Infection and removal of L-forms of Listeria monocytogenes with bred bacteriophage

Phage breeding was employed to produce a bacteriophage (Listeria monocytogenes phage ATCC 23074-B1) which was specific for L-forms of L. monocytogenes. The bred phage was compared to its unbred parent for lytic activity and specificity. It was also tested for its ability to prevent L-form biofilm formation on stainless steel and compared with an organic acid (lactic) at L-form biofilm inactivation on stainless steel. The bred phage lysed only L-forms of L. monocytogenes in broth culture and only plaqued on L-form lawns. Likewise, the unbred phage performed similarly with classical cell-walled culture and lawns. The bred phage successfully inhibited L-form biofilm formation on stainless steel and was as successful as lactic acid (130 ppm) at inactivating pre-formed L-form biofilms. Both reduced viable cell numbers by 3-log cycles over a 6 h period. It appears that phage breeding technology may be an attractive alternative to chemical sanitizers which lack specificity and can be toxic.