Oral Presentation The 3rd Prato Conference on the Pathogenesis of Bacterial Diseases of Animals 2014

Evaluation of the relationship between Chlamydia pecorum genotype and disease using a species-specific multi-locus sequence typing scheme (MLST) (#7)

Martina Jelocnik 1 , Evelyn Walker 1 , Yvonne Pannekoek 2 , Judy Ellem 3 , Peter Timms 1 , Adam Polkinghorne 1
  1. Faculty of Science, Health, Education and Engineering, University of Sunshine Coast, Sippy Downs, Queensland, Australia
  2. Department of Medical Microbiology, Center for Infection and Immunity, Academic Medical Center, Amsterdam, The Netherlands
  3. North West Local Land Services, Narrabri & Walgett , New South Wales , Australia

Chlamydia pecorum is globally associated with several ovine diseases including keratoconjunctivitis and polyarthritis [1]. The exact relationship between the variety of C. pecorum strains reported and the diseases described in sheep remains unclear, challenging efforts to accurately diagnose and manage C. pecorum infected flocks. 

In the present study, we applied C. pecorum Multi Locus Sequence Typing (MLST) [2] to C. pecorum positive samples collected from sympatric flocks of Australian sheep presenting with conjunctivitis, conjunctivitis with polyarthritis, or polyarthritis only and with no clinical disease (NCD) in order to elucidate the exact relationships between the infecting strains and the range of diseases. Using Bayesian phylogenetic and cluster analyses on 62 C. pecorum positive ocular, vaginal and rectal swab samples from sheep presenting with a range of diseases and in a comparison to C. pecorum genotypes from other hosts, one ST ( ST 23) was recognised as a globally distributed strain associated with ovine and bovine diseases such as polyarthritis and encephalomyelitis. A second ST (ST 69), presently only described in Australian animals, was detected in association with ovine as well as koala chlamydial infections. The majority of vaginal and rectal C. pecorum STs from animals with NCD and/or anatomical sites with no clinical signs of disease in diseased animals, clustered together in a separate group, by both analyses. Furthermore, eight/13 detected STs were novel, indicating ovine C. pecorum high strain diversity.

This study provides a platform for strain selection for further research into the pathogenic potential of C. pecorum in animals and highlights targets for potential strain-specific diagnostic test development.  The encroachment of koala habitats by livestock farming along the east coast of Australia is common [3] and raises serious questions over the potential role that cross-host transmission may have in the epidemiology of chlamydial disease in these hosts. 



  1. Yousef Mohamad, K., Rodolakis, A., 2010. Recent advances in the understanding of Chlamydophila pecorum infections, sixteen years after it was named as the fourth species of the Chlamydiaceae family. Vet. Res. 41, 27.
  2. Jelocnik, M., Frentiu, F.D., Timms, P., Polkinghorne, A., 2013. Multi-locus sequence analysis provides insights into the molecular epidemiology of Chlamydia pecorum infections in Australian sheep, cattle and koalas. J. Clin. Microbiol. 51, 2625-2632.
  3. Polkinghorne, A., Hanger, J., Timms, P., 2013. Recent advances in understanding the biology, epidemiology and control of chlamydial infections in koalas. Vet. Microbiol. 165, 214-223.