Detection of CTX-M-15 harboring Escherichia coli isolated from wild birds in Tunisia

Background: The spreading of antibiotic resistant bacteria is becoming nowadays an alarming threat to human and animal health. There is increasing evidence showing that wild birds could significantly contribute to the transmission and spreading of drug-resistant bacteria. However, data for antimicrobial resistance in wild birds remain scarce, especially throughout Africa. The aims of this investigation were to analyze the prevalence of ESBL-producing E. coli in faecal samples of wild birds in Tunisia and to characterize the recovered isolates. Results: One hundred and eleven samples were inoculated on MacConkey agar plates supplemented with cefotaxime (2 mu g/ml). ESBL-producing E. coli isolates were detected in 12 of 111 faecal samples (10.81%) and one isolate per sample was further characterized. beta-lactamase detected genes were as follows: bla(CTX-M-15) (8 isolates), bla(CTX-M-15) + bla(TEM-1b) (4 isolates). The ISEcp1 and orf477 sequences were found respectively in the regions upstream and downstream of all bla(CTX-M-15) genes. Seven different plasmid profiles were observed among the isolates. IncF (FII, FIA, FIB) and IncW replicons were identified in 11 CTX-M-15 producing isolates, and mostly, other replicons were also identified: IncHI2, IncA/C, IncP, IncI1 and IncX. All ESBL-producing E. coli isolates were integron positive and possessed empty integron structures with no inserted region of DNA. The following detected virulence genes were: (number of isolates in parentheses): fimA (ten); papC (seven); aer (five); eae (one); and papGIII, hly, cnf, and bfp (none). Molecular typing using pulsed-field gel electrophoresis and multilocus sequence typing showed a low genetic heterogeneity among the 12 ESBL-producing strains with five unrelated PFGE types and five different sequence types (STs) respectively. CTX-M-15-producing isolates were ascribed to phylogroup A (eleven isolates) and B2 (one isolate). Conclusion: To our knowledge, this study provides the first insight into the contribution of wild birds to the dynamics of ESBL-producing E. coli in Tunisia.