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Chapter 56 : Immunologic Methods for Diagnosis of Spirochetal Diseases
Syphilis is the most common spirochetal disease in the United States, with the most recent estimate being 32,871 newly reported cases in 2002. For the spirochetal diseases, direct dark-field microscopic examination often provides an immediate means of presumptive diagnosis. The direct fluorescent-antibody test for Treponema pallidum (DFA-TP) examination of tissue and body fluids is particularly valuable in the diagnosis of congenital syphilis. Subtyping for T. pallidum done at the Centers for Disease Control and Prevention is based on two genes that exhibit intrastrain variability, the genes encoding the acidic repeat protein (arp) and the T. pallidum repeat (tpr) protein. A diagnosis of leptospirosis should also be considered in cases of unexplained jaundice, aseptic meningitis, and fever of unknown origin. Definitive diagnosis of leptospirosis is made by isolation of leptospires from tissue or body fluids, but leptospires grow slowly on initial isolation and culture is therefore often not useful in patient management. The diagnostic tests discussed in this chapter are the microscopic agglutination test (MAT), which is the standard against which all other serologic tests for leptospirosis are evaluated, and two screening tests, the immunoglobulin M (IgM) dot enzyme-linked immunosorbent assay (ELISA) and the IgM ELISA. The MAT detects agglutinating antibodies and is considered the standard reference test for the diagnosis of leptospirosis.
Key Concept Ranking
- Restriction Fragment Length Polymorphism
B. hermsii in a Giemsa-stained human peripheral blood smear. Magnification, × 1,000.
Characteristics of the order Spirochaetales
Spirochetal diseases of humans
Tests for diagnosis of spirochetal diseases
Reporting results of the RPR card test on serum (quantitative test) a
Reporting system for TP-PA test
PCR assays for diagnosis of leptospirosis in humans