Microbiology

Resistance on Tap

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Science  07 Aug 2009:
Vol. 325, Issue 5941, pp. 656
DOI: 10.1126/science.325_656b
CREDIT: JUPITERIMAGES

Antibiotic-resistant bacteria have become so common in aquatic ecosystems that some researchers suggest their genes should be considered environmental contaminants. Efforts to uncover the means whereby antibiotic resistance propagates are crucial in confronting the overall problem. Using a combination of broad-spectrum culturing methods and quantitative molecular techniques, Xi et al. characterized the prevalence of antibiotic-resistant bacteria, as well as the genes conferring resistance, at various points within water supply networks in the midwestern United States. In most municipalities they sampled, the abundance of antibiotic-resistant bacteria was higher in tap water than in finished water (i.e., water sampled directly after treatment). The quantity of antibiotic-resistant genes in tap water was also greater than in finished water and, remarkably, exceeded the quantities in original source waters as well. Water treatment plants and distribution systems may therefore unintentionally serve as incubators for growth of antibiotic-resistant bacteria and selectively increase antibiotic resistance of bacterial communities through horizontal gene transfer.

Appl. Environ. Microbiol. 75, 10.1128/AEM.00382-09 (2009).

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