CAMP test

Principle

Group B streptococci (S. agalactiae) release CAMP factor, which enhances the beta-lysin of S. aureus and produces an arrowhead of complete hemolysis.

Procedure

• Streak a beta-lysin-producing S. aureus down the centre of a sheep blood agar plate.
• Streak the test organism at right angles, stopping 2–3 mm short; incubate overnight at 35 °C in air.

Results

• Positive: arrowhead-shaped zone of enhanced hemolysis where the test streak approaches the S. aureus streak = GBS (also Listeria)
• Controls: S. agalactiae (positive), S. pyogenes (negative)