Increasing prevalence of ESBL but not AmpC in Escherichia coli and Klebsiella pneumoniae, in Göteborg, 2004-2008

• Introduction: The increasing prevalence of transferable broad-spectrum resistance to beta-lactams, such as Extended Spectrum Beta Lactamases (ESBL) and AmpC, is troublesome, since they confer resistance to cephalosporins and penicillins, and often also are associated with additional resistance. Materials and methods: Resistance for E. coli and Klebsiella pneumoniae isolated from urine (~10.000 isolates/year) and blood (~xxx isolates/year), during 2004-2008 were determined. Cephalosporin resistant isolates were examined for presence of ESBL with a double-disk-assay using clavulanic acid as inhibitory substance. Cefoxitine-resistant strains were analyzed for presence of AmpC with a second double-disk-assay using cloxacillin as inhibitory substance. Positive strains where further tested with PCR assays for ESBL and plasmid AmpC. Results: During 2004-2008 presence of ESBL increased from 0,3–1,5% in urinary and 0,0–1,4 % in blood E. coli. For Klebsiella the corresponding figures were 0,08–0,68% and 0%, respectively. For ESBL-producing E. coli, 60–80% were resistant also to quinolones and trimetoprime. In 2008, the vast a majority of the ESBL-isolates carried CTX-M subtype 1. Approximately 50 % is community-acquired isolates. 0,15-0,23% of the urinary E. coli-strains had phenotypical characteristics indicating AmpC-production. Presence of plasmid-mediated AmpC will be tested. Approximately 50% of these were multidrug resistant. In blood E coli isolates as well as in Klebsiella from urine and blood AmpC was rarely detected (0-2 isolates/year). Discussion and Conclusion: There is a steady increase in ESBL-producing bacteria in our region. However, the frequency of isolates with AmpC is still low. In addition, a majority of these strains are multidrug resistant which is particularly alarming.

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MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper -- Mikrobiologi inom det medicinska området (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine -- Microbiology in the medical area (hsv//eng)

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