Characterisation of the antimicrobial resistance profile of culturable Gram-negative bacterial isolates from green sea turtles (Chelonia mydas) in the Gulf of Thailand

Abstract

Green sea turtles are endangered globally; this is partly due to anthropogenic threats including environmental pollution. This study investigated antimicrobial resistance (AMR) in culturable Gram-negative bacteria from green sea turtles at a rehabilitation centre and wild-stranded green sea turtles in the Gulf of Thailand. Cloacal samples were collected from 126 captive and 13 wild green sea turtles, from which 47 Gram-negative bacterial isolates (24 captive and 23 wild) were identified. Among the identified isolates, Citrobacter spp. exhibited the highest prevalence (31.9 %), followed by Alcaligenes faecalis (8.5 %), Proteus mirabilis (8.5 %), and Vibrio spp. (6.4 %). Many isolates (76.6 %) were resistant to multiple antibiotics. The statistical analysis of AMR across 14 antibiotics revealed significant differences between captive and wild green sea turtles (p = 0.0329). A significantly higher incidence of resistance to cefoxitin (p = 0.0184), ampicillin (p = 0.0027), and amoxicillin-clavulanic acid (p = 0.0255) was observed in captive turtles compared to wild turtles. In contrast, wild turtles exhibited significantly higher resistance to potentiated sulfonamides (p = 0.0388) and tetracyclines (p = 0.0002). These findings indicate that antibiotics that are commonly used in human and veterinary medicine, aquaculture and agriculture are exerting selection pressure on gut bacteria in green sea turtles in Thailand, leading to the development of AMR. While the use of antibiotics to manage infections in turtle rehabilitation facilities is common, selection for AMR in wild green sea turtles may result from anthropogenic activities leading to environmental contamination with antibiotics and other biocides. Strategies to mitigate this problem are urgently needed.