PHAGE BIOCONTROL OF ENTEROPATHOGENIC AND SHIGA TOXIN-PRODUCING Escherichia coli DURING MILK FERMENTATION

TOMAT, DAVID DAMIÁN; MERCANTI, DIEGO JAVIER; BALAGUÉ, CLAUDIA; QUIBERONI, ANDREA DEL LUJÁN

LETTERS IN APPLIED MICROBIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2013 vol. 57 p. 3 - 10

0266-8254

Two bacteriophages, isolated from feces, were assayed as biocontrol agents of pathogenicEscherichia coli during milk fermentation. Phage DT1 was tested on the strain E. coli DH5α,one enteropathogenic E. coli (EPEC) strain and one Shiga toxigenic E. coli O157:H7 (STEC)strain. Phage DT6 was tested on two STEC strains (O157:H7 and non-O157). One additionalassay was performed by using a cocktail of both phages against the O157:H7 STEC strain.Streptococcus thermophilus 10-C, the strain used as lactic starter, reached 109 cfu ml-1 after 4h, while pH values fell to 4.5 after 8 h, regardless of the presence of E. coli strains and/orphages. In absence of phages, E. coli strains reached 4-6 log cfu ml-1 at 5-6 h. E. coli DH5αand O157:H7 STEC strains were rapidly and completely inactivated by phage DT1 and phagecocktail, respectively, while O157:H7 STEC was completely inactivated either by DT1 or byDT6, after 8 h. The EPEC strain was not detected at 1 h (<10 cfu ml-1) but grew afterwards,though at lower rates than without phage. For non-O157:H7 STEC, reductions lower than 1log cfu ml-1 were observed for all sampling times. Phages DT1 and DT6, either individuallyor as a cocktail, effectively reduce O157:H7 STEC counts during milk fermentation, withoutcompromising the starter culture performance.