Antibiotic-Resistant Escherichia coli Strains Isolated from Captive Giant Pandas: A Reservoir of Antibiotic Resistance Genes and Virulence-Associated Genes

SIMPLE SUMMARY: Escherichia coli (E. coli) carrying antibiotic resistance genes (ARGs) and virulence-associated genes (VAGs), which are considered as emerging environmental pollutants, undoubtedly causes adverse health effects on humans and animals. With the implementation of the Wild Release Plan of captive giant pandas, antibiotic-resistant E. coli carrying ARGs/VAGs in giant pandas’ feces that are discharged into the environment may become pollutants for nature. To evaluate the potential threat of E. coli strains from captive giant pandas, we analyzed the distribution and the association of ARGs and VAGs in antibiotic-resistant E. coli. Our results revealed a high prevalence of ARGs and a significant positive association among ARGs and VAGs, suggesting that the continuous monitoring of the impact of the spread of antibiotic-resistant E. coli (carried various ARGs and VAGs) is needed in future studies. ABSTRACT: Recent studies showed that Escherichia coli (E. coli) strains isolated from captive giant pandas have serious resistance to antibiotics and carry various antibiotic resistance genes (ARGs). ARGs or virulence-associated genes (VAGs) carried by antibiotic-resistant E. coli are considered as a potential health threat to giant pandas, humans, other animals and the environment. In this study, we screened ARGs and VAGs in 84 antibiotic-resistant E. coli strains isolated from clinically healthy captive giant pandas, identified the association between ARGs and VAGs and analyzed the phylogenetic clustering of E. coli isolates. Our results showed that the most prevalent ARG in E. coli strains isolated from giant pandas is bla(TEM) (100.00%, 84/84), while the most prevalent VAG is fimC (91.67%, 77/84). There was a significant positive association among 30 pairs of ARGs, of which the strongest was observed for sul1/tetC (OR, 133.33). A significant positive association was demonstrated among 14 pairs of VAGs, and the strongest was observed for fyuA/iroN (OR, 294.40). A positive association was also observed among 45 pairs of ARGs and VAGs, of which the strongest was sul1/eaeA (OR, 23.06). The association of ARGs and mobile gene elements (MGEs) was further analyzed, and the strongest was found for flor and intI1 (OR, 79.86). The result of phylogenetic clustering showed that the most prevalent group was group B2 (67.86%, 57/84), followed by group A (16.67%, 14/84), group D (9.52%, 8/84) and group B1 (5.95%, 5/84). This study implied that antibiotic-resistant E. coli isolated from captive giant pandas is a reservoir of ARGs and VAGs, and significant associations exist among ARGs, VAGs and MGEs. Monitoring ARGs, VAGs and MGEs carried by E. coli from giant pandas is beneficial for controlling the development of antimicrobial resistance.