Chlamydia trachomatis causes both urogenital tract (UGT) and ocular infections. One class of ocular infection is trachoma. Trachoma has a distinctive pathology, encompassing repeated rounds of conjunctivitis, which can lead to chronic inflammation, corneal scarring and blindness. It has long been that while strains that cause UGT infections are essentially all able to cause conjunctivitis, the strains that cause trachoma are rarely associated with UGT infection. Previous genetic studies have shown that the trachoma strains form a single evolutionary lineage within the C. trachomatis species.

This presentation will encompass recent advances in the understanding of the evolutionary structure and dynamics of C. trachomatis. Much of the work described was directed towards understanding better how service providers should respond to instances in which UGT specimens from young children are found to be C. trachomatis positive. While this is regarded as indicative of sexual abuse, a conceivable mechanism by which this can arise is autoinoculation from an ocular C. trachomatis infection. This is particularly relevant to remote northern and central Australia, where trachoma still exists, and where the extent of child sexual abuse is contentious and politically loaded. Understanding the strains associated with trachoma in Australia  could potentially underpin procedures for determining whether or not C. trachomatis in a paediatric UGT specimen is derived from an ocular infection.

Genome sequences of historic trachoma associated C. trachoma isolates from Northern Australia will be presented. The results do not support the established model of a single trachoma lineage. While the isolates possessed alleles of the ompA gene previously associated with trachoma strains, these appeared to be recombined into multiple non-trachoma-associated lineages. Furthermore, there was evidence for acquisition of of pmpEFGH alleles similar to those found in trachoma lineages. It was concluded that ompA and pmpEFGH may be functionally associated with trachoma pathology.

Disclosure of interest statement Much of the work presented was funded by the NHMRC project grants 1004123 and 1060768. Phil Giffard declares no other interests.