AIR Flashcards
Large gram-positive spore-forming rods growing on blood agar as large, raised, β-hemolytic colonies that spread and appear as frosted green-gray glass are most likely:
A. Pseudomonas spp.
B. Bacillus spp.
C. Corynebacterium spp.
D. Listeria spp.
B. Bacillus spp.
Bacillus anthracis and Bacillus 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
A. Motility and β-hemolysis on a blood agar plate
(Both species of Bacillus are catalase and lecithinase positive and produce acid from glucose. B. cereus is β-hemolytic and motile, but B. anthracis is neither.)
Which is the specimen of choice for proof of food poisoning by Bacillus cereus?
A. Sputum
B. Blood
C. Stool
D. Food
D. Food
A suspected Bacillus anthracis culture obtained from a wound specimen produced colonies that had many outgrowths (Medusa-head appearance), but were not β-hemolytic on sheep blood agar. Which test should be performed next?
A. Penicillin (10-unit) susceptibility test
B. Lecithinase test
C. Glucose test
D. Motility test
A. Penicillin (10-unit) susceptibility test
Which of the following tests should be performed for initial differentiation of Listeria monocytogenes from group B streptococci?
A. Gram stain, motility at room temperature, catalase
B. Gram stain, CAMP test, H2S/TSI
C. Oxidase, CAMP test, glucose
D. Oxidase, bacitracin
A. Gram stain, motility at room temperature, 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 = +
Motility (wet prep) = Neg
Motility (media) = Neg (bottle-brush growth in stab culture)
A. Bacillus cereus
B. Listeria monocytogenes
C. Erysipelothrix rhusiopathiae
D. Bacillus subtilis
C. Erysipelothrix rhusiopathiae
(E. rhusiopathiae is catalase negative, whereas
the other three organisms are catalase positive.)
A non-spore-forming, slender gram-positive rod forming palisades and chains was recovered from a vaginal culture and grew well on tomato juice agar. The most likely identification is:
A. Lactobacillus spp.
B. Bacillus spp.
C. Neisseria spp.
D. Streptococcus spp.
A. Lactobacillus spp.
(Lactobacillus spp. are part of the normal flora of the vagina (are not considered a pathogen) and are sometimes confused with the streptococci.)
A Corynebacterium species recovered from a throat culture is considered a pathogen when it produces:
A. A pseudomembrane of the oropharynx
B. An exotoxin
C. Gray-black colonies with a brown halo on Tinsdale’s agar
D. All of these options
D. All of these options
A presumptive diagnosis of Gardnerella vaginalis can be made using which of the following findings?
A. Oxidase and catalase tests
B. Pleomorphic bacilli heavily colonized on vaginal epithelium
C. Hippurate hydrolysis test
D. All of these options
D. All of these options
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?
A. Bacillus spp.
B. Nocardia spp.
C. Corynebacterium spp.
D. Listeria spp.
B. Nocardia spp.
Routine laboratory testing for Treponema pallidum involves:
A. Culturing
B. Serological analysis
C. Acid-fast staining
D. Gram staining
B. Serological analysis
Spirochetes often detected in the hematology laboratory, even before the physician suspects the infection, are:
A. Borrelia spp.
B. Treponema spp.
C. Campylobacter spp.
D. Leptospira spp.
A. Borrelia spp.
(Borrelia spp. are often seen on Wright’s-stained smears of peripheral blood as helical bacteria with 3-10 loose coils. They are gram negative but stain well with Giemsa’s stain.)
Which of the following organisms is the cause of Lyme disease?
A. Treponema pallidum
B. Neisseria meningitidis
C. Babesia microti
D. Borrelia burgdorferi
D. Borrelia burgdorferi
The diagnostic method most commonly used for the identification of Lyme disease is:
A. Serology
B. Culture
C. Gram stain
D. Acid-fast stain
A. Serology
Primary atypical pneumonia is caused by:
A. Streptococcus pneumoniae
B. Mycoplasma pneumoniae
C. Klebsiella pneumoniae
D. Mycobacterium tuberculosis
B. Mycoplasma pneumoniae
Which organism typically produces “fried-egg” colonies on agar within 1-5 days of culture from a genital specimen?
A. Mycoplasma hominis
B. Borrelia burgdorferi
C. Leptospira interrogans
D. Treponema pallidum
A. Mycoplasma hominis
The manganous chloride-urea test is used for the identification of which organism?
A. Mycoplasma pneumoniae
B. Ureaplasma urealyticum
C. Bacillus cereus
D. Borrelia burgdorferi
B. Ureaplasma urealyticum
A gram-positive (gram-variable), beaded organism with delicate branching was recovered from the sputum of a 20-year-old patient with leukemia. The specimen produced orange, glabrous, waxy colonies on Middlebrook’s agar that showed partial acid-fast staining with the modified Kinyoun stain. What is the most likely identification?
A. Rhodococcus spp.
B. Actinomadura spp.
C. Streptomyces spp.
D. Nocardia spp.
D. Nocardia spp.
(All of the listed organisms produce mycelium (aerial or substrate), causing them to appear branched when Gram stained, but only the Nocardia spp. are positive for modified acid-fast stain.)
A direct smear from a nasopharyngeal swab stained with Loeffler methylene blue stain showed various letter shapes and deep blue, metachromatic granules. The most likely identification is:
A. Corynebacterium spp.
B. Nocardia spp.
C. Listeria spp.
D. Gardnerella spp.
A. Corynebacterium spp.
Which of the following is the best, rapid, noncultural test to perform 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 these options
A. 10% KOH test
(The “whiff” test is used for a presumptive diagnosis of an infection with G. vaginalis. A fishlike odor is noted after the addition of 1 drop of 10% KOH to the vaginal washings.)
