Meat Decontamination 731995 ). However, excessive doses of the
above antimicrobials may allow for antimi-
crobial resistance (EFSA 2008 ). Furthermore,
in vitro studies suggest that exposure of
pathogens to sublethal levels of certain meat
decontamination chemical agents may induce
tolerance to lethal levels of the same bio-
cides, as well as to other (heterologous)
stresses (cross - resistance or protection).
Specifi cally, Sampathkumar et al. (2004)
found that pre - treatment of S. enterica
serovar Enteritidis with sublethal levels of
TSP (i.e., 1.5%) increased tolerance to higher
TSP concentrations, and conferred cross -
tolerance to heat (55 ° C) and alkaline pH
(11.0). However, evidence for such cross -
tolerance in situ is still lacking.
Given that several Salmonella strains
implicated in foodborne outbreaks have been
identifi ed as resistant to multiple antibiotics,
the hypothesis that such strains are also resis-
tant to antimicrobial interventions in beef
processing has been tested. Bacon et al.
(2002c) performed a survey for antibiotic
resistant Salmonella strains in eight beef -
packing plants and found that even though
the prevalence of Salmonella was reduced
from 15.4% on hides to 1.3% on carcasses,
approximately 60% of the isolates were resis-
tant to at least one antibiotic. Moreover, the
isolation of two antibiotic resistant Salmonella
strains from carcasses after fi nal washing
suggested potential resistance to decontami-
nation interventions (Bacon et al. 2002c ).
However, studies have found no correlation
between susceptibility to antimicrobial
agents and resistance to heat (55 – 61 ° C) or
low pH (2.3 or 3.0) stress (Bacon et al. 2003a,
b ). Likewise, Arthur et al. (2008) found that
the susceptibility of Salmonella to various
meat decontamination agents, including 2%
acetic or lactic acid, electrolyzed - oxidizing,
and ozonated (6 ppm) water as well as com-
mercial acid (pH 1.6) products, was not infl u-
enced by their multidrug resistance status.
Similarly, the ability of certain E. coli
O157:H7 strains to cause human disease was2003 ). Moreover, even though cells exposed
to acidic environments formed by diluted
organic acid run - off fl uids may be injured by
sanitizing agents and be undetectable with
common plating methods, they may recover
and restore their acid resistance during sub-
sequent exposure to fresh meat decontamina-
tion run - off fl uids (Skandamis et al. 2009 ).
However, the role of acid adaptation on
microbial resistance to decontamination
treatments possibly depends on the microor-
ganism and product storage conditions, since
acid adaptation of L. monocytogenes did not
seem to affect the survival and proliferation
of the organism during storage at 10 ° C of
beef treated with hot water and/or lactic acid
(Ikeda et al. 2003 ). An additional concern is
that organic acid treatments may alter the
natural fl ora of the beef carcass, thereby
reducing the competitive effect of the back-
ground fl ora against enteric pathogens, or
allowing proliferation of acid tolerant organ-
isms, such as lactic acid bacteria or yeasts
and molds, and thus, altering the spoilage
association in fresh meat (Ikeda et al. 2003 ;
Samelis et al. 2002 ).
Concerns were expressed at the European
level about the development of antimicrobial
resistance to chemical agents that may be
used for carcass decontamination. Thus, the
European Food Safety Authority (EFSA)
issued an opinion paper on the potential for
pathogens acquiring “ reduced susceptibility ”
to ClO 2 , ASC, TSP, and PAA applied for
removal of meat surface contamination, or
the potential to develop “ resistance to thera-
peutic agents ” as a result of exposure to the
above biocides (EFSA 2008 ). According to
this opinion, there was no existing evidence
that proper use (in terms of concentration) of
the aforementioned biocides for carcass
decontamination would result in reduced sus-
ceptibility in resistance to therapeutic agents.
Similarly, it has been reported that disinfect-
ing poultry chiller water with 20 ppm ClO 2 is
of negligible risk to human health, due to its
reduction of chlorite and chlorate (Tsai et al.