CAMP test is used to definitively identify which organism, and what is the biochemical basis of the positive result?
- A Streptococcus agalactiae (GBS) — its CAMP factor (sphingomyelinase inhibitor) synergizes with S. aureus beta-toxin (sphingomyelinase) to produce arrowhead haemolysis ✓
- B Listeria monocytogenes — its listeriolysin O synergizes with S. aureus beta-toxin to produce enhanced haemolysis
- C Streptococcus pyogenes — streptolysin O is enhanced by S. aureus delta-haemolysin producing complete lysis
- D Enterococcus faecalis — its cytolysin interacts with S. aureus alpha-toxin to expand the haemolytic zone
Explanation
The CAMP test (Christie, Atkins, Munch-Petersen) is used to identify Streptococcus agalactiae (Group B Streptococcus). The GBS-produced CAMP factor (a protein, not an enzyme) acts synergistically with S. aureus beta-toxin (which is a sphingomyelinase C that partially lyses sheep RBCs). CAMP factor binds to the sphingomyelin-modified membrane sites altered by beta-toxin, resulting in the characteristic arrowhead-shaped enhancement of haemolysis at the junction of the two streaks. Listeria monocytogenes also shows a positive CAMP-like test with listeriolysin O but the arrowhead pattern is the hallmark for GBS.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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