{"id":35576,"date":"2025-06-24T12:34:05","date_gmt":"2025-06-24T12:34:05","guid":{"rendered":"https:\/\/gaviki.com\/blog\/?p=35576"},"modified":"2025-06-24T12:34:07","modified_gmt":"2025-06-24T12:34:07","slug":"macconkey-agar-is-an-example-of-a-medium-that-is-which-of-the-following","status":"publish","type":"post","link":"https:\/\/gaviki.com\/blog\/macconkey-agar-is-an-example-of-a-medium-that-is-which-of-the-following\/","title":{"rendered":"MacConkey agar is an example of a medium that is which of the following"},"content":{"rendered":"\n<p>MacConkey agar is an example of a medium that is which of the following? Choose one or more: A. selective for Gram-negative bacteria B. differential based on ability to ferment mannitol C. general purpose (suitable for Gram-negatives and Gram-positives) D. enriched with blood to support selected human pathogens E. selective for Gram-positive bacteria F. differential based on ability to ferment lactose<\/p>\n\n\n\n<p><strong><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-vivid-cyan-blue-color\">The correct answer and explanation is:<\/mark><\/strong><\/p>\n\n\n\n<p>The correct answers are:<\/p>\n\n\n\n<p><strong>A. selective for Gram-negative bacteria<\/strong><br><strong>F. differential based on ability to ferment lactose<\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Explanation:<\/h3>\n\n\n\n<p>MacConkey agar is a type of <strong>selective and differential medium<\/strong> primarily used in microbiology to isolate and differentiate <strong>Gram-negative bacteria<\/strong>. It is designed to suppress the growth of Gram-positive bacteria while allowing Gram-negative bacteria to grow. This selectivity is achieved by incorporating bile salts and crystal violet dye, which inhibit most Gram-positive organisms.<\/p>\n\n\n\n<p>The medium is also <strong>differential based on the ability of bacteria to ferment lactose<\/strong>. It contains lactose as the primary carbohydrate source and a pH indicator called neutral red. When lactose-fermenting bacteria metabolize lactose, they produce acid, lowering the pH and causing the neutral red dye to turn pink or red. Colonies of lactose fermenters (such as <em>Escherichia coli<\/em>) appear pink or red, sometimes with a surrounding pink zone due to acid production. Non-lactose fermenters (such as <em>Salmonella<\/em> and <em>Shigella<\/em>) remain colorless or take on the natural color of the medium.<\/p>\n\n\n\n<p>Other options are incorrect for the following reasons:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>B. differential based on ability to ferment mannitol:<\/strong> This is not true for MacConkey agar. Mannitol fermentation is tested using Mannitol Salt Agar (MSA), which is different from MacConkey agar.<\/li>\n\n\n\n<li><strong>C. general purpose (suitable for Gram-negatives and Gram-positives):<\/strong> MacConkey agar is not general purpose; it is selective for Gram-negative bacteria.<\/li>\n\n\n\n<li><strong>D. enriched with blood to support selected human pathogens:<\/strong> MacConkey agar is not blood-enriched. Blood agar contains blood to support fastidious organisms, but MacConkey agar does not.<\/li>\n\n\n\n<li><strong>E. selective for Gram-positive bacteria:<\/strong> This is incorrect since MacConkey agar inhibits Gram-positive bacteria rather than selects for them.<\/li>\n<\/ul>\n\n\n\n<p>In summary, MacConkey agar helps isolate Gram-negative bacteria and differentiates them by their ability to ferment lactose, making it very useful in clinical microbiology for identifying pathogens such as <em>E. coli<\/em> and <em>Klebsiella<\/em>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>MacConkey agar is an example of a medium that is which of the following? Choose one or more: A. selective for Gram-negative bacteria B. differential based on ability to ferment mannitol C. general purpose (suitable for Gram-negatives and Gram-positives) D. enriched with blood to support selected human pathogens E. selective for Gram-positive bacteria F. differential [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-35576","post","type-post","status-publish","format-standard","hentry","category-quiz-questions"],"_links":{"self":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/35576","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/comments?post=35576"}],"version-history":[{"count":1,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/35576\/revisions"}],"predecessor-version":[{"id":35577,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/posts\/35576\/revisions\/35577"}],"wp:attachment":[{"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/media?parent=35576"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/categories?post=35576"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/gaviki.com\/blog\/wp-json\/wp\/v2\/tags?post=35576"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}