{"id":297,"date":"2023-09-16T22:07:39","date_gmt":"2023-09-16T21:07:39","guid":{"rendered":"https:\/\/microregistrar.com\/?p=297"},"modified":"2023-09-16T22:07:40","modified_gmt":"2023-09-16T21:07:40","slug":"catalase-test","status":"publish","type":"post","link":"https:\/\/microregistrar.com\/?p=297","title":{"rendered":"Catalase test"},"content":{"rendered":"\n<p><strong>This test detects the catalase enzyme present in most cytochrome-containing aerobic and facultative anaerobic bacteria.<\/strong>&nbsp;The catalase enzyme converts hydrogen peroxide ( H<sub>2<\/sub>O<sub>2<\/sub>&nbsp;) to oxygen and water. This reaction can be observed as the rapid formation of bubbles.<\/p>\n\n\n\n<p><strong>The reaction<\/strong><\/p>\n\n\n\n<p>2 H<sub>2<\/sub>O<sub>2<\/sub>&nbsp;\u2192 2 H<sub>2<\/sub>O + O<sub>2<\/sub><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Catalase positive organisms<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table><tbody><tr><td><strong>Gram-positive organisms<\/strong><\/td><td><em>Staphylococcus, Micrococcus,<br>Aerococcus urinae (Note: Aerococcus viridans is negative),<br>Listeria, Corynebacterium diphtheriae<br>Bacillus (to differentiate from aerotolerant Clostridium. which is negative)<br>Nocardia<br>Rhodococcus equi.<br>Mycobacterium tuberculosis<\/em><\/td><\/tr><tr><td><strong>Gram-negative organisms<\/strong><\/td><td><em>Campylobacter fetus, Campylobacter jejuni, and Campylobacter coli.<br>Enterobacteriaceae (Citrobacter, E. coli, Enterobacter, Klebsiella, Shigella, Yersinia, Proteus, Salmonella, Serratia)<br>Pseudomonas<\/em><\/td><\/tr><tr><td><strong>Fungus<\/strong><\/td><td><em>Aspergillus, Cryptococcus<\/em><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">Can we get a false-positive or false-negative reaction?<\/h2>\n\n\n\n<h4 class=\"wp-block-heading\"><strong>False-positive test<\/strong><\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Catalase test should not be performed on colonies grown on media containing whole red blood cells (e.g. blood agar). Whole red blood cells may contain catalase; the test could be false positive.<\/li>\n\n\n\n<li>Some strains of Aerococcus and Enterococcus may give a false positive reaction due to pseudocatalase formation.<\/li>\n\n\n\n<li>Some inoculating loops or wires (nichrome) can react with the hydrogen peroxide to produce false positive reactions.<\/li>\n\n\n\n<li>Dirty glass test tubes\/ bijoux bottles can also produce false positive results.<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\"><strong>False-negative test<\/strong><\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Older cultures: organisms in older cultures may give a false negative result. The catalase test should ideally be done from culture 18-24 hours old.<\/li>\n\n\n\n<li>Anaerobic bacteria \u2013 Cultures of anaerobic bacteria should be exposed to air for 30 min before testing<\/li>\n\n\n\n<li>Hydrogen peroxide is unstable and must be refrigerated at all times. Avoid any undue exposure to light to prevent a false positive result.<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-table\"><table><tbody><tr><td><strong>Test methods \u2013<\/strong>&nbsp;<strong>multiple methods are available:<\/strong><br><br><strong>Tube or bottle method<\/strong>&nbsp;\u2013 put 4-5 drops of H<sub>2<\/sub>O<sub>2<\/sub>&nbsp;in a test tube or bijoux bottle. Pick a few colonies with a sterile loop and rub them on the inside wall of the tube above the H<sub>2<\/sub>O<sub>2<\/sub>&nbsp;. Cap the bottle\/tube. Tilt the bottle to bring H2O2 over the colonies. Look for bubble formation.<br><br><strong>Agar slant method<\/strong>&nbsp;\u2013 Put 1 ml of H<sub>2<\/sub>O<sub>2<\/sub>&nbsp; on a heavily inoculated 18-24 hr old culture on a nutrient agar slant. Replace the cap. Look for bubble formation.<br><br><strong>Other methods<\/strong>&nbsp;\u2013<br>Test on a glass slide or using a capillary tube<br><br><strong>Positive result<\/strong>&nbsp;\u2013 bubble formation<br>Negative result&nbsp;\u2013 no bubble formation<br><br>Safety:<br>1. The test may produce bacterial-laden aerosol \u2013 this test must be performed by a method (tube\/bottle or agar slant method) or\/and inside a safety cabinet.<br>2. H<sub>2<\/sub>O<sub>2<\/sub>&nbsp;is corrosive; appropriate protection should be taken.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/microregistrar.com\/wp-content\/uploads\/2021\/10\/Capture-1-1024x550.jpg\" alt=\"\" class=\"wp-image-8189\"\/><figcaption class=\"wp-element-caption\"><em>Catalase test (Wikipedia, &nbsp;<a href=\"https:\/\/commons.wikimedia.org\/wiki\/User:Nase\">Nase<\/a>)<\/em><\/figcaption><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>This test detects the catalase enzyme present in most cytochrome-containing aerobic and facultative anaerobic bacteria.&nbsp;The catalase enzyme converts hydrogen peroxide 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