Plasmid-mediated quinolone resistance determinant qnrS1 found in Salmonella enterica strains isolated in the UK.
OBJECTIVE
To determine the prevalence of qnr genes in selected Salmonella enterica and Escherichia coli isolated in the UK.


METHODS
One hundred and eighteen S. enterica and 103 E. coli were screened for qnrA, qnrB and qnrS by PCR. Transferability of qnr plasmids was assessed and isolated plasmids compared with previously identified qnr plasmids by restriction fragment length polymorphism analysis and hybridization experiments. PCRs and sequencing identified co-transferred beta-lactamase genes and mutations in the quinolone resistance-determining region of gyrA.


RESULTS
Only six S. enterica strains belonging to four serotypes (Stanley, Typhimurium, Virchow and Virginia) were positive for qnrS1. qnrS1 was present on plasmids of 13.5 kb (TPqnrS-1a and -1b) in Typhimurium and Virginia isolates, 44 kb (TPqnrS-2) in two Virchow isolates and >148 kb (TPqnrS-3a and -3b) in two Stanley isolates. bla(TEM-1) and a group 9 bla(CTX-M) were co-transferred on TPqnrS-2 and TPqnrS-3b. Hybridization of a qnrS1 probe to digested qnrS1 plasmids suggested qnrS1 on TPqnrS-2 may be located in a similar genetic environment to Shigella qnrS plasmid pAH0376, but in a different environment in the other plasmids.


CONCLUSIONS
This is the first report of plasmid-mediated quinolone resistance in a Salmonella isolate from the UK; five isolates were associated with foreign travel to, or food imported from, the Far East. The presence of qnrS1 on different plasmid backbones in several Salmonella serotypes suggests successful dissemination of plasmids or qnrS1. It is of concern that qnrS1 is being identified in Salmonella serotypes that are commonly implicated in human infection in the UK. Coupled with beta-lactam resistance, it may compromise treatment of vulnerable patient groups.
Hopkins
Katie L
KL
Salmonella Reference Unit, Laboratory of Enteric Pathogens, Health Protection Agency Centre for Infections, London, UK. katie.hopkins@hpa.org.uk
Wootton
Lara
L
Day
Martin R
MR
Threlfall
E John
EJ
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D027081:DNA Gyrase / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004591:Electrophoresis, Polyacrylamide Gel; D005798:Genes, Bacterial / Q000235:genetics* / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics*; D012150:Polymorphism, Restriction Fragment Length; D015363:Quinolones / Q000494:pharmacology*; D012480:Salmonella Infections / Q000382:microbiology*; D019779:Salmonella enterica / Q000187:drug effects* / Q000235:genetics*; D006113:United Kingdom; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism
D000900:Anti-Bacterial Agents; D015363:Quinolones; D001618:beta-Lactamases; D027081:DNA Gyrase