Detection and genomic characterization of Salmonella Infantis and Klebsiella serotypes in loggerhead sea turtles (Caretta caretta), Italy

This study describes the detection and genomic characterization of Salmonella enterica serovar Infantis ST32 and previously unreported Klebsiella serotypes isolated from stranded Caretta caretta along the Italian Adriatic coast. Cloacal and fecal samples collected during rescue and rehabilitation activities yielded multiple isolates identified through MALDI-TOF MS and subjected to antimicrobial susceptibility testing and whole-genome sequencing. Salmonella Infantis isolates displayed a uniform ST32 profile and were recovered from a turtle at admission and from remaining positive animals prior to release. These findings suggest intermittent shedding and possible acquisition of infection during hospitalization. Genomic relatedness among isolates indicated potential intra-facility transmission. In contrast, Klebsiella isolates exhibited heterogeneous profiles, including several multidrug-resistant strains harboring resistance determinants of clinical relevance. The identification of novel Klebsiella serotypes and the first report of S . Infantis ST32 in loggerhead sea turtles expand current knowledge on pathogen diversity in marine reptiles and emphasize their role as sentinels for antimicrobial resistance in marine environments. Overall, these findings highlight the importance of integrating advanced diagnostic and genomic tools into wildlife health monitoring, with implications for rehabilitation practices, environmental surveillance, and zoonotic risk assessment within a One Health framework.