CAMP test - Purpose, Principle, Procedure, Result, Interpretation, History
Introduction to CAMP test
The CAMP test (Christie–Atkins–Munch-Peterson) is based on the microorganism's formation of the substance- a CAMP factor that enlarges the area of β-hemolysis due to the production of β-hemolysin manufactured by Staphylococcus aureus.
History of CAMP test
CAMP test stands for Christie–Atkins–Munch-Peterson. It is the acronym for the names of the three researchers who discovered the phenomenon- Christie, Atkins, and Munch-Peterson.
Purpose of CAMP test
The purpose of the CAMP test is to identify group B β-hemolytic streptococci such as Streptococcus agalactiae from other Streptococcal species. However, evidence has been presented that several groups of streptococci, including group A streptococci and Bartonella henselae, also contain the CAMP factor gene.
Listeria monocytogenes also produce a positive CAMP reaction.
Principle of CAMP test
Certain organisms (including group B Streptococci- S. agalactiae) are not strongly beta-hemolytic on their own. So, they produce a diffusible hemolytic protein (CAMP factor) that acts synergistically with the β-lysin of S. aureus to cause enhanced lysis of RBC.
Principle of CAMP test:
S. aureus produces β-lysin + S. agalactiae produces CAMP factor => resulting in an increased zone of hemolysis in the shape of an arrowhead.
Procedure of CAMP test
The procedure of the CAMP test is as follows:
Streak S. aureus (β-lysin producing strain) straight down the center of a 5% sheep blood agar plate
Streak test organism perpendicular to the streak of S. aureus on BA
The steak of the test organism should be 3-4 cm long (multiple organisms can be tested 2mm apart from each other)
Incubate the inoculated BA at 35°-37°C in ambient air for 18-24 hours.
Observe for an enhanced zone of hemolysis in the shape of an arrowhead at the juncture of two organisms
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Fig: S. agalactiae (top) showing arrowhead β-hemolysis and S. pyogenes (bottom) (Source: ASM MicrobeLibrary)
Interpretation of the CAMP test
The interpretation of the CAMP test can be - negative or positive.
Positive
An enhanced zone of hemolysis in the shape of an arrowhead at the juncture of two organisms (Staphylococcus aureus and test organism) confirms the production of the CAMP factor.
Negative
No enhancement of hemolysis at the juncture of two organisms (Staphylococcus aureus and test organism).