Genetic differences in Chlamydia pecorum between neighbouring sub-populations of koalas (Phascolarctos cinereus)

Koala immunogenetics and chlamydial strain type are more directly involved in chlamydial disease progression in koalas from two south east Queensland koala populations than koala retrovirus subtypes

“…Our findings also strengthen a growing body of data that support the infecting chlamydial strain as an important contributor for chlamydial disease progression in koalas 9,11,12,32 . Our approach was to combine a MLST scheme, which has been shown to be congruent with whole genome phylogeny and is a robust method for investigating genetic diversity 33 , with ompA genotyping, which appears to capture more genetic diversity due to the polymorphic nature of the ompA gene.…”

“…This finding strengthens the known association of ompA genotype F with higher urogenital tract infection loads and chlamydial disease progression in koalas 9,11 . In contrast, ST 69 was associated with resolved urogenital tract infections at MB in this study, while ST 69 has previously been associated with clinical disease in NSW koalas 12 as well as being detected in koalas without clinical signs of disease 33 . We also found that ST 281 appeared to be less pathogenic at HV and was associated with the absence of disease progression and milder urogenital tract disease once progression had occurred.…”

“…Our approach was to combine a MLST scheme, which has been shown to be congruent with whole genome phylogeny and is a robust method for investigating genetic diversity 33 , with ompA genotyping, which appears to capture more genetic diversity due to the polymorphic nature of the ompA gene. This combined approach allows for fine-scale C. pecorum epidemiological investigations 12,34 . At this fine-scale, we determined that chlamydial genotypes belonging to both ST 69 and ompA genotype F appeared to be more pathogenic at HV and were associated with urogenital tract disease progression.…”

“…Conversely, koalas with genotype G infections generally did not progress to disease 10 and Victorian (Vic) koalas with genotype B infections only displayed mild signs of disease 11 . Further, chlamydial strain typing in a New South Wales (NSW) population, using Multi-Locus Sequence Typing (MLST), suggested that increased disease expression in the population may have been due to the introduction of a novel chlamydial strain 12 . Another identified predictor of disease progression in koalas is the load of chlamydial organisms in the urogenital tract 13 .…”

Chlamydiae from Down Under: The Curious Cases of Chlamydial Infections in Australia

“…Until a more comprehensive set of Cpec whole genome sequences from koalas and Australian livestock (only 5 genomes from each have been published thus far) is available [133,134], Cpec-specific MLST and ompA genotyping have proven to be effective molecular epidemiology tools for characterising strains infecting these hosts [98,100,[135][136][137][138]. Whilst highlighting an unexpected level of diversity for not just Australian strains but the global Cpec population, these tools have provided the following important epidemiological observations in Australia: (a) a single host can harbour two distinct strains at different anatomical sites, (b) a mixture of genetically diverse strains can circulate in a single population, (c) the same strain can infect two different hosts (e.g., koala and sheep or sheep and cattle( Figure 1B)) and (d) some koala strains are more genetically similar to livestock strains than they are to other koala strains ( Figure 1B) [136][137][138]. Molecular genotyping studies also suggested that certain Cpec genotypes may demonstrate tissue tropisms and pathogenicity.…”