Detection of Chlamydia ibidis in the neck skin microbiome of broiler carcasses at the end of slaughter.

Chlamydia is the etiological agent of chlamydiosis in wild and domestic birds, mammals, and humans. In this study, Chlamydia reads were detected in the microbiome of the neck skin of 76 broiler carcasses collected in the same slaughterhouse at the end of the chilling tunnel. The carcasses originated from four different flocks of female Ross 308, reared in two broiler houses located in Northern Italy. One flock from each poultry house was sampled in 2019, and one flock in 2023. The carcass neck skin microbiome was investigated by shotgun metagenomic sequencing. Chlamydia reads displayed a mean relative abundance of 7.38%, with significant differences between carcasses obtained from the two poultry houses, sampled at both sampling times. Chlamydia ibidis was the prevalent species among time points and poultry houses. The zoonotic potential of C. ibidis and foodborne transmission have never been demonstrated. However, it is known that the genus Chlamydia has "spore"-like extracellular forms able to survive for months outside the host. Therefore, the presence of C. ibidis reads on broiler carcasses at the end of the chilling tunnel deserves further investigation. The results of this study highlight the feasibility of microbiome investigations to detect unexpected biological hazards in foods.