THE EFFECT OF AERATION, INITIAL INOCULUM AND MEAT MICROFLORA ON THE GROWTH-KINETICS OF LISTERIA-MONOCYTOGENES IN SELECTIVE ENRICHMENT BROTHS

The effect of increased aeration, initial inoculum and the meat microflora on the growth kinetics of Listeria monocytogenes in meat samples enriched in Listeria selective broth were investigated. Growth rate and lag phase duration were calculated following linear regression analysis on the growth data. Neither aeration or variations in the initial inoculum levels altered the length of the lag phase or the growth rate of L. monocytogenes. The growth kinetics of the meat microflora was similar under all of the experimental conditions investigated. Overall the meat microflora was shown to have a faster growth rate than L. monocytogenes in selective media. Organisms growing during Listeria selective enrichment were identified as Lactobacillus plantarum, Lactobacillus delbrueckii and pseudomonads. The implications of the growth of these organisms in Listeria selective broths are discussed.