Sewage dilution and loss of antibiotic resistance and virulence determinants in E. coli

The possession of potential virulence factors (serum resistance, aerobactin production, colicin production) and antibiotic resistance was evaluated in 418 E. coli strains isolated from river water. The strains were isolated from 11 points showing different levels of contamination. From the data obtained, it can be concluded that bacteria from less contaminated water present less antibiotic resistance and virulence factors than those isolated from highly contaminated water. This situation suggests that E. coli strains producing plasmid encoded antibiotic resistance and/or virulence factors, survive less well in aquatic environments without selective pressure) than the sensitive non-virulent ones.