Prevalence and characterization of uropathogenic Escherichia coli harboring plasmid-mediated quinolone resistance in a Tunisian university hospital

The prevalence of plasmid-mediated quinolone resistance (PMQR) determinants was investigated in a Tunisian collection of 300 uropathogenic Escherichia coli. PMQR genes were detected in 68 isolates (22.7%) as follows: aac(6′)-Ib-cr (n = 66), qnrB1 (n = 3), qnrA6 (n = 1), and qnrS1 (n = 1). Three isolates carried the 2 determinants aac(6′)-Ib-cr and qnrB1. aac(6′)-Ib-cr was usually carried on IncF-type plasmids (n = 47/60) and frequently associated with blaCTX-M-15 (n = 60). Substitutions in gyrA and parC genes were detected in 57.5% of strains. A major cluster including 29 isolates was individualized, 28 of them belonged to the virulent ST131 clone. In our hospital, the high prevalence of PMQR in E. coli isolates was due to horizontal transfer but also to the spread of ST131 clone.