Molecular detection and characterization of Chlamydiaceae from seagulls associated to anthropogenic environments in Argentina.

Chlamydiaceae is a Gram-negative obligate intracellular bacterial family that includes pathogens and zoonotic species. Birds are recognized as reservoirs of Chlamydia, with C. psittaci identified as the main agent of avian chlamydiosis. This study reports the detection and molecular characterization of Chlamydiaceae in three gull species (Larus dominicanus, Chroicocephalus maculipennis and Chroicocephalus cirrocephalus) that frequented anthropogenic environments in Argentina. A total of 121 gulls were captured at a household sanitary landfill in Buenos Aires province and at an open landfill receiving fishing discards in Chubut province. A single multimucosal swab of each gull was collected and stored in SPG transport medium. Screening was conducted using qPCR targeting the Chlamydiaceae 23S rRNA gene, along with species-specific qPCR assays for C. psittaci, C. gallinacea, and C. avium. A short segment of the 16S rRNA gene and a longer fragment comprising the 16S rRNA gene, 16S/23S intergenic spacer region, and a portion of the 23S rRNA gene were used for sequencing and phylogenetic analysis. Attempts to culture the bacteria in VERO cells were unsuccessful. Twenty-three gull samples tested positive for the Chlamydiaceae 23S rRNA gene; however, none were positive when they were tested using species-specific qPCRs. Phylogenetic analysis revealed that most strains clustered with Chlamydia-like organisms previously detected in gulls and Magellanic penguins from Argentina. Two gulls were phylogenetically clustered with C. abortus, a known zoonotic species. Additionally, two sequences showed 93.53-93.78% and 93.13-93.14% identity with members of the recently described genus Chlamydiifrater. These findings confirm the circulation of Chlamydiaceae in gulls from the study area and provide the first evidence of chlamydial infection in Chroicocephalus maculipennis and Chroicocephalus cirrocephalus highlighting the potential role of gulls as reservoirs and disseminators of chlamydial agents.