Clostridium botulinum growing on egg yolk agar showing the lipase reaction after 72 hours of incubation.
C. botulinum is a strictly anaerobic bacterium that when grown on egg yolk agar, its colonies will exhibit a lipase reaction, described as the shiny area around each colony.
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CDC/ Courtesy of Larry Stauffer, Oregon State Public Health Laboratory
CDC - National Center for Emerging and Zoonotic Infectious Diseases (NCEZID); Division of Foodborne, Waterborne, and Environmental Diseases (DFWED); Botulism: General Information