[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fxLN3MUwXCdr5RPjwZYIDpOj8CHyjOmngWTgoKXPtZbg":3,"$fNm0tBis5KMMbIFJK-l-MCvVFlO6XqSImb1cMFHQE_Y8":32,"$f3Ft0rKFJHppdzE-vuveecxx1BUcg9iOlMLtyzf_MJDg":63},[4,8,12,16,20,24,28],{"title":5,"slug":6,"path":7},"About Microbeonline.com","about-microbeonline-com","\u002Fabout-microbeonline-com\u002F",{"title":9,"slug":10,"path":11},"About Me","about-me","\u002Fabout-microbeonline-com\u002Fabout-me\u002F",{"title":13,"slug":14,"path":15},"Advertise with Us","advertise-us","\u002Fadvertise-us\u002F",{"title":17,"slug":18,"path":19},"Privacy Policy","privacy-policy","\u002Fprivacy-policy\u002F",{"title":21,"slug":22,"path":23},"Abbreviations","abbreviations","\u002Fabbreviations\u002F",{"title":25,"slug":26,"path":27},"Microbes","microbes","\u002Fmicrobes\u002F",{"title":29,"slug":30,"path":31},"Books","recommended-books","\u002Frecommended-books\u002F",{"type":33,"data":34},"blog",{"slug":35,"title":36,"description":37,"seoTitle":38,"seoDescription":38,"author":39,"createdDate":40,"lastUpdatedDate":41,"draft":42,"category":43,"image":38,"body":44,"faq":45,"tags":61,"related":62},"camp-test-principle-procedure-results","CAMP Test: Principle, Procedure, and Results","CAMP test principle, procedure, and result interpretation for identifying Streptococcus agalactiae (Group B Strep), including the arrowhead hemolysis mechanism",null,"Acharya Tankeshwar","2013-11-08","2026-07-16",false,"biochemical-tests","The CAMP test is used for the presumptive identification of **Group B** beta-hemolytic streptococci; *Streptococcus agalactiae*. The test is effective for the “prompt and reliable” identification of [*Streptococcus agalactiae*](\u002Fstreptococcus-agalactiae-gbs-properties-pathogenesis-diagnosis\u002F) in the clinical lab. The result appears in as little as 18 hours and requires few manipulations.\n\n**A naming caution before anything else:** CAMP has nothing to do with cyclic AMP. If you have done any biochemistry, that is the association your brain will reach for, and it is wrong here. CAMP is an eponym: **C**hristie, **A**tkins, and **M**unch-**P**etersen, the three researchers who described this synergistic hemolysis in 1944.\n\n## Principle of CAMP Test\n\nThe basis of the CAMP test is the enhanced hemolytic activity of beta-hemolysin-producing strains of *Staphylococcus aureus* by an extracellular protein ( CAMP factor) produced by group B streptococci. **Synergistic hemolysis** in the [blood agar plate](\u002Fblood-agar-composition-preparation-uses-and-types-of-hemolysis\u002F) results from the interaction of the beta-hemolysin with the factor. Both hemolytic and non-hemolytic strains of group B streptococci show this phenomenon.\n\n![CAMP Test - CAMP Test Positive (arrowhead increased zone of hemolysis)](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FCAMP-Test-Positive.jpg)Figure: CAMP Test Positive (arrowhead increased zone of hemolysis)\n\n## Quality control\n\nTest each lot of beta-lysin reagent or disks with a positive and negative control by streaking them in a line parallel to the test organism.\n\n**Organisms**\n\n- CAMP test positive: *S. agalactiae* ATCC 13813\n- CAMP test negative: *Streptococcus pyogenes* ATCC 19615\n- Periodically use an in-house laboratory strain of *Arcanobacterium haemolyticum*to demonstrate the reverse CAMP test for training purposes.\n\n## Procedure for CAMP test\n\n**Standard Method**\n\n- Firstly, make a single straight line streak of beta-hemolysin producing [*Staphylococcus aureus*](\u002Fstaphylococcus-aureusdisease-properties-pathogenesis-and-laboratory-diagnosis\u002F) down the center of a blood agar plate,\n- Then, inoculate a streak of the test organism *(beta-hemolytic streptococci to be identified)* **perpendicular to the staphylococcal streak**. Take care not to intersect the staphylococcal streak.\n\n> Note: Make these streaks in such a way that, after incubation, the growth of the two organisms will not be touching.\n\n- The streptococcal streak should be 3 to 4 cm long.\n- Similarly, inoculate known group A and B streptococcal strains on the same plate as negative and positive controls.\n- Ensure labeling the location of each streak on the back of the plate.\n- Finally, incubate the plate at 35°C in ambient air for 18-24 hours.\n\n**Disk method**\n\n- Firstly, place disks containing beta-lysin of S. aureus on a warmed blood agar plate.\n- Then, streak microorganisms 2 to 3 mm from the edge of the disk.\n- Finally, incubate the plate overnight at 35°C in ambient air. *(Avoid CO2, candle jar, or anaerobic incubation.)*\n\n**Spot rapid method**\n\n- At first, place one drop or a 10 μl loopful of CAMP liquid reagent next to a presumptive *S. agalactiae* colony growing on a blood agar plate.\n\n> Note: Do not worry if the liquid touches or engulfs the colony.\n\n- Then, incubate the plate right side up to prevent the spot CAMP reagent from running over the plate’s surface for 20 min at 35°C.\n- After that, examine the plate with transmitted light for a zone of enhanced hemolysis next to the colony.\n- Again, re-incubate for up to 30 min if the reaction is initially negative. Use a hand lens if necessary for examining the plate.\n- Refrigeration may enhance reaction after incubation.\n\n## Results and Interpretations\n\n![CAMP Test - CAMP test : A.Streptococcus agalactiae(positive) B.Streptococcus pyogenes(Negative)Image Source: ASM](https:\u002F\u002Fassets.microbeonline.com\u002Fblogs\u002FCAMP-Test-Figure.jpg)Figure: CAMP test : A. *Streptococcus agalactiae* (positive) B. *Streptococcus pyogenes* (Negative) Image Source: ASM\n\n- CAMP Test: A positive test is the formation of a distinct arrowhead of hemolysis at the intersection of the staphylococcus and test organism streaks. If any gram-positive, catalase-negative, beta-hemolytic cocci, bacitracin-resistant, trimethoprim-sulfamethoxazole-resistant shows such arrowhead hemolysis, it can be reported as group B. streptococci (*Streptococcus agalactiae*).\n- A positive **reverse CAMP test** or phospholipase D is indicated by a distinct arrow of no hemolysis at the intersection of the two hemolytic organisms. *C. perfringens* is reverse CAMP positive.\n- In the disk test, a positive result is indicated by a distinct crescent- or arc-shaped zone of complete hemolysis at the intersection of the disk of beta-lysin and the isolate.\n- In the rapid spot test, the presence of clear enhanced hemolysis only where the diffused hemolysis overlaps is a positive result.\n- A negative test is a lack of enhanced hemolysis near the colony being tested.\n\n### Other organisms that give a standard (positive) CAMP reaction\n\nBesides *S. agalactiae*, these give an enhanced-hemolysis CAMP reaction (not to be confused with the reverse CAMP organisms below):\n\n1. *Listeria monocytogenes*\n2. *Rhodococcus equi*\n3. Certain *Corynebacterium* species (e.g., *C. glucuronolyticum*, *C. striatum* group)\n\n## Limitation of CAMP test\n\n1. Some group A streptococci will be CAMP test positive if the test plate is incubated in a candle jar, in a CO2 atmosphere, or under anaerobic conditions. Therefore, ambient air incubation should be used.\n2. *S. pyogenes* can give a reaction that may be interpreted as positive. When there is confusion, check for [the pyrrolidonyl-β-naphthylamide (PYR) test](\u002Fpyrrolidonyl-arylamidase-pyr-test-principle-procedure-results\u002F). *S. pyogenes* is PYR positive, whereas *S. agalactiae* is PYR negative.\n3. It has a 98% sensitivity for detecting *S. agalactiae*, so isolates with a negative CAMP test could still be *S. agalactiae* and may require further testing.\n4. The reaction may be very weak if the agar is too thin or hemolyzed.\n\n### Reverse CAMP Test\n\nThe name \"reverse CAMP\" covers two related but distinct bench observations. Keeping them apart is what prevents misreading a plate.\n\n**1. Inhibition of staphylococcal beta-hemolysin.** Some organisms produce a phospholipase that blocks the *S. aureus* beta-hemolysin instead of enhancing it. Where the test organism approaches the staph streak, hemolysis is suppressed, giving a triangular zone (arrowhead) of **inhibited** hemolysis. The organisms that behave this way include *Arcanobacterium haemolyticum* (phospholipase D), *Corynebacterium pseudotuberculosis*, and *C. ulcerans*.\n\n**2. Two-toxin synergy to identify *Clostridium perfringens*.** In the reverse CAMP test used for *C. perfringens*, *S. agalactiae* is streaked as the **source of CAMP factor** and *C. perfringens* is the test organism. The alpha-toxin of *C. perfringens* (a phospholipase C) and the GBS CAMP factor act together, producing the classic **bow-tie** zone of enhanced hemolysis at the junction. Note the naming trap: here *S. agalactiae* is the reagent, not the reverse-CAMP-positive organism, and the result is **synergy** (extra hemolysis), which is the opposite of the inhibition pattern above.\n\nSo a single \"reverse CAMP\" label spans an **arrow of no hemolysis** (inhibition) and a **bow-tie of extra hemolysis** (*C. perfringens* synergy). Always confirm which version the protocol in front of you is describing.\n\n## Where students actually get confused\n\n- **The arrowhead is not made by GBS alone.** A common misread is treating the arrowhead as something *S. agalactiae* produces by itself. It does not. The visible clearing appears only where the GBS CAMP factor and the *S. aureus* beta-hemolysin diffuse into the same zone. No staph streak, no arrowhead, even for a strong CAMP-factor producer.\n- **A bow-tie is not a strong forward CAMP.** Students who have seen a forward arrowhead sometimes read any junction clearing as \"very positive.\" The bow-tie belongs to the *C. perfringens* reverse test, where GBS is only the reagent. Reporting it as a forward CAMP positive misidentifies the organism.\n- **\"Listeria is CAMP positive\" is a forward result, not reverse.** *Listeria monocytogenes* enhances hemolysis toward the *S. aureus* streak, exactly like GBS. It is easy to slot it mentally next to *C. perfringens* under \"reverse,\" which is wrong. Because *Listeria* and GBS give the same arrowhead, they are separated by catalase (Listeria positive, GBS negative) and Gram morphology (rod vs. coccus), not by CAMP shape.\n\n## Key exam facts in one table\n\n| Feature | Detail | Memory hook |\n| --- | --- | --- |\n| What CAMP stands for | Christie, Atkins, Munch-Petersen | Not cyclic AMP |\n| Identifies | Streptococcus agalactiae (GBS) |  |\n| Mechanism | Synergy: CAMP factor + S. aureus beta-hemolysin | Neither organism alone produces it |\n| Positive result | Arrowhead zone of complete hemolysis | At the streak junction |\n| Sensitivity | \\~98% | Negative ≠ automatic exclusion |\n| False-positive risk | Some GAS strains under CO2\u002Fanaerobic incubation | Use ambient air |\n| Resolves ambiguity | PYR test (GAS positive, GBS negative) |  |\n| Reverse CAMP positive organisms | *C. perfringens, Arcanobacterium haemolyticum* | Arrow of *no* hemolysis |\n\n## **How to Remember**\n\n**The arrow is a collaboration, not a solo.** Neither organism makes the arrowhead alone. *S. aureus* beta-hemolysin partially damages the red cells; GBS CAMP factor on its own does nothing visible. Where the two diffusing substances overlap, the partial damage is finished off completely, and that overlap zone is the arrowhead, pointing toward the *Staph* streak because that is where the synergy is strongest. This is the same synergy logic covered in the *S. agalactiae* article.\n\n**Standard arrow = enhanced hemolysis; reverse arrow = no hemolysis.** A positive standard CAMP is an arrow of *extra* clearing (synergy). A positive reverse CAMP is an arrow of *absent* clearing (inhibition). Same arrow shape, opposite biology. Always know which version you are reading.\n\n**PYR breaks the GAS tie.** If a beta-hemolytic strep gives a borderline CAMP under the wrong incubation, PYR settles it: *S. pyogenes* (GAS) is PYR-positive, *S. agalactiae* (GBS) is PYR-negative.\n\n**References and further readings**\n\n1. Tille PM. *Bailey and Scott's Diagnostic Microbiology.* 15th ed. St. Louis: Elsevier; 2022.\n2. Procop GW, Church DL, Hall GS, Janda WM, Koneman EW, Schreckenberger PC, Woods GL. *Koneman's Color Atlas and Textbook of Diagnostic Microbiology.* 7th ed. Philadelphia: Wolters Kluwer; 2017.\n3. Leber AL, editor. *Clinical Microbiology Procedures Handbook.* 4th ed. Washington, DC: ASM Press; 2016. doi:10.1128\u002F9781555818814\n4. Christie R, Atkins NE, Munch-Petersen E. A note on a lytic phenomenon shown by group B streptococci. *Aust J Exp Biol Med Sci.* 1944;22:197-200.",[46,49,52,55,58],{"question":47,"answer":48},"Does the CAMP test detect cyclic AMP?","No. Despite the name overlap, CAMP here is an eponym for Christie, Atkins, and Munch-Petersen, the researchers who first described the phenomenon in 1944. It has nothing to do with the cyclic AMP signaling molecule.",{"question":50,"answer":51},"Why does a negative CAMP test not fully rule out Streptococcus agalactiae?","The CAMP test has approximately 98% sensitivity for GBS, not 100%. A negative result on a strongly suspected isolate should prompt further testing, such as hippurate hydrolysis or latex agglutination, rather than an automatic exclusion.",{"question":53,"answer":54},"What is the difference between a standard positive CAMP test and a positive reverse CAMP test?","A standard positive CAMP test shows an arrowhead zone of enhanced, complete hemolysis where the two streaks meet, seen with S. agalactiae. A positive reverse CAMP test shows an arrow of inhibited hemolysis instead, seen with organisms like Clostridium perfringens and Listeria. Same arrow shape, opposite underlying biology.",{"question":56,"answer":57},"Why does neither organism alone produce the CAMP arrowhead?","Because the arrowhead is the product of two substances acting together. Staphylococcus aureus beta-hemolysin partially damages the red blood cells in the agar, and Group B Streptococcus produces CAMP factor, which on its own causes no visible hemolysis. Only where the two diffusing substances overlap does the partial damage get completed into full hemolysis, forming the arrowhead that points toward the staphylococcal streak. It is a synergy, so both organisms are required.",{"question":59,"answer":60},"How do you tell Group A from Group B streptococci if the CAMP test is ambiguous?","Use the PYR test. Some Group A streptococci can give a CAMP reaction that looks positive, especially if the plate is incubated in CO2 or anaerobically instead of ambient air. PYR resolves it: Streptococcus pyogenes (Group A) is PYR positive, while Streptococcus agalactiae (Group B) is PYR negative. Incubating the CAMP plate in ambient air, as the standard method requires, also prevents most of these false positives.",[],[],[64,70,77,82,86,90,95,100,104,108],{"slug":65,"name":39,"description":66,"image":67,"body":68,"postCount":69},"acharya-tankeshwar","Editor-in-chief","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Ftankeshwar-acharya-author-microbeonline.jpg","***Tankeshwar Acharya, MSc (Medical Microbiology)***\n\n*Tankeshwar Acharya is an Assistant Professor in the Department of Microbiology at Patan Academy of Health Sciences (PAHS), Nepal, where he has been teaching and practicing clinical microbiology for over 14 years. He is the founder of Microbe Online, one of the leading free microbiology education resources on the web, covering bacteriology, mycology, parasitology, immunology, and clinical laboratory diagnostics written from direct experience in both the classroom and the diagnostic laboratory.*",433,{"slug":71,"name":72,"description":73,"image":74,"body":75,"postCount":76},"ashma-shrestha","Ashma Shrestha","SEO Copywriter and Science Communicator\nKathmandu, Nepal","https:\u002F\u002Fassets.microbeonline.com\u002Fauthors\u002Fashma-shrestha.png","Ashma Shrestha holds a Master of Science in Medical Microbiology from the Institute of Science and Technology (IOST), Tribhuvan University, Nepal, where she developed a strong foundation in virology, molecular biology, and diagnostic microbiology.\n\nShe now works as an SEO Copywriter at Resolution Digital, where she combines her scientific training with research-driven content strategy. She is certified in Google Analytics and Google Business Profile (GBP), and brings a data-informed approach to science communication writing content that is not only accurate but structured to reach and serve the students who need it most.\n\nAt microbeonline, Ashma contributes articles primarily in virology and molecular biology, areas she finds most compelling for their mechanistic depth and their growing clinical relevance. Her writing reflects the same standard the site is built on: factual rigor, clear explanation of the *why* behind microbiology concepts, and content that helps students move from memorization to genuine understanding.\n\nShe is passionate about making complex microbiological concepts accessible without sacrificing accuracy; a skill that sits at the intersection of her scientific training and her professional work in content and SEO.",81,{"slug":78,"name":79,"description":80,"image":38,"body":38,"postCount":81},"sushmita-baniya","Sushmita Baniya","Author \u002F Contributor",32,{"slug":83,"name":84,"description":80,"image":38,"body":38,"postCount":85},"samikshya-acharya","Samikshya Acharya",20,{"slug":87,"name":88,"description":80,"image":38,"body":38,"postCount":89},"alisha-tripathi","Alisha Tripathi",6,{"slug":91,"name":92,"description":93,"image":38,"body":38,"postCount":94},"aastha-shrestha","Aastha Shrestha"," Author \u002F Contributor",10,{"slug":96,"name":97,"description":98,"image":38,"body":38,"postCount":99},"guest-author","Guest Author","Guest Author \u002F Contributor",2,{"slug":101,"name":102,"description":80,"image":38,"body":38,"postCount":103},"srijana-khanal","Srijana Khanal",18,{"slug":105,"name":106,"description":98,"image":38,"body":38,"postCount":107},"dr-poonam-acharya","Dr. Poonam Acharya",1,{"slug":109,"name":110,"description":80,"image":38,"body":111,"postCount":112},"nisha-rijal","Nisha Rijal","**Nisha Rijal** is a microbiologist and quality assurance specialist. She served for nearly 12 years as a microbiologist at the National Public Health Laboratory (NPHL), Nepal's national reference laboratory, and continues to work as a consultant microbiologist in international public health organization. ",51]