Exam 4 - (CH 23) The Spirochetes Textbook Review Questions

Question 1

In patients with a leptospiral bacteremia, ______ antibodies are detected within one week after onset of disease and may persist in high titers for many months.

A. IgA
B. IgG
C. IgE
D. IgM

Answer 1

D. IgM

Question 2

In contrast to both Treponema and Borrelia organisms, spirals of Leptospira are

A. tightly coiled and can appear like a chain of cocci.
B. loosely coiled and can appear like filamentous rods.
C. palisading.
D. pleomorphic and can appear like Corynebacteria.

Answer 2

A. tightly coiled and can appear like a chain of cocci.

Question 3

Toward the end of the first week as symptoms of leptospiremia appear which of the following specimens should be collected?

A. Sputum
B. Eschar biopsy
C. Cerebrospinal fluid (CSF)
D. Hair

Answer 3

C. Cerebrospinal fluid (CSF)

Question 4

All pathogenic Borrelia are

A. arthropod-borne.
B. sexually transmitted.
C. transmitted by aerosols.
D. transmitted by fomites.

Answer 4

A. arthropod-borne

Question 5

The most common and productive specimen for the laboratory diagnosis of Borrelia burgdorferi sensu lato is

A. duodenal biopsy.
B. serum for serology.
C. sputum.
D. none of the above.

Answer 5

B. serum for serology.

Question 6

The causative agent of pinta is

A. Treponema pallidum subsp. pertenue.
B. Treponema carateum.
C. Borrelia burgdorferi.
D. Borrelia recurrentis.

Answer 6

Treponema carateum

Question 7

The Venereal Disease Research Laboratory (VDRL) reagent is

A. charcoal.
B. immunoglobulin.
C. cardiolipin.
D. flocculation.

Answer 7

C. cardiolipin

Question 8

Which stage of syphilis infection is associated with aortitis, aneurysms, and aortic valve insufficiency?

A. Primary
B. Secondary
C. Tertiary
D. Congenital

Answer 8

C. Tertiary

Question 9

The VDRL test on CSF has

A. high specificity, but low sensitivity.
B. high specificity and high sensitivity.
C. low specificity, but high sensitivity.
D. low specificity and low sensitivity.

Answer 9

A. high specificity, but low sensitivity.

Question 10

Treponema pallidum subsp. pertenue is the causative agent of

A. endemic syphilis.
B. pinta.
C. typhus.
D. yaws.

Answer 10

D. yaws.

Question 11

What are the general characteristics of spirochetes?

Answer 11

The spirochetes are slender, flexuous, helix-shaped, motile, unicellular bacteria ranging from 0.1 to 0.5 µm wide and from 5 to 20 µm long, with one or more complete turns in the helix. They differ from other bacteria in that they have a flexible cell wall around which several fibrils are wound.

Question 12

What risk factors are associated with Borrelia spp. endemic relapsing fever?

Answer 12

Geographic location, season, outdoor exposure, and a history of tick bites are risk factors for endemic relapsing fever.

Question 13

Which tickborne species of Borrelia is associated with a rash or skin lesion?

Answer 13

B. burgdorferi sensu lato, the causative agent of Lyme disease

Question 14

What is the significance on infectious disease transmission of finding partially engorged ticks attached to skin?

Answer 14

Pathogen transmission is more probable the longer the vector is attached.

Question 15

What is the test of choice for the laboratory diagnosis of relapsing fever (borreliosis)?

Answer 15

Peripheral blood smear stained with Giemsa stain is the test of choice for the laboratory diagnosis of relapsing fever borreliosis.

Question 16

Name the four strains within the genus Treponema that are pathogenic for humans.

Answer 16

1. T. pallidum subsp. pallidum (syphilis)
2. T. pallidum subsp. pertenue (yaws)
3. T. carateum (pinta)
4. T. pallidum subsp. endemicum (endemic syphilis or bejel).

Question 17

What are the stages of a T. pallidum subsp. pallidum infection? Is the final stage usually seen in developed countries?

Answer 17

Primary, secondary, and tertiary are the three stages of syphilis. In the United States, the tertiary stage of the disease is not often seen because most patients are adequately treated with antimicrobial agents before the tertiary stage is reached.

Question 18

Where are most cases of leptospiroses contracted within the United States, and why is this important when considering the typical incubation period of the infection?

Answer 18

Most cases are contracted in Hawaii. Because the incubation period is typically 10 to 12 days, it is likely that visitors to Hawaii can become infected but not show symptoms until they return home.

Question 19

Differentiate between treponemal and nontreponemal serologic tests for syphilis.

Answer 19

The treponemal tests for syphilis detect antibodies specific for treponemal antigens. The nontreponemal tests are nonspecific and detect reaginic antibodies that develop against lipids released from damaged cells. Both tests are sensitive in the secondary stage. However, the nontreponemal tests are less sensitive than the treponemal tests in late syphilis and have a lower specificity.

Question 20

What is the recommended method for the laboratory diagnosis of Lyme borreliosis?

Answer 20

The first tier is an immunofluorescent antibody or enzyme immunoassay screen. Positive or equivocal results are confirmed with a Western blot, which is the second tier.

Question 21

Points to Remember

Answer 21

■ Spirochetes are slender, flexuous, helically shaped, motile bacteria.
■ Leptospires are most likely to enter the human host through small breaks in the skin or intact mucosa. ■ The incubation period of leptospirosis is usually 10 to 12 days but ranges from 3 to 30 days. The onset of clinical illness is generally abrupt, with nonspecific, influenza-like constitutional symptoms, such as fever, chills, headache, severe myalgia, and malaise.
■ The pathogenic borreliae are commonly arthropod-borne (by a tick or louse) and cause relapsing fever and Lyme disease.
■ B. recurrentis and similar species cause relapsing fever. The relapses are caused by immune evasion, including antigenic variation. During the course of a single infection, borreliae systematically change their surface antigens.
■ During the febrile period, diagnosis of relapsing fever is readily made by Giemsa or Wright staining of blood smears. Relapsing fever is the only spirochetal disease in which the organisms are visible in blood with bright-field microscopy.
■ Laboratory diagnosis of Lyme disease caused by B. burgdorferi sensu lato is accomplished by two-tiered serology. Initial positive or equivocal EIA results are confirmed with Western blot.
■ Treponemes can cross the placenta and be transmitted from an infected mother to her fetus. Congenital syphilis affects many body systems and is therefore severe and mutilating. All pregnant women should have serologic testing for syphilis early in pregnancy.