Sunday, August 12, 2012
Columbia Hall, Terrace Level (Washington Hilton)
Anthropogenic chemicals of emerging concerns (CEC) have been detected in river waters and sediments and could be responsible for selection of resistant bacteria. The objective of this study is to assess the presence of extended-spectrum beta-lactamase (ESBL) genes in the Clinton River, the main branch of which flows into the Great Lakes water system. The river water and sediments samples were collected and processed. Bacterial isolates were identified using Phoenix BD Systems and confirmed by 16S rRNA sequence analysis. Both human and fish pathogens (Salmonella typhimurium, Shigella dysenteriae, Klebsiella pneumoniae, Aeromonas sobria, Aeromonas caviae, Aeromonas veronii, Yersinia ruckeri, and Pseudomonas cepacia) were identified. Antibiotic susceptibilities of the bacteria were determined by the Kirby-Bauer disc diffusion test. Of a total of 136 bacterial isolates tested for antibiotic susceptibility, 39% were resistant to cefotaxime (CTX) (6% were ESBL producers), 38% to chloramphenicol (CHL), 17% to tetracycline (TET), 15% to ciprofloxacin (CIP) and 13% to gentamicin (GEN). Multidrug resistance was prevalent with common resistance patterns of CTX TET CHL GEN CIP (0.74%), CTX CHL GEN CIP (1.47%) and CTX TET CHL (6.62%). All of the eight ESBL-positive bacteria amplified for the blaCTX-M-1 gene. The presence of bacteria resistant to third and fourth generation cephalosporins in the water and sediments of urban Clinton River is worrisome, since this could be a reservoir for the dissemination of resistant human and fish pathogens to the Great Lakes water system that is a major source of drinking water for the population living in Canada and USA.