Identification of the Listeria monocytogenes virulence factors involved in the CAMP reaction

There is a need to identify the virulence factors involved in the synergistic lysis of erythrocytes (CAMP reaction) by Listeria monocytogenes and either Staphylococcus aureus or Corynebacterium equi, in order to assess the relationship between the CAMP reaction and virulence of L. monocytogenes. The ability of various L. monocytogenes mutants to secrete listeriolysin O and phospholipases, and to produce lysis of sheep blood agar was determined. The results suggest that the CAMP reaction with Coryne. equi involves listeriolysin O and Coryne. equi cholesterol oxidase, and that the reaction with Staph. aureus involves either of the phospholipases C produced by L. monocytogenes. A modified CAMP test, which incorporates cholesterol oxidase into sheep blood agar, is proposed for the rapid (4-6 h) identification of L. monocytogenes.