For the first time, researchers of the Menzies School of Health Research and the UK's Wellcome Trust Sanger Institute have sequenced the bacterium Chlamydia trachomatis. Their work has revealed that through genetic exchange C. trachomatis bacteria causing sexually transmitted disease can become agents for trachoma, a leading cause of blindness.
C. trachomatis is the major cause of sexually transmitted infections (STIs) worldwide. It is also the cause of trachoma, a neglected tropical disease that affects about 2.2 million people worldwide. Australia is the only developed country where trachoma remains endemic among some of its Indigenous communities.
It has previously been assumed that types of C. trachomatis causing trachoma were completely separate from those bacteria causing STIs, representing a distinct phylogenetic lineage.
However, as the researchers show in a report in Nature Communications, this is not necessarily the case.
They analysed genome sequences from frozen Chlamydia isolates that had been collected from children with trachoma in the 1980s and 1990s. They found two isolates that did not belong to the classical trachoma lineage, but instead were related to C. trachomatis baceria causing STIs.
The researchers show that these bacteria became infectious to the eye after having acquired one or two gene variants from trachoma causing C. trachomatis types.
It is now known that Chlamydia bacteria can readily exchange genes.
This could be clinically significant as it means there is continued potential for new trachoma causing types to emerge.
The outcome of this study also demonstrates the value of long term storage of clinical and biological material, and its analysis with modern high technology. There remain many important unanswered questions about C. trachomatis, which in many ways remains an enigmatic pathogen, even when this study has revealed some of its secrets
