Mechanisms of resistance in multiple-antibiotic-resistant Escherichia coli strains isolated from drinking and recreational, salmaster waters

Abstract number: 1733_522

Cernat R., Balotescu C., Ivanescu D., Nedelcu D., Lazar V., Bucur M., Valeanu D., Tudorache R., Mitache M., Dragoescu M.

Aim: To delineate the clonal diversity and transmission patterns, and to investigate the occurrence and distribution of various resistance genes in multiple antibiotic resistant E. coli strains isolated from various aquatic sources.

Methods: 100 environmental Escherichia coli isolated from drinking water (50) and marine water (50) in Constanta and Bucharest were previously characterised for their virulence, pathogenicity, antibiotic resistance and plasmid profile. 30 strains from this group showed multiple-antibiotic resistance and have been further investigated by PCR, multiplex PCR and sequencing, for the presence of TEM-, SHV- and CTX-M-like extended-spectrum b-lactamases, blaIMP1, blaOXA, sul1, sul2 and sul3 genes, dfr-A like genes, tet efflux resistance genes, class 1, class 2 and class 3 integrons with the corresponding gene cassettes, respectively. Clonal diversity was assessed through PFGE of XbaI-digested genomic DNA.

Results:E. coli isolates showed 16 unrelated PFGE patterns. All strains were ampicillin resistant, blaTEM1a and blaTEM1b genes being identified in 40% of the strains while group 1 and group 8 of blaCTX-M genes were present in 90% of the strains. Most of the retrieved sequences were identical or very similar to b-lactamase genes previously characterised from clinical isolates. None of blaSHV, blaOXA and blaIMP1 genes retrieved. 20% of E. coli strains were kanamycin resistant, and the aphA1 and aphA2 genes were detected. The tetA, tetB and tetD genes were found in all the strains. A relatively high prevalence has been also obtained for dfrA17 (70%), dfrA12 (50%), sul1 (50%) and sul2 (60%) genes. Class 1 integrons were the only found in resistant bacteria and harboured 6 different cassette arrays, most common being dfrA17-aadA5.

Conclusions: All aquatic multiresistant E. coli strains showed a wide viariety of antibiotic resistance genes. Therefore, the aquatic ecosystem may play a key role as acceptor and donor of transmissible antimicrobial resistance mechanisms. The inclusion of some resistance genes inside class 1 integrons constitutes an effective means to spread antibiotic resistance among bacteria from different ecosystems.

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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