The Laboratory Diagnosis of Chlamydia Infections

Abstract

Bacteria of the genus Chlamydia belong to the order Chlamydiales, within the family Chlamydiaceae. These intracellular parasites have a different biphasic reproductive cycle than other bacteria. The important Chlamydiaceae are Chlamydia trachomatis, Chlamydophila pneumoniae and Chlamydophila psittaci. Chlamydia trachomatis and Clamydophila pneumoniae are primary human pathogens. Chlamydia trachomatis is transmitted by sexual contact. It is the causative agent of LGV (lymphogranuloma venoreum) and ocular trachoma in humans. Chlamydophila pneumoniae causes bronchitis, atypical pneumonia, sinusitis, pharyngitis, and inflammatory atherosclerosis. Chlamydia psittaci is the causative agent of psittacosis (pneumonia). It primarily causes infection in birds and domestic animals, and sometimes in humans. Chlamydia trachomatis laboratory diagnosis is based on cytological examination (Giemsa), antigen detection (with enzyme-linked immunosorbent assay and direct immunofluorescence staining), nucleic acid-based tests (nucleic acid probe tests and nucleic acid amplification tests—NAAT), cell culture (in vivo and in vitro), and detection of antibodies (especially microimmunofluorescence—MIF and enzyme immunoassay—EIA, for the diagnosis of LGV). The most specific test in diagnosis is cell culture, and the most sensitive is nucleic acid-based test. NAAT and MIF tests are successful in the diagnosis of C. pneumoniae infections. The diagnosis of psittacosis is usually made by serological testing, and species-specific MIF testing should be performed to confirm.