CAMP Test- Principle, Procedure, Types, Results, Uses, Limitations

CAMP test is a simple and rapid biochemical test that can help identify certain bacteria based on their ability to produce a specific protein called CAMP factor. The test is mainly used to differentiate Streptococcus agalactiae (Group B Streptococcus) from other beta-hemolytic streptococci. It can also be used to identify some gram-positive rods that produce CAMP factor, such as Listeria monocytogenes, Rhodococcus equi, and some Corynebacterium species.

The main objective of the CAMP test is to differentiate Streptococcus agalactiae from other beta-hemolytic Streptococci. Another objective is to detect the ability of an organism to produce the CAMP factor. The test can also be used to determine the presence of staphylococcal beta-hemolysin.

The CAMP test is based on the synergistic action of two hemolytic factors: one produced by Streptococcus agalactiae and the other by Staphylococcus aureus. The test relies on the enhanced hemolysis caused by the interaction between the CAMP factor and the beta-hemolysin of S. aureus.

The CAMP test is mainly used to test for the presence of the CAMP factor in Gram-positive cocci that are catalase-negative and grow in pairs and chains. This includes beta-hemolytic Streptococci, especially Streptococcus agalactiae. The test can also be used to test for some Gram-positive rods, such as Listeria monocytogenes and Rhodococcus equi.

Media

The most commonly used medium for the CAMP test is blood agar, which is a nutrient-rich medium that supports the growth of a wide range of bacteria and allows the detection of hemolytic reactions.

Reagent

The main reagent used for the CAMP test is beta-lysin, which is a hemolytic toxin produced by some strains of Staphylococcus aureus.

Supplies

• Sterile wooden applicator sticks or bacteriologic loops
• Distilled water
• Petri dish and slide
• Incubator
• CO2 generator or candle jar (optional)

The CAMP test can be performed either via the standard test on blood agar plates or the disk method.

Standard Method

1. S. aureus is streaked on the blood agar in a straight line across the center of the plate.
2. The unknown microorganism is then streaked in the same manner perpendicular to the staphylococcus while avoiding the touching of the organism to the previously streaked area.
3. The positive control organism is streaked parallel to and approximately 1 inch from the unknown organism.
4. Each streak on the plates is labeled on the back of the plate.
5. The plate is incubated overnight at 35°C in a CO2 incubator.

Disk Method

1. The disk is removed from the vial and placed on a warmed Blood Agar Plate.
2. The microorganism is streaked about 2 to 3 mm from the edge of the disk.
3. The plate is incubated overnight at 35°C in a CO2 incubator.

Quality control is an essential step to ensure the validity and reliability of the CAMP test results. The following are some of the quality control measures for the CAMP test:

• Test each lot of beta-lysin reagent or disks with a positive and negative control.
• Use Streptococcus agalactiae ATCC 13813 as a positive control and Streptococcus pyogenes ATCC 19615 as a negative control.
• Periodically use an in-house laboratory strain of Arcanobacterium haemolyticum to demonstrate the reverse CAMP test for training purposes.
• Incubate the plates at 35°C in ambient air for 18-24 hours.
• Check the plates for enhanced hemolysis at the intersection of the test organism and Staphylococcus aureus streaks or disks.
• Report the results as positive or negative for CAMP test. Confirm the identity of Streptococcus agalactiae by other biochemical tests.

The results of the CAMP test are based on the presence or absence of enhanced hemolysis at the point of interaction between the test organism and the Staphylococcus aureus strain or the beta-lysin disk. A positive CAMP test is indicated by a distinct arrowhead or flame-shaped zone of enhanced hemolysis, while a negative test shows no enhancement of hemolysis. A reverse CAMP test can also be performed to identify some staphylococcal species that produce phospholipase D.

The CAMP test is mainly used to differentiate Streptococcus agalactiae from other beta-hemolytic Streptococci. It can also be used to identify Listeria monocytogenes and determine the ability of an organism to produce the CAMP factor. The test provides valuable information for the diagnosis, treatment, and prevention of infections caused by these microorganisms.

• The CAMP test is not a definitive test for the identification of S. agalactiae or other CAMP-positive organisms.
• The test may give false-negative or false-positive results.
• The test may not be reliable for some Gram-positive rods or Gram-negative bacteria.
• The test may be affected by the quality of the blood agar plate, the incubation conditions, and the interpretation of the results.

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