Micro Review 1
Relapsing fever in humans is caused by: A. Spirillum minor B. Brucella abortus C. Leptospira interrogans D. Borrelia recurrentis
D
The reagents used to detect the phenylalanine deaminase reaction in gram negative rods is(are) A. sulfanilic acid and alpha-naphthylamine B. p-aminodimethylbenzaldehyde C. alpha-naphthol and potassium hydroxide D. ferric chloride
D
A discharge from an ear in chronic otitis reveals an oxidase-negative, gram negative rod that is resistant to tetracycline and colistin on a routine Kirby-Bauer antimicrobial susceptibility test and gives the following biochemical reactions: Phenylalanine deaminase (PDA): positive Ornithine: Positive Hydrogen sulfide: positive Indole: Negative Urease: positive Citrate: Positive Lysine negative The organism described is: A. Citrobacter freundii B. Morganella morganii C. Proteus mirabilis D. Proteus vulgaris
C
A female student came to the university health center with symptoms of urethritis and vaginitis. She complained of a burning and discomfort in the vulvovaginal area, accompanied by a watery, fishy, discharge. What type of specimen prep should be ordered and what do you expect to see? A. Gram Stain, Filamentous branching rods B. Wet Prep, Trichomonas vaginalis C. Wet Prep, Clue Cells D. Gram Stain. Budding Yeast
C
A gram positive non-spore forming aerobic rod which has been implicated in stillbirths and spontaneous abortions is: A. Clostridium sp B. Corynebacterium pseudotuberculosis C. Listeria monocytogenes D. Bacillus cereus
C
Primary atypical pneumonia is caused by: A. Streptococcus pneumoniae B. Mycoplasma pneumoniae C. Klebsiella pneumoniae D. Mycobacterium tuberculosis
B- "Primary atypical pneumonia" is called primary because it develops independently of other diseases. The infection causes a cold agglutinin to form which has anti-I specificity.
Enterics ALWAYS - 3 things
1. Ferment glucose, 2. Are catalase positive 3. Reduce nitrate to nitrite
A 0.01 loop is used to inoculate a urine culture. 37 colonies grow on the blood agar plate and 23 colonies grow on the MacConkey plate. What is the CFU/ml for this culture that should be reported? A. 3,700 cfu/ml B. 2,300 cfu/ml C. 37,000 cfu/ml D. 23,000 cfu/ml
A
A CSF is plated to routine microbiological media, incubated at 35oC in CO2 and examined after 24 hours. Consider these results: Chocolate agar: few smallish, grayish-colorless colonies MacConkey agar: no growth 5% sheep BAP: no growth Gram stain: gram-negative coccobacilli To confirm the identification the following should be performed: A. oxidase test and ALA or X and V factors B. catalase test and coagulase test C. CTA carbohydrate utilization D. oxidase test and catalase
A
A culture from a patient with pyoderma grows a predominance of beta-hemolytic colonies on sheep blood agar at 18 hours of growth. The isolate is susceptible to 0.04 units of bacitracin, bile esculin-negative, hippurate hydrolysis-negative and catalase-negative. The most likely identification of this organism is: A. Streptococcus pyogens B. Streptococcus agalactiae C. Streptococcus gallalyticus D. Enterococcus faecalis
A
A doctor sends a sputum specimen to the laboratory. The Gram stain shows many gram-positive cocci in chains and pairs. Many alpha-hemolytic colonies are seen on the blood agar plate. It is not clear, however, whether the organisms are Streptococcus pneumoniae or alpha hemolytic streptococci. Which of the following tests would make this differentiation? A. bile solutbility B. esculin hydrolysis C. bacitracin susceptibility D. catalase
A
A gram-negative rod isolated from a wound culture grows on blood agar as a beta hemolytic colony, ferments lactose, produces an acid slant and butt on both Kliglers Iron agar (KIA) and Triple sugar iron (TSI) agar, and is oxidase positive. The LAO for this organism is +/+/= and it is VP+, Esculin + and inositol negative. What is the identification of this organism? A. Aeromonas hydrophila B. Escherichia coli C. Serratia marcescens D. Enterobacter cloacae
A
A large gram-positive, spore forming bacillus had been isolated from a wound on the arm of a man working in a leather factory. Which tests would help identify the organism as Bacillus anthracis? A. lack of hemolysis on BAP, non-motile B. catalase and coagulase results C. enterotoxin production and presence of B-lysin D. bacitracin and optochin
A
A non-spore forming, slender catalase negative gram-positive rod forming long chains was recovered from a vaginal culture and grew well on Tomato Juice agar. The most likely identification of this organism is: A. Lactobacillus spp. B. Bacillus spp. C. Neisseria spp. D. Streptococcus spp.
A
A quality control regimen is set up for the following tests: Phenylalanine deaminase (PDA) Indole production Voges-Proskauer (VP) Which pair of stock organisms would you select as suitable to verify the performance of these three tests? A. Klebsiella pneumoniae, Proteus vulgaris B. Proteus vulgaris, Escherichia coli C. Escherichia coli, Enterobacter aerogenes D. Enterobacter aerogenes, Klebsiella pneumoniae
A
According to the Kirby-Bauer standard antimicrobial susceptibility testing method, how should the zone size be interpreted 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 0.05 McFarland's standard
A
After reading and recoding Kirby-Bauer sensitivity zone sizes and quality control for Escherichia coli, you notice that all of the zones fall below the acceptable QC limits. Which of the following could be the cause of the erroneous results? 1. Turbidity of trypticase soy broth adjusted to McFarland 3.0. 2. Thickness of Mueller-Hinton agar is 8 mm 3. Mueller-Hinton agar plates incubated at 35oC for 16 to 18 hr in 10% CO2 4. pH of Mueller-Hinton agar set to 7.2 to 7.4 A. If 1, 2 and 3 are correct B. If 1 and 3 are correct C. If 2 and 4 are correct D. If all are correct
A
An acute infectious respiratory outbreak occurs in the overcrowded area of a United States-Mexico border town. A 5 year old girl was admitted to the hospital 48 hours ago and has expired. Her 7 year old brother was admitted as a prime candidate in the epidemic. Physical examination of the male child reveals fever and pseudomembranous, white patchy growth in the pharynx along with a swollen cheek, but no sore throat. The probable diagnosis is: A. Diphtheria B. Epiglottis C. Pertussis D. Trench mouth
A
Biochemically, the Enterobacteriaceae are gram negative rods that are found in wounds, fluids, urine, respiratory tract, CSF, and blood stream infections. What characteristics define an organism in the Enterobacteriaceae? A. Ferment glucose, reduce nitrate to nitrite, and are catalase positive B. Ferment glucose, produce indophenol oxidase, and are catalase positive C. Ferment lactose, reduce nitrite to nitrogen gas and are phenylalanine positive D. Ferment lactose, produce indophenol oxidase and are catalase negative
A
Lancefield grouping of the streptococci by latex agglutination determines: A. cell wall carbohydrate content B. cell wall lipid content C. cell wall protein content D. cell wall lipopolysaccharide content
A
Micrococcus and Staphylococcus species are differentiated by which test(s)? A. Fermentation of glucose (OF tube) B. Catalase test C. Gram stain D. All of the above
A
Providencia spp. are closely related to Proteus spp. and both can cause Urinary Tract Infections (UTIs). Providencia may be differentiated from Proteus by demonstrating which of the following sets of results? A. phenylalanine deaminase positive, H2S negative B. phenylalanine deaminase negative, H2S positive C. phenylalanine deaminase negative, H2S negative D. phenylalanine deaminase positive, H2S positive
A
Twenty patients on a surgical ward develop urinary tract infections after catheterization. The organism grew on blood agar as a beta-hemolytic organism and on MacConkey Agar as a lactose fermenter (LF). In each instance the oxidase negative gram negative rod produced the same biotype and is resistant only to tetracycline. Additional biochemical results are as follows: Phenylalanine deaminase (PDA): negative Urease: negative Hydrogen sulfide (H2S): negative Lysine decarboxylase: negative Ornithine decarboxylase: positive Indole: positive Citrate: negative Motility negative The most probable identity of this organism is: A. Escherichia coli B. Enterobacter cloacae C. Edwardsiella tarda D. Proteus vulgaris
A
Which group of tests is positive for both Morganella morganii and Proteus spp., common pathogens in wounds? A. Motility, urea, and phenylalanine deaminase B. H2S, glucose fermentation, and Urea C. Oxidase, MR and VP D. Indole, citrate, and urea
A
Which of the following is used in the rapid, noncultural Whiff test performed when Gardnerella vaginalis is suspected in a patient with vaginosis? A. 10% KOH test B. 3% H2O2 test C. 30% H2O2 test D. All of the above
A
Which of the following pairs of organisms would give you the expected quality control reactions (positive and negative) for MacConkey agar and Simmon citrate agar? A. Escherichia coli and Salmonella enteritidis B. Escherichia coli and Morganella morganii C. Klebsiella pneumoniae and Escherichia coli D. Pseudomonas aeruginosa and Shigella boydii
A
Which test group best differentiates Acinetobacter baumanii from Pseudomonas aeruginosa? A. Oxidase, motility, 42C growth B. MacConkey growth, 37C growth, catalase C. Blood agar growth, oxidase, catalase D. Oxidase, TSI reaction, MacConkey growth
A
Bacillus cereus can best be differentiated from other Bacillus sp. by which tests? A. Lecithinase B. Oxidase C. Motility D. Beta hemolysis
A B cereus = lecthinase pos on egg yolk agar
An alpha-hemolytic organisms with a colony count of greater than 100,000 CFU/ml is isolated from a midstream clean-catch urine specimen. It gram stains as gpc. Biochemical testing results show that the isolate is bile esculin-positive and grows in the presence of 6.5% NaCl. What is the most probable identity of this isolate? What rapid test could have also been performed to confirm its ID? A. Enterococcus sp., PYR B. Streptococcus agalactiae, P disk susceptibility C. Group D streptococcus, PYR D. Viridans streptococcus group, P disk susceptibility
A Enterococcus is a pathogen in the urine and grows as a gamma or slightly alpha colony. It is Bile Esculin positive, grows in 6.5% NaCl and is PYR positive.
Which of the following organisms is sensitive to a disc of bacitracin with a concentration of 0.04 A. Group A streptococci B. Group B streptococci C. Group C streptococci D. Group D streptococci
A Group A Streptococci (S. pyogenes) is suceptible to 0.04u of bacitracin. Any zone = "S"
Klebsiella sp. and Enterobacter sp. are both responsible for Urinary Tract Infections (UTIs). The two organisms are very similar in biochemical reactions but may be differentiated on the basis of the characteristic listed below. Which of the following statements is true? A. Klebsiella is nonmotile, Enterobacter is motile B. Klebsiella is motile, Enterobacter is nonmotile C. Klebsiella is a non-lactose fermenter, Enterobacter is a lactose fermenter D. Klebsiella is phenylalanine deaminase negative, Enterobacter is phenylalanine deaminase positive
A Kleb= motility neg Enterobacter= motility pos
An organism isolated from a vaginal swab is oxidase-positive, catalase positive and on Gram stain appears to be a gram-negative coccobacillus. The organism does not ferment glucose. What organism might this be? A. Moraxella osloensis B. Neisseria gonorrhoeae C. Neisseria meningitidis D. Pseudomonas aeruginosa
A Moraxella osloensis is a genital tract commensal which may be misidentified as Neisseria gonorrhoeae. It is, unlike N. gonorrhoeae, glucose negative.
A bloody stool from a 26 year old female after 3 days of severe diarrhea showed the following results at 48 hours: MacConkey agar - few lactose fermenting normal flora with moderate non-lactose fermenting colonies Hektoen enteric agar - few yellow colonies, moderate blue-green colonies Campylobacter blood agar and Clostridium difficile agar - no growth Clear colonies taken from MacConkey agar and blue-green colonies from Hektoen agar tested negative for oxidase, indole, urea, motility and H2S but tested positive for ONPG and Ornithine What is the most likely identification of this isolate? A. Shigella sonnei B. Salmonella typhi C. Proteus vulgaris D. Escherichia coli
A S. sonnei is a non-motile enteric pathogen. It gives negative reactions for everything except ONPG (test for late lactose fermentation) and Ornithine. It is only 1 of 3 non-motile enterics: Shigella sp, Klebsiella sp. and Yersinia sp.
A gnr from a stool culture grew as a medium, gray colony on blood agar and as a non-lactose fermenter on MacConkey Agar. The organism was PDA negative, H2S negative, VP negative and non-motile. It was also ornithine +, Urea negative, and ONPG+. This isolate was determined to be the causative agent of an outbreak of gastrointestinal disease in the community. What organism and which situation below would most likely be associated with this outbreak? A. Shigella sonnei direct contact or unchlorinated water B. Salmonella spp. improperly cooked chicken eaten two to four hours after cooking C. Salmonella typhi ingestion of seafood that is cooked and recontaminated D. Shigella spp. ingestion of swimming pool water
A- Of the 4 Shigella spp. it is the most reactive being ornithine and ONPG + which Shigella A,B and C give negative reactions for ornithine and ONPG.
A non-fermenting gram negative rod recovered from an eye wound is oxidase positive, motile with polar monotrichous flagella, and fails to grow at 42C. Colonies on blood agar are dry, wrinkled, smooth, and buff to light brown in color. On MacConkey agar, the organism is a NLF. The LAO is =/=/=. OF/O + and OF/F neg. It is Motile and Nitrate negative. What is the ID of this organism? A. Pseudomonas stutzeri B. Pseudomonas fluorescens C. Pseudomonas alcaligenes D. Brevundimonas diminuta
A- Pseudomonas stutzeri grows as a dry wrinkled, tan to brown colony. A key characteristic is that it has a =/=/= LAO. Most Pseudomonads have a =/+/= LAO
A sputum specimen grows out a mucoid organism that is a lactose fermener (LF) on MacConkey Agar. The organism is Voges-Proskauer (VP) + and non-motile. What end product of glucose fermentation does the test detect and what organism genus are you most likely dealing with? A. Acetoin; Klebsiella sp. B. Nitrite, Serratia sp. C. Acetic Acid, Enterobacter sp. D. Hydrogen sulfide, Klebsiella sp
A- The end product of the VP test is Acetoin. There are 3 Enterobacteriacae that are VP +: Klebsiella (non-motile) Enterobacter (motile lactose fermenter on MAC) and Serratia (motile non-lactose fermenter on MAC that produces a red or red-orange pigment; is ONPG+)
On a sheep blood agar plate, Haemophilus influenzae from a respiratory culture satellites around colonies of 1. non-pathogenic Neisseria species 2. Staphylococcus epidermidis 3. Staphylococcus aureus 4. Escherichia coli A. 1 and 3 are correct B. 2 and 4 are correct C. 4 only is correct D. All are correct
A- Haemophilus influenzae will not grow on Blood Agar unless it is in the proximity of another organism that can provide the X and V factor. It satellites around: 1. Staphylococcus aureus: the beta zone of S. aureus provides the hemin (X) factor from hemolysis and the S. aureus provides the NAD (V) factor. This is the most clear cut case of satellitium between H. influenzae and another organism. 2. Some species of non-pathogenic Neisseria spp. can provide X and V factors
What is the purpose of adding 0.025 - 0.050% sodium polyanethol sulfonate (SPS) to nutrient broth media for the collection of blood cultures? A. Inhibits phagocytosis, coagulation, and complement B. Promotes formation of a blood clot C. Enhances growth of anaerobes D. Functions as a preservative
A- SPS is added to broth in blood culture bottles to prevent complement activation, coagulation and phagocytosis
A beta-hemolytic gpc isolated from the blood of a newborn gives the following results: Catalase negative Bacitracin: resistant CAMP reaction: positive Sodium hippurate: positive Bile esculin: negative 6.5% sodium chloride: negative The organism can be identified as: A. Streptococcus agalactiae B. Streptococcus durans C. Streptococcus equinus D. Streptococcus pyogenes
A- The organism is Streptococcus agalactiae Catalase neg CAMP test + Sodium hippurate + Group B Strep infections contracted from the mother during birth can cause sepsis and meningitis innewborns.
Situation: Source of specimen - sputum culture 1. Hemolysis: alpha hemolytic 2. Colonial morphology: small grayish-white colonies on 5% sheep BAP 3. Gram stain: gram positive cocci 4. Catalase: negative 5. BAP with bacitracin disc: resistant 6. BAP with optochin disc: resistant 7. Bile esculin test: negative 8. Growth in 6.5% NaCl: negative Choose the best presumptive ID below: A. The organism belongs to the viridans streptococci B. The organism is a member of the group D streptococci C. Correct identification of the organism requires further tests D. The organism is a member of the family Micrococcaceae
A- Viridans strep are fairly non-reactive organisms
All species of the genus Neisseria have the capacity to oxidize: A. tetramethyl-p-phenylenediaminedihydrochloride B. glucose C. poly-B-hydroxybuteric acid D. para-dimethylaminobenzaldehyde
A- also known as oxidase
Cerebrospinal fluid (CSF) should be cultured immediately, but if delayed the specimen should be: 1. Stored at room temperature for no longer than 24 hours 2. Refrigerated at 4-6oC 3. Incubated at 37oC and cultured as soon as possible 4. Frozen at -20oC A. 1 and 3 are correct B. 2 and 4 are correct C. 1,2, and 3 are correct D. 4 only is correct
A-Because CSF can contain fastidious organisms such as Haemophilus influenzae or Neisseria meningitidis, the best way to store a sample that cannot be plated is in a 35-37oC incubator or at room temperature. Never refrigerate or freeze CSF. This will kill fastidious organisms. It is always best to plan ahead and process CSF samples immediately for microbiology.
A sputum sample from a patient with pneumonia gave the following direct gram stain results. >25 polys <10 epis A/alpha gpc in pairs and chains M/gpdc F/gamma gpc in chains F/gpr Culture plating produced many colonies of a gram-negative diplococci on both blood agar and chocolate plates and no growth on MacConkey agar. Catalase: positive Oxidase: positive DNAse: positive Tributyrin hydrolysis: positive Glucose: negative Sucrose: negative Lactose: negative Maltose: negative Fructose: negative Lactose: negative Is the sample acceptable? Given the results below, what is the mostly likely identification of this isolate? A. Acceptable collection, Moraxella catarrhalis B. Acceptable collection, Neisseria flavescens C. Recollect, Neisseria sicca D. Recollect, Neisseria meningitidis
A. Moraxella cattharalis does not utilize carbohydrates
A 20 year old man with urethritis who had been treated with penicillin returns to the outpatient clinic the following week. A possible cause of his symptoms is Chlamydia trachomatis. A urethral specimen is collected two hours after the patient voids. How can this infection be confirmed by the laboratory? A. Inoculate the specimen onto selective media B. Confirm by DNA/RNA Probe C. Perform a direct Gram stain for gram-negative rods D. ID the organism on the Maldi-tof
B
A burn patient grows out a gram negative rod that grows on Blood Agar and on MacConkey agar as a non-lactose fermenter. Which genera are positive for phenylalanine deaminase? A. Enterobacter, Escherichia, and Salmonella B. Morganella, Providencia, and Proteus C. Klebsiella and Enterobacter D. Proteus, Escherichia, and Shigella
B
A leg wound culture from a hospitalized 70 year old diabetic male grew motile, non-lactose fermenting colonies on MacConkey agar. H2S: negative Indole: negative methyl red: negative VP: positive PDA: negative DNAse: positive Citrate: positive Urea: negative Gelatin: positive ONPG positive Ornithine and lysine decarboxylase: positive Arginine decarboxylase: negative Given these following biochemical reactions at 24 hours, what is the most probable organism and what else would you most likely see on culture plates? A. Escherichia coli, beta hemolysis on blood agar B. Serratia marcescens; red or orange picment C. Proteus mirabilis; swarming on blood agar D. Enterobacter cloacae, A/A on KIA slant
B
A lumbar puncture is performed on an 82 year old woman who is receiving immunosuppressive therapy. The direct Gram stain of the CSF reveals small gram-positive rods and numerous white blood cells. At 18 hours, a small translucent colony type grows on sheep blood agar with a narrow zone of beta hemolysis. Identification of this isolate could be made by demonstration of: 1. Tumbling motility 2. Metachromatic granulation 3. Bile esculin hydrolysis 4. Capsule formation A. 1, 2 and 3 are correct B. 1 and 3 are correct C. 4 only is correct D. All are correct
B
A non-lactose fermenting gnr was isolated from a stool culture and run for ID on the Maldi-tof. An indeterment ID was the result Which of the following biochemical tests can best differentiate Shigella species from a non-lactose fermenting 2Escherichia coli? A. H2S, Motility, Citrate B. Motility, Lysine, Indole C. MR, VP, Lysine D. Urea, Ornithine, ONPG
B
A presumptive group B streptococcus is tested for the CAMP reaction. The isolate in question is streaked perpendicular to, but not touching, a streak of beta-lysin producing Staphylococcus aureus. The test should be incubated: Anaerobically in ambient air in a candle jar or with 5% CO2 A. 3 only B. 2 only C. 2 and 3 D. 1, 2 or 3
B
A rapid presumptive diagnosis of Gardnerella vaginalis from vaginal secretions is usually made using which of the following findings? Oxidase and catalase tests Wet prep/gram stain showing pleomorphic bacilli heavily colonized on vaginal epithelium Hippurate hydrolysis test Whiff test A. If 1 and 3 are correct B. If 2 and 4 are correct C. If only 4 is correct D. If none are correct
B
A gram positive branching filamentous organism recovered from a sputum specimen was found to be positive with a modified acid-fast stain method. What is the most likely presumptive identification of tis organism? A. Bacillus spp. B. Nocardia spp C. Corynebacterium spp. D. Listeria spp.
B- The filamentous branching gram positive rods include: Streptomyces - aerobic -usually non-pathogenic Actinomyces - anaerobic Nocardia - aerobic The aerobic gpbranching rod that is pathogenic is Nocardia sp.
A stool culture from an adult appears to have two lactose-negative colony types on Hektoen (HE) and Xylose-lysine-deoxycholate (XLD) agars. One colony type retains the original color of each medium and the other has black centers. Stool screen data are as follows: Medium Isolate 1 Isolate 2 Triple sugar iron (TSI): AK/A, no gas, H2S negative A/A, gas, H2S positive Lysine iron agar (LIA): Lysine - neg, H2S - neg Red slant,lysine-neg,H2S-pos Urease: Negative Positive Motility: Negative Positive Indole Negative Positive Ornithine: Negative Negative Based on these data and additional biochemical testing, what is the identification of each isolate and what are important next steps: A. #1 Shigella, #2 Edwardsiella, Set up Susceptibility testing on both isolates B. #1 Shigella; ID species by serotyping, #2 Proteus vulgaris; no follow-up C. #1 Yersinia enterocolitica, perform cold enrichment #2 Proteus vulgaris; no follow-up Set up Salmonella agglutinations D. Report the culture as negative for enteric pathogens
B
A urine culture on a 22 year old female grows out >100,000 CFU/ml of a small white colony. The organism is catalase + and coagulase negative. What is the most likely ID of this organism? What additional test can help identify this isolate.? A. Staphylococcus epidermidis, "S" to 5 ug of lysostaphin B. Stahylococcus saprophytics, "R" to 5 ug of novobiocin C. Streptococcus agalactiae, "R" to 10 units of penicillin D. Streptococcus pyogenes, "S" to 0.04 units of bacitracin
B
After 24 hours of incubation, a dialysate fluid culture is growing grayish-white, nonhemolytic colonies on sheep blood agar and flat, clear colonies on MacConkey that looked purple-ish pink at 48 hours. The gram stain revealed a gncb. The organism is oxidase-negative. The organism was LAO =/=/= and non-motile. It used glucose, lactose and xylose oxidatively. The organism isolated is most likely to be identified as: A. Aeromonas hydrophila B. Acinetobacter baumanii C. Elizabethkingae menigoseptica D. Pseudomonas aeruginosa
B
An isolate of Klebsiella pneumoniae is known to produce carbapenemase. Which antibiotics will it not reepond to therapeutically? A. colistin and rifampin B. amoxicillin, cefazolin, and imipnem C. sulfamethoxazole and trimethoprim-sulfamethoxazole D. tetracycline and doxycycline
B
In a broth dilution of an organism, the lowest concentration of an antibiotic in which no growth of the organism is visually detectable is called the A. minimum bactericidal concentration B. minimum inhibitory concentration C. minimum susceptible concentration D. minimum lethal concentration
B
Purulent material is obtained from a carbuncle and submitted for bacterial culture. The direct smear reveals moderate gram-positive cocci and abundant polymorphonuclear leukocytes. The culture shows growth in the primary thio broth in the top of the tube, on the sheep blood agar and no growth on the MacConkey agar plate. The colonies on the blood agar plate are butyrous, white and beta-hemolytic and were catalase positive. Both glucose and mannitol are fermented. Although the slide coagulase test is negative, the tube coagulase test is positive. The most probable identity of this isolate is: A. Micrococcus lysodeikticus B. Staphylococcus aureus C. Staphylococcus epidermidis D. Staphylococcus saprophyticus
B
Select the media of choice for recovery of Vibrio cholerae from a stool specimen. A. MacConkey agar and thioglycolate broth B. Alkaline peptone water (APW) broth and Thiosulfate-citrate-bile-sucrose (TCBS) agar C. Blood agar and selenite-F broth D. CNA and trypticase soy broth (TSB)
B
The ortho-nitrophenyl b-galactopyronoside (ONPG) test is most useful when differentiating: A.Salmonella spp. from Pseudomonas spp. B. Shigella spp. from some strains of E. coli C. Klebsiella spp. from Enterobacter spp. D. Proteus vulgaris from Salmonella spp.
B
To check for positive and negative reactions for the following tests, select the appropriate set of quality control microorganisms for the test assays indicated: Bile esculin hydrolysis 6.5% sodium chloride growth tolerance Bacitracin susceptibility Sodium Hippurate hydrolysis A. Streptococcus pyogenes, viridans streptococcus, Enterococcus sp. B. Streptococcus pyogenes, Streptococcus agalactiae, Enterococcus sp. C. Staphylococcus aureus, Streptococcus pyogenes, Enterococcus sp. D. Streptococcus agalactiae, viridans streptococcus, Enterococcus
B
A tiny gram-negative rod is isolated from a gingival abscess. The catalase negative, oxidase positive organism is a facultative anaerobe that pits the surface of sheep blood and chocolate agars but does not grow on MacConkey agar. The organism gives off the odor of hypochlorite bleach when plates are opened. The most probable identity of this organism is: A. Acinetobacter baumanii B. Eikenella corrodens C. Elizabethkingae menigosepticum D. Haemophilus influenzae
B "fight and bite" wounds. Its most distinguishing characteristics are 1) colony morphology which at 48 hrs is dry and show pitting of the agar and 2) the bleach smell given off by cultures of Eikinella. the organism is catalase negative and oxidase positive, LAO +/=/+ and does not ferment/oxidize sugars.
A physician inquires about repeated sputum specimens, negative on routine bacterial culture, that are reported to contain only normal oropharyngeal flora. The patient is a 67 year old man who smokes 15 to 20 cigarettes a day and has persistent cough, malaise, and a fever of 102 to 105 C. Treatment with routine antimicrobials such as penicillin and cephalothin has not been effective; the cough and fever persist. The most recent direct Gram stain of sputum shows 3+ PMNs, mucus present, and rare epithelial cells. A possible etiologic agent is: A. Haemophilis influenzae B. Legionella pneumophila C. Pseudomonas aeruginosa D. Streptococcus pneumoniae
B- Legionella pneumophila is a respiratory infection seen in older males who are smokers. It does not grow on routine media and requires BYCE (buffered yeast cystine extract) to grow.
A child presents with a typical paroxysmal "whoop" type cough and lymphocytosis. The specimen of choice and most appropriate primary culture medium to isolate the suspected etiologic agent are: A. Nasopharyngeal, chocolate agar B. Nasopharyngeal, Regan-Lowe Agar C. Throat, chocolate agar D. Throat, Bordet-Gengou agar
B- Whooping cough is caused by Bordetella pertussis which is best collected from the nasopharynx as a nasopharyngeal swab or aspirate. There are two special media on which Bordetella grows: 1. Bordet-Gengou agar 2. Regan-Lowe Agar
Two siblings arrive at the emergency room. Both had antecedent sore throats about 2 to 3 weeks earlier that grew beta-hemolytic streptococci; now they present with different clinical symptoms. The brother displays edema and hypertension, and red blood cell casts are seen in the urine. The sister complains of fever and joint pains and has rapid heart beat. The diseases that these siblings have and the causative organism is: A. Erysipelas and glomerulonephritis from Erysipelothrix B. Glomerulonephritis and rheumatic fever from Group A streptococcus C. Rheumatic fever and scarlet fever from Group A streptococcus D. Scarlet fever and erysipelas from Erysipelothrix
B- This case present the typical sequelae post group A Streptococcus (S. pyogenes infection). Rheumatic fever and glomerulonephritis.
A gram-negative coccobacillary organism that is isolated from synovial fluid on chocolate agar resembles either a Moraxella sp or Neisseria gonorrhoeae. The single best test to distinguish between these organisms is: A. Beta hemolysis B. Glucose degradation C. Motility D. Oxidase production
B- Neisseria gonorrhoeae is glucose + and Moraxella sp. is glucose negative
Pre-reduced and vitamin K1 supplemented Brucella blood agar plates are recommended isolation media for: A. Mycobacterium marinum and Mycobacterium avium-intercellulare B. Bacteroides spp., Peptostreptococcus, and Clostridium spp. C. Proteus spp. D. Enterococcus spp
B-Pre-reduced and vitamin K1 supplemented Brucella blood agar plate are used for the isolation of Anaerobes. The addition of hemin and Vitamin K1 to this agar supports the growthof fastidious bacteria such as Bacteroides species and gram-positive spore bearers like Clostridium sp. Peptostreptococcus also grows on this media.
A 4 year year old male, with a history of playing in sandbox in a feral cat area, has a urine specimen submitted for a direct dark-field examination. No organisms are seen in the specimen. Which medium should be inoculated in an attempt to isolate the suspected organism? A. Blood cystine dextrose agar B. PPLO agar C. Fletcher's semisolid media D. Chopped meat glucose media
C
A 47 year old male with open sores was seen in the out-patient clinic. A gram stain of the material from the sores revealed gram-positive cocci in clusters and many poly-morphonuclear cells. Which of the following media is most appropriate for the isolation of the etiologic agent? A. MacConkey agar B. Chocolate agar C. 5% Sheep blood agar D. Thayer-Martin agar
C
A gram-negative rod biochemically compatible with the genus Salmonella fails to agglutinate in the polyvalent somatic antisera for Salmonella serotyping. What is the next step in the definitive identification of this organism? A. Report the organism as a nontypeable Salmonella species and send the isolate elsewhere for additional identification. B. Wash a suspension of the isolate in saline and retest it in the Salmonella polyvalent antiserum C. Boil a saline suspension of the organism for 15 minutes, cool and retype in Salmonella polyvalent antiserum D. Retest the isolate using the individual somatic antisera from each serogroup, A through E
C
A gram-positive coccus recovered from a leg ulcer from a 31 year old diabetic patient showed pale yellow, creamy, beta-hemolytic colonies on blood agar. The gram stain showed gpc in clusters. Given the following test results, what is the most likely identification? Catalase: positive Glucose OF: positive/open tube negative/sealed tube Mannitol salt: No growth Slide coagulase: negative A. Staphylococcus aureus B. Staphylococcus epidermidis C. Micrococcus spp. D. Streptococcus spp.
C
Aeromonas hydrophila found in a blood culture may be differentiated from a hemolytic, slow lactose-fermenting Escherichia coli by which of the following biochemical tests? A. Glucose fermentation B. Indole C. Oxidase D. Urease
C
After debridement, a wound culture was obtained from a 15 year old female burn patient which grew on blood agar as a silvery colony and on MacConkey as a NLF. The following results were obtained. Oxidase: positive Catalase: positive Motility: positive Lysine decarboxylase: negative Glucose: positive for oxidation Ornithine decarboxylase: negative Maltose: negative for oxidation Arginine dihydrolase: positive Penicillin: resistant Aminoglycosides: susceptible Colistin: susceptible These results indicate which of the following organisms and what is another characteristic of the organism? A. Acinetobacter baumanni, oxidase positive B. Moraxella lacunata, gncb C. Pseudomonas aeruginosa, grows at 42C D. Acinetobacter lwoffi, oxidase negaive
C
An early morning clean-catch midstream urine specimen yields these results on urinalysis: Appearance: yellow, cloudy Protein: 1+ Specific Gravity: 1.025 Blood: negative pH: 8.0 Ketones: negative Glucose: negative Bilirubin: negative Nitrite: positive Leukocyte esterase: positive Microscopic: No casts, 15 to 25 WBC/HPF, many bacterial present The results of this urinalysis indicate that: A. The bacteria present are the result of collection into a non-sterile container and correlate with a probable original count of <104 CFU/ml B. The bacteria present are the result of a delay of several hours in processing the urine specimen and correlate with a probable original count of <104 CFU/ml C. Significant urinary tract infection that correlates with a probable original count of >105 CFU/ml. D. Nephrotic syndrome should be considered, and the bacteria are merely coincidental.
C
Culture of a finger wound specimen from a meat packer produced short gram-positive rods with a slightly alpha to no hemolysis on blood agar. The organism did not grow on MacConkey agar. Given the following test results at 48 hours growth, what is the most likely identification of this isolate? Catalase: negative H2S (TSI): positive Motility: motile Gelatin media: negative hydrolysis (with bottle brush growth in stab culture) A. Bacillus cereus B. Listeria monocytogenes C. Erysipelothrix rhusiopathiae D. Bacillus subtilis
C
In interpreting a minimal inhibitory concentration (MIC) by the macro broth dilution method, you determine that the tube that shows visible turbidity has a final dilution factor of 1:32. Since two fold serial dilutions are made from the working stock of 0.256 mg/dl, with tube 1 containing a 1:2 dilution the MIC for this isolate is: A. 4 ug/dl B. 8 ug/dl C. 16 ug/dl D. 32 ug/dl
C
Mycoplasma differ from bacteria in that mycoplasma: A. do not cause disease in humans B. cannot grow in artificial media C. lack cell walls D. are serologically antigenic
C
Susceptibility testing is performed on a Staphylococcus aurues isolate from a blood culture Results were as follows: Antibiotic Interpretation oxicillin resistant cefazolin susceptible clindamycin susceptible erythromycin susceptible trimehoprim/sufametoxazole susceptible What is your next course of action? A. ceftiaxone should be reported instead of cefazolin B. clindamycin should be tested for inducible resistance prior to reporting C. the cefazolin result should be changed to resistant since the oxacillin result is resistant D. the trimethoprim/sulfamethoxazole result should be removed since all S. aureus are resistant
C
The beta-galactosidase test is used in the identification of which Neisseria species? A. Neisseria gonorrhoeae B. Neisseria meningitidis C. Neisseria lactamica D. Neisseria flavescens
C
A direct smear on an endocervical specimen revealed intracellular gram-negative kidney-bean shaped diplococci. The specimen was inoculated onto a modified Thayer-Martin agar plate and, after 24 hours incubation under CO2, grayish-white, translucent, glistening colonies resembling gonococci were observed. The MLS sub-cultured the colony to chocolate agar. Growth from the chocolate agar was used to perform cysteine tellurite agar (CTA) carbohydrate utilization tests with glucose, maltose, sucrose, lactose and fructose. After 24 hours incubation the MLS was surprised to see that both glucose and maltose had been degraded. What is the best next step? A. Report the organism as Neisseria meningitidis B. Report the organism as Neisseria gonorrhoeae C. Check the purity of the organism on the maltose by subbing to CA and then re-testing the suspected gonococcal culture with glucose and maltose. D. Perform a rapid fermentation test using these same carbohydrates.
C Since Neisseria gonorrhoeae is glucose + but maltose negative and N. meningitidis would not be expected in this site, the best thing to do would be to check the purity of the culture. G.C. is best identified by a vaginal swab using PCR probe methods since the purity of the collection is not an issue.
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 - Corynebacterium diphtheriae can be collected with a thin swab which is threaded through the nose to the nasopharynx.
A stool culture grows out a gn curved rod. The organism grows as a beta hemolytic colony on blood agar and as a non-lactose fermenter on MacConkey agar. The colonies grew as clear green colonies on Thiosulfate - Citrate-Bile salts -Sucrose (TCBS agar) Triple sugar iron (TSI) alk/acid Catalase: positive H2S: negative Nitrate: positive Oxidase: positive Lysine: positive Inositol: negative Salicin: negative LAO +/=/+ Virbio Static Agent: "S" Grows in 3-8% NaCl The most probable presumptive identification of this isolate is: A. Aeromonas hydrophila B. Vibrio cholerae C.Vibrio parahaemolyticus D. Yersinia enterocolitica
C- Vibrio parahaemolyticus is an oxidase+ catalase + curved gnr which does not utilize sucrose (a characteristic that differentiates it from V. cholerae.
A dairy farmer who has an intermittent fever, progressive weakness, and night sweats is suspected of having undulant fever. Blood and bone marrow samples were taken for culture. A slow growing gncb demonstrating bipolar staining grew on enriched blood based media. The etiologic agent is catalase and oxidase positive and non-motile and requires an atmosphere of 10% CO2 to grow and also demonstrates urease-positivity in 1 to 2 hours . What is the ID of this organism? A. Bacillus anthracis B. Bacillus cereus C. Brucella abortus D. Brucella melitensis
C- Colonies are small, convex, smooth, translucent, gamma hemolytic and slightly yellow and opalescent after 48 hours of incubation. the organism grows well in commercial blood culture bottles and can usually be detected within 5 to 7 days in these systems. Brucella abortus is a rapid urease producer and H2S + it is inhibited by the dye thionine.
An 8 year old female patient complains of a very sore throat. The throat swab that was submitted for a throat culture workup and grows F/Diphtheroids; M/alpha- beta-, and nonhemolytic Streptococci; F/Staphylococci, and M/yellow, dry Neisseria. The next step is to: A. Report it as normal throat flora B. Ask for a repeat collection to get a better specimen C. Identify the beta hemolytic streptococcus species D. Identify the Neisseria species
C- In a throat culture the beta Streptococci must be worked up as a potential pathogen.
Physical examination of a 20-year old male seen in the emergency room reveals nuchal rigidity and a temperature of 102oF. Direct gram stain of the cerebrospinal fluid revealed numerous polymorphonuclear leukocytes and a few gram-negative diplococci some intracellular. The isolate grew on sheep blood agar and chocolate agar but not on MacConkey agar and is oxidase-positive. Acid production occurs in the cysteine trypticase agar (CTA) carbohydrates as follows: Glucose: acid production Lactose: no change Maltose: acid production Sucrose: no change The most appropriate action to take is: A. Identify the organism as Neiserria lactamica and report B. Identify the organism as Moraxella and set up additional tests to determine the species C. Identify the organism as Neisseria meningitidis and report D. Perform an antimicrobial susceptibility test as a confirmation of the identification.
C- N. meningitidis is glucose and maltose positive
A businessman who was working in Vietnam develops a bronchial pneumoniae three weeks after returning home. Sputum cultures yielded growth of a gram negative rod which grew as a dry, wrinkled colony on blood agar and on MacConkey. AT 24 hours, the organism was a NLF on MacConkey but showed pink pigment on the MacConkey plate at 48 hours. The organism was OF/F neg and OF/O pos, and oxidase +. The LAO of the organism was =/+/= and it grew at 42oC as well as at 37oC. The most probable organism is: A. Brucella abortus B. Pasteurella multocida C. Burkholderia pseudomallei D. Vibrio cholerae
C-wrinkled colony characteristic
A Moeller ornithine decarboxylase test was performed on an isolate suspected of being Proteus. The MLS believes the organism is Proteus mirabilis rather than Proteus vulgaris. After 24 hours incubation the test tube appeared bright yellow. The control was purple. Which of the following conclusions can be made about these results? A. The organism is ODC positive and is, therefore, Proteus mirabilis B. The organism is ODC negative and is, therefore, probably Proteus mirabilis C. The organism is ODC negative and is, therefore, Proteus vulgaris D. Results are inconclusive and should be repeated
D
A patient entered the emergency room with a high fever, lung congestion and a productive cough. Suspecting pneumonia, the attending physician requested a sputum culture. Twenty-four hours later a predominant growth of an alpha hemolytic transparent, mucoid, glistening colonies grew which stained as gram-positive lancet shaped diplococci from blood agar. A bile solubility test was performed but there was no lysis of the organisms. What is the BEST next step in identifying this organism? A. repeat the optochin susceptibility test B. report the organism as an alpha-streptococcus, not S. pneumoniae C. perform a Neufeld quelling test D. set the isolate up with an optochin disk
D
A pustule drainage submitted for culture is plated onto primary media. After an 18 hour incubation, the sheep blood agar plate reveals a predominance of beta-hemolytic, white porcelain-like colonies. Gram stain shows gram-positive cocci that are catalase-positive. The most appropriate test for additional identification of the isolate is: A. Bacitracin B. Bile esculin C. Bile solubility D. Coagulase
D
Cold enrichment of feces (incubation at 4 C in phosphate-buffered saline prior to subculture onto enteric media enhances the recovery of: A. Enterotoxigenic E. coli B. Salmonella paratyphi A C. Vibrio parahemolyticus D. Yersinia enterocolitica
D
Culture of MTM medium of a vaginal swab produced several colonies of gram-negative diplococci that were catalase and oxidase positive and superoxol negative. Glucose: positive Sucrose: positive Lactose: negative Maltose: positive Given the carbohydrate reactions, select the most likely identification of the gndc and state if it is pathogenic or normal flora. A. Neisseria gonorrhoeae, pathogen B. Neisseria lactamica, pathogen C. Neisseria flavescens, normal flora D. Neisseria sicca, normal flora
D
Urine cultured from the catheter of an 18 year old female patient produced >100,000 col/ml on a colistin-naldixic acid (CNA) plate. Colonies were catalase positive, coagulase negative by the latex agglutination slide method. The best single test for identification is: A. Lactose fermentation B. Urease C. Tube coagulase D. Novobiocin susceptibility
D
Which of the following organism pairs will give the appropriate positive and negative reactions for quality control testing of the test listed? A. Gram stain: Escherichia coli, Neisseria meningitidis B. Indole: Escherichia coli, Proteus vulgaris C. Nitrate reduction: Escherichia coli, Pseudomonas aeruginosa D. Oxidase: Pseudomonas aeruginosa, Escherichia coli
D
A female patient is suspected of having a Neisseria gonorrhoeae infection. The medium of choice for cultivation of this organism from a genial culture is: A. media containing sterol and yeast extract B. blood agar C. MacConkey agar D. Thayer-Martin agar
D Thayer Martin agar is a good medium for isolation of Neisseria gonorrhoeae because it contains antibiotics that suppress normal flora especially flora from the female genial tract.
To establish a definitive diagnosis of diphtheria, what type of samples would be collected 1. nasopharyngeal swab 2. sample of the pseudomembrane 3. swab of cutaneous lesion 4. bronchial aspirate What must be confirmed in the identification process? A. 1 and 3, catalase reaction B. 2 and 4, growth on tellurite media C. 4 only, v shapes on gram stain D. 1,2, and 3, Toxin production
D- Corynebacterium diphtheriae is virulent because of the toxin it produces. Only toxin producing stains of C. diphtheriae cause diphtheria. Diphtheria can be respirator or cutaneous and, therefore, specimens that may be collected include nasopharyngeal swabs, throats swabs, samples of the pseudomembrane and cutaneous samples. Definitive identification of a C. diphtheriae isolate as a true pathogen requires toxin production by the isolate in question.
To eliminate the antibacterial properties of blood and simultaneously introduce an adequate volume of blood for recovery of microorganisms from septicemia, the recommended broth-to-blood ratio in a blood culture bottle is approximately A. 1:2 B. 2:1 C. 1:10 D. 10:1
D- Blood contains natural inhibitors of bacterial growth including complement, lysozyme and WBCs. In addition, although blood cultures should be collected before antimicrobial treatment is started, sometimes cultures are drawn after antimicrobials are started. The optimal ratio of broth to blood is 5:1 to 10:1. The dilution aids in negating the bacericidal effects of normal serum. 0.025% to 0.050% SPS can also be added to the bottle and serves to inhibit complement, coagulation and phagocytosis.
A tracheal aspirate yields a pure culture of an alpha-hemolytic gram positive coccus that is catalase-negative. Select the best test to perform in the subsequent identification process, the most likely organism if this test is positive, and the result for the test you would expect. A. CAMP test, Streptococcus agalactiae, arrow head formation B. Coagulase, Staphylococcus aureua, positive C. Susceptibility to bacitracin, Streptococcus pyogenes, 18mm or greater D. Susceptibility to ethylhydrocupreine-hydrochloride, Streptococcus pneumoniae, 14 mm or greater
D- Ethylhydrocupreine-hydrochloride=optochin
A bronchia lavage grows out a mucoid gram negative rod that is a lactose fermenter on MacConkey agar. The organism is set up to an ID panel. The MLS believes the isolate is a Klebsiella which is a common pathogen in the respirator tract. Which single test best separates Klebsiella oxytoca from Klebsiella pneumoniae and what is the principle of the test? NH4 A. Urease, conversion of urea to NH4 B. Sucrose, Fermentation causing a pH change C. Citrate, color change in presence of high pH D. Indole; deamination of tryptophan
D- Kleb pneumo= indole neg(=/=/= MIO) Kleb oxy-indole positive(=/+/= MIO)
Which of the following organisms is the cause of Lyme disease? A. Treponema pallidum B. Neisseria meningitidis C. Babesia microti D. Borrelia burgdorferi
D- Lyme disease is caused by the bacterium Borrelia burgdorferi and rarely, Borrelia mayonii. It is transmitted to humans through the bite of infected blacklegged ticks. Typical symptoms include fever, headache, fatigue, and a characteristic skin rash called erythema migrans. It is diagnosed by serological testing or PCR.
Neisseria meningitidis can be differentiated from Neisseria gonorrhoeae by demonstration of acid production from what carbohydrate? What are the optimum incubation conditions for these two organism? A. 37C aerobically, sucrose B. 42C, under increased CO2, lactose C. 35C under increased CO2, glucose D. 35C, under increased CO2, maltose
D-Neisseria meningitidis and Neisseria gonorrhoeae grow best on Chocolate or Thayer-Martin agar at 35C, under increased CO2 (at least 5%). N. gonorrhoeae is glucose + maltose neg N. meningitidis is glucose + maltose +