Control of Escherichia coli O157 on beef at 37, 22 and 4°C by T5-, T1-, T4-and O1-like bacteriophages

© 2015 Elsevier Ltd. Efficacy of four bacteriophages (phages) and a cocktail for biocontrol of Escherichia coli O157 was assessed on beef samples stored at 4, 22 and 37°C. Samples (3×3×1cm) were contaminated with E.coli O157 (10⁴CFU/cm²) and treated with single phages: T5-like (T5), T1-like (T1), T4-like (T4) and O1-like (O1), or a cocktail at two titers: multiplicity of infection (MOI)=1000 and MOI=10. In contrast to previous studies, use of virucidal solution prevented over-estimation of phage efficacy. Irrespective of temperature and MOIs, T5 was most (P<0.001) and O1 least (P<0.05) effective for biocontrol of E.coli O157, with relative efficacy of other phages temperature dependent. At 4°C, T1 (P<0.05) and cocktail (P<0.001) were more effective than T4. In contrast, T4 was equally (P=0.08, at 37°C) or less effective (P=0.003, at 22°C) than T5. Phages were more effective (P<0.001) against E.coli O157 at warmer temperatures and high MOI. As the beef supply chain includes hours of storage or transport at temperatures near 4°C, this study demonstrates phages could significantly reduce E.coli O157 during this period.