Occurrence of ESBL-producing Escherichia coli in outflow from a wastewater treatment plant

Abstract number: 1732_282

Galvin S., Morris D., Hickey P., Cormican M.

Objectives: This study describes the isolation of extended spectrum b-lactamase (ESBL) producing E. coli strains in outflow from a municipal secondary wastewater treatment plant. The role the environment plays in the dissemination, maintenance and amplification of antimicrobial resistance is an area of increased scrutiny. Few studies have examined surface waters and effluent for the presence of antimicrobial resistant organisms.

Methods: Six samples (1 per week) were collected from the outflow of a municipal secondary wastewater treatment plant between August and September 2006. These were screened for the presence of E. coli resistant to ampicillin, cefoxitin, cefotaxime, and ciprofloxacin. Resistant isolates were tested for susceptibility to sixteen antimicrobial agents by Clinical Laboratory Standards Institute (CLSI) disk diffusion methods, including the following b-lactams: ampicillin, cefpodoxime, cefotaxime and ceftazidime. ESBL production was confirmed by the CLSI combination disk method for ESBL production using cefpodoxime. Confirmed ESBL producers were screened for blaTEM, blaSHV and blaCTX-M by PCR using specific primers. Relatedness of ESBL producers was determined by pulsed field gel electrophoresis (PFGE) using XbaI.

Results: Thirty-four isolates of E. coli resistant to one or more antimicrobial agents tested were identified. Seven (21%) were confirmed as ESBL producers. All 7 confirmed ESBL producers were resistant to 3 or more antimicrobial agents tested. PCR revealed a blaTEM gene in all 7, and a blaCTX-M group 1 gene in 3 isolates. PFGE analysis identified 5 pulsed field profiles (PFPs). These were isolated from samples taken on 3 separate dates. Isolates with indistinguishable PFPs were isolated from samples taken on different dates. Isolates with distinguishable PFPs were isolated on the same date.

Conclusion: This is the first report of the occurrence of ESBL-producing E. coli in the outflow from a secondary wastewater treatment plant and reflects the extent to which this resistance phenomenon is now very widely disseminated.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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