High Prevalence of oqxAB in Escherichia coli Isolates from Domestic and Wild Lagomorphs in Italy

This study aimed to identify and characterize class 1 and 2 integrons and plasmid-mediated quinolones resistance (PMQR) genes in a collection of 113 multidrug resistance (MDR) Escherichia coli isolated from farm and wild lagomorphs between 2006 and 2008 in Northern Italy. Strains were examined for antimicrobial susceptibility by agar disk diffusion method and E-test for colistin (COL); integrons and gene cassettes content by real-time polymerase chain reaction (PCR) and DNA sequencing; PMQR genes by PCR and DNA sequencing; clonal relatedness by multilocus sequence typing; and plasmids by PCR-based replicon typing. Class 1 integrons were detected in 69 isolates (47 farm rabbits, 14 wild rabbits, and 8 wild hares). No class 2 integrons were found. Five different gene cassettes arrays were identified (aadA1, dfrA1-aadA1, orf in682-dhfrA5, orf in682-dfrA5-orfD ins21, and dfrA17-aadA5). Fifteen percent (17/113) of isolates carried oqxAB, no other PMQR determinants. All but one oqxAB-positive E. coli strains were recovered from farm rabbits. Seven out of 17 strains were associated with the predominant ST238 and carried from three to six different plasmid types, such as IncF, IncHI1, IncI1, IncN, IncP, IncX1, IncY, and ColE. COL resistance was identified in 6/113 strains (5.3%). This study provides new insights on the resistance phenotypes and the prevalence and dissemination of oqxAB in E. coli from farm and wild lagomorphs, suggesting that these animals may be reservoir of these genetic determinants in Italy and thus a potential source of PMQR E. coli for humans. PMQR mediated by oqxAB has not been detected in farm and wild lagomorphs before.