JAC Advance Access originally published online on November 6, 2006
Journal of Antimicrobial Chemotherapy 2007 59(1):106-109; doi:10.1093/jac/dkl435
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Molecular epidemiology of multiresistant Escherichia coli isolates from community-onset urinary tract infections in Cornwall, England
1 Centre for Infections, Health Protection Agency London, UK 2 Department of Clinical Microbiology, Royal Cornwall Hospital Truro, UK
Received 9 August 2006; returned 25 September 2006; revised 2 October 2006; accepted 3 October 2006
*Correspondence address. Antibiotic Resistance Monitoring and Reference Laboratory, Centre for Infections, Health Protection Agency, London NW9 5EQ, UK. Tel: +44-20-8327-7255; Fax +44-20-8327-6264; E-mail: neil.woodford{at}hpa.org.uk
Objectives: To study the clonality of gentamicin-resistant, extended-spectrum ß-lactamase (ESBL)-negative and ESBL-producing Escherichia coli isolated from community-onset urinary tract infections (UTIs) in Cornwall.
Methods: Isolates were identified by API, susceptibilities were determined by local disc testing, and MICs were determined at the reference laboratory, both interpreted using BSAC guidelines. blaCTX-M genes were sought by PCR, and isolates were compared by PFGE.
Results: In the years 2004 and 2005, 69 E. coli were submitted by Truro (Cornwall) laboratory for reference laboratory testing: these included 14 gentamicin-resistant, ESBL-negative isolates; 45 with group 1 CTX-M enzymes; seven with group 9 CTX-M enzymes; and three with non-CTX-M ESBLs. By PFGE, nine gentamicin-resistant, ESBL-negative E. coli were distinct (<85% similarity) from all the ESBL producers, but three were related to producers of group 1 CTX-M enzymes, and two isolates were related to a non-CTX-M ESBL producer. An outbreak strain was identified, represented by 11 gentamicin-resistant and one gentamicin-susceptible isolates, all with group 1 CTX-M enzymes, and two gentamicin-resistant, ESBL-negative isolates. This was distinct by PFGE from nationally distributed CTX-M-producing strains. Five of nine patients infected with this strain had been on the same ward in a local hospital; four presented with community-onset UTIs; one inpatient developed a hospital-acquired bacteraemia. Of the other four patients presenting with community-onset UTIs, three were admitted to different hospitals and the fourth had only attended an outpatient clinic.
Conclusions: Community-onset, ESBL-producing and non-producing E. coli were diverse. Two ESBL-negative isolates were closely related to a local CTX-M-producing outbreak strain, suggesting gain or loss of a blaCTX-M-carrying plasmid. An outbreak strain was linked with prior hospital admission and appeared not to represent genuine community acquisition.
Keywords: cephalosporins , ESBLs , resistance , Enterobacteriaceae
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