CAMP test

The CAMP test, short for Christie-Atkins-Munch-Petersen test, is a microbiological test used primarily to identify Streptococcus agalactiae (Group B Streptococcus, GBS). The test relies on the production of the CAMP factor, a diffusible, heat-stable protein produced by S. agalactiae.

Principle:

The CAMP factor acts synergistically with the beta-lysin produced by Staphylococcus aureus. Beta-lysin is a sphingomyelinase that enhances the lysis of red blood cells. When S. agalactiae and beta-lysin-producing S. aureus are grown in close proximity on blood agar, the CAMP factor produced by S. agalactiae enhances the hemolytic activity of the S. aureus beta-lysin. This results in an enlarged zone of synergistic hemolysis in the area where the two organisms interact.

Procedure:

A streak of beta-lysin-producing Staphylococcus aureus is made down the center of a sheep blood agar plate. The S. agalactiae isolate to be tested is then streaked perpendicularly to the S. aureus streak, without touching it. After incubation, the plate is observed for a characteristic arrowhead-shaped zone of enhanced hemolysis at the intersection of the two streaks.

Interpretation:

• Positive CAMP test: An arrowhead-shaped zone of enhanced hemolysis at the intersection of the S. aureus and test organism streaks indicates the production of CAMP factor and identifies the organism as Streptococcus agalactiae.
• Negative CAMP test: The absence of an arrowhead-shaped zone of enhanced hemolysis indicates that the organism does not produce CAMP factor.

Clinical Significance:

The CAMP test is an important tool in identifying Streptococcus agalactiae, a significant cause of neonatal infections such as sepsis, pneumonia, and meningitis. Rapid and accurate identification of GBS is crucial for implementing appropriate prophylactic measures to prevent these infections in newborns.