Abstract
Chlamydia comprises a group of obligate intracellular bacterial parasites responsible for a variety of diseases in humans and animals, including several zoonoses. Chlamydia trachomatis causes diseases such as trachoma, urogenital infection and lymphogranuloma venereum with severe morbidity. Chlamydia pneumoniae is a common cause of community-acquired respiratory tract infections. Chlamydia psittaci, causing zoonotic pneumonia in humans, is usually hosted by birds, while Chlamydia abortus, causing abortion and fetal death in mammals, including humans, is mainly hosted by goats and sheep. We used multi-locus sequence typing to asses the population structure of Chlamydia. In total, 132 Chlamydia isolates were analyzed, including 60 C. trachomatis, 18 C. pneumoniae, 16 C. abortus, 34 C. psittaci and one of each of C. pecorum, C. caviae, C. muridarum and C. felis. Cluster analyses utilizing the Neighbour-Joining algorithm with the maximum composite likelihood model of concatenated sequences of 7 housekeeping fragments showed that C. psittaci 84/2334 isolated from a parrot grouped together with the C. abortus isolates from goats and sheep. Cluster analyses of the individual alleles showed that in all instances C. psittaci 84/2334 formed one group with C. abortus. Moving 84/2334 from the C. psittaci group to the C. abortus group resulted in a significant increase in the number of fixed differences and elimination of the number of shared mutations between C. psittaci and C. abortus. C. psittaci M56 from a muskrat branched separately from the main group of C. psittaci isolates. C. psittaci genotypes appeared to be associated with host species. The phylogentic tree of C. psittaci did not follow that of its host bird species, suggesting host species jumps. In conclusion, we report for the first time an association between C. psittaci genotypes with host species.
Highlights
Chlamydia comprises a group of obligate intracellular bacterial parasites responsible for a variety of diseases in humans and animals, including several zoonoses
Significant linkage disequilibrium was detected for C. psittaci, C. abortus, C. trachomatis and C. pneumoniae (Table S2)
Phylogenetic analysis of all 132 strains of Chlamydia using the Neighbour-Joining algorithm with the maximum composite likelihood model of the single 3120 base pairs sequence of the aligned concatenated loci resulted in a tree comparable to that obtained with 16S rRNA gene and 23S rRNA gene sequences [1] and to the previous reported tree based on concatenated sequences of 6 Multi-locus sequence typing (MLST) loci [7] (Fig. 1)
Summary
Chlamydia comprises a group of obligate intracellular bacterial parasites responsible for a variety of diseases in humans and animals, including several zoonoses. It was proposed in 1999 that the single genus of Chlamydia should be reassigned into two genera, Chlamydia and Chlamydophila, based on clustering analyses of the 16S rRNA and 23S rRNA genes [1], which has not been widely accepted by the chlamydial research community. C. pneumoniae often causes mild or subclinical infections, its persistence in the host can lead to the establishment of chronic pathologies and has been implicated with arteriosclerosis [9] and coronary heart diseases [10,11]. Transmission of C. psittaci from birds to humans is frequently reported and veterinarians, poultry farmers, bird breeders and pet shopkeepers are in particular at high risk [17,18,19,20,21,22,23,24,25,26,27]
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