8.6 Aerobic Gram-Positive Rods, Spirochetes, Mycoplasmas and Ureaplasmas, and Chlamydiae

Question 1

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.

Answer 1

B. Bacillus spp.

Question 2

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

Answer 2

A. Motility and β-hemolysis on a blood agar plate

Question 3

Which is the specimen of choice for proof of food poisoning by B. cereus?
A. Sputum
B. Blood
C. Stool
D. Food

Answer 3

D. Food

Question 4

A suspected B. 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

Answer 4

A. Penicillin (10-unit) susceptibility test

Question 5

Which of the following tests should be performed for initial differentiation of L. 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

Answer 5

A. Gram stain, motility at room temperature, catalase

Question 6

Culture of a finger wound specimen from a meat packer produced short gram-positive, non–spore-forming bacilli on a blood agar plate showing 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 (gel media 22 oC) = + (bottle-brush growth in stab culture)
A. Bacillus cereus
B. Listeria monocytogenes
C. Erysipelothrix rhusiopathiae
D. Bacillus subtilis

Answer 6

C. Erysipelothrix rhusiopathiae

Question 7

Nonspore-forming, slender, gram-positive, rod-forming palisades and chains were 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.

Answer 7

A. Lactobacillus spp.

Question 8

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 agar
D. All of these options

Answer 8

D. All of these options

Question 9

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

Answer 9

D. All of these options

Question 10

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.

Answer 10

B. Nocardia spp.

Question 11

Routine laboratory testing for Treponema pallidum involves:
A. Culturing
B. Serological analysis
C. Acid-fast staining
D. Gram staining

Answer 11

B. Serological analysis

Question 12

Spirochetes often detected in the hematology laboratory while scanning a blood film, even before the physician suspects the infection, are:
A. Borrelia spp.
B. Treponema spp.
C. Campylobacter spp.
D. Leptospira spp.

Answer 12

A. Borrelia spp.

Question 13

Which of the following organisms is the cause of Lyme disease?
A. Treponema pallidum
B. Neisseria meningitidis
C. Babesia microti
D. Borrelia burgdorferi

Answer 13

D. Borrelia burgdorferi

Question 14

The diagnostic method most commonly used for the identification of Lyme disease is:
A. Serology
B. Culture
C. Gram staining
D. Acid-fast staining

Answer 14

A. Serology

Question 15

Primary atypical pneumonia is caused by:
A. Streptococcus pneumoniae
B. Mycoplasma pneumoniae
C. Klebsiella pneumoniae
D. Mycobacterium tuberculosis

Answer 15

B. Mycoplasma pneumoniae

Question 16

Which organism typically produces “fried egg” colonies on agar within 1 to 5 days of culture obtained from a genital specimen?
A. Mycoplasma hominis
B. Borrelia burgdorferi
C. Leptospira interrogans
D. Treponema pallidum

Answer 16

A. Mycoplasma hominis

Question 17

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

Answer 17

B. Ureaplasma urealyticum

Question 18

18. 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 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.

Answer 18

D. Nocardia spp.

Question 19

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.

Answer 19

A. Corynebacterium spp.

Question 20

Which of the following is the best, rapid, nonculture test to perform when G. 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

Answer 20

A. 10% KOH test

Question 21

Which is the test of choice for the confirmation of Chlamydia trachomatis infection in urine?
A. Enzyme immunoassay antigen testing
B. PCR molecular testing
C. Culture using McCoy and Hela cells
D. Microimmunofluorescence (MIF) test

Answer 21

B. PCR molecular testing

Question 22

Which test is the most reliable for the detection of M. pneumonia in serum and for the confirmation of diagnosis?
A. EIA testing and direct antigen testing
B. Cold agglutinin testing using group O RBCs
C. Culture on SP4 glucose broth with arginine
D. Complement fixation

Answer 22

A. EIA testing and direct antigen testing

Question 23

Identify the following bacterium–specimen pairing that is mismatched (specimen not appropriate for isolation):
A. Chlamydia (Chlamydophila) psittaci–fecal swab
B. Chlamydia trachomatis–first voided urine
C. Chlamydia trachomatis–endocervical swab
D. Chlamydia pneumonia–throat swab or sputum

Answer 23

A. Chlamydia (Chlamydophila) psittaci–fecal swab

Question 24

Which of the following organisms are transmitted to animals and humans after a tick bite?
A. Leptospira spp.
B. Chlamydia and Mycoplasma spp.
C. Neisseria sicca
D. Ehrlichia and Anaplasma spp.

Answer 24

D. Ehrlichia and Anaplasma spp.

Question 25

Following a hike in the woods, a young male noted a tick on his ankle. He removed the tick, but 2 weeks later, he 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?
A. Lymph node biopsy, skin scraping
B. Blood, CSF, skin biopsy
C. Hair, fingernails
D. Saliva, sputum

Answer 25

B. Blood, CSF, skin biopsy

Question 26

Partially acid-fast, gram-positive, filamentous-branching bacteria that fragmented into rods and cocci were seen in a sputum sample from a patient with HIV infection. Which of the following is the most likely presumptive identification?
A. Rhodococcus equi
B. Streptococcus spp.
C. Bacillus subtillus
D. Corynebacterium spp. (diphtheroids)

Answer 26

A. Rhodococcus equi

Question 27

An asymptomatic 25-year-old female patient with persistent nongonococcal urethritis (NGC) and pelvic inflammatory disease (PID) was suspected of being infected with Mycoplasma genitalium. Which category of testing should not be utilized to establish a final identification?
A. Nucleic acid amplification test (NAAT)
B. Real time PCR
C. PCR
D. Culture

Answer 27

D. Culture