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Behavior of Listeria monocytogenes in pH-modified chicken salad during refrigerated storage.

* Listeria monocytogenes is the causative agent of listeriosis.

* The incidence of listeriosis in the United States is relatively low (~2,500 cases per year).

* But listeriosis has a fatality rate of ~20 percent.

* Other consequences of infection can include septicemia, meningitis, and stillbirth.

* Populations that are most susceptible to listeriosis include pregnant women and individuals with a predisposing disease or diminished immune function.

* A zero tolerance has been established in the United States for L. monocytogenes in processed ready-to-eat (RTE) foods.

* That means <1 CFU per two 25-g samples.

* This policy also applies to processed dairy and meat food products.

* Controlling the behavior of L. monocytogenes in foods is problematic because the microorganism

--is halotolerant,

--is ubiquitous in raw ingredients and the processing environment,

--is capable of survival or growth over a broad pH range (pH 4.4-9.6) and a broad temperature range (<1[degrees]C-45[degrees]C), and

--is capable of survival or growth in atmospheres of varied oxygen content.

* Storage and display of ready-to-eat foods such as protein-based salads present a unique challenge.

* Limited information is currently available about prevalence, growth, survival, and inactivation of L. monocytogenes in protein-based salads.

* The study reported here assessed the growth and inactivation kinetics of L. monocytogenes in commercially produced pasteurized chicken salad.

* Different levels of acidity (pH 4.0, 4.6, and 5.2) were assessed during storage at 5.0[degrees]C, 7.2[degrees]C, and 21.1[degrees]C (41[degrees]F, 45[degrees]F, and 70[degrees]F).

* Inactivation was seen at all pH levels and at all temperatures after varying lengths of time.

* A wide variety of resources, including the FDA Bad Bug Book, suggest that L. monocytogenes is capable of growing within the pH and temperature environment selected in this study.

* The USDA Pathogen Modeling Program also suggests that growth would occur under many of the conditions studied, with inactivation predicted only at the lower pH (4.0).

* Although these resources are invaluable tools for the food industry to use, it is important to study specific food systems.

* The complexity of food systems potentially gives rise to interactions of several factors:



--antimicrobial ingredients,

--the physical and chemical properties of the food, and

--even the physical positioning of ingredients and microorganisms throughout the food.

* These interactions can appreciably influence microbial behavior.

* The identification and quantification of these interactive effects in food systems will be an extensive process.

* The adaptive nature of L. monocytogenes must also be considered in the development of future experiments.
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Title Annotation:Practical Stuff!
Publication:Journal of Environmental Health
Geographic Code:1USA
Date:Jul 1, 2005
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