{"id":5913,"date":"2015-03-21T14:20:32","date_gmt":"2015-03-21T18:20:32","guid":{"rendered":"http:\/\/blogs.nejm.org\/hiv-id-observations\/?p=5913"},"modified":"2021-12-21T17:45:23","modified_gmt":"2021-12-21T22:45:23","slug":"id-learning-unit-coagulase-negative-staph-and-the-anti-zebra-residents-report","status":"publish","type":"post","link":"https:\/\/blogs.nejm.org\/hiv-id-observations\/index.php\/id-learning-unit-coagulase-negative-staph-and-the-anti-zebra-residents-report\/2015\/03\/21\/","title":{"rendered":"ID Learning Unit:  Coagulase-Negative Staph, and the &#8220;Anti-Zebra&#8221; Residents&#8217; Report"},"content":{"rendered":"<p><a href=\"http:\/\/blogs.nejm.org\/hiv-id-observations\/wp-content\/uploads\/sites\/2\/2015\/03\/CoNS-in-blood-culture.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"alignright wp-image-5923\" src=\"http:\/\/blogs.nejm.org\/hiv-id-observations\/wp-content\/uploads\/sites\/2\/2015\/03\/CoNS-in-blood-culture.jpg\" alt=\"CoNS in blood culture\" width=\"435\" height=\"155\" srcset=\"https:\/\/blogs.nejm.org\/hiv-id-observations\/wp-content\/uploads\/sites\/2\/2015\/03\/CoNS-in-blood-culture.jpg 802w, https:\/\/blogs.nejm.org\/hiv-id-observations\/wp-content\/uploads\/sites\/2\/2015\/03\/CoNS-in-blood-culture-300x107.jpg 300w\" sizes=\"auto, (max-width: 435px) 100vw, 435px\" \/><\/a>At the risk of betraying a deep streak of nerdiness, I confess to being a huge fan of\u00a0Residents&#8217; Report. This infatuation goes back to my medical student days, when the occasional chance to watch the Chief Medical Resident &#8212; who seemed the smartest doctor on the planet &#8212; lead a discussion of\u00a0an interesting case inspired all kinds of\u00a0aspirations.<\/p>\n<p>Alas, I was never chosen to be Chief Resident, but have been lucky enough to sit in on my fair share of Residents&#8217; Reports over the years, including one this past week.\u00a0And so glad I did, as current Chief Resident <a href=\"https:\/\/physiciandirectory.brighamandwomens.org\/details\/12439\/mary-montgomery-infectious_disease-boston\" target=\"_blank\" rel=\"noopener\">Mary Montgomery<\/a>\u00a0tried a new twist on the genre: Instead of presenting a fascinating rare case &#8212; a <a href=\"http:\/\/en.wikipedia.org\/wiki\/Zebra_%28medicine%29\" target=\"_blank\" rel=\"noopener\">&#8220;zebra&#8221;<\/a> &#8212; or a challenging ongoing diagnostic dilemma, she\u00a0chose a couple of extremely non-zebroid (that&#8217;s a word) cases that involved coagulase-negative staph (CoNS), a bug\u00a0that frankly most of us think is pretty ho-hum.<\/p>\n<p>But you know what? It was a great report,\u00a0educational and entertaining, and here&#8217;s what we learned\u00a0about this commonly encountered (but frequently challenging) entity:<\/p>\n<ul>\n<li>In the microbiology lab, a coagulase test is done on suspected staph isolates, looking for tell-tale clumping of plasma. Clumps = coagulase-positive (<em>Staph aureus<\/em>); no clumps = coagulase-negative. <strong><a href=\"https:\/\/youtu.be\/XKyg0qdGmaI\" target=\"_blank\" rel=\"noopener\">Watch!<\/a><\/strong><\/li>\n<li>There are over 30 species of CoNS, with <em>Staph epidermidis<\/em> the most common &#8212; but you rarely see micro reports listing <em>Staph epidermidis<\/em>, since identifying the particular CoNS species is rarely helpful.<\/li>\n<li><em>Staph saprophyticus<\/em> is a CoNS species that is the <strong><a href=\"http:\/\/cid.oxfordjournals.org\/content\/40\/6\/896.full\" target=\"_blank\" rel=\"noopener\">second most common cause of uncomplicated UTIs in young women.<\/a>\u00a0<\/strong>Fortunately, it&#8217;s sensitive to most antibiotics used to treat UTIs.<\/li>\n<li>CoNS are the most common isolates from blood cultures, and also the most common contaminants. Distinguishing true- from false-positive blood cultures can be tricky, in particular with CoNS, and\u00a0<strong><a href=\"http:\/\/jama.jamanetwork.com\/article.aspx?articleid=396384\" target=\"_blank\" rel=\"noopener\">this home-grown study<\/a><\/strong>\u00a0provides some guidance &#8212; indeed, it&#8217;s\u00a0incorporated into our ancient electronic medical record. (See above image &#8212; soon to be retired, alas, in a move of <a href=\"http:\/\/www.epic.com\/\" target=\"_blank\" rel=\"noopener\">EPIC<\/a> proportions.) Question: Has this study been updated by anyone?<\/li>\n<li>Clinically important infections with CoNS frequently involve prosthetic joints, mechanical heart valves, indwelling vascular catheters, ventricular shunts, vascular grafts, pacemaker or defibrillator leads, orthopedic hardware &#8212; in short, artificial ingredients!<\/li>\n<li>Treatment of choice for CoNS infection acquired in the hospital is vancomycin, since more than 80% are resistant to beta lactam antibiotics.<\/li>\n<li>CoNS are good at sticking to things, and have a virulence\u00a0factor called <span style=\"color: #000000\">arginine catabolic mobile element (ACME)<strong>,<\/strong> which they unfortunately sometimes decide to\u00a0<strong><a href=\"http:\/\/jid.oxfordjournals.org\/content\/197\/11\/1523.full#ref-4\" target=\"_blank\" rel=\"noopener\">transfer to MRSA.<\/a>\u00a0<\/strong>I hate when they do that.<\/span><\/li>\n<li>Production\u00a0of biofilms &#8212; slime, think of the stuff that makes rocks slippery in a\u00a0stream &#8212;\u00a0makes CoNS difficult to clear from prosthetic material. Here&#8217;s a <strong><a href=\"http:\/\/www.hypertextbookshop.com\/biofilmbook\/working_versionOld\/index.html\" target=\"_blank\" rel=\"noopener\">whole book about biofilms<\/a>,<\/strong>\u00a0great for leisure reading.<\/li>\n<li>Among antibiotics, <a href=\"http:\/\/aac.asm.org\/content\/37\/12\/2522.short\" target=\"_blank\" rel=\"noopener\"><strong>rifampin seems to be the best at penetrating biofilms,<\/strong><\/a> hence its use as adjunctive therapy for many infections involving\u00a0prosthetic material.<\/li>\n<li><a href=\"http:\/\/cid.oxfordjournals.org\/content\/46\/2\/232.long\" target=\"_blank\" rel=\"noopener\"><strong>Around 8% of <em>native<\/em>\u00a0valve endocarditis is due to CoNS<\/strong><\/a>, and these patients have a\u00a0high likelihood of requiring surgery. In my anecdotal experience they have an extremely indolent course, but not when the CoNS is <em>Staph lugdunensis.<\/em><\/li>\n<li>Speaking of,\u00a0<strong><em><a href=\"http:\/\/www.ncbi.nlm.nih.gov\/pubmed\/?term=lugdunensis+abscess\" target=\"_blank\" rel=\"noopener\">Staph<\/a><\/em><a href=\"http:\/\/www.ncbi.nlm.nih.gov\/pubmed\/?term=lugdunensis+abscess\" target=\"_blank\" rel=\"noopener\"><em> lugdunensis<\/em> is a particularly aggressive\u00a0form of CoNS<\/a>,<\/strong> a wolf in sheep&#8217;s clothing that acts much more like <em>Staph aureus<\/em> than its wimpy coagulase negative brethren. It&#8217;s usually sensitive to beta lactams, too.<\/li>\n<\/ul>\n<p>Of course I could go on and on about this last bug\u00a0&#8212; we ID doctors adore\u00a0<em>Staph lugdunensis<\/em>, which is both fun to say and is one of those factoids that separates us from the mere mortals out there who can&#8217;t be bothered to remember this arcane stuff.<\/p>\n<p>Here&#8217;s a tip for you non-ID doctors: \u00a0You can really impress your ID specialist friends by bringing up\u00a0<em>Staph lugdunensis<\/em>\u00a0when discussing a case, or even just in casual conversation:<\/p>\n<blockquote><p><strong>Non-ID doctor:<\/strong> Hey, have you watched the new <em>House of Cards<\/em> season yet?<br \/>\n<strong>ID doctor:<\/strong> No, am waiting until\u00a0I have time to\u00a0binge-watch it.<br \/>\n<strong>Non-ID doctor:<\/strong> Makes sense. By the way, <em>Staph lugdunensis.<\/em><br \/>\n<strong>ID doctor:<\/strong> Impressive!<\/p><\/blockquote>\n<p>Yes, I know. Time to get a life.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>At the risk of betraying a deep streak of nerdiness, I confess to being a huge fan of\u00a0Residents&#8217; Report. This infatuation goes back to my medical student days, when the occasional chance to watch the Chief Medical Resident &#8212; who seemed the smartest doctor on the planet &#8212; lead a discussion of\u00a0an interesting case inspired [&hellip;]<\/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":[1014,483,1038,1041,1044],"class_list":["post-5913","post","type-post","status-publish","format-standard","hentry","category-health-care","category-infectious-diseases","category-medical-education","category-patient-care","tag-coagulase-negative-staph","tag-id-learning-unit","tag-staph-epidermidis","tag-staph-lugdunensis","tag-staph-saprophyticus"],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/blogs.nejm.org\/hiv-id-observations\/index.php\/wp-json\/wp\/v2\/posts\/5913","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=5913"}],"version-history":[{"count":0,"href":"https:\/\/blogs.nejm.org\/hiv-id-observations\/index.php\/wp-json\/wp\/v2\/posts\/5913\/revisions"}],"wp:attachment":[{"href":"https:\/\/blogs.nejm.org\/hiv-id-observations\/index.php\/wp-json\/wp\/v2\/media?parent=5913"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.nejm.org\/hiv-id-observations\/index.php\/wp-json\/wp\/v2\/categories?post=5913"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.nejm.org\/hiv-id-observations\/index.php\/wp-json\/wp\/v2\/tags?post=5913"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}