Background: Bacteria especially Escherichia coli (E. coli) possess several mechanisms enabling them to respond to changing environment and to out compete other bacteria. E. coli strains are known to produce bacteriocins, one of which is colicin. Colicins are effective against closely related enterobacteriaceae and are considered viable alternatives to antibiotics.

Objective: To identify colicin producing strains of E. coli and subject some indicator organisms to the colicin produced, then compare the effect of colicin with standard antibiotics in other to establish the choice of colicin as an alternative to some antibiotics.

Methods: In this study Twelve (12) E. coli strains were isolated from food, water soil and anal swabs. They confirmed and identified as E. coli. The isolates were subjected to stress condition to stimulate colicin production. The colicin produced was tested against three indicator organisms namely Salmonella Sp, Klebsiella Sp and Staphylococcus aureus. Comparative antibiotic susceptibility test against standard antibiotics and the colicin produced was carried out. E. coli isolates were also subjected to antibiotic sensitivity test to determine the resistance profile of the colicin producing strains of E. coli. Plasmid amplification to identify colicin plasmid was also carried out to determine the relationship between colicin production and resistance to antibiotics of colicinogenic  E. coli. Result obtained showed that five out of the twelve strains of E. coli isolated from water produced colicin that showed high antibacterial activity against the indicator organisms. The comparative antibiotic resistance profile revealed that the colicin had better antibacterial activities than some of the antibiotics used. Furthermore, colicinogenic E. coli also showed resistance to some of antibiotics used. The plasmid amplification showed the colicinogenic E. coli to possess high molecular weight (4kb) colicin plasmid while the gene sequencing revealed the presence of ColF and ColR plasmids.

Conclusion: The result of this work underscores the fact that colicin is a viable alternative to standard antibiotics. Its use as treatment therapy can be explored, especially in the search for alternatives to antibiotics considering the high level of bacteria resistance to standard antibiotics.