Virulence capabilities of endemic bacteriophages against Colistin and Extended spectrum beta-lactam resistant non-O157 Escherichia coli strains
STEC Escherichia coli O157 and non-O157 strains are known to cause severe food-borne infections as that may occur as either sporadic case or outbreak cases in humans even in countries with advance public health policies. The treatment of these infections caused by bacteria pathogens is generally achieved through the administration of antibiotics. However, the use of antibiotics in the treatment of STEC infections is generally discouraged since antibiotics have been reported to increase the release of shiga-toxins thus increasing the severity of disease. In addition, some previous studies have revealed that large proportions of environmental STEC strains are multi-drug resistant and this therefore indicates the need to search for other alternative control strategies. This study assesses the potential of using endemic bacteriophages as control agents against Colistin and Extended spectrum beta-lactam non-O157 Shiga-toxin producing-E. coli (STEC).A In the present study, non-O157 STEC strains were targeted and they were successfully isolated from cattle faeces samples. Isolates belonged to the serogroups O111, O104, O161 and O145, with O111 and O145 that are classified as non-O157 E. coli "big six" STEC group. The prevalence and antibiotic resistance profiles of shiga-toxin producing non- O157 E. coli strains isolated were determined. The strains were further characterised by molecular methods for the presence of shiga-toxin virulence genes and antibiotic resistance genes of Colistin and Extended spectrum beta lactams. Two hundred and forty-two (242) non-O157 Escherichia coli strains were isolated and a large proportion (104; 42.97%) of the 242 isolates possessed the stx₁ gene while 161 (66.52%) of these possessed the stx₂ gene. On testing these isolates for their resistance to Colistin and ESBLs agents, multiple antibiotic resistance (MAR) was observed in some of the isolates. A proportion of 6.19% isolates were resistant, 41.32% were intermediate resistant and 52.48% were susceptible to Colistin, while (83.06%) of them were confirmed to also be ESBL-producing isolates phenotypically. In addition, the ESBL genes blαοΧΑ, blαѕнѵ and blαтϵм were detected in 20 (66.67%), 11 (36.67%), 6 (20%) and 5 (16.67%) of the isolates respectively. Bacteriophages were successfully isolated in this study using confirmed environmental non-O157 E. coli STEC bacterial hosts strains obtained in this study. The isolated phages possessed visible heads, neck and tail regions based on electron microscopy data. Phage virulence assays revealed that these phages displayed lytic potentials. Three of the employed bacteriophages BNEO1575E, BNEO1574D and BNEO1574C were able to inhibit bacterial growth of more than one bacterial strain. These findings indicate that phages isolated in this study have displayed characteristics of being effective agents for biological control of environmental non-O157 STEC strains that also possess multidrug resistant determinants. These findings are of great epidemiological significance given the recent detection and clinical implications of Colistin and ESBL-producing bacteria strains particularly in hospital settings.