Molecular characterization of atypical Chlamydia and evidence of their dissemination in different European and Asian chicken flocks by specific real‐time PCR

Abstract

Summary Chlamydia psittaci is a zoonotic pathogen associated primarily with avian chlamydiosis. New chlamydial agents with suspected zoonotic potential were recently detected from domestic poultry in Germany and France indicating that the spectrum of Chlamydiaceae encountered in birds is not confined to a single chlamydial species. For further characterization, a specific real‐time PCR targeting the conserved 16S rRNA gene was developed and validated for a specific detection of these atypical Chlamydiaceae. In order to address the epidemiological importance of the new chlamydial agents and their distribution, Chlamydiaceae‐positive chicken samples collected from flocks from five different countries were examined. The results confirmed that C. psittaci is not the predominant chlamydial species among chickens examined and suggested that the new chlamydial agents could putatively be widespread in poultry flocks (France, Greece, Croatia, Slovenia and China at least) justifying their systematic investigation when poultry samples are submitted to laboratories for avian chlamydiosis diagnosis. Besides, 16S rRNA‐based dendrogram, including sequences from both isolates of the new chlamydial agents or positive samples as well as representative sequences from species belonging to the order Chlamydiales, showed the new chlamydial agents to form a distinct line of descent separated from those of other chlamydial species, but clearly grouped within the family Chlamydiaceae. Finally, the phylogenetic tree inferred from the multi‐locus sequence typing based on four housekeeping fragments (gatA, gidA, enoA and hflX) and the ompA‐based dendrogram showed an almost identical topology of the new chlamydial agents with that recovered by 16S rRNA‐based dendrogram. Interestingly, partial ompA gene sequences displayed considerable diversity among isolates.

Multilocus Sequence Analysis Provides Insights into Molecular Epidemiology of Chlamydia pecorum Infections in Australian Sheep, Cattle, and Koalas

“…The number of synonymous substitutions detected in C. pecorum was comparable to those observed in Chlamydia abortus and C. psittaci (31). Our Australian C. pecorum strains had diversity of 0.4 ST/per strain, which is consistent with observations across the Chlamydiae in general (31,44).…”

“…To resolve these issues, multiple sequence alignments of the seven HK genes from the recently available C. pecorum E58 genome (23), and draft genomes of three koala C. pecorum isolates isolated from SEQLD and the sheep C. pecorum polyarthritis type strain IPA (Polkinghorne, unpublished), as well as other Chlamydia species, were performed, which revealed a number of single nucleotide polymorphisms that may affect the efficiency of PCR amplification using the pan-Chlamydiales degenerate primers. Due to sequence divergence within the Chlamydiaceae family, Zocevic and colleagues (44) were also able to amplify only gatA, enoA, gidA, and hlfX using the pan-Chlamydiales. The newly designed C. pecorum-specific HK gene primers reported here amplified the desired sequences with high efficiency and specificity and were tested against genomic DNA samples extracted from cultured Australian C. psittaci and koala C. pneumoniae isolates (data not shown).…”

Outbreak of psittacosis in a group of women exposed to Chlamydia psittaci-infected chickens

“…C. gallinacea is a newly described chlamydial species [10]. Recent surveys on the prevalence of C. gallinacea in poultry flocks in four European countries and China revealed a prevalence that could even exceed that of C. psittaci [11], at least for chickens and turkeys. These data were recently confirmed by a survey conducted on Chlamydiaceae prevalence in French slaughtered poultry birds, which revealed that C. gallinacea is mainly encountered in chickens and turkeys, while C. psittaci is most often detected in ducks [25].…”

“…All Chlamydiaceae PCR-positive samples from humans and animals were re-analysed using previously described real-time PCR assays for C. psittaci [16] and C. gallinacea [11]. In addition, a new enoA-based real-time PCR protocol for C. gallinacea was developed in this study.…”

“…Based on currently available data, using both broadrange and specific diagnostic tools, it seems likely that C. gallinacea is widely disseminated among poultry and C. avium is frequently found in pigeons. PCRbased tools have been developed for their specific detection [11,12]. The aetiological importance of these new agents in humans or birds is at present not well understood.…”