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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOPMENT OF PREDICTIVE MICROBIAL MODELS FOR FOOD SAFETY AND THEIR ASSOCIATED USE IN INTERNATIONAL MICROBIAL DATABASES

Location: Residue Chemistry and Predictive Microbiology

Title: Mathematical modeling of growth of non-O157 Shiga Toxin-producing Escherichia coli in raw ground beef

Authors
item Huang, Lihan
item Tu, Shu-I
item Phillips, John
item Fratamico, Pina

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 3, 2012
Publication Date: April 1, 2012
Citation: Huang, L., Tu, S., Phillips, J.G., Fratamico, P.M. 2012. Mathematical modeling of growth of non-O157 Shiga Toxin-producing Escherichia coli in raw ground beef. Journal of Food Science. 77(4)217-225.

Interpretive Summary: Shiga toxin-producing Escherichia coli (STEC) are a group of potential fatal foodborne pathogens that have caused outbreaks and sporadic cases of human infections worldwide. This study investigated the growth kinetics of STEC in raw ground beef. Mathematical models were developed to predict the growth of STEC in ground beef. The results can be used by regulatory agencies for risk assessment.

Technical Abstract: The objective of this study was to investigate the growth of Shiga toxin-producing Escherichia coli (STEC, including serogroups O45, O103, O111, O121, and O145) in raw ground beef and to develop mathematical models to describe the bacterial growth under different temperature conditions. Three primary growth models were evaluated, including the Baranyi model, the Huang 2008 model, and a new growth model that is based on the communication of messenger signals during bacterial growth. A five strain cocktail of freshly prepared STEC was inoculated to raw ground beef samples and incubated at temperatures ranging from 10 to 35C at 5C increments. Minimum relative growth (greater than 1 log10 cfu/g) was observed at 10C, while at other temperatures, all three phases of growth were observed. Analytical results showed that all three models were equally suitable for describing the bacterial growth under constant temperatures. The maximum cell density of STEC in raw ground beef increased exponentially with temperature, but reached a maximum of 8.53 log10 cfu/g of ground beef. The specific growth rates estimated by the three primary models were practically identical and can be evaluated by either the Ratkowsky square-root model or a Belehrádek-type model. The temperature dependence of lag phase development for all three primary models was also developed. The results of this study can be used to estimate the growth of STEC in raw ground beef at temperatures between 10 and 35C.

Last Modified: 8/22/2014