Molecular epidemiology of plasmid mediated quinolone resistance and report on QNRS 1 gene of multidrug resistant commensal Escherichia coli from pigs

The authors briefly discuss the quinolone resistance in Gram-negative bacteria, and give information about the main characteristics and genes of plasmid-mediated quinolone resistance (PMQR). They briefly review the molecular epidemiology methods: PCR microarray technology, the multilocus sequence typing (MLST) and the PCR-based plasmid replicon typing (PBRT), which they used, together with other known methods (PCR, plasmid analysis, and cloning/sequencing) in these studies. The authors aimed to report the results of their earlier studies of SZMOLKA et al. (38) on PMQR of porcine E. coli in two large piggeries in Hungary and Romania. The study identified PMQR E. coli strains in 34% of piglets in the Romanian pig farm. Clonality of six qnrS1 E. coli strains representing that farm was established by MLST, and the qnrS1 plasmids were characterized by plasmid transfer and by PBRT. Microarray studies were performed using AMR05 and Ec03 PCR-microarray systems for the detection of similar to 130 antimicrobial resistance and virulence genes of E. coli. As a result, the six tested qnrS1 strains were assigned to three different MIST types. PCR-based replicon typing proved that they all carry IncN plasmids, representing the first IncN-borne qnrS1 gene identified in E. coli from food producing animals. There were no virulence genes associated with IncN type qnrS1 plasmids, but they were responsible for the co-transfer of bla(TEM-1) and tet(A) genes responsible for ampicillin and tetracycline resistance. The genetic environment of the qnrS1 gene showed >= 99% homology with the corresponding resistance region of the pINF5 plasmid from Salmonella Infantis isolated from chicken carcass and of IncN plasmids isolated from human clinical E. coli strains. Thus, the data suggests that transfer of qnr51 plasmids occurs between Salmonella and E. coli of animal and human origin with pigs representing one of the potential reservoirs.