Aerobic Gram (+) Bacilli 💨 Flashcards
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An isolate with the appropriate colony and microscopic morphol- ogy may be suspected to be Bacillus anthracis if it is:
a. β-Hemolytic on SBA
b. Nonmotile
c. Catalase-negative
d. Gram-negative, non–spore forming
Nonmotile
An aerobic, gram-positive, spore-forming bacillus was isolated
from raw vegetables that were associated with an outbreak of gastroenteritis. The organism produced β-hemolysis, was cata- lase-positive, and was motile. The most likely organism is:
a. Bacillus anthracis
b. Nocardia asteroides
c. Bacillus cereus
d. Tsukamurella spp.
c. Bacillus cereus
Bacillus cereus is most noted for causing:
a. Food poisoning
b. Meningitis
c. Sexually transmitted disease
d. Urinary tract infections
a. Food poisoning
Which forms of infection are caused by Bacillus anthracis?
a. Injectional
b. Inhalation
c. Gastrointestinal d. Cutaneous
e. All of the above
e. All of the above
The functionality of lethal factor requires the presence of what other protein from Bacillus anthracis to form an active toxin?
a. Edema factor
b. D-glutamic acid c. cAMP
d. Protective antigen
d. Protective antigen
Describe the appearance of spore-forming bacteria seen with the spore stain.
In the spore stain, vegetative cells are red, but the spores stain green.
Corynebacterium species often appear as ______________ on Gram stain.
a. Pleomorphic gram-positive club-shaped bacilli that appear in palisades or in V and L formations
b. Branching gram-positive bacilli that appear as fine, intertwin- ing, delicate filaments
c. Short, thin gram-positive bacilli that appear in chains
d. Large square-ended, gram-positive or gram-variable bacilli in chains where the ends of the single cells fit snugly
together
Pleomorphic gram-positive club-shaped bacilli that appear in palisades or in V and L formations
The biochemical tests performed on a gram-positive bacillus were
consistent with Corynebacterium diphtheriae. As a definitive test, the laboratory scientist should now:
a. Perform an Elek test to determine whether the organism
produces exotoxin
b. Subculturetheorganismtocystine-telluriteagarandexamine
for black colonies
c. Prepare a methylene blue stain and examine for metachro-
matic granules
d. Gram stain the isolate and observe for its pleomorphic
morphology
Perform an Elek test to determine whether the organism
produces exotoxin
Respiratory diphtheria is common in the United States, and the
natural hosts for C. diphtheriae are humans and birds
a. True
b. False
b. False
True infections with nondiphtheria Corynebacterium spp., such as C. jeikeium or C. striatum, are often in immunocompromised patients or patients who have had:
a. Insertion of hardware or prosthetic devices
b. Coronary artery bypass surgery
c. Vitamin B12 deficiency
d. A lengthy hospital stay
Insertion of hardware or prosthetic devices
A _________ test can help to differentiate which clinically signifi- cant Corynebacterium spp. recovered from urine samples?
a. Gelatin hydrolysis; C. ulcerans
b. Reverse CAMP; C. pseudotuberculosis
c. Alkaline phosphatase; C. amycolatum
d. Urease; C. urealyticum
Urease; C. urealyticum
after birth. A gram-positive rod is recovered from blood cultures from the newborn. The isolate has the characteristics listed. What is the most likely identity of the isolate?
Weakly β-hemolytic on SBA
Gram-positive bacilli, no spores observed Catalase-positive Hydrogen-sulfide-negative
Motile at room temperature
a. Erysipelothrix rhusiopathiae
b. Listeria monocytogenes
c. Corynebacterium ureilyticum
d. Gardnerella vaginalis
Listeria monocytogenes
A commercial fisherman who had red sores on his hands was seen by his physician. Biopsy and culture of one of the lesions was performed. The culture grew an organism with the charac- teristics listed. What is the most likely organism?
Nonhemolytic on SBA
Gram-positive bacilli, no spores observed Catalase-negative Hydrogen-sulfide-production-positive
Growth in gelatin resembled a test-tube brush
a. Rhodococcus equi
b. Listeria monocytogenes
c. Lactobacillus acidophilus
d. Erysipelothrix rhusiopathiae
Erysipelothrix rhusiopathiae
A 42-year-old man from Guatemala cuts his bare feet on thorns while walking. A subcutaneous abscess develops, and when the patient is seen by a physician, his foot is swollen. When the wound is pressed by the physician, purulence is expressed along with some soft, white granules. A filamentous organism that is partially acid-fast is recovered from the granules. This is most likely an __________ mycetoma caused by ____________.
a. Actinomycotic, Pseudallescheria boydii
b. Actinomycotic, Nocardia brasiliensis
c. Eumycotic, Madurella mycetomatis
d. Eumycotic, Tsukamurella paurametabola
Actinomycotic, Nocardia brasiliensis
What other organisms can give similar clinical and laboratory findings as Listeria monocytogenes? How are these organisms differentiated from L. monocytogenes?
Streptococcus agalactiae (group B Streptococcus) and Enterococcus spp. can produce clinical laboratory findings similar to those for L. monoctogenes. Initial differentiation between L. monocytogenes and similar microorganisms can be made by the Gram stain, catalase test, and esculin hydrolysis.
A 17-year-old boy presented to an emergency department with a history of multiple episodes of febrile pharyngitis followed in 10 to 14 days with extensive desquamation of his hands and feet. The reoccurrences have followed several courses of antimi- crobial therapy including amoxicillin and cephalosporins. Rapid group A streptococci screens and cultures have been consistently negative for Streptococcus pyogenes. A specimen with a request for an alternative agent was submitted to a reference laboratory. The results listed were observed. The patient was subsequently treated with erythromycin, and he recovered. What was the etio- logic agent?
SBA: dry, wrinkled, slightly hemolytic colony, which at 48 hours is a dark spot sunken in the agar
Catalase-negative Nitrate-negative Reverse-CAMP-test-positive
a. Corynebacterium diphtheriae
b. Arcanobacterium haemolyticum
c. Listeria monocytogenes
d. Rhodococcus equi
Arcanobacterium haemolyticum
A sample is sent to the laboratory from a female patient sus-
pected to have bacterial vaginosis. Which of the following would be an appropriate medium for this specimen?
a. Loeffler medium
b. HBT agar
c. CBTA
d. BCYE
HBT agar
Remel HBT Bilayer Medium is a solid medium recommended for use in qualitative procedures for selective isolation and presumptive identification of Gardnerella vaginalis. Gardnerella vaginalis is a venereally transmitted bacterium that is associated with a clinical syndrome called bacterial vaginosis.
A 57-year-old man from New York City presents to the emer-
gency department with diarrhea, arthralgia, abdominal pain, malabsorption, and weight loss of 10 lb over the last month. A duodenal biopsy is performed, but no infectious agent is recov- ered on culture media. However, on Gram stain, a gram-positive rod is observed in macrophages in the biopsy tissue. The organ- ism is identified by 16S rRNA gene sequencing. What is the most likely identity of this organism?
a. Bacillus anthracis
b. Nocardia asteroides
c. Tropheryma whipplei
d. Erysipelothrix rhusiopathiae
Tropheryma whipplei
two spore-forming gram (+) bacilli
Bacillus spp.
Clostridium spp.
the only obligate anaerobe
Clostridium
Bacillus
- spore location
- catalase reaction
Central/subterminal spore
catalase positive
Side note:
Bacillus anthracis
✓Grampositive(+)in chains; “bamboo – fishing rod appearance”
✓capsulated (polypeptide D-glutamic acid)
✓ Grampositivearranged singly; “boxcar”
✓ central/subterminalspores
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