OUTER-MEMBRANE PROTEIN-2 GENE-SEQUENCES INDICATE THAT CHLAMYDIA-PECORUM AND CHLAMYDIA-PNEUMONIAE CAUSE INFECTIONS IN KOALAS

Chlamydial infection in koalas causes conjunctivitis, rhinitis, urinar y tract disease and female infertility. The chlamydial strains respons ible have previously been designated as Chlamydia psittaci and have be en subdivided into two types, I and II. In the present study we determ ined the DNA sequence of a 530 bp segment of the omp 2 gene from seven koala chlamydial strains, the type strain of C. pecorum, and the hors e strain N16, and compared these with previously reported omp 2 gene s equences from 10 other chlamydial strains. Omp 2 sequence data clearly separated the seven koala strains into two genetic groups. Koala omp 2 group A corresponds to the previous type I designation and includes a conjunctival strain and a systemic disease-causing strain. The koala group A omp 2 sequence is 93% similar to the human C. pneumoniae IOL- 207 strain and also 99% similar to the horse strain, N16. We propose t hat these koala strains be referred to as koala C. pneumoniae in futur e. Koala omp 2 group B corresponds to the previous koala type II desig nation and includes three urogenital tract strains plus two ocular str ains. The koala group B omp 2 sequence is 99% similar lo the C. pecoru m type strain, VR628, while being only 77% similar to the EAE C. psitt aci strain and only 71% similar to the koala group A strains. We propo se that these koala strains be referred to as koala C. pecorum in futu re. The fact that two different species of Chlamydia infect koalas rei nforces the observation that chlamydial species are not host restricte d and makes us rethink the epidemiology of chlamydial disease in this marsupial.