Enterococcal distribution and responses toenvironmental waters
Abstract: The release of antibiotics and pharmaceuticals into environmental waters contribute to the increasing risk of antibiotic resistant bacteria. The spread of antibiotic resistant bacteria in the environment increases the health risks to the community. Enterococci are fecal indicator bacteria (FIB) in aquatic environments for determining water quality. In order to study enterococcal distribution and their response to environmental waters, we first screened for fecal indicator bacteria and their antibiotic resistance. Samples were collected from different locations of inland waters near Örebro city, Sweden at 4 time points during 2010 and 2011. Waters were filtered and the bacteria were cultured on selective media. We observed that the distribution of fecal indicator bacteria was higher at Svartån at Naturens Hus (≤705 CFU/100 ml for enterococci and ≤5867 CFU/100 for E. coli) near the effluent of the wastewater treatment plant (WWTP) than other locations tested. The eastern side of Hjälmaren lake, Storhjälmaren, had the lowest number of FIB (0 CFU/100 ml for enterococci and ≤2 CFU/100 ml for E.coli). Isolated E. coli, E. faecalis and E. faecium were evaluated for antibiotic resistance. We observed that ≤18% of E. coli environmental isolates and 12% of E. faecium and E. feacalis isolates were resistant to antibiotics during 2010 and 2011. Fifteen percent of these were multi antibiotic resistant (MAR) enterococci in 2010 and 31% in 2011. Tetracycline resistance was the most widespread antibiotic resistance found in FIB insolates. Extended spectrum β-lactamase expressing E. coli strains were found to also be MAR. Vancomycin and imipenem resistance was found in E. faecium isolate. Our results suggest that WWTP contributes to the distribution of FIB and antibiotic resistance. Secondly we aimed to evaluate the cellular responses of human and bacterial cells in environmental waters. We found that the pro-inflammatory response (IL-1β and TNF-α) of THP-1 cell was significantly higher in Svartån at Naturens Hus downstream of WWTP than the other locations. Based on this we evaluated E. feacalis responses to the same water. There were no statistical significant changes in gene response found in E. feacalis isolates, suggesting that environmental waters contain unidentified substances can effect on human cells responses but not bacteria. In this report we conclude that transferring of MAR strains in the environmental waters were increased annually in enterococci and E. feacalis did not initiate a response to the unknown substances that are present in river.
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