The first genomic insight into Chlamydia psittaci sequence type (ST)24 from a healthy captive psittacine host in Australia demonstrates evolutionary proximity with strains from psittacine, human, and equine hosts.

The research article details a study which investigates the genomic sequence of Chlamydia psittaci, a pathogen that affects birds, humans, and horses, extracted from a captive blue-fronted parrot in Australia. The study further analysed the genetic relation between the sequence type (ST)24 strain found in the parrot and those identified in humans, horses, and wild birds.

Background of the Study

• The research is centered around Chlamydia psittaci, which is a pathogenic bacterium that infects a variety of hosts including birds, humans and horses.
• This study was driven by the scarcity of knowledge about the genetic identity of the strain in captive psittacine hosts, despite previous research on the ST24 strains in horses, wild psittacine birds, and humans.

The Process and Findings

• The bacterium was detected in the feces of a healthy blue-fronted parrot.
• The genomic DNA of the C. psittaci strain, named BF_amazon_parrot13, was sequenced and analysed.
• The strain was found to belong to the ST24 lineage and carried the ompA genotype A.
• A further comparison was made against the genomes of 31 previously published strains of ST24 using single-nucleotide variant (SNV) based comparison.
• The study found that despite differences in time, hosts, and geographical locations, the parrot’s strain showed a close genetic proximity with the strains from Australian horses (with a maximum difference of just 13 SNVs).

Significance and Implications

• BF_amazon_parrot13 represents the first complete discovery of C. psittaci ST24 genome from a captive psittacine in Australia.
• The study enhances understanding of the potential health risks and transmission routes of the ST24 strain of the pathogen among various hosts including humans, horses, wild and domesticated birds.
• The close genetic similarity with strains identified in Australian horses provides new insights into the possible zoonotic transmission of the bacterium.
• The study underscores the relevance of whole-genome sequencing in tracking and managing diseases that can cross species, suggesting that a one-health approach may be beneficial.