Experimental inoculation of chicken broilers with C. gallinacea strain 15-56/1

Chlamydia gallinacea in Brazilian backyard chicken farms

Avian chlamydiosis is a bacterial infectious disease of birds, considered until recently caused only by Chlamydia psittaci, that now includes the newly described species C. buteonis, C. avium, and C. gallinacea, associated with several avian hosts. Since its recognition as a species in 2014 and having chickens as one of its main hosts, C. gallinacea has already been described in backyard poultry on all continents. The present study aimed to survey by molecular techniques the presence and species of Chlamydia spp. in backyard chickens from three states of the southern region of Brazil (Paraná-PR, Santa Catarina-SC, and Rio Grande do Sul-RS). DNA extracted from cloacal swab samples were tested by polymerase chain reaction (PCR) for different species of Chlamydia, namely Chlamydiaceae (23 S rRNA gene), C. psittaci (ompA gene), C. avium (enoA gene) and C. gallinacea (gidA and enoA genes). The 16 S rRNA gene was used for sequencing and phylogenetic analysis. A total of 582 backyard chicken samples were collected and grouped in 238 pools, from 134 properties in 59 municipalities. Chlamydiaceae was detected in 25.2% (60/238) of the samples, in 38.8% (52/134) of the properties and in 66.1% (39/59) of the municipalities. None of the samples yielded positive PCR results for C. psittaci or C. avium. For C. gallinacea, the overall percentage was 16.3% (39/238) according to the results of gidA and enoA genes. Sequence analysis confirmed that the samples corresponded to C. gallinacea. This is the first report of C. gallinacea in Brazil.

New insight on chlamydiae

This article provides an overview of the current knowledge on chlamydiae, which are intracellular bacteria belonging to the Chlamydiaceae family. Whole-genome sequencing leads to great increases in the available data about Chlamydia spp. Recently, novel chlamydial taxons in various hosts living in different environments have been recognised. New species and taxons with Candidatus status have been recorded mainly in birds and reptiles. Chlamydia gallinacea is an emerging infectious agent in poultry with indirectly confirmed zoonotic potential. Recently, a new group of avian C. abortus strains with worldwide distribution in various wild bird families has been described. The definition of C. abortus species became outdated with the discovery of these strains and has been amended. It now includes two subgroups, mammalian and avian, the latter including all isolates hitherto referred to as atypical C. psittaci or C. psittaci/C. abortus intermediates.

Whole Genome Sequencing and Comparative Genomic Analysis of Chlamydia gallinacea Field Strains Isolated from Poultry in Poland

Chlamydia gallinacea is an intracellular bacterium belonging to the Chlamydiaceae family. Poultry is considered to be the major reservoir of this agent, which has worldwide distribution and a particularly consistent worldwide occurrence in chicken flocks. The bacterium has been linked to respiratory disease in humans but without definitive confirmation; nevertheless, while it has not been proved to be the cause of human respiratory disease, a recent report from Italy verified its bird-to-human transmission. This aspect being significant for public health, more research is needed to gain insight into the infection biology of C. gallinacea. In this study, the genomes of eleven novel C. gallinacea field strains from different regions of Poland were analyzed comparatively. It was confirmed that C. gallinacea strains are closely related, with at least 99.46% sequence identity. They possess a conservative genome structure involving the plasticity zone with a complete cytotoxin, the type three secretion system, inclusion membrane proteins, polymorphic membrane proteins, hctA and hctB histone-like proteins, and the chlamydial protease-like activating factor exoenzyme, as well as plasmids. Genetic diversity seems to be restricted. However, some genetic loci, such as ompA and multi-locus sequence typing target genes, are diverse enough to enable high-resolution genotyping and epidemiological tracing.