Abstract
Escherichia coli (E. coli) is currently one of the most predominant human food-borne pathogens. In the dairy industry, recently, attention has been drawn to the potential use of bacteriophages (phages) to control bacteria in dairy products. In this study, a cocktail of three Escherichia coli bacteriophages (EcoM-AG2, EcoM-AG3 and EcoM-AG10) was tested to evaluate its ability to control Escherichia coli O126:H7 in experimentally contaminated skim milk. In Tryptic Soy Broth (TSB), there was an E. coli growth suppression of 1.8, 5.7 and 8.9 logs in phage treatments compared to controls over 8 days, at 4, 10 and 25°C, respectively. While in skim milk, the phage cocktail reduced E. coli populations by 1.2, 1.0 and 8.3 log compared to control samples over 15 days, at 4, 10 and 25°C, respectively. The phage population was relatively stable in skim milk during the experiments. The overall results in this study indicate that phages may be useful in the control of E. coli in dairy products by preventing growth and significant reducing of bacterial numbers. However, the phages didnât eliminate all the E. coli in skim milk tested at 4 and 10°C, but complete elimination of E. coli was verified after 3 days of phage treatment at 25°C. Therefore they are more likely to be used as a hurdle approach, incorporated to other treatments without compromising food quality. Future research about phage-bacteria interaction in milk is required.
Highlights
Escherichia coli (E. coli) is one group of the most common bacteria found in the gastrointestinal tract of human and a majority of them are not harmful
The cultures were incubated overnight (20 to 24 hr) at 37°C and reached a cell level around 109 Colony Forming Unit (CFU)/mL
The word “control” in all figures here refers to positive controls mentioned in the “Materials and Methods” section, which means that only bacteria and phage buffer, rather than phages were added to the Tryptic Soy Broth (TSB)/skim milk samples
Summary
Escherichia coli (E. coli) is one group of the most common bacteria found in the gastrointestinal tract of human and a majority of them are not harmful. There are six enteric pathotypes of E. coli that can cause human diseases (Bell and Kyriakides, 1999; Sussman, 1997): Enteropathogenic E. coli (EPEC). E.g. O126, O127, O158, Enterotoxigenic E. coli (ETEC). E.g. O115, O148, O153, Vero-cytotoxigenic E. coli (VTEC) (Includes Enterohaemorrhagic E. coli, EHEC). E.g. O157, O163, O168, Enteroinvasive E. coli (EIEC). E.g. O144, O152, O164, Enteroaggregative E. coli (EAggEC) and diffusely adherent E. coli (DAEC)
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