Chapter 7.6 - Aerobic Gram Positive (HARR)

Bacillus spp

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:

Motility and β-hemolysis on a blood agar plate

Bacillus anthracis and Bacillus cereus can best be differentiated by which tests?

Food

Which is the specimen of choice for proof of food poisoning by Bacillus cereus?

A. Penicillin (10-unit) susceptibility test

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?

Gram stain, motility at room temperature, catalase

Which of the following tests should be performed for initial differentiation of Listeria monocytogenes from group B streptococci?

Lactobacillus spp

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:

All of these options:

• A pseudomembrane of the oropharynx

• An exotoxin

• Gray-black colonies with a brown halo on Tinsdale’s agar

A Corynebacterium species recovered from a throat culture is considered a pathogen when it produces:

All of these options:

• Oxidase and catalase tests

• Pleomorphic bacilli heavily colonized on vaginal epithelium

• Hippurate hydrolysis test

A presumptive diagnosis of Gardnerella vaginalis can be made using which of the following findings?

Nocardia spp.

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?

Serological analysis

Routine laboratory testing for Treponema pallidum involves:

Borrelia spp.

Spirochetes often detected in the hematology laboratory, even before the physician suspects the infection, are:

Borrelia burgdorferi

Which of the following organisms is the cause of Lyme disease?

Serology

The diagnostic method most commonly used for the identification of Lyme disease is:

Mycoplasma pneumoniae

Primary atypical pneumonia is caused by:

Mycoplasma hominis

Which organism typically produces “fried-egg” colonies on agar within 1–5 days of culture from a genital specimen?

Ureaplasma urealyticum

The manganous chloride–urea test is used for the identification of which organism?

Nocardia spp.

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?

Corynebacterium spp.

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:

10% KOH test

Which of the following is the best, rapid, noncultural test to perform when Gardnerella vaginalis is suspected in a patient with vaginosis?

PCR molecular testing

Which is the test of choice for the confirmation of Chlamydia trachomatis infection in urine?

EIA testing and direct antigen testing

Which test is the most reliable for the detection of Mycoplasma pneumonia in serum and for the confirmation of diagnosis?

Chlamydia (Chlamydophila) psittaci: fecal swab

Identify the following bacterium and specimen pairing that is mismatched (specimen not appropriate for isolation).

Ehrlichia and Anaplasma spp.

Which of the following organisms are transmitted to animals and humans after a tick bite?

Blood, CSF, and skin biopsy

Following a hike in the woods, a young male noted a tick on his ankle. He removed the tick, but 2 weeks later noticed a circular, bull’s eye rash at the site of the bite. Which specimen(s) should be obtained to establish a diagnosis of Lyme borreliosis?