Detection of zoonotic bacteria in wild Australian freshwater turtles

Freshwater turtles are long-lived, abundant components of Australian aquatic ecosystems, yet little is known about the diversity and prevalence of zoonotic bacteria they may carry. In this study, we conducted one of the most comprehensive surveys to date of zoonotic microorganisms associated with wild Australian freshwater turtles. A total of 257 individuals representing 10 species across 6 genera were sampled from multiple riverine and wetland systems. Using next generation sequencing, we detected 18 confirmed zoonotic bacterial species spanning 10 genera, including Acinetobacter, Vibrio, Plesiomonas, Campylobacter, and Clostridium. Nearly half of all turtles (49.8%) were shedding at least one zoonotic taxon at the time of capture, with some individuals carrying multiple species simultaneously. Several additional isolates from genera with known zoonotic potential could not be resolved to species level, highlighting gaps in current reference databases and the need for improved genomic characterisation. No Salmonella spp. were detected, consistent with previous research suggesting a low risk of reptile-associated salmonellosis from Australian freshwater turtles. Shedding prevalence varied markedly among turtle species and locations, suggesting that host ecology and environmental conditions influence bacterial acquisition and persistence. Due to data sparsity for many taxa, analyses were limited to descriptive assessments. Overall, these findings demonstrate that Australian freshwater turtles harbour a diverse assemblage of bacteria with zoonotic relevance and may act as reservoirs within aquatic environments. Continued surveillance, integration of genomic tools, and consideration of human-wildlife interaction contexts, including cultural harvesting, will be important for assessing public health implications and informing conservation and biosecurity strategies.