A 25-year-old man has several enlarged lymph nodes and a maculopapular rash. 2 months ago, he had a painless penile ulcer that resolved spontaneously. Secondary stage syphilis is suspected.
a) What are the microscopic examination methods required to reach a diagnosis?
Ø Dark ground microscopy
Ø Immunofluorescent microscopy
b) Name the cardiolipin antibody tests that could assist in his diagnosis.
Ø Venereal Disease Research Laboratory test (VDRL)
Ø Rapid Plasma Reagin test (RPR)
c) Why is it necessary to confirm the positive results by one of the treponemal antibody tests?
Ø To prevent false positive results
d) Write briefly about the Treponema pallidum-particle agglutination test.
Ø Gelatin particles are sensitized with T.pallidum antigens
Ø The test is performed in a microdilution plate with diluted patient’s serum
Ø Antibodies against T.pallidum react with the sensitized gelatin particles
Ø A mat of agglutinated particles indicate a positive result
Ø This test is similar to the FTA-Abs test in specificity and sensitivity
A 20-year-old male presents to the outpatient clinic with a history of fever and a dry cough. Chest X-ray shows consolidation of the right lower lobe of lung. He was primarily diagnosed as pneumonia. Gram stain of sputum revealed many pus cells but no bacteria. Mycoplasma pneumoniae is suspected to be the causative agent.
a) What is the non-specific serological test that can support the diagnosis?
Cold agglutination technique
b) State the principal for your answer in (a).
IgM antibodies bind to the class I antigen on the surface of group O human RBCs at 4oC
c) What antibiotics should be used to treat this patient?
Tetracycline or erythromycin
Give a short account on laboratory diagnosis of infections caused by the TWAR strain.
1. Cell culture isolation using Cycloheximide-treated McCoy cells.
2. Serologic diagnosis by complement fixation or microimmunofluorescence test.
Ø A fourfold titre increase in either IgM or IgG titre is diagnostic
Ø A single IgM titre of >16 or IgG of >512 is suggestive of recent infection
3. PCR – to diagnose current infection