Contribution of drinking water for the dissemination of Gram-positive and Gram-negative bacteria harbouring antibiotic resistance genes in Portugal

Abstract number: P2051

Magalhães R., Abreu C., Silva R., Peixe L., Machado E., Novais C., Sousa J.

Objectives: To assess the contribution of nontreated water for human use in the spread of Gram-positive (GP) and Gram-negative (GN) bacteria harbouring antibiotic (AB) resistance or virulence genes.

Methods: Drinking water samples [mines, wells, springs from residential, forest or agricultural areas (n = 5); springs from not specified areas (n = 7)] were collected (North/Centre-2006) and, after enrichment, plated on Slanetz-Bartley and MacConkey agar with/without AB. AB susceptibility was done by disk diffusion method (CLSI) and ESBL expression (in GN) was searched by double disk synergy test. Species were identified by API ID32GN (in GN) or PCR (in GP). Characterisation of AB resistance genes/genetic elements, virulence factors (in GP) or E. coli phylogenetic groups was done by PCR.

Results: We identified 42 enterococci (7 E. faecalis, 1 E. faecium, 6 E. hirae, 28 Enterococcus sp) and 33 Gram-negative (18 Enterobacteriaceae – 1 E. coli belonged to phylogroup A; 1 P. mendocina, 8 S. maltophilia, 2 A. baumannii, 1 A. hydrophila, 1 V. parahaemolyticus, 2 C. violaceum). Decreased susceptibility to AB was seen in all sample types to ciprofloxacin-69%, quinupristin-dalfopristin-48%, erythromycin-45%, tetracycline-38%, minocycline-36%, nitrofurantoin-33%, high level of resistance (HLR) to gentamicin-21%, HLR-streptomycin-5% or chloramphenicol-2% in enterococci, and to streptomycin-58%, kanamycin-36%, trimethoprim-27%, tetracyclines-18%, chloramphenicol-18% or sulfonamides-12% in Gram-negative bacteria. The following resistance genes/virulence factors were seen: ermB (31% of all isolates), tetM (40%), tetL (17%), tetS (7%), aac(6')-Ie-aph(2")-Ia (21%), asa1 (24%), gel (11%) in enterococci, and class 1 integrons variable regions (6%), sul3 (3%), tetA (3%), and blaTEM-1 (6%) in Gram-negative isolates. Although 2 Enterobacteriaceae were DDST(+) no blaTEM/SHV/CTX-M were seen. We could not amplify vanA/B/C1/C2, tetO/K, cyl/esp/hyl genes in GP and intI1/2/3, sul1/2, qnrA, tetB/G in GN.

Conclusion: Our data suggest that AB resistance genes or putative virulence factors known to be spread in several environments are present in human drinking water both in areas possibly contaminated by humans and in locations that apparently do not have antibiotic selective pressure. The presence of different AB resistance genes/genetic structures is of concern since such bacteria might be consumed by different hosts and/or be involved in gene capture, enriching local environment metagenome.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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