Chapter 22 – Growth and Survival of Microbial Pathogens in Cheese

Cheesemaking evolved centuries ago as a means of preserving raw milk via fermentation. Selection of the beneficial natural flora in milk (i.e., lactobacilli, streptococci, and lactococci), or a direct addition of these organisms as starter cultures, helps to preserve products and allows competition with microbial contaminants, including human pathogens. Cheeses can become contaminated with pathogens as a result of their presence in the raw milk used for cheesemaking and subsequent survival during the cheesemaking process. Alternatively, bacterial pathogens can contaminate cheese via postprocessing contamination if sanitation and other measures in the processing plant are not sufficient to prevent recontamination. Although infrequent, cheeses have been linked with documented cases and outbreaks of foodborne illness. The combination and interaction of a number of factors, including acidity, salt content, and water activity, will dictate the potential for survival and growth of microbial pathogens. This chapter provides an overview of microbial pathogens in cheese and the factors that affect their growth and survival.