MOLECULAR EPIDEMIOLOGY OF TRACHOMA IN A GAMBIAN VILLAGE

The application of a diagnostic and genotyping technique based on the polymerase chain reaction (PCR) to the study of trachoma epidemiology in the Gambian village of Jali is reported. PCR based on the major out er membrane protein (MOMP) gene of Chlamydia trachomatis appears to be more sensitive than either isolation or antigen detection by enzyme i mmunoassay; it had a specificity of 95% and sensitivity of 51% against clinical signs. PCR genotyping identified genotypes A and B of Chlamy dia trachomatis circulating in Jali. Sequencing revealed a Pst1 restri ction endonuclease site in the amplified MOMP gene of some B strains b ut not others; Pst1 digestion of the PCR product proved an easy method of distinguishing these strains. The distribution of serotypes and B strain variants shows a significant degree of household clustering (p< 0.001). PCR based genotyping combined with strain typing provides a ne w and powerful epidemiological tool for the study of transmission even ts in trachoma.