The growth of Salmonella typhimurium on irradiated, raw, skinless chicken breast

Salmonella typhimurium was inoculated onto 1 g cubed samples of irradiated, raw, skinless chicken breast, which were then incubated at 30°C under humid conditions. Kinetic growth data was obtained by means of viable counts performed on triplicate samples over a 24 h period. In addition, the spatial arrangement of cells on samples taken 6, 12 and 24 h after inoculation was observed by scanning electron microscopy. The population entered exponential growth approximately 3 h after inoculation, and maintained a constant rate of growth for approximately 13 h before entering a stationary phase. A generation time of 0.74 h was recorded. Scanning electron microscopy observations revealed colonial development from loose clusters of cells at 6 h to discrete, compact microcolonies (approximately 40 μm in diameter) by 12 h. By 24 h colonies were well-developed (approximately 600–700 μm in diameter) with a well-defined colony periphery. The results of this study give insight into the growth and development of bacteria on meat tissue, and serve to highlight that the nature of such growth is quite different from that in dispersed liquid culture systems, i.e. those traditionally used to model such growth.