Listeria monocytogenes CAMP reaction
Investigation article published in Clinical Microbiology Reviews
July 1st, 1992
As highlighted by a Letter to the Editor recently published in Clinical Microbiology Reviews (8), there is controversy over reported results of the CAMP reaction of Listeria monocytogenes with Rhodococcus equi.
On the basis of previous reports (6, 7, 10, 11), Bergey`s Manual of Systematic Bacteriology (9) defined L. monocytogenes and Listeria ivanovii as CAMP negative and CAMP positive, respectively, with R. equi. This test was thereafter adopted as a fundamental criterion for the identification of the hemolytic Listeria species (5). The problem is that a number of investigators, including us, found that hemolytic
L. monocytogenes strains give a positive synergistic hemolysis reaction with R. equi (1-4, 12-14). We have observed (13) that a circular or racket-shaped well-defined zone of complete hemolysis develops (with different degrees of intensity depending on the hemolytic activity of the strain) from a streak of L. monocytogenes in the vicinity of R. equi. This lytic phenomenon could be distinguished from that of L.ivanovii, which is typically semicircular or shovel shaped. However, in certain cases (especially when highly hemolytic
L. monocytogenes strains are tested and when the test is performed on blood agar instead of washed erythrocyte agar), the R. equi CAMP reactions of both Listeria species are similar and can be confused.
Vazquez JA., Dominguez L., Fernandez-Garayzabal JF. and Suarez G.
 | Departamento de Sanidad Animal. Facultad de Veterinaria. Universidad Complutense (UCM). |
| Servicio de Identificación y Caracterización Microbiana (ICM). Centro de Vigilancia Sanitaria Veterinaria (VISAVET). Universidad Complutense (UCM). |
