{"id":584,"date":"2022-01-23T20:10:26","date_gmt":"2022-01-23T14:25:26","guid":{"rendered":"https:\/\/microbiologypractical.com\/?p=149"},"modified":"2022-01-27T02:22:38","modified_gmt":"2022-01-26T20:37:38","slug":"indole-test-objective-principle-media-procedure-and-results","status":"publish","type":"post","link":"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/","title":{"rendered":"Indole Test- Principle, Media, Procedure, Types, Results, Uses"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_65 counter-hierarchy ez-toc-counter ez-toc-custom ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title \" >Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #0a0a0a;color:#0a0a0a\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #0a0a0a;color:#0a0a0a\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/#indole-test-definition\" title=\"Indole Test Definition\">Indole Test Definition<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/#objectives-of-indole-test\" title=\"Objectives of Indole Test\">Objectives of Indole Test<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/#microorganisms-tested\" title=\"Microorganisms Tested\">Microorganisms Tested<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/#principle-of-indole-test\" title=\"Principle of Indole Test\">Principle of Indole Test<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/#media-reagents-and-supplies-used\" title=\"Media, Reagents, and Supplies Used\">Media, Reagents, and Supplies Used<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/#reagents-used\" title=\"Reagents Used\">Reagents Used<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/#kovacs-reagent\" title=\"Kovac&#8217;s reagent\">Kovac&#8217;s reagent<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/#ehrlichs-reagent\" title=\"Ehrlich&#8217;s reagent\">Ehrlich&#8217;s reagent<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/#supplies-used\" title=\"Supplies Used\">Supplies Used<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/#procedure-of-indole-test\" title=\"Procedure of Indole Test\">Procedure of Indole Test<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/#a-rapid-spot-test\" title=\"A. Rapid Spot Test\">A. Rapid Spot Test<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/#b-tube-test\" title=\"B. Tube Test\">B. Tube Test<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/#result-interpretation-of-indole-test\" title=\"Result Interpretation of Indole Test\">Result Interpretation of Indole Test<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-14\" href=\"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/#a-spot-test\" title=\"A. Spot Test\">A. Spot Test<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-15\" href=\"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/#b-tube-test-2\" title=\"B. Tube Test\">B. Tube Test<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-16\" href=\"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/#uses-of-indole-test\" title=\"Uses of Indole Test\">Uses of Indole Test<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-17\" href=\"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/#limitations-of-indole-test\" title=\"Limitations of Indole Test\">Limitations of Indole Test<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-18\" href=\"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/#references-and-sources\" title=\"References and Sources\">References and Sources<\/a><\/li><\/ul><\/nav><\/div>\n<h2><span class=\"ez-toc-section\" id=\"indole-test-definition\"><\/span><strong>Indole Test Definition<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Indole test is a biochemical test conducted on bacterial species to detect their ability to produce indole from tryptophan in the presence of a group of enzymes called &#8216;tryptophanase&#8217;.<\/p>\n<ul>\n<li>It is a qualitative test that tests the conversion of tryptophan into indole.<\/li>\n<li>The test is performed as a part of the IMViC test that is used to differentiate the members of the Enterobacteriaceae family.<\/li>\n<li>It is important in the identification of different bacteria like <em>Escherichia coli, Proteus, Morganella<\/em>, etc.<\/li>\n<li>It plays a central role in the characterization of coliforms which is indicated by the various variations of the indole test and in combination with other biochemical tests.<\/li>\n<li>It is still used as a traditional method to distinguish indole-positive <em>E. coli<\/em> from indole-negative <em>Enterobacter<\/em> and <em>Klebsiella<\/em>.<\/li>\n<li>A variation of the test, called Ehrlich&#8217;s reagent (using ethyl alcohol instead of isoamyl alcohol) is used when the test has to be performed on non-fermenters and anaerobes.<\/li>\n<\/ul>\n<h3><span class=\"ez-toc-section\" id=\"objectives-of-indole-test\"><\/span><strong>Objectives of Indole Test<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ul>\n<li>To detect the formation of indole from tryptophan by the enzymatic action of tryptophanese.<\/li>\n<li>To differentiate members of family Enterobacteriaceae, especially <em>E. coli<\/em> from <em>Enterobacter<\/em> and <em>Klebsiella.<\/em><\/li>\n<\/ul>\n<h3><span class=\"ez-toc-section\" id=\"microorganisms-tested\"><\/span><strong>Microorganisms Tested<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ul>\n<li>Fresh growth of a Gram-negative rod on a medium that does not contain dyes and contains tryptophan, e.g., BAP or CHOC.<\/li>\n<li>Anaerobic Gram-positive rods.<\/li>\n<li>Anaerobic Gram-negative rods.<\/li>\n<\/ul>\n<h2><span class=\"ez-toc-section\" id=\"principle-of-indole-test\"><\/span><strong>Principle of Indole Test<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>The ability of an organism to split indole from the amino acid tryptophan is due to the presence of tryptophanase. Tryptophan is an amino acid that undergoes deamination and hydrolysis in the presence of the enzyme tryptophanase. Reductive deamination of tryptophan results in the production of indole via the intermediate molecule <strong>indole pyruvic acid. <\/strong>During the deamination process, the tryptophanase catalyzes the removal of the amino group (-NH<sub>2<\/sub>) from the tryptophan molecule. The enzyme requires <strong>pyridoxal phosphate<\/strong> as a coenzyme. The final products of the catalysis reaction are indole, pyruvic acid, ammonium (NH<sub>4<\/sub><sup>+<\/sup>), and energy. Indole, if present, combines with the aldehyde in the reagent to produce a pink to red-violet quinoidal compound (benzaldehyde reagent) or a blue to green color (cinnamaldehyde reagent). The indole combines with Kovac&#8217;s reagent (hydrochloric acid and p-dimethylaminobenzaldehyde in amyl alcohol) solution to form a yellow or cherry red coloration. The amyl alcohol is water-insoluble and thus, forms a red-colored oily layer at the top of the broth. In the rapid spot test, indole is detected directly from a colony growing on a medium rich in tryptophan. The indole combines with the p-dimethylaminocinnamaldehyde (DMACA) present on the filter paper at an acid pH to produce a blue to the blue-green compound.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"media-reagents-and-supplies-used\"><\/span><strong>Media, Reagents, and Supplies Used<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<h3><span class=\"ez-toc-section\" id=\"reagents-used\"><\/span><strong>Reagents Used<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ul>\n<li>For the spot test, 5% <em>p<\/em>-dimethylaminobenzaldehyde or 1% <em>p<\/em>dimethylaminocinnamaldehyde is prepared in 10% (v\/v) concentrated HCl.<\/li>\n<li>For the tube method, Kovac&#8217;s reagent is used for aerobic organisms, and Ehrlich&#8217;s reagent is used for anaerobes and weak indole producers.<\/li>\n<\/ul>\n<h3><span class=\"ez-toc-section\" id=\"kovacs-reagent\"><\/span><strong>Kovac&#8217;s reagent<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n<table style=\"width: 61.1465%;\">\n<tbody>\n<tr>\n<td style=\"width: 38.7525%;\" width=\"229\"><strong>Ingredients <\/strong><\/td>\n<td style=\"width: 22.296%;\" width=\"196\"><strong>Concentration <\/strong><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 38.7525%;\" width=\"229\">p-dimethylaminobenzaldehydre<\/td>\n<td style=\"width: 22.296%;\" width=\"196\">50 gram<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 38.7525%;\" width=\"229\">Hydrochloric acid<\/td>\n<td style=\"width: 22.296%;\" width=\"196\">250 ml<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 38.7525%;\" width=\"229\">Amyl Alcohol<\/td>\n<td style=\"width: 22.296%;\" width=\"196\">750 ml<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<ul>\n<li>The medium used with this reagent is either broth containing tryptophan, motility- indole-ornithine agar, or sulfide-indole-motility agar (SIM).<\/li>\n<\/ul>\n<h3><span class=\"ez-toc-section\" id=\"ehrlichs-reagent\"><\/span><strong>Ehrlich&#8217;s reagent<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n<table style=\"width: 61.3057%;\">\n<tbody>\n<tr>\n<td style=\"width: 39.1506%;\" width=\"235\"><strong>Ingredients <\/strong><\/td>\n<td style=\"width: 22.0306%;\" width=\"190\"><strong>Concentration <\/strong><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 39.1506%;\" width=\"235\">p-dimethylaminobenzaldehydre<\/td>\n<td style=\"width: 22.0306%;\" width=\"190\">1 gram<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 39.1506%;\" width=\"235\">Hydrochloric acid<\/td>\n<td style=\"width: 22.0306%;\" width=\"190\">20 ml<\/td>\n<\/tr>\n<tr>\n<td style=\"width: 39.1506%;\" width=\"235\">Ethyl alcohol<\/td>\n<td style=\"width: 22.0306%;\" width=\"190\">95 ml<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<ul>\n<li>The medium used with Ehrlich&#8217;s reagent is heart infusion or anaerobic medium with tryptophan.<\/li>\n<\/ul>\n<h3><span class=\"ez-toc-section\" id=\"supplies-used\"><\/span><strong>Supplies Used<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ul>\n<li>Sterile loop, swab, or stick for inoculation<\/li>\n<li>Filter paper (optional)<\/li>\n<\/ul>\n<h2><span class=\"ez-toc-section\" id=\"procedure-of-indole-test\"><\/span><strong>Procedure of Indole Test<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<h3><span class=\"ez-toc-section\" id=\"a-rapid-spot-test\"><\/span><strong>A. Rapid Spot Test<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ul>\n<li>A piece of filter paper is taken and is moistened with the reagent.<\/li>\n<li>A well-isolated colony from an 18-24-hour culture is taken with an inoculating loop and rubbed onto the moist filter paper.<\/li>\n<li>The paper is then observed for the appearance of the color.<\/li>\n<\/ul>\n<h3><span class=\"ez-toc-section\" id=\"b-tube-test\"><\/span><strong>B. Tube Test<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ul>\n<li>The broth medium or the agar medium in the tube is stabbed with the colony taken from an 18-24-hour culture.<\/li>\n<li>For the liquid medium, a small portion of the inoculated broth is taken in a separate tube.<\/li>\n<li>The tubes are then incubated at 37\u00b0C for 24 hours.<\/li>\n<li>For Kovac&#8217;s reagent, three drops of Kovac&#8217;s&#8217; reagent are added down the side of the tube, and the color change is observed at the meniscus.<\/li>\n<li>For Ehrlich&#8217;s reagent, 0.5 ml of xylene is added to the tube and inverted to mix well. Further, six drops of Ehrlich&#8217;s indole reagent are added down the side of the tube, and the color is observed below the xylene layer.<\/li>\n<\/ul>\n<h2><span class=\"ez-toc-section\" id=\"result-interpretation-of-indole-test\"><\/span><strong>Result Interpretation of Indole Test<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<h3><span class=\"ez-toc-section\" id=\"a-spot-test\"><\/span><strong>A. Spot Test<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ul>\n<li>The development of blue color within 20 seconds indicates the presence of indole.<\/li>\n<li>A negative result is indicated by no color or the appearance of a slightly pink color on the filter paper.<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-548\" src=\"https:\/\/microbenotes.com\/wp-content\/uploads\/2018\/07\/Result-Interpretation-of-Spot-Indole-Test.jpg\" alt=\"Result\u00a0Interpretation of\u00a0Spot Indole Test\" width=\"800\" height=\"420\" srcset=\"https:\/\/microbenotes.com\/wp-content\/uploads\/2018\/07\/Result-Interpretation-of-Spot-Indole-Test.jpg 800w, https:\/\/microbenotes.com\/wp-content\/uploads\/2018\/07\/Result-Interpretation-of-Spot-Indole-Test-300x158.jpg 300w, https:\/\/microbenotes.com\/wp-content\/uploads\/2018\/07\/Result-Interpretation-of-Spot-Indole-Test-768x403.jpg 768w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/><\/p>\n<p><strong>Figure:<\/strong> Spot Indole Test. <strong>Image Source:<\/strong> <a href=\"https:\/\/www.vetbact.org\/index.php?displayextinfo=35\" target=\"_blank\" rel=\"noopener noreferrer\">VetBact<\/a>.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"b-tube-test-2\"><\/span><strong>B. Tube Test<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n<ul>\n<li>The formation of pink-red coloration (cherry red ring) in the reagent at the point of contact between the reagent and the medium indicates a positive result.<\/li>\n<li>The absence of color or the appearance of slightly yellow color indicates a negative result.<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-31136\" src=\"https:\/\/microbenotes.com\/wp-content\/uploads\/2018\/05\/Indole-Test.jpg\" alt=\"Indole Test\" width=\"800\" height=\"420\" srcset=\"https:\/\/microbenotes.com\/wp-content\/uploads\/2018\/05\/Indole-Test.jpg 800w, https:\/\/microbenotes.com\/wp-content\/uploads\/2018\/05\/Indole-Test-300x158.jpg 300w, https:\/\/microbenotes.com\/wp-content\/uploads\/2018\/05\/Indole-Test-768x403.jpg 768w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/><\/p>\n<p><strong>Figure:<\/strong> Indole Test. <strong>Image Source:<\/strong>\u00a0Bailey and Scott\u2019s Diagnostic Microbiology. Elsevier.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"uses-of-indole-test\"><\/span><strong>Uses of Indole Test<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<ul>\n<li>The indole test is used to test an organism&#8217;s ability to utilize tryptophan and produce indole.<\/li>\n<li>The test is used to differentiate members of the Enterobacteriaceae family as a part of the IMViC test.<\/li>\n<li>The test also differentiates <em>Proteus mirabilis<\/em> from other <em>Proteus<\/em> species.<\/li>\n<li>This test differentiates indole-positive <em>E. coli<\/em> from indole-negative <em>Enterobacter<\/em> and <em>Klebsiella.<\/em><\/li>\n<li>The test further differentiates <em>K<\/em>. <em>pneumoniae<\/em>(indole negative) from <em>K. oxytoca<\/em>\u00a0(indole positive) and <em>Citrobacter freundii<\/em>\u00a0(indole negative) from\u00a0<em>Citrobacter koseri<\/em>\u00a0(indole positive).<\/li>\n<\/ul>\n<h2><span class=\"ez-toc-section\" id=\"limitations-of-indole-test\"><\/span><strong>Limitations of Indole Test<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<ul>\n<li>Detectable indole will diffuse to colonies within 5 mm of a 2- to 3-mm colony, giving false-positive results.<\/li>\n<li>Media that contain dyes (e.g., <a href=\"https:\/\/microbenotes.com\/eosin-methylene-blue-emb-agar\/\" target=\"_blank\" rel=\"noopener noreferrer\"><strong>EMB<\/strong><\/a>, MAC) shouldn&#8217;t be used.<\/li>\n<li>The growth medium must contain an adequate amount of tryptophan. Do not use <a href=\"https:\/\/microbenotes.com\/mueller-hinton-agar-mha\/\" target=\"_blank\" rel=\"noopener noreferrer\"><strong>Mueller-Hinton agar<\/strong> <\/a>for the test, because tryptophan is destroyed during the acid hydrolysis of casein.<\/li>\n<li>Only the cinnamaldehyde reagent can be used for spot testing of anaerobic microorganisms. It is a more sensitive reagent, but it is less stable.<\/li>\n<li>Do not use a plate with a nitrate disk to perform the indole test, as nitrate can interfere with the spot indole test by inducing false-negative results.<\/li>\n<li>If the rapid indole test is negative, the isolate could be positive in the more sensitive tube test. Extraction with xylene is the most sensitive test. Xylene substitutes are less sensitive.<\/li>\n<li>For fastidious Gram-negative rods, such as <em>C. hominis, <\/em>a heavy inoculum and extraction are necessary.<\/li>\n<\/ul>\n<h2><span class=\"ez-toc-section\" id=\"references-and-sources\"><\/span><strong>References and Sources<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n<ul>\n<li><span style=\"font-size: 10pt;\">Biochemical Tests for the Identification of Aerobic Bacteria. (2016).\u00a0<em>Clinical Microbiology Procedures Handbook, 3.17.1.1\u20133.17.48.3.<\/em>DOI:10.1128\/9781555818814.ch3.17.1\u00a0<\/span><\/li>\n<li><span style=\"font-size: 10pt;\">Maria P. MacWilliams. 2009. Indole test protocol.<\/span><\/li>\n<li><span style=\"font-size: 10pt;\">Kovac&#8217;s Indole Reagent R008. HiMedia Laboratories.<\/span><\/li>\n<li><span style=\"font-size: 10pt;\">5% &#8211; https:\/\/asm.org\/getattachment\/200d3f34-c75e-4072-a7e6-df912c792f62\/indole-test-protocol-3202.pdf<\/span><\/li>\n<li><span style=\"font-size: 10pt;\">3% &#8211; https:\/\/microbiologyinfo.com\/indole-test-principle-reagents-procedure-result-interpretation-and-limitations\/<\/span><\/li>\n<li><span style=\"font-size: 10pt;\">2% &#8211; https:\/\/himedialabs.com\/TD\/R008.pdf<\/span><\/li>\n<li><span style=\"font-size: 10pt;\">2% &#8211; http:\/\/universe84a.com\/indole-test-introduction\/<\/span><\/li>\n<li><span style=\"font-size: 10pt;\">1% &#8211; https:\/\/en.wikipedia.org\/wiki\/Indole_test<\/span><\/li>\n<li><span style=\"font-size: 10pt;\">1% &#8211; https:\/\/catalog.hardydiagnostics.com\/cp_prod\/Content\/hugo\/IndoleTestRgnts.htm<\/span><\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Indole Test Definition Indole test is a biochemical test conducted on bacterial species to detect their ability to produce indole from tryptophan in the presence of a group of enzymes &#8230; <a title=\"Indole Test- Principle, Media, Procedure, Types, Results, Uses\" class=\"read-more\" href=\"https:\/\/microbenotes.com\/indole-test-objective-principle-media-procedure-and-results\/\" aria-label=\"Read more about Indole Test- Principle, Media, Procedure, Types, Results, Uses\">Read more<\/a><\/p>\n","protected":false},"author":11,"featured_media":31136,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[5678,776,777,5680,5677,5679],"custom":{"td_video":"","featured_image":"https:\/\/microbenotes.com\/wp-content\/uploads\/2018\/05\/Indole-Test.jpg","author":{"name":"Anupama Sapkota","avatar":"https:\/\/secure.gravatar.com\/avatar\/0e9c86afc1670c49efeb260138ec905b?s=96&d=mm&r=g"},"categories":[{"term_id":702,"name":"Biochemical Test","slug":"biochemical-test","term_group":0,"term_taxonomy_id":702,"taxonomy":"category","description":"<strong>Biochemical tests are the tests that are performed on different bacteria for their identification on the basis of their biochemical activities towards different biochemical compounds.<\/strong>\r\n<ul>\r\n \t<li>Biochemical tests are one of the traditional methods for the identification of microorganisms, usually performed with phenotypic identification.<\/li>\r\n \t<li>For many years these methods were employed extensively, and they continue to be used nowadays, especially in some laboratory routines where a particular type of microorganism has to be identified rapidly.<\/li>\r\n \t<li>The ability of microorganisms to utilize certain biomolecules, resulting in useful organic compounds for themselves forms the basis of various biochemical tests.<\/li>\r\n \t<li>Biochemical tests are of different types, where the identification or distinction between different microorganisms is made on various bases.<\/li>\r\n \t<li>One of the traditional methods commonly used is a simple visual detection of the growth of the organism in the presence of essential nutrients by increased turbidity in the liquid medium.<\/li>\r\n \t<li>In other tests, however, the results are based on the change in color of the medium as a result of the change in the pH of the medium.<\/li>\r\n \t<li>Microorganisms can be classified into different groups on the basis of their reaction to such tests. Some tests even allow the distinction of microorganisms to the species level.<\/li>\r\n \t<li>Biochemical tests are thus, essential as they are inexpensive and relatively simple to perform.<\/li>\r\n \t<li>The physiology of bacteria and other microorganisms differs from one another, which allows for the differentiation of such microorganisms.<\/li>\r\n \t<li>Biochemical tests, however, have some disadvantages. Despite being inexpensive and allowing both quantitative and qualitative information about the diversity of microorganisms present in a sample, these methods are laborious and time-consuming, and results are only observed after several days.<\/li>\r\n \t<li>In some cases, false positives are obtained, especially when considering similar microbial species.<\/li>\r\n<\/ul>","parent":0,"count":114,"filter":"raw","cat_ID":702,"category_count":114,"category_description":"<strong>Biochemical tests are the tests that are performed on different bacteria for their identification on the basis of their biochemical activities towards different biochemical compounds.<\/strong>\r\n<ul>\r\n \t<li>Biochemical tests are one of the traditional methods for the identification of microorganisms, usually performed with phenotypic identification.<\/li>\r\n \t<li>For many years these methods were employed extensively, and they continue to be used nowadays, especially in some laboratory routines where a particular type of microorganism has to be identified rapidly.<\/li>\r\n \t<li>The ability of microorganisms to utilize certain biomolecules, resulting in useful organic compounds for themselves forms the basis of various biochemical tests.<\/li>\r\n \t<li>Biochemical tests are of different types, where the identification or distinction between different microorganisms is made on various bases.<\/li>\r\n \t<li>One of the traditional methods commonly used is a simple visual detection of the growth of the organism in the presence of essential nutrients by increased turbidity in the liquid medium.<\/li>\r\n \t<li>In other tests, however, the results are based on the change in color of the medium as a result of the change in the pH of the medium.<\/li>\r\n \t<li>Microorganisms can be classified into different groups on the basis of their reaction to such tests. Some tests even allow the distinction of microorganisms to the species level.<\/li>\r\n \t<li>Biochemical tests are thus, essential as they are inexpensive and relatively simple to perform.<\/li>\r\n \t<li>The physiology of bacteria and other microorganisms differs from one another, which allows for the differentiation of such microorganisms.<\/li>\r\n \t<li>Biochemical tests, however, have some disadvantages. Despite being inexpensive and allowing both quantitative and qualitative information about the diversity of microorganisms present in a sample, these methods are laborious and time-consuming, and results are only observed after several days.<\/li>\r\n \t<li>In some cases, false positives are obtained, especially when considering similar microbial species.<\/li>\r\n<\/ul>","cat_name":"Biochemical Test","category_nicename":"biochemical-test","category_parent":0}]},"_links":{"self":[{"href":"https:\/\/microbenotes.com\/wp-json\/wp\/v2\/posts\/584"}],"collection":[{"href":"https:\/\/microbenotes.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/microbenotes.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/microbenotes.com\/wp-json\/wp\/v2\/users\/11"}],"replies":[{"embeddable":true,"href":"https:\/\/microbenotes.com\/wp-json\/wp\/v2\/comments?post=584"}],"version-history":[{"count":0,"href":"https:\/\/microbenotes.com\/wp-json\/wp\/v2\/posts\/584\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/microbenotes.com\/wp-json\/wp\/v2\/media\/31136"}],"wp:attachment":[{"href":"https:\/\/microbenotes.com\/wp-json\/wp\/v2\/media?parent=584"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/microbenotes.com\/wp-json\/wp\/v2\/categories?post=584"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/microbenotes.com\/wp-json\/wp\/v2\/tags?post=584"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}