Detection of RpoS Gene in Escherichia Coli O157:H7 and non-O157 and Their Survival Pattern in Water Treatment Methods

Abstract

This study aimed to detect presence of RpoS gene in Escherichia coli O157:H7 and non-O157 and investigate their survival pattern in different water treatment methods. A total of fifteen serologically and molecularly identified E. coli was selected from a previous work, out of which eight were Escherichia coli O157 and seven were E. coli non-O157. From among these, S30 and S89 identified isolates served as presentative E. coli O157:H7 and non-O157 respectively for survival studies. The water treatment methods used employed included: use of silver, lime, storage, acidification (low pH), high temperature and Moringa oleifera. Survival pattern of the test organisms under the influence of these methods were carried out using standard techniques. Molecular detection of stress response gene, RpoS, in the fifteen (15) test organisms was performed following manufacturer’s instruction. Results showed that for both test organisms, silver was bactericidal at high concentration while storage allows their survival up till 21 days though with a reduction in cfu. Both organisms showed low survival at pH 9 while E. coli O157:H7 and non-O157 could survive at pH 4 and 6 respectively. E. coli O157:H7 survived better than non-O157 at high concentration of lime. While both survived at low temperature, E. coli O157:H7 survive better at 60oC. Sunlight and chlorine showed mild and complete bactericidal action respectively with increased exposure time for both test organisms. Moringa oleifera was only effective at a reduced concentration on the two organisms. Detection of RpoS genes showed that only 66.7% carried the gene in them while 33.3% did not. Findings from this study show that the possession of stressed genes in bacteria causing waterborne disease could allow these organisms to survive water treatment methods adopted in many under developed countries or rural communities. This suggests a threat to health of these communities.