Characterization of the koala biovar of Chlamydia pneumoniae at four gene loci - ompAVD4 ompB, 16S rRNA, groESL spacer region

Koalas are infected with two species of Chlamydia, C. pecorum and C. pneumo niae. While it is known that significant genetic diversity occurs in the C. pecorum strains infecting koalas, very little is known about the C. pneumo niae strains that infect this host. In the current study, 10 isolates of ko ala C, pneumoniae were analysed at four gene loci and found to be different to both the human and horse C. pneumoniae strains at all loci (biovar diff erences ranging from 0.3% at groESL up to 9.0% at ompAVD4). All koala biova r isolates studied were found to be 100% identical at ompAVD4 (all 10 isola tes) and at ompB (all three isolates) genes. This lack of allelic polymorph isms at ompAVD4 has now been observed for koala C. pneumoniae, human C. pne umoniae, guinea pig inclusion conjuctivitis C, psittaci and feline conjucti vitis C. psittaci and may be correlated to a lack of antibody response to t he chlamydial major outer membrane protein (MOMP) in these same strain/host combinations. This study also provides the first documented case of natura l C. pneumoniae infection causing a severe and extended respiratory episode in a captive koala population. This captive episode is in contrast to most free-range observations in which koala C. pneumoniae is rarely documented as causing respiratory, ocular or urogenital tract disease.