Bacteriology Practice Questions & Ratio

MEDICAL LABORATORY SCIENCE • BACTERIOLOGY PRACTICE QUESTIONS + ANSWERS & RATIONALIZATIONS • • • • • • • • • • All of the following are metallic mordant except: a. Alum b. Iron c. Copper d. Iodine → halogen Most Critical Step of Gram Staining? a. Decolorization b. Counterstaining c. Washing d. Primary staining Which microorganism may cause spoilage of unopened bacon in a vacuum-sealed container? a. Lactobacillus b. Listeria c. E. coli d. Clostridium Which is a gram positive bacilli and H2S positive? a. Erysipelothrix b. Nocardia c. Cardiobacterium d. Neisseria What is the color of a non acid-fast organism? a. Blue → (more common than green) b. Green c. Red d. Purple Mycolic acid in cell wall, except: a. Nocardia b. Gordonia c. Streptomyces d. Corynebacterium Common cause of food poisoning? a. S. aureus b. E. coli c. C. botulinum d. lactobacillus CSF of px is positive for Limulus lysate test: a. Bacterial Meningitis → gram neg b. Tubercular Meningitis c. Viral meningitis d. Fungal Meningitis All of the following are appropriate when attempting to isolate N. gonorrhoeae from a genital specimen except: a. Transport the gential swab in charcoal transport medium b. Plate the specimen on modified Thayer-Martin medium c. Plate the specimen on New York City or MartinLewis agar d. Culture specimens in ambient oxygen at 37C The most common cause for failure of GasPak anaerobe jar to establish an asequate environment for anaerobic incubation is: a. Failure of the oxidation-reduction potential indicator system due to deterioration of methylene blue b. the failure of the packet to generate adequate H2 and/or CO2 c. Condensation of water on inner surface of the jar d. Catalysts that have become inactivated after repeated use • • • • • • • • • A dermatophyte was isolated from A. capitis (ringworm of the scalp), it exhibit exhibit fluorescence on a wood’s lamp but fails to grow on a rice medium. What is the possible identity of the organism? a. M. audoinii b. M. canis Growth in broth, except: a. Diffuse → spreading (slanted/plated media) b. Flocculent c. Pellicle d. Turbid Sensitivity testing commonly required except: a. Acinetobacter b. Enterococci c. Enterobacteriaceae d. Listeria monocytogenes After satisfactory performance of 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 In disk diffusion susceptibility testing, as an antimicrobial agent diffuses away from the disk, the concentration of antibiotic is: a. Increased b. Decreased c. Unchanged d. Inoculum dependent Thirty percent exhausted, 70% recirculated: a. Class I BSC b. Class II A1 BSC c. Class II B1 BSC d. Class II B2 BSC Sterile, screw-cap container tube, except: a. Join fluid b. Sputum c. Urine d. Wound abscess → aerobic swab w/ Stuart’s or Amie’s Patient preparation for Sputum: a. Gargle w/ H2O b. Gargle w/ Alcohol c. Gargle w/ Listerine d. Do not gargle Which of the following is the most appropriate method for collecting a urine specimen form a patient with an indwelling catheter? a. Remove the catheter, cut the tip, and submit it for culture b. Disconnect the catheter from the bag, and collect urine from the terminal end of the catheter c. Colelct urine directly from the bag d. Aspirate urine aseptically from the catheter tubing CSF should be cultured immediately, but if delayed, the specimen should be: a. Refrigerated at 4-6C b. Frozen at -20C c. Stored at room temp for no longer than 24 hrs d. Incubated at 37C and cultured ASAP 1 • • • • • • What test will help differentiate Staphylococcus from Micrococcus? a. Gram stain b. Catalase test c. Modified oxidase d. All of these Gray, translucent, smooth, glistening, may have dry claylike consistency? a. N. elongata b. Moraxella catarrhalis c. N. gonorrhoeae Large, nonpigmented or gray, opaque, smooth; friable “hockey puck” consistency; colony may be moved intact over surface of agar? a. N. elongata b. Moraxella catarrhalis c. N. gonorrhoeae Gram-negative diplococci was isolated on BAP at 25C. positive for utilization of glucose and maltose a. N. gonorrhoeae → non maltose fermenter b. N. meningitidis → BAP, CAP @ 37C c. N. subflava → grows at 25C d. M. catarrhalis → nonfermenter of CHO Three blood cultures taken from a 30-year-old cancer patient receiving chemotherapy and admitted with a urinary tract infection grew lactose-negative, motile, gramnegative rods prior to antibiotic therapy. Given the following biochemical reactions, which is the most likely organism? H2S (TSI) = + Indole = + (P. vulgaris pos vs. P. mirabilis neg) MR = + VP = Neg Citrate = Neg Urease = + DNase = + Phenylalanine deaminase = + Gelatin hydrolysis = + Ornithine decarboxylase = Neg a. Proteus vulgaris b. Proteus mirabilis c. Serratia marcescens (H2S neg) d. Klebsiella pneumoniae The following results were obtained from a pure culture of gram-negative rods recovered from the pulmonary secretions of a 10-year-old cystic fibrosis patient with pneumonia: Oxidase = + Motility = + Glucose OF (open) = + Gelatin hydrolysis = + Pigment = Red Arginine dihydrolase = + (nonfluorescent) Growth at 42°C = + Flagella = + (polar, monotrichous) Which is the most likely organism? a. Burkholderia pseudomallei b. Pseudomonas stutzeri c. Burkholderia cepacia d. Pseudomonas aeruginosa • • • • • Before sending an unknown isolate of E. coli to a reference lab, it should be test for the fermentation of a what CHO agar? a. Sorbitol b. Mannitol c. TSI d. MacConkey A sputum culture from a 13-year-old cystic fibrosis patient grew a predominance of short, gram-negative rods that tested oxidase negative. On MacConkey, chocolate, and blood agar plates, the organism appeared to have a lavender-green pigment. Further testing showed: Motility = + DNase = + Glucose = + (oxidative) Maltose = + (oxidative) Lysine decarboxylase = + Esculin hydrolysis = + What is the most likely identification? a. Stenotrophomonas maltophilia b. Acinetobacter baumannii c. Pseudomonas aeruginosa d. Burkholderia (P.) cepacian Respiratory specimen, beta-hemolytic organism requiring X & V factors: a. H. aprophilus b. H. ducreyi c. H. influenzae d. H. hemolyticus - only beta hemolytic haemophilus CSF sample, non-hemolytic requiring X & V factors: a. H. aprophilus b. H. ducreyi c. H. influenzae d. H. hemolyticus Which group of tests best differentiates Helicobacter 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 → H. pylori vs. C. jejuni → • • • Positive Hippurate hydrolysis: S. agalactiae, L. monocytogenes, G. Vaginalis, C. jejuni Capnophilic Brucella that H2S positive will not grow in Thionine but will grow in the presence of basic fuchsin? a. B. abortus b. B. mellitensis Brucella that do not require CO2 but grows in the presence of Thionine and basic fuchsin? a. B. abortus b. B. melitensis The ethanol shock procedure is used to differentiate: a. Actinomyces and Bifidobacterium b. Prevotella and Porphyromonas c. Clostridium and Bacteroides d. Bacteroides and Actinomyces 2 • • • • • • • A flexible calcium alginate nasopharyngeal swab is the collection device of choice for recovery of which organism from the nasopharynx? a. Staphylococcus aureus b. Streptococcus pneumoniae c. Corynebacterium diphtheriae d. Bacteroides fragilis → C. diphtheriae must be recovered from the deep layers of the pseudomembrane that forms in the nasopharyngeal area. A flexible calcium alginate nasopharyngeal swab is the best choice for collecting a specimen from the posterior nares and pharynx. Which mycobacterium is associated with Crohn’s disease? a. M. marinum b. M. paratuberculosis c. M. avium d. M. gordonae Which of the following can be used as a control for rapid and slow growers a. MTB & M. bovis b. M. bovis & M. kansasii c. MTB & M. fortuitum Acid-fast staining of a smear prepared from digested sputum showed slender, slightly curved, beaded, red mycobacterial rods. Growth on Middlebrook 7H10 slants produced buff-colored microcolonies with a serpentine pattern after 14 days at 37°C. Niacin and nitrate reduction tests were positive. What is the most probable presumptive identification? a. Mycobacterium tuberculosis b. Mycobacterium ulcerans c. Mycobacterium kansasii d. Mycobacterium avium–intracellulare complex The urease test is needed to differentiate Mycobacterium scrofulaceum from which of the following mycobacteria? a. M. gordonae b. M. kansasii c. M. avium–intracellulare complex d. M. bovis → Biochemically, M. scrofulaceum is identical to M. gordonae, except for the urease reaction for which M. scrofulaceum is positive and M. gordonae is negative Growth inhibition by thiophene-2-carboxylic hydrazide (T2H) is used to differentiate M. tuberculosis from which other Mycobacterium specie? a. M. bovis b. M. avium–intracellulare complex c. M. kansasii d. M. marinum → The T2H test differentiates M. tuberculosis from M. bovis. M. tuberculosis is not inhibited by T2H A branching ram-posiitve, partially acid-fast organism is isolated from a bronchia washing on a 63-year-old woman receiving chemotherapy. The organism does not hydrolyze casein, tyrosine, or xanthine. The most likely identification is: a. Actinomadura madurae b. Streptomyces somaliensis c. Nocardia caviae d. Nocardia asteroides → Nocardia asteroides are partially acid fast and do not hydrolyze the substrates casein, tyrosine, or xanthine • • • • • • • • Which actinomycete is partial acid-fast, has extensive aerial hyphae, and is lysozyme resistant? a. Nocardia sp. b. Rhodococcus sp. c. Gordonia sp. d. Tsukamurella sp. Positive result in the bile solubility test: a. Clearing of the medium b. Arrowhead zone of hemolysis c. Brown-black precipitated d. Lysed colonies Negative result in CAMP test: a. Clearing of the medium b. Arrowhead zone of hemolysis c. No hemolysis d. No enhancement of hemolysis There is no danger when handling a dimorphic fungus in: a. Mold phase b. Yeast phase Which microsporum that exhibits fluorescence on a Wood’s lamp but fails to grow on a rice medium? a. M. audouinii b. M. canis Which tissues are affected by Trichophyton? a. Skin b. Nails c. Hair d. All of these All of the following fungi are associated with Chromoblastomycosis, except: a. Fonsacaea b. Phialophora c. Cladosporium d. Exophiala → Mycetoma All of these viruses are ether-resistant except: a. Adenoviridae b. Papovaviridae c. Parvoviridae d. Herpesviridae → enveloped (ether-sensitive) 3