Competitive Exclusion of Escherichia coli O157 using Non Pathogenic Colicin Producing Escherichia coli Strains

This research evaluated the ability of various non-pathogenic colicin producing strains of E. coli to inhibit the growth of E. coli O157 and Shiga-toxin producing strains. Selected strains were able to inhibit the growth of O157:H7 in a laboratory environment.

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Objectives

To provide an alternate approach to controlling E. coli O157:H7 proliferation and colonization of dairy premises and intestinal tract of beef and market cows.

Conclusions

Three strains being effective colicin producers were isolated and further tested against 90 STEC cultures belonging to different serogroups. The two human isolates inhibited growth of all STEC strains to the extent of 92-95%. Colicin produced by two strain inhibited growth of E. coli O157:H7 to the extent of 95-100% in 2 hours. Colicin produced by two isolates when combined and tested against the growth of E. coli O157 showed 100% inhibition in 2 hours.  It was established that the colicin produced was proteinaceous in nature and the inhibitory effect was not due to the presence of bacteriophages.

Deliverable

The bacteria producing colicins can be potentially used as an alternate approach to control E. coli O157:H7 proliferation and colonization of dairy premises and intestinal tract of beef and market cows by using them as competitive inhibitors.