Exam 4 - (CH 24) Chlamydia, Rickettsia, and Similar Organisms Textbook Review Questions

Question 1

Which of the following describes the reticulate body of Chlamydiae?
A. Infectious sporelike body resistant to environmental physical stress
B. Noninfectious MOMP made up primarily of lipopolysaccharide
C. Infectious form made primarily of ketodeoxyoctonate
D. Large, less dense noninfectious form that divide by binary fission

Answer 1

D. Large, less dense noninfectious form that divide by binary fission

Question 2

Trachoma is associated with serotypes
A. A, B, Ba, and C.
B. C, L, R and T.
C. 1 and 16.
D. O, K, and H.

Answer 2

A. A, B, Ba, and C.

Question 3

The lymphogranuloma venereum Chlamydia trachomatis serovars have been linked to
A. Jarisch-Herxheimer reaction.
B. Parinaud oculoglandular conjunctivitis.
C. D-glucose-6-phosphate deficiency.
D. erythema migrans.

Answer 3

B. Parinaud oculoglandular conjunctivitis.

Question 4

Until the development of ______, chlamydial cell culture was considered the gold standard for detecting Chlamydia trachomatis infection.
A. direct fluorescent antibody (DFA)
B. rapid plasma reagin (RPR)
C. nucleic acid amplification tests (NAATs)
D. enzyme-linked immunosorbent assay (ELISA)

Answer 4

C. nucleic acid amplification tests (NAATs)

Question 5

Diagnosis of psittacosis is usually based on a history of exposure to
A. pigs.
B. birds.
C. horses.
D. ticks.

Answer 5

B. birds.

Question 6

Rickettsiae are
A. nonmotile.
B. gram-positive bacilli.
C. gram-positive cocci in clusters.
D. extracellular pathogens.

Answer 6

A. nonmotile.

Question 7

Boutonneuse fever is caused by
A. Rickettsia prowazekii.
B. Rickettsia.
C. Rickettsia conorii.
D. Orientia tsutsugamushi.

Answer 7

C. Rickettsia conorii.

Question 8

Morulae are most commonly associated with this genus
A. Orientia.
B. Anaplasma.
C. Ehrlichia.
D. Coxiella.

Answer 8

C. Ehrlichia.

Question 9

Coxiella burnetii is the causative agent of
A. human granulocytic anaplasmosis.
B. murine typhus.
C. Brill-Zinsser disease.
D. Q fever.

Answer 9

D. Q fever.

Question 10

Which of the following does not have peptidoglycan in the cell wall?
A. Chlamydia
B. Mycoplasma
C. Rickettsia
D. Virus

Answer 10

C. Rickettsia

Question 11

Which of the following has a pear-shaped elementary body?
A. Chlamydia trachomatis
B. Chlamydophila psittaci
C. Rickettsia akari
D. Chlamydia pneumoniae

Answer 11

D. Chlamydia pneumoniae

Question 12

1. What organisms should be considered as possible causes of neonatal conjunctivitis?

Answer 12

The two common causes of neonatal conjunctivitis are Neisseria gonorrhoeae and Chlamydia trachomatis. The prophylactic use of erythromycin eye drops has helped control this serious disease.

Question 13

What stains should be performed on conjunctival scraping for microscopic examination for the diagnosis of inclusion conjunctivitis?

Answer 13

Although the Giemsa stain is easy to perform on eye scrapings, it is not very sensitive for detecting C. trachomatis and requires expertise. A direct fluorescent antibody stain is more reliable. Alternatively, an antigen detection assay or nucleic acid amplification test could be performed.

Question 14

For the neonate described in the Case in Point, what other clinical conditions could have resulted from infection with the causative organisms?

Answer 14

The infant in the Case in Point was infected with C. trachomatis. This organism can cause a variety of infections in neonates, including pneumonia and pharyngeal and enteric infections.

Question 15

What STD is caused by Chlamydia trachomatis serotypes L1, L2, L2a, L2b, and L3?

Answer 15

Lymphogranuloma venereum (LGV)

Question 16

How does LGV differ from other sexually transmitted diseases caused by C. trachomatis?

Answer 16

LGV differs from other diseases caused by C. trachomatis because the serovars causing this disease are more invasive. These serovars are able to survive inside mononuclear cells and are carried into the lymphoid tissue, where they produce a strong inflammatory response.

Question 17

With what types of infections are associated with Chlamydophila pneumoniae?

Answer 17

Chlamydophila pneumoniae is thought to be a common cause of pharyngitis and pneumonia. This organism might be associated with atherosclerosis and coronary heart disease.

Question 18

What is psittacosis or ornithosis?

Answer 18

Psittacosis, an infection caused by Chlamydophila psittaci, typically manifests as pneumonia. Because of the highly contagious nature of C. psittaci, cultures for diagnosis are not recommended. Diagnosis is best made by detecting antibodies to the bacterial antigens.

Question 19

What is the most common laboratory method used to diagnose rickettsial diseases? Explain.

Answer 19

Serologic assays are the most commonly used testing method for the diagnosis of rickettsial diseases. Unfortunately, antibodies are generally detected in convalescent specimens too late to affect treatment. The immunofluorescent antibody test is the methodology most commonly used.

Question 20

What cells do the Ehrlichia and Anaplasma species typically infect in humans?

Answer 20

Ehrlichia spp. generally infect monocytes and macrophages. They prevent phagolysosome formation and survive within phagosomes. The Anaplasma spp. are unusual in that they preferentially infect granulocytes. They also prevent phagosome-lysosome fusion and survive within phagosomes.

Question 21

How does Coxiella burnetii differ from the Rickettsia spp.?

Answer 21

Coxiella burnetii is a facultative intracellular parasite that develops within the phagolysosome of infected cells. Rickettsia spp. prevent phagolysosome formation and develop within a phagosome. C. burnetii forms spores, whereas Rickettsia spp. do not. In addition, although C. burnetii is known to infect more than 12 genera of ticks and other arthropods, it is generally not transmitted by arthropods. C. burnetii, unlike the Rickettsia spp., has been grown in cell-free media.

Question 22

Points to Remember

Answer 22

■ Chlamydiae and rickettsiae are obligate intracellular organisms.
■ Chlamydia trachomatis is the most common sexually transmitted bacterial pathogen, and certain serovars are associated with trachoma, which can result in blindness.
■ The LGV strains of C. trachomatis are more invasive, producing a more serious infection and pronounced antibody response.
■ NAATs are better assays for the diagnosis of C. trachomatis infections compared with cultures.
■ Chlamydophila pneumoniae is a relatively common respiratory tract pathogen considered responsible for many cases of community-acquired pneumonia.
■ Chlamydophila psittaci is the cause of psittacosis, also known as parrot fever or ornithosis. This bacterium produces lower respiratory tract infections in humans.
■ The Rickettsia spp. are important human pathogens responsible for a number of diseases, including RMSF, rickettsialpox, and typhus.
■ The Rickettsia, Orientia, Ehrlichia, and Anaplasma are typically transmitted to humans by the bites of arthropods.
■ Ehrlichia and Anaplasma are intracellular parasites of white blood cells— mononuclear cells and granulocytes, respectively.
■ Coxiella burnetii is the causative agent of Q fever. Infection is most often transmitted by inhalation of dried birthing fluids. The ingestion of unpasteurized milk is also a risk factor.