Escherichia coli with extended-spectrum β-lactamase and plasmid-mediated quinolone resistance genes in great cormorants and mallards in Central Europe

Faecal Escherichia coli strains were isolated from great cormorants (Phalacrocorax carbo) and mallards (Anas platyrhynchos), which are commonly occurring waterbirds in Europe, and studied for resistance to cephalosporins and fluoroquinolones. Cloacal swabs or faeces from great cormorants and mallards in Central Europe were cultivated to isolate Escherichia coli strains with extended-spectrum -lactamase (ESBL) and plasmid-mediated quinolone resistance (PMQR) genes. Ten ESBL-producing E. coli with the bla(CTX-M-15) or bla(CTX-M-27) gene were isolated from eight great cormorants (1.6, n499). The bla(CTX-M) genes were harboured by plasmids of F and I1 incompatibility groups. CTX-M-27-producing isolates were identified as the epidemiologically important B2-O25b-ST131 clone. No ESBL-producing E. coli was isolated from 305 mallards. Eight E. coli isolates with PMQR genes [six aac(6)-Ib-cr and two qnrS1] were detected in six great cormorants (1.2). Seventeen strains with qnrS1 were detected in 17 mallards (6). The PMQR genes were located on plasmids of incompatibility groups F, N or X2. ESBL and PMQR genes were found on conjugative plasmids, enabling the horizontal spread of resistance. Both great cormorants and mallards can spread epidemiologically important antimicrobial-resistant E. coli isolates to water bodies throughout Europe.