article · BMC Microbiology
Antibiotic-resistant bacteria pose an increasing risk to human and animal welfare, with wild birds potentially acting as vectors for their environmental spread. An assessment of 111 wild bird faecal samples collected in Tunisia revealed that just over ten percent carried extended-spectrum beta-lactamase producing Escherichia coli. Detailed characterisation identified the blaCTX-M-15 resistance gene across all positive samples, occasionally alongside blaTEM-1b. Analysis of the surrounding genetic environment showed conserved flanking sequences, diverse plasmid replicons including IncF and IncW, and empty integron structures. Several virulence genes, notably fimA and papC, were also detected among the isolates. Genetic typing demonstrated relatively low diversity, sorting the isolates into five sequence types and predominantly into phylogroup A. These findings demonstrate that wild avian populations in Tunisia harbour and potentially disseminate clinically relevant, drug-resistant bacterial strains across natural habitats.
Wild birds travel across broad geographic ranges, potentially serving as mobile reservoirs that spread antimicrobial-resistant bacteria across ecosystems, livestock facilities, and human communities. Identifying high-priority resistance genes such as blaCTX-M-15 in avian wildlife clarifies environmental transmission routes. This evidence helps public health and conservation bodies recognise wildlife surveillance as an essential component of integrated strategies to monitor and manage global drug resistance.
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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. One hundred and eleven samples were inoculated on MacConkey agar plates supplemented with cefotaxime (2 μg/ml). ESBL-producing E. coli isolates were detected in 12 of 111 faecal samples (10.81%) and one isolate per sample was further characterized. β-lactamase detected genes were as follows: blaCTX-M-15 (8 isolates), blaCTX-M-15 + blaTEM-1b (4 isolates). The ISEcp1 and orf477 sequences were found respectively in the regions upstream and downstream of all blaCTX-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). 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.
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DOI: 10.1186/s12866-018-1163-2
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