Characterization of Lytic Phages Isolated from Effluent Water and Soil against E. coli O157:H7

Abstract

Escherichia coli O157:H7 commensally lives in the rumen of food animals, making it an important foodborne pathogen. It can be transmitted through direct and indirect contact with animals or manure of animals carrying E. coli O157:H7, mediating its transfer to water and food products, which could cause infections to human upon consumption. E. coli O157:H7 is currently an emerging food-borne pathogen of severe public health concern. To this effect, bacteriophages can provide alternative measures for its control. This study was aimed at isolation and characterization of lytic phages isolated from effluent water and soil against E. coli O157:H7 as potential biocontrol agents. Fifty environmental bacteria and four phages were isolated from six different locations; Student Village Hostel_1and 2, Old JUTH_1and 2 and Angwa Rukuba_1 and 2 and were examined for their physiological and morphological characteristics. The fifty environmental bacteria isolates were characterized and screened to determine the permissive host for the four phages as the antibiotics susceptibility profile of the environmental isolates were determined. Three isolates EIA_18 (Escherichia coli), EIA_19 (Bacillus spp) and EIA_26 (Pseudomonas aeruginosa) were observed to be permissive host for the phages. The phages were screened against E. coli O157:H7 and other eleven selected pathogenic bacteria. The four phages displayed broad lytic activity against shiga toxin-producing E. coli O157:H7 and some of the selected pathogenic bacteria. These four lytic phages were designated as ECPA_1, ECPA_2, ECPA_3 and ECPA_4. Despite isolation from different locations, further characterization showed that they displayed a high degree of similarities. While all the phages were relatively stable over a wide range of salinity, temperatures, NaCl, Chloroform and pH values, their range of infectivity or lytic profile was rather wide against E. coli O157:H7 and some of the selected pathogenic bacteria, while few of the selected pathogenic bacteria showed no activity. This study showed that the isolated bacteriophages are the dominant E. coli O57:H7-infecting phages harboured in the selected areas within Jos metropolis and due to their favourable characteristics can be exploited in the formulation of phage cocktails for the bio-control of E. coli O157:H7.