Lab CE ID methods

All of the following are true about all members of Enterobacteriaceae except: a. They are all gram negative b. They are all oxidase positive c. They are all bacilli d. They all ferment glucose

They are all oxidase positive Enterobactericeae = oxidase negative Plesiomonas is the only organism of the Enterobactericeae family that is oxidase positive. It is new to the family.

Urease reaction in Christensen's urea agar slant shows tube 1 (pink slant and butt) and tube 2 (pink slant, yellow butt) This shows: a. weak activity b. strong activity c. slant only inovulated d. use of outdated medium

Weak activity Weak activity = pink slants, i.e. Klebsiella Strong activity = pink slants and pink butts, i.e. Proteus

A positive oxidase reaction rules out which of the following "look-alike" bacteria that resemble N. gonorrhoeae? a. Moraxella catarrhalis b. Pastuerella multocida c. Acinetobacter baumanni d. Kingella kingae

Acinetobacter baumanni N. gonorrhoeae = oxidase positive Acinetobacter baumanni = oxidase negative Kingella kingae, Pastuerella multocida, Moraxella catarrhalis = oxidase positive

A clumping of bacterial cells on a negative slide coagulase test results from bacterial production of: a. Coagulase-reacting factor b. Free coagulase c. Bound coagulase d. Fibrinogen

Bound coagulase Slide coagulase test based on detection of bound coagulase/clumping factor produced on bacterial cell wall. This factor reacts with fibrinogen in plasma, producing fibrin strands that agglutinate.

This species must be handled in a Class II safety cabinet. It is: - Small gram negative coccobacilli - Strict aerobes - Grows on Sheep Blood agar, Chocolate agar - Nonmotile - Catalase, urease, nitrate positive - Mostly oxidase positive It is: a. Brucella b. Kingella c. Moraxella d. Acinetobacter

Brucella Brucella is a human pathogen causing brucellosis Kingella = normal flora of upper human respiratory tract = catalase & urease negative Moraxella is normal mucosal flora with low virulence Acinetobacter is nitrate negative

Of the following organisms, which is the least pathogenic to humans? a. Corynebacterium ulcerans b. Bacillus anthracis c. Listeria monocytogenes d. Nocardia brasiliensis

Corynebacterium ulcerans is considered a zoonosis and occurs with close animal contact. Bacillus anthracis (anthrax) & Listeria monocytogenes (neonatal infections) are obvious pathogenic organisms. Nocardia brasiliensis causes subcutaneous infections

Strept group G causes what problems? a. Endometritis in pregnant female b. Liver abscess c. Deep wound cellulitis d. Acute suppurative pharyngitis

Deep wound cellulitis Deep wound cellulitis = Group G Endometritis = Group B/S. agalactiae Liver abscess = Group F/S. milleri Acute suppurative pharyngitis = Group C/S. equi

India ink is used to visualize: a. Flagella b. Shape c. Capsule d. Cytoplasm

Capsule India Ink aids in visualization of polysaccharide yeast capsules like Cryptococcus neoformans

Which of the following microscopic techniques is best suited for direct exam of syphilis? a. light microscopy b. phase-contrast microscopy c. dark-field microscopy d. electron microscopy

Dark-field microscopy Syphilis = Treponema pallidum, a spirochete that cannot be cultured outside body Dark-field microscopy = spirochetes Phase-contrast microscopy = live organisms/unstained cells Electron microscopy = viruses

On MAC biplate, large, smooth colonies that are yellow/white on BAP, pink w/ bile salts on MAC. KIA shows acid/acid and positive indole. This organism is: a. E. coli b. Shigella sonnei c. Edwardsiella tarda d. Klebsiella pneumoniae

E. coli E. coli matches the colony appearances. On KIA, A/A reaction shows both glucose and lactose fermentation, matching E. coli. E. coli = only indole positive Enterobacteriaceae. Shigella sonnei = indole negative Edwardsiella tarda = non lactose fermenter, but ferments glucose. On MAC, shows clear colonies and on KIA shows K/A Klebsiella pneumonia = mucoid lactose fermenter, indole negative

Which of the following organisms is least likely to produce a capsule or slime layer? a. E. coli b. Klebsiella pneumoniae c. Streptococcus pneumoniae d. P. aeruginosa

E. coli K. pneumonia highly mucoid on agar, showing capsule. S. pneumoniae highly mucoid on agar, showing capsule P. aeruginosa is known to produce capsule/slime layer

Which of the following combos would show positive and negative controls? a. Beta hemolysis: E coli and Strept pyogenes b. Catalase: S. aureus and S. epidermidis c. Hydrogen sulfide: Proteus mirabilis and Salmonella typhi d. Indole: E. coli and Klebsiella pneumonia

E. coli is indole positive, K. pneumonia is indole negative Best control for beta hemolysis = S. aureus (positive) and S. pneumonia (negative) E. coli and Strept. pyogenes are variable beta hemolytic Best catalase control = Staph. aureus (positive) and Strept. Pyogenes (negative) S. epidermidis = catalase positive Best hydrogen sulfide control = P. mirabilis (positive) and E. coli (negative) S. typhi = hydrogen sulfide positive

Non-hemolytic organism isolated from blood culture shows yellow in 6.5% NaCl broth and darkening of slant in bile esculin agar. This isolate is: a. S. pneumonia b. Enterococcus spp. c. Strept. agalactiae d. Strept. bovis

Enterococcus spp. Enterococcus = 6.5% NaCl positive (yellow); bile esculin positive (dark slant) Strept. bovis = 6.5% NaCl negative, bile esculin positive Strept. pneumonia, Strept. agalactiae = Bile esculin negative

Set of tubes in Hugh and Leifson O/F basal medium with glucose and a pH indicator of bromthymol blue. Image of green tubes demonstrates a reaction of: a. Glucose-fermenter b. Glucose-oxidizer c. Glucose non-oxidizer d. Sucrose-fermenter

Glucose non-oxidizer Aka nonsaccharolytic. Green = no reaction, so no fermentation or oxidation of glucose. In OF medium, positive = yellow

All of the following are Brucella characteristics except: a. Oxidase negative b. Stain faintly as gram negative coccobacilli or short rods c. Urea positive d. Nonmotile

Oxidase negative Brucella = Oxidase positive Urea positive Nonmotile Faint stainer

Which is a nonfermenter? a. E. coli b. P. aeruginosa c. Yersinia enterocolitica d. Serratia marcescens

P. aeruginosa = nonfermenter Serratia marcescens, Yersinia enterocolitica, E. coli = fermenters, part of Enterobacteriaceae family

A nitrate test is performed on a glucose fermenter. When nitrate reagents were added, no color change occurs. When zinc dust was added, no color develops. How should test be reported? a. Positive for nitrite and negative for molecular nitrogen b. Negative for molecular nitrogen and negative for nitrate production c. Positive for molecular nitrogen and negative for nitrite production d. Negative for nitrate and negative for nitrite reduction

Positive for molecular nitrogen and negative for nitrite production Nitrate to nitrite result = negative and when zinc dust was added, no color developed, indicating molecular nitrogen must have been produced from nitrate

Which of the following choices can rule out Enterobacteriaceae? a. Beta hemolysis on blood agar b. Pink red colonies on MAC c. Positive oxidase reaction d. Positive esculin reaction

Positive oxidase reaction Enterobacteriaceae = oxidase negative Enterobacteriaceae = variable esculin reaction Enterobacteriaceae = variable lactose fermenters/pink on MAC Enterobacteriaceae = variable beta hemolytic

This test on all swarming Proteus species can differentiate Proteus mirabilis and Proteus vulgaris: a. catalase b. indole c. oxidase d. motility

Proteus mirabilis = indole negative Proteus vulgaris = indole positive All Proteus/Enterobacteriaceae = oxidase negative All Proteus = motile. Catalase is just to differentiate Staph. and Strept.

On chocolate agar, granular wrinkled, yellow-pigmented colonies after 48 hours of incubation from cystic fibrosis patient. On blood agar, flat, granular, slightly wrinkled colonies. On MAC, clear colonies and: - no pyocyanin production - Positive oxidase - Nitrate reducer This organism is: a. Pseudomonas stutzeri b. Burkholderia cepacia c. Elizabethkingia meningoseptica d. Acinetobacter baumannii

Pseudomonas stutzeri = positive oxidase, nitrate reducer, non-lactose fermenter, and non-pyocanin producer has clear MAC colonies (pyocanin producer would produce green colonies) Berkholderia cepacia = small, convex colonies with no wrinkles, not nitrate reducer Elizabethkingia meningoseptica = does not grow on MAC Acinetobacter baumannii = are white, smooth with no wrinkles on BAP and oxidase negative

Among the following nonfermenters, which can hydrolyze esculin? a. Paracoccus yeei b. Psychrobacter immobilis c. Shewanella putrifaciens d. Rhizobium radiobacter

Rhizobium radiobacter These are all non-lactose fermenters, but Rhizobium radiobacter is the only to hydrolyze esculin. It is linked to implanted medical devices.

Isolate is catalase negative, gram positive coccus on BAP. P disk has 5 micrograms of optochin and zone is 16 mm. Streaked perpendicular to beta-lysin producing strain of S. aureus w/ no arrow of hemolysis. Presumptive ID is: a. S. pneumoniae b. S. agalactiae c. S. pyogenes d. Viridans strept

S. pneumoniae Optochin differentiates S. pneumoniae from other strept. The streak = negative, so it can't be agalactiae which is CAMP positive

On MAC biplate, large gray colonies observed growing on blood agar. Smaller smooth convex colonies with deep red pigment on MAC. Red pigment doesn't extend into adjacent agar. Positive reaction growing on DNase agar. What is this? a. Proteus vulgaris b. Serratia marcescens c. Providencia stuartii d. Citrobacter koseri

Serratia marcescens Serratia marcescens = red pigment. Even though red suggests lactose fermentation, it doesn't spread into adjacent agar, so it isn't lactose fermentation (Serratia is a non-lactose fermenter). Also, marcescens = positive DNase confirms this ID. Other confirmations positive = ornithine decarboxylase, citrate, Voges Proskauer, gelatin hydrolysis Proteus vulgaris, Providencia stuartii, and Citrobacter koseri = DNase negative

Gram positive cocci on BAP w/ narrow zones of beta hemolysis. Slide coagulase is negative, tube coagulase is positive. This organism is: a. Micrococcus luteus b. Staph. Aureus c. Staph. Epidermidis d. Staph saprophyticus

Staph. Aureus Coagulase is confirmed by positive tube coagulase test

What is the most likely organism? - Positive cocci - Catalase positive - Coagulase negative - Bacitracin resistant - Novobiocin resistant a. Micrococcus b. Staphylococcus epidermidis c. Staphylococcus saprophyticus d. Staphylococcus aureus

Staphylococcus saprophyticus Staphylococcus saprophyticus matches that profile. Micrococcus = bacitracin sensitive Staphylococcus epidermidis = bacitracin sensitive S. aureus = coagulase positive

Which statements about assays for antigenic detection of both Clostridium difficile toxins A and B is true? a. The antigenic assays give rapid results b. The assays can only detect simultaneous production of toxin A and toxin B c. The assays provide a high level of sensitivity d. Assays that detect toxin A alone will detect all clinically significant strains

The antigenic assays give rapid results Antigenic assays are easily performed and are fast, compared to cultures and cell cytotoxicity assays. However, their sensitivities are not very good.

Diagnosis of diphtheria must be confirmed by a. observing metachromatic granules in a methylene blue stain of oropharyngeal swab b. recovering corynebacterium diphtheria in a culture c. performing a biochemical ID of a culture isolate d. determining that a culture isolate is a toxin-producing strain

determining that a culture isolate is a toxin-producing strain Non-toxin-producing strains of C. diphtheria can colonize upper respiratory tract. Only strains with B phage that produce diphtheria toxin = full-blown syndrome

All of the following would be suitable for ID of bacterial antigens except: a. agglutination reactions b. gram stain reactions c. immunofluorescence methods d. precipitin reactions

gram stain reactions Gram stain reactions don't help bind to cell membrane antigens. All other reactions are related to antigen measurement or ID

Acinetobacter spp. are similar to Neisseria spp. EXCEPT Acinetobacter spp. are generally: a. gram negative coccoids b. catalase negative c. oxidase negative d. motile

oxidase negative Acinetobacter spp. strictly aerobic, Gram-negative coccobacilli or gram-negative cocci on gram stain Oxidase negative Catalase positive Nonmotile Most Neisseria are: Gram negative diplococci on gram stain Aerobic Nonmotile Oxidase positive Catalase positive