Abstract

The effect of oxidative stress on expression of virulence factors and the effect of low temperature stress on toxin production among Escherichia coli serotypes isolated from wastewater and river water samples were determined. Oxidative stress due to chemicals, salts, alcohol or low temperature stress exerted various degrees of lethality to the bacterial cells with bacterial strains losing their potential to express virulence factors with time. The cell kill index (CKI) increases as temperature stress (-5, -18 and -28°C) increases with time. However, the rate of loss of expression of virulence factors or viability was slower in isolates from wastewater and abattoir compared to those from river water. Contamination of food or drinking water sources with these strains should be prevented to avoid human infection with disease conditions such as diarrhea, urinary tract infections and gastroenteritis.

Key words: Antimicrobial resistance, beta-lactamase, haemolysin, hydrophobicity, serum resistance, verotoxins