title: Effects of residual antibiotics in groundwater on Salmonella typhimurium: changes in antibiotic resistance, in vivo and in vitro pathogenicity.
abstract: An outbreak-causing strain of Salmonella enterica serovar Typhimurium was exposed to groundwater with residual antibiotics for up to four weeks. Representative concentrations (0.05, 1, and 100 μg L(-1)) of amoxicillin, tetracycline, and a mixture of several other antibiotics (1 μg L(-1) each) were spiked into artificially prepared groundwater (AGW). Antibiotic susceptibility analysis and the virulence response of stressed Salmonella were determined on a weekly basis by using human epithelial cells (HEp2) and soil nematodes (C. elegans). Results have shown that Salmonella typhimurium remains viable for long periods of exposure to antibiotic-supplemented groundwater; however, they failed to cultivate as an indication of a viable but nonculturable state. Prolonged antibiotics exposure did not induce any changes in the antibiotic susceptibility profile of the S. typhimurium strain used in this study. S. typhimurium exposed to 0.05 and 1 μg L(-1) amoxicillin, and 1 μg L(-1) tetracycline showed hyper-virulent profiles in both in vitro and in vivo virulence assays with the HEp2 cells and C. elegans respectively, most evident following 2nd and 3rd weeks of exposure.
authors: Department of Chemical and Environmental Engineering, University of California, Riverside, CA 92521, USA. swalker@engr.ucr.edu
authors: Berat Z
authors: BZ
authors: Haznedaroglu
authors: Marylynn V
authors: MV
authors: Yates
authors: Morris F
authors: MF
authors: Maduro
authors: Sharon L
authors: SL
authors: Walker
mesh_terms: D000658:Amoxicillin / Q000032:analysis / Q000633:toxicity; D000900:Anti-Bacterial Agents / Q000032:analysis / Q000633:toxicity*; D024881:Drug Resistance, Bacterial / Q000187:drug effects / Q000502:physiology*; D060587:Groundwater / Q000737:chemistry*; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000472:pathogenicity / Q000502:physiology; D013752:Tetracycline / Q000032:analysis / Q000633:toxicity; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D000900:Anti-Bacterial Agents; D014874:Water Pollutants, Chemical; D000658:Amoxicillin; D013752:Tetracycline