Effects of Bacteriophage on Inhibition and Removal of Multispecies Biofilms of Escherichia coli O157 and Non-O157

Shiga toxin-producing Escherichia coli, especially E. coli O157 is an important foodborne pathogen capable ofcoexisting in multispecies biofilms found in almost all the natural environments. Biofilm cells are usually more resistant than planktonic cells against environmental stresses. Thus, E. coli O157 in biofilms is a serious food safety concern. This study describes the characterization of a bacteriophage FP43 isolated from bovine intestine and the ability of FP43 to inhibit and remove multi species biofilms of E. coli O157 strain 196 and non-O157 strain 104. Phage FP43 has a short latent period of 15 min and a large burst size of 98 PFU/cell, with great stability at temperatures ranging from 4 to 60°C and pH from 4 to 9.

To evaluate the effects of FP43 on E. coli,in microplate, biofilm formation was determined by crystal violet stainingas well as viable counts of biofilm and planktonic cells by conventional plating method. Phage FP43 decreased biofilm adhesionof E. coli cells with equal proportions of E. coli O157 and non-O157 by 82.4%. Viable counts were also reduced by 2.76 and 2.85 log in E. coli O157 and total biofilm cells after 6-h infection, respectively, compared with control. In planktonic cells, E. coli O157 and total counts decreased by 3.44 and 3.62 log after a 4-h phage treatment, respectively. Moreover, after a 6-h exposure to phage FP43, more than 60% of established biofilms were removed, and E. coli O157 and total viable counts in biofilm were decreased by 2.07 and 1.93 log, respectively. These findings suggest that phage FP43 seems to be a potential agent against E. coli O157 in multi species biofilms.