Predictive models for growth of Salmonella typhimurium DT104 from low and high initial density on ground chicken with a natural microflora

A single strain (ATCC 700408) of Salmonella typhimurium DT104 was used to investigate and model growth from a low (1.12 log10 mpn g−1) and high (3.7 log10 cfu g−1) initial density on ground chicken with a natural microflora. Kinetic data for growth of the pathogen on ground chicken were fit to a primary model to determine lag time (λ), maximum specific growth rate (μ) and maximum population density (Nmax). Secondary models for λ, μ and Nmax, as a function of temperature (10-40 °C), were developed and compared among initial densities. Variation of pathogen growth among replicates (n=4 or 5) was higher at 10-18 °C than at 22-40 °C and was higher for Nmax than λ and μ. Prediction problems were observed when secondary models developed with one initial density were used to predict λ, μ and Nmax from the other initial density, especially at 10-18 °C and for Nmax. These results indicated that variation of growth among replicate challenge studies and initial density are important factors to consider when developing predictive models for growth of S. typhimurium DT104 on ground chicken with a natural microflora.