Biology Reference
In-Depth Information
Pre-harvest control measures also include probiotics, bacteriophages, and
treatment with chlorate, neomycin sulfate and other dietary supplements. Pro-
biotics may prevent colonization by competing with STEC for environmen-
tal niches, by producing antibacterial compounds, or by promoting a healthy
immune system (
Berry and Wells, 2010
).
Lactobacillus acidophilus
alone or in
combination with other probiotics has been shown to reduce
E. coli
O157:H7
shedding in cattle and prevalence on hides (
Brashears et al., 2003
). Bacterio-
phages that directly lyse STEC have been shown to eliminate
E. coli
O157:H7
in vitro
, but results in animal models have been variable (
Raya et al., 2006
;
Rozema et al., 2009
). The USDA is currently reviewing treatment of cattle with
chlorate, which is toxic to
E. coli
O157:H7 after its reduction in the intestine to
chlorite (
Callaway et al., 2002
). Finally, measures that control STEC persistence
in manure (e.g. treatment with carbonate or alkali) or cattle pen surfaces (e.g.
providing dry bedding) may also reduce
E. coli
O157:H7 prevalence (
Berry and
Wells, 2010
).
Post-harvest measures focus on reducing STEC contamination of cattle car-
casses through hide washes, steam pasteurization, organic acid or hot water
washes, or combinations of these treatments (
Berry and Wells, 2010
) (
Table
5.5
). Furthermore, individual beef processing plants and the FSIS routinely col-
lect and test ground beef and beef trim samples for
E. coli
O157:H7 contamina-
tion (
Koohmaraie et al., 2007
). In addition, FDA has recently approved gamma
irradiation of ground beef to eliminate contaminating bacteria such as EHEC
(
Hijaz and Smith, 2010
). Further, outbreaks associated with ground beef from
fast food restaurants in the US have been diminished by raising cooking tem-
peratures, and those associated with dairy products and fruit juices have been
diminished by pasteurization (
Dodd and Powell, 2009
;
Berry and Wells, 2010
).
Consumers are advised to kill contaminating bacteria by cooking ground beef
to an internal temperature of 160°F and to avoid cross contamination between
meat and other food products through stringent hygienic practices in the kitchen
(
Kassenborg et al., 2004
).
The recent increased frequency of vegetable-associated STEC outbreaks has
highlighted the need to develop effective treatments to eliminate STEC con-
tamination of vegetables, and compared to efforts to prevent beef contamina-
tion, development of post-harvest control measures for other food sources of
STEC is still in its infancy. In this regard, the efficacy of several antimicro-
bial agents such as sodium hypochlorite, peroxyacetic acid, acidic electrolyzed
water, aqueous chlorine dioxide, and irradiation is currently under investigation.
CONCLUSION
STEC are zoonotic pathogens that cause food-borne disease outbreaks asso-
ciated with ground beef and fresh produce worldwide. The lethal complica-
tions associated with STEC disease and the severe economic impact on the food
industry cause STEC to be regarded as an exceptionally hazardous pathogen.
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