Molecular evidence of Chlamydia pecorum and arthropod-associated Chlamydiae in an expanded range of marsupials

Delaney Burnard,Jonathan K Webb,Peter Timms,Andrea Reiss,Martina Jelocnik,Janine Carrucan,Adam Polkinghorne,Amber Gillett,Wilhelmina M Huston,Cheyne Flanagan,Scott Carver,Sean Fitzgibbon

doi:10.1038/s41598-017-13164-y

Abstract

The order Chlamydiales are biphasic intracellular bacterial pathogens infecting humans and domesticated animals. Wildlife infections have also been reported, with the most studied example being Chlamydia pecorum infections in the koala, an iconic Australian marsupial. In koalas, molecular evidence suggests that spill-over from C. pecorum infected livestock imported into Australia may have had a historical or contemporary role. Despite preliminary evidence that other native Australian marsupials also carry C. pecorum, their potential as reservoirs of this pathogen and other Chlamydia-related bacteria (CRBs) has been understudied. Mucosal epithelial samples collected from over 200 native Australian marsupials of different species and geographic regions across Australia were PCR screened for Chlamydiales. Previously described and genetically distinct C. pecorum genotypes and a range of 16S rRNA genotypes sharing similarity to different CRBs in the broader Chlamydiales order were present. One 16S rRNA Chlamydiales genotype recently described in Australian ticks that parasitise native Australian marsupials was also identified. This study provides further evidence that chlamydial infections are widespread in native fauna and that detailed investigations are required to understand the influence these infections have on host species conservation, but also whether infection spill-over plays a role in their epidemiology.

Highlights

Evidence that infections by obligate intracellular bacterial pathogens in the order Chlamydiales are generally prevalent in wildlife is increasing[1], but their impact on the overall health of populations remains unclear[1,2]
Nucleotide BLAST analysis of the single sequence results revealed the presence of one previously described and six novel genotypes belonging to the order Chlamydiales[14,15] (Table 2, Fig. 1)
C. pecorum 16S rRNA genotype P787 and C. pecorum genotype 1 accounted for 44.4% of the partial 16S rRNA Chlamydiales genotypes obtained, suggesting that C. pecorum is more abundant among non-koala marsupials than previously thought

Summary

Introduction

Evidence that infections by obligate intracellular bacterial pathogens in the order Chlamydiales are generally prevalent in wildlife is increasing[1], but their impact on the overall health of populations remains unclear[1,2]. C. pecorum has been reported in the greater glider, mountain brushtail possum and western barred bandicoot[10,11]; with C. pneumoniae detected in western barred bandicoots[12] Some of these marsupials exhibited signs of chlamydiosis, such as ocular disease, there is little evidence that C. pecorum has the same pathogenic effect on these marsupials as it does on koalas. Reports such as these, suggest there may be complex and dynamic origins of Chlamydiales in marsupials, further complicating our understanding of this pathogen’s evolution. Chlamydial diversity was sampled from non-koala marsupials across a range of geographic regions in Australia alongside a small subset of wild koalas for comparison

Methods

Results

Discussion

Conclusion