The CAMP test is a laboratory procedure primarily used for the presumptive identification of Streptococcus agalactiae (Lancefield group B).
Purpose of the CAMP Test
The primary purpose of the CAMP test is to differentiate Streptococcus agalactiae from other beta-hemolytic streptococci. Streptococcus agalactiae produces a diffusible extracellular protein called the CAMP factor, which enhances the beta-hemolysis of Staphylococcus aureus.
How the CAMP Test Works
The test involves streaking a beta-hemolytic Staphylococcus aureus strain down the center of a sheep blood agar plate. The Streptococcus species being tested is then streaked perpendicular to the S. aureus streak, without touching it.
- If the Streptococcus species produces the CAMP factor (Streptococcus agalactiae), the CAMP factor will enhance the beta-hemolysis produced by S. aureus. This results in a characteristic arrowhead-shaped zone of enhanced hemolysis at the intersection of the two streaks.
- If the Streptococcus species does not produce the CAMP factor, there will be no enhancement of hemolysis, and no arrowhead-shaped zone will be observed.
Interpreting the Results
- Positive CAMP test: Arrowhead-shaped zone of enhanced hemolysis indicates the presence of the CAMP factor, suggesting Streptococcus agalactiae.
- Negative CAMP test: Absence of the arrowhead-shaped zone of enhanced hemolysis suggests the absence of the CAMP factor, indicating the Streptococcus species is not Streptococcus agalactiae.
Variations of the CAMP Test
While the standard overnight CAMP test is commonly used, a rapid 30-minute spot CAMP test has also been developed and compared to the standard overnight test with good correlation.
Importance
The CAMP test is a simple and rapid method for presumptively identifying Streptococcus agalactiae. Early and accurate detection is crucial in settings such as prenatal screening, as Streptococcus agalactiae can cause serious infections in newborns.
