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Evidence that human Chlamydia pneumoniae was zoonotically acquired

G S A Myers1, S A Mathews, M Eppinger

  • 1Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD 21201, USA. gmyers@som.umaryland.edu

Journal of Bacteriology
|September 15, 2009
PubMed

Insights

Genomic analysis suggests the koala strain of Chlamydia pneumoniae is ancestral to human strains. This indicates humans may have originally acquired this respiratory pathogen through zoonotic transmission from animals.

Area of Science:

  • Genomics
  • Microbiology
  • Zoonotic Diseases

Background:

  • Chlamydia pneumoniae is a significant human pathogen causing respiratory illness.
  • While initially considered exclusively human, C. pneumoniae's host range now includes various animals.
  • Koalas are frequently infected with Chlamydia species, including C. pneumoniae.

Purpose of the Study:

  • To investigate the evolutionary origins of human Chlamydia pneumoniae.
  • To compare the koala C. pneumoniae strain with human isolates using genomic data.
  • To determine if koalas serve as a reservoir for human C. pneumoniae.

Main Methods:

  • Whole-genome shotgun sequencing of the koala C. pneumoniae strain (LPCoLN).
  • Comparative genomic analysis of pseudogene and single-nucleotide polymorphism (SNP) distribution.
  • Phylogenetic analysis of conserved genes and SNPs against human C. pneumoniae isolates.

Main Results:

  • The koala C. pneumoniae isolate (LPCoLN) was sequenced.
  • Genomic and phylogenetic analyses revealed the koala isolate is basal to human isolates.
  • Evidence suggests adaptation to humans involved gene decay and plasmid loss.

Conclusions:

  • Compelling genomic and phylogenetic evidence supports a zoonotic origin for human C. pneumoniae.
  • Humans were likely originally infected by an animal C. pneumoniae strain.
  • The pathogen adapted to humans, losing reliance on an animal reservoir for transmission.

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