Gut microbiota isolated from the European pond turtle (Emys orbicularis) and its antimicrobial resistance

The aim of the study was to isolate cultivable gut microbiota from European pond turtles kept at the Lithuanian Zoo and to determine antimicrobial resistance of the isolates. The study subjects included 8 elderly turtles living at the Lithuanian Zoo for about 50 years as well as their offspring - 24 young individuals (1-2 years old) that were hatched at the same zoo. Animals were not exposed by treatment with antimicrobials during the last 3 years. Gut samples were taken from the cloaca and inoculated onto universal media. Isolates then were identified using sequence analysis of 16S rRNA. The antimicrobial susceptibility testing was performed using the agar diffusion method according to Kirby-Bauer. Clinical breakpoints according to CLSI whenever possible, were used for interpretation of susceptibility. Bacterial isolates resistant to at least three antimicrobials of different classes were treated as multi-resistant. Fifty-two bacterial isolates were obtained and identified from turtle gut samples. The most prevalent genera included Aeromonas, Chryseobacterium and Citrobacter. Fifty percent of the isolates obtained from elderly turtles (CI 95% - 19.01-80.99) and 54.8% (CI 95% - 39.75-69.85) of the isolates from young animals were identified as multi-resistant. The most common resistance rates of the isolates from both groups of the turtles were observed toward ampicillin (86.6%), ciprofloxacin (61.5%) and gentamicin (40.4%). The lowest number of resistant isolates were detected toward combination of sulfamethoxazole-trimethoprim (26.9%). The study revealed that European pond turtles kept in captivity are carriers of multi-resistant bacteria however, further studies need to be performed to investigate whether the resistant microorganisms are natural microbiota for this species or they were acquired in the zoo.