Prevalence and distribution of plasmid-mediated quinolone resistance genes in clinical isolates of Escherichia coli lacking extended-spectrum beta-lactamases.
OBJECTIVE
The aac(6')-Ib-cr gene has been described in plasmids from CTX-M-15-producing Escherichia coli in the worldwide ST131 lineage, but has not been systematically sought in other quinolone-resistant strains in the UK. A rise in quinolone resistance in bacteraemia isolates in the UK preceded the increased prevalence of CTX-M-producing strains. This study aimed to describe the presence of plasmid-encoded quinolone resistance genes in historical and current strains of E. coli not producing extended-spectrum beta-lactamases (ESBLs).


METHODS
Ciprofloxacin-resistant, non-ESBL-producing E. coli isolates included nationally distributed isolates from the BSAC UK bacteraemia surveillance programme between 2001 and 2005, urinary isolates from a regional project in 2000 and local strains in 2006. The aac(6')-Ib-cr gene was detected using PCR followed by restriction fragment length polymorphism analysis. Multiplex PCR was used to detect qnr genes. Isolates with aac(6')-Ib-cr were assessed for aminoglycoside susceptibilities and were serotyped.


RESULTS
The prevalence of the aac(6')-Ib-cr gene was 3% and 9% in current local urinary and historic national bacteraemia quinolone-resistant non-ESBL-producing E. coli, respectively. Of 521 regional urinary E. coli isolates from 2000, 14 were norfloxacin-resistant, none of which carried the aac(6')-Ib-cr gene. National positive bacteraemia isolates from 2001/2 were type O102-ST405 and, in 2004/5, types O1-ST645 and O25-ST131. Positive local urinary isolates from 2006 included serotypes O1 and O25.


CONCLUSIONS
In the UK, aac(6')-Ib-cr occurs in E. coli in the absence of CTX-M-15, but with a restricted serotype distribution. Its presence in widespread bacteraemia isolates of a single type from 2001 to 2002, prior to the spread of CTX-M-15 in Britain, might suggest a lineage from which plasmid recombination occurred in man or other species.
Jones
G Ll
GL
Department of Microbiology, Shrewsbury and Telford NHS Trust, Mytton Oak Road, Shrewsbury SY3 8XQ, UK.
Warren
R E
RE
Skidmore
S J
SJ
Davies
V A
VA
Gibreel
T
T
Upton
M
M
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016470:Bacteremia / Q000453:epidemiology / Q000382:microbiology; D016172:DNA Fingerprinting; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000145:classification* / Q000187:drug effects* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000235:genetics; D006801:Humans; D008826:Microbial Sensitivity Tests; D010957:Plasmids; D016133:Polymerase Chain Reaction / Q000379:methods; D012150:Polymorphism, Restriction Fragment Length; D015995:Prevalence; D015363:Quinolones / Q000494:pharmacology*; D012703:Serotyping; D006113:United Kingdom / Q000453:epidemiology; D014552:Urinary Tract Infections / Q000382:microbiology; D001618:beta-Lactamases / Q000096:biosynthesis*
D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; D015363:Quinolones; D001618:beta-Lactamases