Agriculture Reference
In-Depth Information
11
Biological Control of Human Pathogens
on Produce
John Andrew Hudson, Craig Billington, and
Lynn McIntyre
Introduction
Reported outbreaks of foodborne disease associated with the consumption of fresh
produce are increasing in frequency, and examples of the particular foods and patho-
gens involved have already been compiled (Beuchat 2002). Current methods for
controlling pathogens in fresh produce are therefore either not suffi ciently effective
or not being used effectively. Existing methods are based primarily on chemical treat-
ments, such as chlorine applied postharvest, which can have signifi cant disadvantages
(Sapers 2006), and consumers are concerned about chemical additions to their food
(Food Standards Agency 2007). In response, efforts have been made to fi nd alterna-
tives. One option is to develop treatments that use biocontrol, in which organisms, or
products derived from them, are used to control pathogens. It is anticipated that such
treatments would be perceived favorably by consumers as “clean, green, and natural”
alternatives.
The potential for using biocontrol as a means of controlling human pathogens on
plant products is shown through observations that the natural microbiota on plants
provides some defense against the growth of human pathogens. For example, the
growth of Listeria monocytogenes in endive was prevented by the presence of bacteria
isolated from the plant. Faster growth of the pathogen occurred when the endive had
been chemically sanitized, indicating that the native microbiota inhibited the pathogen
(Carlin and others 1996). Similar results have been found for the microbiota on fresh-
cut spinach (Babic and others 1997), baby carrots, and green pepper (Liao 2007). The
potential therefore exists for the microbial ecology of produce to be manipulated to
control human pathogens, and it has been suggested that an understanding of produce
microbial communities is the key to pathogen control (Beuchat 2002).
Recently effort has been focused on using pathogen-specifi c bacteriophages to
achieve the control of pathogens in produce. Other biocontrol options include the use
of protective cultures, typically pseudomonads or lactic acid bacteria (LAB), or natural
antimicrobial compounds such as bacteriocins, naturally occurring plant volatiles, and
nonvolatile essential oils. Space limitations preclude a fully comprehensive coverage
of all potential biocontrols, so we have focused wherever possible on examples that
describe biocontrol in vivo on fresh produce. Other methods (Gould 1996) could be
examined in the future.
The Connection between Control of Human and Plant Pathogens
A great deal of information is available concerning the biocontrol of plant pathogens
(Shoda 2000; Wilson and Wisniewski 1989). Plant and human pathogens have been
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