Characterization of a further microimmunofluorescence serotype of Chlamydia: TRIC type G

Antichlamydial antibody in tears and sera, and serotypes of Chlamydia trachomatis isolated from schoolchildren in Southern Tunisia

A predominance of TRIC serotype A has been isolated from schoolchildren in a population in Southern Tunisia with severe hyperendemic trachoma. The serotyping results correspond precisely with the serological findings in patients' tears and sera. Geometric mean titres of serum or tear antibody in defined populations or areas can thus give a useful indication of the prevalent serotypes. Collection of tear fluids on sponges is a more practical method than collection by filter paper strips and gives higher levels of antibody. The presence of antibody to Chlamydia trachomatis in tears correlates well with the presence of infectious agent in the eye and with the intensity of conjunctival inflammatory disease. The measurement of antichlamydial tear antibody can thus provide a meaningful index of the prevalence and intensity of active trachoma in a population. The role these antibodies may play in resistance to re-infection is not yet clear.

Modification of the microimmunofluorescence test to provide a routine serodiagnostic test for chlamydial infection

A modification of the microimmunofluorescence test to provide a practicable routine serodiagnostic test for detecting and characterising chlamydial infection is described which uses four antigen pools, one of which corresponds with each of the four main clinical and epidemiological types of chlamydial infection. The three subgroup A Chlamydia (Chlamydia trachomatis) pools are: pool 1, hyperendemic trachoma TRIC agent serotypes A, B, and C; pool 2, paratrachoma TRIC agent serotypes D, E, F, G, H, I, and K; pool 3, lymphogranuloma venereum (LGV) agent serotypes L1, L2, and L3. Pool 4 contained four representative isolates of subgroup B Chlamydia (Chlamydia psittaci). For routine purposes sera need be screened only against these four representative antigen pools. This will detect antibody and indicate which clinical and epidemiological type of chlamydial infection is implicated, thereby clearly distinguishing those infections that are due to C. psittaci. The pattern of the cross-reactions may indicate the individual serotype involved, and further titration requiring a maximum of four individual antigens is sufficient to determine the serotype. The slight loss in sensitivity (twofold) is more than compensated for by the reduction in cost and the tenfold increase in the total number of sera which can be examined.

Infection of the eye, genitalia, and rectum by a new serotype (type G) of TRIC agent. Clinical and laboratory aspects

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