Deck 16: Listeria, Corynebacterium, and Similar Organisms

Question 1

The organism that exhibits characteristic end-over-end tumbling motility when incubated in nutrient broth at room temperature for 1 to 2 hours is

A)Listeria monocytogenes.
B)Corynebacterium diphtheriae.
C)Bacillus anthracis.
D)Bacillus cereus.

Answer 1

A
Listeria monocytogenes can be presumptively identified by observation of motility by direct wet mount. The organism exhibits characteristic end-over-end tumbling motility when incubated in nutrient broth at room temperature for 1 to 2 hours.

Question 2

Patients who are immunocompromised and pregnant women should avoid eating soft cheeses such as Mexican-style, feta, brie, Camembert, and blue-veined cheese to prevent

A)foodborne listeriosis.
B)staphylococcal food poisoning.
C)gastric gangrene.
D)salmonella infection.

Answer 2

A
Prevention of foodborne listeriosis may be accomplished by patients who are immunocompromised by avoiding soft cheeses such as Mexican-style, feta, brie, Camembert, and blue-veined cheese. Additionally, leftover or ready-to-eat foods such as hot dogs or cold cuts should be thoroughly heated before consumption.

Question 3

A bacterium described as being coryneform has which type of morphology?

A)Short rods with rounded ends arranged singly, in "palisades" of parallel cells
B)Short rods in pairs that remain connected after cell division to form V or L shapes
C)Bacilli that resemble and are often referred to as Chinese letters
D)All of the above are correct.

Answer 3

D
Most of the genera in this chapter (except Listeria, Rothia, and Oerskovia) are classified as coryneform bacteria, that is, they are gram-positive, short or slightly curved rods with rounded ends; some have rudimentary branching. Cells are arranged singly, in "palisades" of parallel cells, or in pairs that remain connected after cell division to form V or L shapes. Groups of these morphologies seen together resemble and are often referred to as Chinese letters.

Question 4

Primary inoculation to a Loeffler slant, overnight incubation, and subculture of any growth to cystine-tellurite blood agar is no longer recommended for recovery of

A)Corynebacterium diphtheriae.
B)Bacillus anthracis.
C)Bacillus cereus.
D)Corynebacterium jeikeium.

Question 5

A catalase-positive, gram-positive bacillus that is not acid-fast, does not branch, and does not form spores could possibly belong to which group of bacteria?

A)Corynebacterium
B)Bacillus
C)Actinomyces
D)Mycobacterium

Question 6

The isolation of a small gram-positive, catalase-positive rod with a narrow zone of beta hemolysis isolated from blood or CSF should be used as strong presumptive evidence for

A)listeriosis.
B)diphtheria.
C)pertussis.
D)tetanus.