Questions and Answers
What organism causes syphilis?
Which microscopy techniques can be used to see Treponema pallidum?
Which of the following statements about syphilis is true?
What is the primary mode of transmission for syphilis?
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What treatment is Treponema pallidum sensitive to?
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Congenital syphilis can occur through which of the following means?
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What is the incubation period for primary syphilis?
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Which of the following describes a primary chancre in syphilis?
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What characterizes the secondary stage of syphilis?
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After the symptoms of secondary syphilis subside, what stage does the disease enter?
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What does the early latent stage of syphilis indicate?
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Which symptom is NOT commonly associated with secondary syphilis?
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How does primary syphilis typically present in females?
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What temperature and duration are required to reheat activated serum tested after 4 hours?
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What is the characteristic of serological tests for syphilis during secondary syphilis?
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Which of the following is NOT a cause of false-positive results in syphilis testing?
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Which fluid can the VDRL test be performed on?
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What is one disadvantage of the VDRL test?
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How should serum specimens be handled before testing in the VDRL test?
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What does a medium or large flocculation particle result indicate in the VDRL test?
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What should be done if sera exhibit slight roughness during VDRL testing?
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What type of test is the RPR test classified as?
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What component is added to the RPR antigen to eliminate the need for heat inactivation of serum?
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What is the main purpose of charcoal particles in the RPR test?
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Why might non-treponemal tests like RPR revert to negative after therapy?
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What aspect of non-treponemal tests is considered a limitation?
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Which condition is NOT likely to cause a false positive in non-treponemal tests?
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What does a uniform gray result in the RPR test indicate?
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Which of the following is a characteristic of non-treponemal tests like RPR?
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What is a common feature of non-treponemal assays like RPR and VDRL?
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What type of antibodies are produced first during a rickettsial infection?
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What is the principle behind the Weil-Felix test?
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Which Proteus species antigen reacts with antibodies to the scrub typhus group?
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In the Weil-Felix test, which organism is associated with a strong reaction to OX-19 antigen?
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Which of the following OX antigens is NOT associated with the typhus group antibodies?
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What cross-reaction activity is considered for the establishment of the Weil-Felix test?
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Which Proteus species antigens can react with antibodies to the spotted fever group?
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How is the Weil-Felix test interpreted in terms of reactions?
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Study Notes
Syphilis Overview
- Caused by the spirochete Treponema pallidum, a Gram-negative motile organism.
- Unable to grow in artificial media; undetectable by light microscopy due to size (0.15 μm in diameter, 5-15 μm in length).
- Visible through dark field microscopy and phase contrast techniques.
- Stainable using silver impregnation and fluorescent antibody techniques.
- Sensitive to penicillin.
Epidemiology
- Incidence declined significantly post-1940s due to penicillin.
- Over 70,000 new cases reported annually.
- Third most common sexually transmitted disease (STD), chronic and slowly progressive.
Mode of Transmission
- Primarily through direct sexual contact (90-96% of cases).
- Can also spread via blood transfusion or from an infected mother to fetus during pregnancy (congenital syphilis).
- Accidental exposure is possible, particularly for medical personnel.
Clinical Features
- Incubation Period: 10 to 90 days (average 21 days).
- Symptoms vary across stages of infection.
Primary Syphilis
- Characterized by a single, painless chancre appearing 2-10 weeks post-exposure.
- Chancre is usually indurated and located on the genitalia (90%) or lips (5-10%).
- In females, the chancre may occur in the cervix.
- Fluid from the chancre is highly infectious; spirochetes can be identified using dark field microscopy.
- Chancre typically heals spontaneously in 3-8 weeks; positive serological tests in 80% of cases.
Secondary Syphilis
- Occurs 6-8 weeks after the primary chancre resolves.
- Features disseminated lesions including skin rashes, mucosal ulcers, and condylomata.
- Other symptoms include lymphadenopathy, fever, headache, and malaise.
- Highly infectious stage with near-universal positivity in serological tests.
- Can progress to early latent, late latent, or tertiary syphilis stages.
Latent Stage
- Defined by positive serology in the absence of clinical symptoms.
- Early latent refers to infections acquired within the last 12 months.
Serological Testing
- Tests must account for heat inactivation if performed more than 4 hours after original sample collection; cerebrospinal fluid is also valid for testing.
- False-Negative Results: Possible in the first three months of syphilis infection or during late stages.
- False-Positive Results: Can occur due to various conditions like HIV, Lyme disease, malaria, systemic lupus erythematosus, etc.
Non-Treponemal Tests
-
VDRL Test:
- Performed on serum or CSF; must use fresh antigen.
- Requires heat inactivation and microscopic reading for results.
- Reactive tests have medium/large flocculation; non-reactive tests show dispersion or slight roughness.
-
RPR Test:
- Macroscopic circle card test featuring cardiolipin, cholesterol, and lecithin antigen mixed with unheated serum.
- Presence of antibodies leads to agglutination, visible as black clumps against a white background.
- Quick results, inexpensive, and does not require specialized equipment.
- Can help monitor treatment response.
Limitations of Non-Treponemal Tests
- Subjective results and nonspecificity may lead to false positives from various conditions like lupus and Epstein-Barr virus.
Weil-Felix Reaction
- An agglutination test based on cross-reactivity of antigens between some Proteus and Rickettsia species.
- Uses Proteus antigens OXK, OX2, and OX19 to detect antibodies associated with rickettsial infections.
- Cross-reactions help diagnose different rickettsial groups:
- Typhus group reacts with OX19.
- Scrub typhus group reacts with OXK.
- Spotted fever group reacts with both OX2 and OX19.
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Description
Explore the serological tests commonly used for bacterial infections, focusing on syphilis serology. Learn about the causative agent Treponema pallidum and the characteristics of this spirochete organism. This quiz will help you understand the essential aspects of diagnosing syphilis and its implications.