Abstract
BackgroundEscherichia coli O157:H7 is a highly virulent human pathogen with severe consequences following infection, which claims many lives worldwide. A suggested method for controlling this bacterium is the competitive elimination through using probiotic bacteria that prevent its colonization. Some nonpathogenic E. coli strains that produce antibacterial colicins are among these probiotic bacteria. We aimed to isolate and characterize the colicinogenic E. coli strains from diarrheic and healthy sheep that inhibit E. coli O157:H7, which could be used as possible probiotic sources. A total of 292 E. coli isolates (146 from each diarrheic and healthy sheep) were screened for the presence of colicin and virulence genes. The phylogenetic group/subgroup determination was performed by PCR. In vitro evaluation of inhibitory effect of colicinogenic isolates on E. coli O157:H7 was done phenotypically.ResultsThe frequency of diarrhea associated colicinogenic E. coli isolates was significantly higher than those isolated from healthy sheep. An association between ETEC and the genes coding for colicin-V & colicin-Iab in diarrheic E. coli isolates was observed. Moreover, there was an association between ipaH and Colicin-V encoding genes. Furthermore, E. coli isolates showing bacteriocinogeny while possessing no virulence genes had a frequency of 97.67 and 11.94% in healthy and diarrheic isolates, respectively. Of these strains, five isolates (3.42%) from diarrheic and twenty-five isolates (17.12%) from healthy sheep inhibited O157:H7 strain. Additionally, colicin E1 and colicin Iab genes were more prevalent in B1 phylogroup.ConclusionsThese results signified that healthy sheep could be considered as a potential source for anti-O175:H7 bacterial isolates.
Highlights
Escherichia coli O157:H7 is a highly virulent human pathogen with severe consequences following infection, which claims many lives worldwide
These results signified that healthy sheep could be considered as a potential source for anti-O175:H7 bacterial isolates
Zhao et al, [10] developed the first competitive- exclusion system against E. coli O157:H7 by isolating colicinogenic E. coli isolates from cattle, but little information was provided about the types of colicins produced by these isolates and the extent of resistance among naturally present E. coli O157:H7 isolates [11]
Summary
Escherichia coli O157:H7 is a highly virulent human pathogen with severe consequences following infection, which claims many lives worldwide. Some nonpathogenic E. coli strains that produce antibacterial colicins are among these probiotic bacteria. A total of 292 E. coli isolates (146 from each diarrheic and healthy sheep) were screened for the presence of colicin and virulence genes. The clinical symptoms of E. coli O157:H7 vary wildly from mild diarrhea to hemolytic uremic syndrome (HUS) leading to kidney failure. The severity of these symptoms depends on the immune status of the patient and the infection dose of the bacteria [2, 3]. One proposed approach for the control of E. coli O157:H7 is through the competitive elimination, Host animal species can effect on the type of produced colicin and bovine isolates would be expected to show. Zhao et al, [10] developed the first competitive- exclusion system against E. coli O157:H7 by isolating colicinogenic E. coli isolates from cattle, but little information was provided about the types of colicins produced by these isolates and the extent of resistance among naturally present E. coli O157:H7 isolates [11]
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