contamination in a variety of foods. Importantly, ListShield™ was
also found not to impact the organoleptic properties (including
taste, sight, and smell) of foods. To the best of our knowledge, this is
the first publication to demonstrate that phage application does not
alter the organoleptic qualities of foods. The levels of challenge
bacteria used to experimentally contaminate the foods were very
high and are unlikely to be encountered in real life settings. Thus, it is
possible that phage bio-control may be even more effective in
commercial food processing facilities, where much lower levels of
L. monocytogenes are usually found to be contaminating foods. In
that context, our studies in the smoked salmon processing facility
showed that L. monocytogenes was no longer detectable in any of the
ListShield™ treated salmon fillets, essentially resulting in
L. monocytogenes-free food product. Ultimately, the efficacy of phage
bio-control must be evaluated in real life processing environments.
Even if complete eradication of L. monocytogenes is not achieved as
the result of phage treatment, our data show that the reduction of
L. monocytogenes levels in RTE foods could be very significant. It re
mains to be determined what overall impact such reduction may have
on the decrease of foodborne listeriosis and on improving public
health in general. From that perspective, the FDA and United States
Department of Agriculture's (USDA) recent jointly published a quan
titative assessment of the relative risk to public health from foodborne
L. monocytogenes. The assessment included modeling a series of “what
if” scenarios, one of which modeled a reduction in levels of contam
ination. This model predicted that a one log (tenfold) pre-retail
reduction in contamination with L. monocytogenes would reduce the
annual number of deaths in the elderly population attributed to deli
meats by nearly 50% (USDA, 2003). Our results show that this type of
reduction is achievable with the ListShield™ treatment, at least in the
laboratory conditions. Thus, if our results are reproduced in the real
life food processing environment, public health implications of using
lytic phages to reduce or eliminate L. monocytogenes in various foods
could be very positive and significant.