Abstract
Wild birds are considered as a reservoir for avian chlamydiosis posing a potential infectious threat to domestic poultry and humans. Analysis of 894 cloacal or fecal swabs from free-living birds in Poland revealed an overall Chlamydiaceae prevalence of 14.8% (n = 132) with the highest prevalence noted in Anatidae (19.7%) and Corvidae (13.4%). Further testing conducted with species-specific real-time PCR showed that 65 samples (49.2%) were positive for C. psittaci whereas only one was positive for C. avium. To classify the non-identified chlamydial agents and to genotype the C. psittaci and C. avium-positive samples, specimens were subjected to ompA-PCR and sequencing (n = 83). The ompA-based NJ dendrogram revealed that only 23 out of 83 sequences were assigned to C. psittaci, in particular to four clades representing the previously described C. psittaci genotypes B, C, Mat116 and 1V. Whereas the 59 remaining sequences were assigned to two new clades named G1 and G2, each one including sequences recently obtained from chlamydiae detected in Swedish wetland birds. G1 (18 samples from Anatidae and Rallidae) grouped closely together with genotype 1V and in relative proximity to several C. abortus isolates, and G2 (41 samples from Anatidae and Corvidae) grouped closely to C. psittaci strains of the classical ABE cluster, Matt116 and M56. Finally, deep molecular analysis of four representative isolates of genotypes 1V, G1 and G2 based on 16S rRNA, IGS and partial 23S rRNA sequences as well as MLST clearly classify these isolates within the C. abortus species. Consequently, we propose an expansion of the C. abortus species to include not only the classical isolates of mammalian origin, but also avian isolates so far referred to as atypical C. psittaci or C. psittaci/C. abortus intermediates.
Highlights
IntroductionChlamydiae are widely distributed throughout the world, causing a variety of diseases both in humans and animals, including zoonotic infections
The family Chlamydiaceae comprises a group of obligatory intracellular bacteria within the single genus Chlamydia (C.) which includes eleven species [1] and two candidate species [2,3].Chlamydiae are widely distributed throughout the world, causing a variety of diseases both in humans and animals, including zoonotic infections
Chlamydiaceae seem to be common in Polish wild birds, such as swans and mallards, which often live close to humans so that zoonotic implications have to be assumed
Summary
Chlamydiae are widely distributed throughout the world, causing a variety of diseases both in humans and animals, including zoonotic infections. Based on the ompA gene which encodes the major immunogenic protein of chlamydiae, avian C. psittaci has been classified into fifteen genotypes, each one more or less closely associated with certain bird species. Seven of these genotypes (A-F, E/B) are predominant whereas the other eight genotypes (1V, 6N, Mat116, R54, YP84, CPX0308, I and J) were described as provisional [6,7,8,9,10]. Whereas C. psittaci had been considered for a long time to be the sole species hosted by birds, recent evidence suggested that other chlamydial species, such as C. abortus, C. pecorum, C. trachomatis, C. suis and C
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