Dissemination of extended-spectrum beta-lactamase producers in natural environments in Northern Portugal

Abstract number: p917

Rocha  J., Neto Ferreira  H.


The aim of this study was to detect ESBL producers, in natural water streams reaching the sea and compare with those isolated from sea water samples. Our previous work, showed contamination of marine coastal water with antimicrobial resistant bacteria, namely ESBL (extended-spectrum b-lactamases) producers. This question alerted us to the origin of this contamination. In that way, it was our purpose to look for possible contamination sources, in water streams reaching the beach.


Natural water streams (probably including raining water streams) reaching the sea, were collected in July 2004 and 2005 (beach season, in Portugal), from 3 beaches of the Porto area. Isolates were selected by membrane filtration technique and the filters were placed on Mac Conkey agar and Mac Conkey agar with ceftazidime (2°mg/l) or cefotaxime (2°mg/l). Colonies of lactose fermenters were randomly selected and screened for ESBL production by the double disc synergy test. Identification of the selected strains was achieved by classic biochemical tools and ID 32 GN. Susceptibility to antimicrobial agents was determined according to the CLSI guidelines. b-lactamases were characterized by isoelectric focusing.


The natural water streams accessed, in this work, seem to be impacted by faecal contamination of unknown origin, with antimicrobial resistant strains, namely ESBL producers. At least 4 water streams isolates, were able to transfer the ESBL gene, by conjugation.


Our tries to understand coastal sea water contamination with ESBL producers, showed that natural water streams reaching the seashore, are, in at least some part, responsible for seawater contamination with ESBL producers. Future work intends to find the origin of contamination of these natural environments. This situation seems relevant in terms of public health and environmental protection, once these are some of the beaches used by the Porto population. The incoming of ESBL producers to natural environments and the transferability of the ESBL genes by conjugation, might provide a track for environmental dissemination of resistant bacteria and genes, that may create a source of transferable traits for environmental bacteria, influencing natural reservoirs of resistance.

Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Location: Oxford, UK
Presentation type:
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