Virulence of Listeria monocytogenes, a foodborne pathogen, has been attributed in humans to the presence of hemolysins and oxidative enzymes that permit entrance and survival in macrophages and intestinal cells. Levels of hemolysin, catalase, and iron in sterile skim milk, meat, and various media inoculated and incubated under various conditions were determined. High-iron media and aeration increased growth and induced production of several catalases based on SDS-PAGE analysis. Reduced aeration increased hemolysin activity, but growth and catalase production were reduced. At refrigerator temperatures, L. monocytogenes strain Scott A grew in milk and media, but populations remained static in meat samples.

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