# Antibiotic Resistance of Bacteria Isolated from Clinical Samples and Organs of Rescued Loggerhead Sea Turtles (Caretta caretta) in Southern Italy

## TL;DR

This study examines antibiotic resistance in bacteria from loggerhead sea turtles in Italy, showing how prior antibiotic use increases resistance and highlights the need for better antimicrobial management.

## Contribution

The study provides new insights into antibiotic resistance patterns in wild loggerhead sea turtles and emphasizes the importance of antimicrobial stewardship in wildlife.

## Key findings

- Vibrionaceae was the most common bacterial family, with resistance rates below 10.5%.
- Enterobacteriaceae and Morganellaceae showed the highest resistance rates and multidrug-resistant strains.
- Prior antibiotic treatment in turtles was linked to increased resistance, stressing the need for improved antimicrobial use.

## Abstract

Antimicrobial resistance is threatening health and the economy worldwide, not only in clinical settings, but also in livestock and wildlife management. Among the numerous wild animals affected, sea turtles are particularly exposed to antibiotics, due to biological and habitat characteristics. This study analysed the hospitalisation records in a sea turtle rescue centre in southern Italy during the last decade, focusing on the antibiotic resistance of bacteria isolated from clinical samples and organs. Resistance patterns to 7 antibiotics were examined in 138 bacteria isolated from 60 loggerhead sea turtles, highlighting 6 main bacterial families with different resistance rates. Vibrionaceae represented the predominant family, although the resistance rates did not exceed 10.5%. Similar results were described for Shewanellaceae, whereas the less represented families were those with the highest resistance rates and numbers of multidrug-resistant strains, especially Enterobacteriaceae and Morganellaceae. Previous antibiotic therapies appeared to enhance resistance, emphasizing the need to improve antimicrobial stewardship. Isolated bacteria are considered opportunistic pathogens, but their antibiotic resistance might compromise treatment and rehabilitation, potentially affecting the population health of these endangered species. Given the possible transfer of resistance across species, these findings should be considered from a One Health perspective, including other animals, humans and the environment.

Antimicrobial resistance affects all environments, endangering the health of numerous species, including wildlife. Increasing anthropic pressure promotes the acquisition and dissemination of antibiotic resistance by wild animals. Sea turtles, being particularly exposed, are considered sentinels and carriers of potential zoonotic pathogens and resistant strains. Therefore, this study examined the antibiotic resistance profiles of bacteria isolated from loggerhead sea turtles hospitalised in a rescue centre of Southern Italy over a 9-year period. Resistance to ceftazidime, doxycycline, enrofloxacin, flumequine, gentamicin, oxytetracycline and sulfamethoxazole-trimethoprim was evaluated for 138 strains isolated from the clinical samples or organs of 60 animals. Gram-negative families were the most isolated: Vibrionaceae were predominant, followed by Shewanellaceae, Pseudomonadaceae, Enterobacteriaceae and Morganellaceae. These last three families exhibited the highest proportion of resistance and multidrug-resistant strains. Among the three Gram-positive families isolated, Enterococcaceae were the most represented and resistant. The opportunistic behaviour of all the isolated species is particularly concerning for diseased sea turtles, especially considering their resistance to commonly utilised antibiotics. Actually, the multiple antibiotic resistance was higher when the sea turtles were previously treated. Taken together, these findings highlight the need to improve antimicrobial stewardship and monitor antibiotic resistance in wildlife, to preserve the health of endangered species, along with public and environmental health.