConkey agar b. Blood agar c. TCBS agar d. XLD agar • • Which group of tests differentiates H. pylori from C. jejuni? a. Catalase, oxidase, and gram stain b. Catalase, oxidase, and nalidixic acid sensitivity c. Catalase, oxidase, and cephalothin sensitivity d. Urease, nitrate, and Hippurate hydrolysis Which among the following tests should be done first in order to differentiate Aeromonas spp. from the Enterobacteriaceae? a. Urease b. OF glucose c. Oxidase d. Catalase 6