First report on extended-spectrum beta-lactamase (ESBL) producing Escherichia coli from European free-tailed bats (Tadarida teniotis) in Portugal: A one-health approach of a hidden contamination problem

Highlights: • ESBL detection in Escherichia coli from European free tailed-bats (Tadarida teniotis). • High prevalence of CTX-M-1 and CTX-M-3 beta-lactamases. • Bats are potential vectors of antimicrobial-resistant bacteria in the environment. • First report on ESBL-producing E. coli from bats in Portugal. -- Abstract: The main aim of this study was to characterize the diversity of extended-spectrum beta-lactamases (ESBLs) in Escherichia coli isolates from European free tailed-bats (Tadarida teniotis) in Portugal. ESBL-producing E. coli isolates were recovered from 14 of 146 faecal samples (9.6%) and a total of 19 isolates were completely characterized. The more prevalent beta-lactamase genes detected were bla_CTX-M-1 (57.9%) and bla_CTX-M-3 (36.8%), followed by bla_SHV (31.6%), bla_TEM (21.1%), bla_OXA (10.5%) and bla_CTX-M-9 (10.5%). Among other associated resistance genes studied, tet(A) and tet(B) were predominant and fimA was the main virulence factor detected. Phylogroups D (47.4%) and A (31.6%) were the more prevalent, followed by group B2 (21.1%). Bats are reservoirs of antimicrobial-resistant bacteria and resistance determinants and is important in further studies to identify the main sources of pollution in the environment, such as water or insects that may contain these multiresistant organisms.