{"id":2833,"date":"2012-06-15T07:05:16","date_gmt":"2012-06-15T11:05:16","guid":{"rendered":"http:\/\/blogs.nejm.org\/?p=2833"},"modified":"2015-06-04T15:14:29","modified_gmt":"2015-06-04T19:14:29","slug":"id-learning-unit-the-d-test","status":"publish","type":"post","link":"https:\/\/blogs.nejm.org\/hiv-id-observations\/index.php\/id-learning-unit-the-d-test\/2012\/06\/15\/","title":{"rendered":"ID Learning Unit — The D Test"},"content":{"rendered":"

I suppose it’s not surprising that we’d follow-up the Etest<\/a> with the D test, though perhaps if I were being alphabetical, the order would have been reversed.<\/p>\n

\"\"<\/a>The D test is important, because it screens for a form of clindamycin resistance in MRSA that might otherwise not be detected — the “inducible” kind, which can be associated with treatment failures. About half<\/a> of MRSA isolates have this form of resistance.<\/p>\n

Here’s how it works:<\/p>\n

    \n
  1. Take some erythromycin-resistant, clindamycin-“sensitive” MRSA, spread it on a culture plate<\/li>\n
  2. Drop an erythromycin disk on the left side of the plate, and a clindamycin disk on the right<\/li>\n
  3. If there’s a flattening of the zone of inhibition between<\/em> the two disks, then the test is positive, confirming inducible clindamycin resistance<\/li>\n
  4. Report that bug as clindamycin resistant<\/li>\n<\/ol>\n

    First, critical thinkers will wonder why this is important, since we obviously don’t give erythromycin with clindamycin to an actual patient. My big-picture explanation is that it’s a marker for easily inducible resistance even without the erythro being present.<\/p>\n

    And second, note the critical step of putting the clindamycin disk on the right<\/em> — otherwise the shape of the zone of inhibition won’t be a “D”, and everyone will be confused because who knows what to call that shape.<\/p>\n

    (That second part was a joke.)<\/p>\n

     <\/p>\n

     <\/p>\n

     <\/p>\n","protected":false},"excerpt":{"rendered":"

    I suppose it’s not surprising that we’d follow-up the Etest with the D test, though perhaps if I were being alphabetical, the order would have been reversed. The D test is important, because it screens for a form of clindamycin resistance in MRSA that might otherwise not be detected — the “inducible” kind, which can […]<\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3,5,6,8],"tags":[189,260,483,630],"class_list":["post-2833","post","type-post","status-publish","format-standard","hentry","category-health-care","category-infectious-diseases","category-medical-education","category-patient-care","tag-clindamycin","tag-d-test","tag-id-learning-unit","tag-mrsa"],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/blogs.nejm.org\/hiv-id-observations\/index.php\/wp-json\/wp\/v2\/posts\/2833","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.nejm.org\/hiv-id-observations\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.nejm.org\/hiv-id-observations\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.nejm.org\/hiv-id-observations\/index.php\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.nejm.org\/hiv-id-observations\/index.php\/wp-json\/wp\/v2\/comments?post=2833"}],"version-history":[{"count":0,"href":"https:\/\/blogs.nejm.org\/hiv-id-observations\/index.php\/wp-json\/wp\/v2\/posts\/2833\/revisions"}],"wp:attachment":[{"href":"https:\/\/blogs.nejm.org\/hiv-id-observations\/index.php\/wp-json\/wp\/v2\/media?parent=2833"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.nejm.org\/hiv-id-observations\/index.php\/wp-json\/wp\/v2\/categories?post=2833"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.nejm.org\/hiv-id-observations\/index.php\/wp-json\/wp\/v2\/tags?post=2833"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}