Quantification of the relative effects of temperature, pH, and water activity on inactivation of Escherichia coli in fermented meat by meta-analysis.

Outbreaks of Escherichia coli infections linked to fermented meats have prompted much research into the kinetics of E. coli inactivation during fermented meat manufacture. A meta-analysis of data from 44 independent studies was undertaken that allowed the relative influences of pH, water activity (a(w)), and temperature on E. coli survival during fermented meat processing to be investigated. Data were reevaluated to determine rates of inactivation, providing 484 rate data points with various pH (2.8 to 6.14), a(w) (0.75 to 0.986), and temperature (-20 to 66 degrees C) values, product formulations, and E. coli strains and serotypes. When the data were presented as an Arrhenius model, temperature (0 to 47 degrees C) accounted for 61% of the variance in the ln(inactivation rate) data. In contrast, the pH or a(w) measured accounted for less than 8% of variability in the data, and the effects of other pH- and a(w)-based variables (i.e., total decrease and rates of reduction of those factors) were largely dependent on the temperature of the process. These findings indicate that although temperatures typically used in fermented meat manufacture are not lethal to E. coli per se, when other factors prevent E. coli growth (e.g., low pH and a(w)), the rate of inactivation of E. coli is dominated by temperature. In contrast, inactivation rates at temperatures above approximately 50 degrees C were characterized by smaller z values than those at 0 to 47 degrees C, suggesting that the mechanisms of inactivation are different in these temperature ranges. The Arrhenius model developed can be used to improve product safety by quantifying the effects of changes in temperature and/or time on E. coli inactivation during fermented meat manufacture.

Egg-associated Salmonella outbreak in an aged care facility, New South Wales, 2008.

Salmonellosis is a bacterial disease that causes acute gastroenteritis, with sudden onset of headache, abdominal pain, diarrhoea, nausea and sometimes vomiting. Infection is often associated with the consumption of foods prepared using raw eggs. During July to August 2008 an outbreak at an aged care facility (ACF) in New South Wales was confirmed as Salmonella Typhimurium phage type 44 (Stm 44) in eight of 45 residents. Two additional probable cases also occurred. Cases were located in each unit of the ACF and for 5 cases, onset of diarrhoea was between 45 to 64 hours (median of 46 hours) after consumption of a dessert containing raw eggs. Onset for 5 further cases occurred up to 9 days after this meal. Eggs were supplied to the ACF from a local farm. Stm 44 was detected on an egg in an unopened box at the ACF from this supplier. The raw-egg dessert was epidemiologically implicated as the likely source of the Salmonella and delayed onset cases may have resulted from ingestion of a smaller dose of Salmonella, or ongoing transmission through cross-contamination of kitchen machinery or surfaces. This outbreak demonstrates that inadequate cooking of eggs continues to pose a risk for Salmonella infection in settings with vulnerable populations. The findings of the investigation provide support for the importance of food safety regulations and demand further advocacy for measures to reduce the risks associated with the distribution, storage and preparation of shell eggs.