THE GROWTH OF SALMONELLA-TYPHIMURIUM ON IRRADIATED, RAW, SKINLESS CHICKEN BREAST

Salmonella typhimurium was inoculated onto 1 g cubed samples of irradi ated, raw, skinless chicken breast, which were then incubated at 30 de grees C under humid conditions. Kinetic growth data was obtained by me ans of viable counts performed on triplicate samples over a 24 h perio d. In addition, the spatial arrangement of cells on samples taken 6, 1 2 and 24 h after inoculation was observed by scanning electron microsc opy. The population entered exponential growth approximately 3 h after inoculation, and maintained a constant rate of growth for approximate ly 13 h before entering a stationary phase. A generation time of 0.74 h was recorded. Scanning electron microscopy observations revealed col onial development from loose clusters of cells at 6 h to discrete, com pact microcolonies (approximately 40 mu m in diameter) by 12 h. By 24 h colonies were well-developed (approximately 600-700 mu m 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, a nd serve to highlight that the nature of such growth is quite differen t from that in dispersed liquid culture systems, i.e. those traditiona lly used to model such growth. (C) 1997 Elsevier Science B.V.