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Key Images
https://upload.medbullets.com/topic/104183/images/250px-staphylococcus_aureus_gram.jpg
Snapshot
  • A 23-year-old woman presents to the emergency department with fever, chills, and watery diarrhea. Her symptoms began approximately 1 day after menstruation began. Her temperature is 102°F (38.9°C), blood pressure is 75/50 mmHg, pulse is 125/min, and respirations are 20/min. Physical examination is notable for a diffuse erythematous rash and desquamation of the palms and soles. (Toxic shock syndrome)
    <table style="width: 100%; background-color: #ffffff; border: 0px solid #cccccc;" border="0" cellspacing="0">
    <tbody>
    <tr style="background-color: #f4f4f4;">
    <td><strong>Snapshot</strong></td>
    </tr>
    <tr>
    <td>
    <ul>
    <li>A</li>
    </ul>
    </td>
    </tr>
    <tr>
    <td style="color: #000000; font-family: Arial, Helvetica, sans-serif; font-size: medium;" bgcolor="#F4F4F4"><strong><span style="font-size: medium">Introduction</span></strong></td>
    </tr>
    <tr>
    <td style="color: #000000; font-family: Arial, Helvetica, sans-serif; font-size: medium;" height="1" bgcolor="#ffffff">
    <div>
    <ul>
    <li>Classification
    <ul>
    <li><span style="color: #0000cc;">Gram-positive cocci in clusters</span>&nbsp;<a style="font-family: Arial, Helvetica, sans-serif;" title="This clinical image demonstrates gram-positive cocci in clusters, indicative of Staphylococcus aureus." href="https://upload.medbullets.com/topic/104183/images/250px-staphylococcus_aureus_gram.jpg"><img src="/images/camera.gif" alt="" /></a></li>
    </ul>
    </li>
    <li>Microbiology
    <ul>
    <li style="font-family: Arial, Helvetica, sans-serif;">transmission
    <ul style="font-family: Arial, Helvetica, sans-serif;">
    <li>contaminated foods
    <ul>
    <li>custards</li>
    <li>mayonnaise/potato salad</li>
    <li>canned meats</li>
    </ul>
    </li>
    </ul>
    </li>
    <li style="font-family: Arial, Helvetica, sans-serif;">properties
    <ul>
    <li><span style="color: #0000cc;">facultative anaerobes</span></li>
    <li><span style="color: #0000cc;">catalase-positive</span> 
    <ul style="font-family: Arial, Helvetica, sans-serif;">
    <li>neutralizes its own H2O2, which causes the human's phagocytes to not have the ability to produce reactive oxygen species to combat infection in patient's with chronic granulomatous disease&nbsp;<a href="/immunology/105009/chronic-granulomatous-disease"><img src="/images/topic.png" alt="" /></a></li>
    </ul>
    </li>
    <li><span style="color: #0000cc;">coagulase positive</span> 
    <ul style="font-family: Arial, Helvetica, sans-serif;">
    <li>coagulase activates prothrombin, leading to clotting
    <ul>
    <li>leads to fibrin formation around this organism</li>
    </ul>
    </li>
    <li>differentiates <em>S. aureus</em>&nbsp;from <em>S. epidermidis&nbsp;</em>and <em>S. saprophytic</em></li>
    </ul>
    </li>
    <li><span style="color: #0000cc;">&beta;-hemolytic</span> 
    <ul style="font-family: Arial, Helvetica, sans-serif;">
    <li>complete hemolysis of red blood cells on an agar plate</li>
    </ul>
    </li>
    <li><span style="color: #0000cc;">appears gold</span><span style="font-family: Arial, Helvetica, sans-serif;"> in sheep blood agar</span></li>
    <li><span style="color: #0000cc;">protein A</span><span style="font-family: Arial, Helvetica, sans-serif;">&nbsp;<a style="font-size: medium;" title="question" href="#101563"><img src="/images/question_step_1.png" alt="" /></a></span> 
    <ul style="font-family: Arial, Helvetica, sans-serif;">
    <li>binds to the Fc region of the IgG antibody
    <ul>
    <li>this presents opsonization and phagocytosis</li>
    </ul>
    </li>
    </ul>
    </li>
    <li style="font-family: Arial, Helvetica, sans-serif;">hemolysins
    <ul style="font-family: Arial, Helvetica, sans-serif;">
    <li>damages red blood cells, platelets, neutrophils, and macrophages</li>
    </ul>
    </li>
    <li style="font-family: Arial, Helvetica, sans-serif;">leukocidins
    <ul style="font-family: Arial, Helvetica, sans-serif;">
    <li>damages white blood cells</li>
    </ul>
    </li>
    <li><span style="color: #0000cc;">penicillinase</span> 
    <ul style="font-family: Arial, Helvetica, sans-serif;">
    <li>a secreted form of <span style="font-size: medium;">&beta;</span>-lactamase, which makes <em>S. aureus</em>&nbsp;resistant to penicillins</li>
    </ul>
    </li>
    <li style="font-family: Arial, Helvetica, sans-serif;">toxins
    <ul>
    <li><span style="color: #0000cc;">exfoliative toxin</span> 
    <ul>
    <li>causes skin sloughing, as seen in&nbsp;<span style="color: #0000cc;">staphylococcal scalded skin syndrome</span></li>
    </ul>
    </li>
    <li><span style="color: #0000cc;">heat stable enterotoxin</span> 
    <ul style="font-family: Arial, Helvetica, sans-serif;">
    <li>leads to food poisoning</li>
    </ul>
    </li>
    <li><span style="color: #0000cc;">toxic shock syndrome toxin (TSST)</span><span style="font-family: Arial, Helvetica, sans-serif;">&nbsp;<a style="font-size: medium;" title="question" href="#109726"><img src="/images/question_step_1.png" alt="" /></a></span> 
    <ul style="font-family: Arial, Helvetica, sans-serif;">
    <li>leads to staphylococcal toxic shock syndrome</li>
    </ul>
    </li>
    </ul>
    </li>
    </ul>
    </li>
    </ul>
    </li>
    </ul>
    </div>
    </td>
    </tr>
    <tr>
    <td style="color: #000000; font-family: Arial, Helvetica, sans-serif; font-size: medium;" bgcolor="#F4F4F4"><strong><span style="font-size: medium">Diseases</span></strong></td>
    </tr>
    <tr>
    <td>&nbsp;</td>
    </tr>
    <tr>
    <td>
    <table style="margin: 0px auto; padding: 0px; vertical-align: baseline; border-spacing: 0px; color: #000000; font-family: Arial, Helvetica-Neue, Helvetica, sans-serif; font-size: 16px; width: 613px; border-image: initial !important; border: 1px solid #f4f4f4;" border="1" cellspacing="0" align="center">
    <tbody style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">
    <tr style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; background-color: #d4f2cd;">
    <td style="margin: 0px; padding: 1px; vertical-align: middle; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; line-height: 1.3; text-align: center; width: 95%; border-image: initial !important; border: 1px solid #f4f4f4;" colspan="3"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; font-size: x-small;"><strong style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;"><em style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">S. aureus </em><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">Associated Diseases</span></span></span></strong></span></td>
    </tr>
    <tr style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; text-align: center; background-color: #f4f4f4;">
    <td style="margin: 0px; padding: 1px; vertical-align: middle; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; line-height: 1.3; width: 110px; border: 1px solid #f4f4f4 !important;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;"><strong style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">Disease</strong><br /></span></span></span></span></span></td>
    <td style="margin: 0px; padding: 1px; vertical-align: middle; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; line-height: 1.3; width: 137px; border: 1px solid #f4f4f4 !important;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline; font-size: small;"><strong style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">Clinical Presentation<br /></span></strong></span></td>
    <td style="margin: 0px; padding: 1px; vertical-align: middle; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; line-height: 1.3; width: 139px; border: 1px solid #f4f4f4 !important;"><strong style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">Comments</span></span></span></span></span></strong></td>
    </tr>
    <tr style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">
    <td style="margin: 0px; padding: 1px; vertical-align: middle; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; line-height: 1.3; font-family: Arial, Helvetica-Neue, Helvetica, sans-serif; border: 1px solid #f4f4f4 !important;"><span style="font-size: small;">Toxic shock syndrome</span></td>
    <td style="margin: 0px; padding: 1px; vertical-align: middle; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; line-height: 1.3; font-family: Arial, Helvetica-Neue, Helvetica, sans-serif; border: 1px solid #f4f4f4 !important;" valign="middle">
    <ul style="margin: 16px 0px; padding: 0px 0px 0px 20px; border: 0px; vertical-align: baseline; list-style-position: initial; list-style-image: initial;">
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">Symptoms</span></span> </span>
    <ul style="margin: 0px; padding: 0px 0px 0px 20px; border: 0px; vertical-align: baseline; list-style-position: initial; list-style-image: initial;">
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">nausea and vomiting</span></li>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">watery diarrhea</span></li>
    </ul>
    </li>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">Physical exam</span> </span>
    <ul>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">fever</span></li>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">diffuse erythematous rash</span></li>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">palm and sole desquamation</span></li>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">hypotension</span></li>
    </ul>
    </li>
    </ul>
    </td>
    <td style="margin: 0px; padding: 1px; vertical-align: middle; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; line-height: 1.3; font-family: Arial, Helvetica-Neue, Helvetica, sans-serif; border: 1px solid #f4f4f4 !important;" valign="middle">
    <ul style="margin: 16px 0px; padding: 0px 0px 0px 20px; border: 0px; vertical-align: baseline; list-style-position: initial; list-style-image: initial;">
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">Can be caused by leaving tampons in place for a long period of time </span>
    <ul>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">stimulates toxic shock syndrome toxin-1 (TSST-1) release, penetrating the vaginal mucosa, and cross-linking the<span style="color: #000000;"> &beta;&nbsp;re</span>gion of the T-cell receptor to MHC class II </span>
    <ul>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">leads to an overwhelming release of </span>
    <ul>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">IL-1 and IL-2</span></li>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">IFN-&gamma;</span></li>
    </ul>
    <ul>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">TNF-&alpha;</span></li>
    </ul>
    </li>
    </ul>
    </li>
    </ul>
    </li>
    <li><span style="font-size: small;">Treatment </span>
    <ul>
    <li><span style="font-size: small;">source control </span>
    <ul>
    <li><span style="font-size: small;">removing the tampon or surgical suture that enabled the production of TSST-1</span></li>
    </ul>
    </li>
    <li><span style="font-size: small;">antibiotics </span>
    <ul>
    <li><span style="font-size: small;">the choice depends on drug sensitivity testing</span></li>
    <li><span style="font-size: small;">will not cure the disease but may help as it can eliminate TSST-1 producing <em>S. aureus</em></span></li>
    </ul>
    </li>
    </ul>
    </li>
    </ul>
    </td>
    </tr>
    <tr style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">
    <td style="margin: 0px; padding: 1px; vertical-align: middle; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; line-height: 1.3; font-family: Arial, Helvetica-Neue, Helvetica, sans-serif; border: 1px solid #f4f4f4 !important;"><span style="font-size: small;">Staphylococcal skin syndrome</span></td>
    <td style="margin: 0px; padding: 1px; vertical-align: middle; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; line-height: 1.3; font-family: Arial, Helvetica-Neue, Helvetica, sans-serif; border: 1px solid #f4f4f4 !important;" valign="middle">
    <div><span style="font-size: small;"><br /></span></div>
    <ul style="margin: 0px; padding: 0px 0px 0px 20px; border: 0px; vertical-align: baseline; list-style-position: initial; list-style-image: initial;">
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">Physical exam</span> </span>
    <ul style="margin: 0px; padding: 0px 0px 0px 20px; border: 0px; vertical-align: baseline; list-style-position: initial; list-style-image: initial;">
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">fever</span></li>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">erythematous rash with skin sloughing</span></li>
    </ul>
    </li>
    </ul>
    </td>
    <td style="margin: 0px; padding: 1px; vertical-align: middle; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; line-height: 1.3; font-family: Arial, Helvetica-Neue, Helvetica, sans-serif; border: 1px solid #f4f4f4 !important;" valign="middle">
    <ul style="margin: 16px 0px; padding: 0px 0px 0px 20px; border: 0px; vertical-align: baseline; list-style-position: initial; list-style-image: initial;">
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">Exfoliative toxin destroys keratinocyte attachments to the stratum granulosum</span></li>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">Typically seen in newborns, children, and adults with renal insufficiency</span></li>
    </ul>
    </td>
    </tr>
    <tr style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">
    <td style="margin: 0px; padding: 1px; vertical-align: middle; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; line-height: 1.3; font-family: Arial, Helvetica-Neue, Helvetica, sans-serif; border: 1px solid #f4f4f4 !important;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">Gastroenteritis</span><br /></span></span></span></td>
    <td style="margin: 0px; padding: 1px; vertical-align: middle; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; line-height: 1.3; font-family: Arial, Helvetica-Neue, Helvetica, sans-serif; border: 1px solid #f4f4f4 !important;" valign="middle">
    <ul style="margin: 16px 0px; padding: 0px 0px 0px 20px; border: 0px; vertical-align: baseline; list-style-position: initial; list-style-image: initial;">
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">Symptoms</span></span> </span>
    <ul style="margin: 0px; padding: 0px 0px 0px 20px; border: 0px; vertical-align: baseline; list-style-position: initial; list-style-image: initial;">
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">nausea</span></li>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">vomiting</span></li>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">abdominal pain</span></li>
    </ul>
    </li>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">Physical exam</span></span> </span>
    <ul style="margin: 0px; padding: 0px 0px 0px 20px; border: 0px; vertical-align: baseline; list-style-position: initial; list-style-image: initial;">
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">watery diarrhea</span></li>
    </ul>
    </li>
    </ul>
    </td>
    <td style="margin: 0px; padding: 1px; vertical-align: middle; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; line-height: 1.3; font-family: Arial, Helvetica-Neue, Helvetica, sans-serif; border: 1px solid #f4f4f4 !important;" valign="middle">
    <div style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">
    <ul style="margin: 16px 0px; padding: 0px 0px 0px 20px; border: 0px; vertical-align: baseline; list-style-position: initial; list-style-image: initial;">
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">Staphylococci can produce exotoxin as it grows in food </span>
    <ul>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">pre-formed toxin because ingested, which causes intestinal peristalsis, resulting in </span>
    <ul>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">nausea</span></li>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">vomiting</span></li>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">abdominal pain</span></li>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">watery diarrhea</span></li>
    </ul>
    </li>
    </ul>
    </li>
    </ul>
    </div>
    </td>
    </tr>
    <tr style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">
    <td style="margin: 0px; padding: 1px; vertical-align: middle; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; line-height: 1.3; font-family: Arial, Helvetica-Neue, Helvetica, sans-serif; border: 1px solid #f4f4f4 !important;" align="left" valign="middle"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">Pneumonia</span></span></span></td>
    <td style="margin: 0px; padding: 1px; vertical-align: middle; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; line-height: 1.3; font-family: Arial, Helvetica-Neue, Helvetica, sans-serif; border: 1px solid #f4f4f4 !important;" align="left" valign="middle">
    <ul style="margin: 16px 0px; padding: 0px 0px 0px 20px; border: 0px; vertical-align: baseline; list-style-position: initial; list-style-image: initial;">
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;"><span style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;">Physical exam</span> </span>
    <ul style="margin: 0px; padding: 0px 0px 0px 20px; border: 0px; vertical-align: baseline; list-style-position: initial; list-style-image: initial;">
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">fevers</span></li>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">chills</span></li>
    </ul>
    </li>
    </ul>
    </td>
    <td style="margin: 0px; padding: 1px; vertical-align: middle; font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; line-height: 1.3; font-family: Arial, Helvetica-Neue, Helvetica, sans-serif; border: 1px solid #f4f4f4 !important;" align="left" valign="middle">
    <ul style="margin: 16px 0px; padding: 0px 0px 0px 20px; border: 0px; vertical-align: baseline; list-style-position: initial; list-style-image: initial;">
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">Typically seen as a superinfection after an influenza upper respiratory infection</span>
    <ul>
    <li style="margin: 0px; padding: 0px; border: 0px; vertical-align: baseline;"><span style="font-size: small;">results in a lobar consolidation and lung parenchymal cavitations</span></li>
    </ul>
    </li>
    </ul>
    </td>
    </tr>
    <tr>
    <td align="left" valign="middle"><span style="font-size: small;">Osteomyelitis</span></td>
    <td align="left" valign="middle">
    <ul>
    <li><span style="font-size: small;">Physical exam</span>
    <ul>
    <li><span style="font-size: small;">fever</span></li>
    <li><span style="font-size: small;">warm and swollen tissue over bone</span></li>
    </ul>
    </li>
    </ul>
    </td>
    <td align="left" valign="middle">
    <ul>
    <li><span style="font-size: small;"><em>S. aureus</em>&nbsp;spreads to the bone hematogenously</span></li>
    <li><span style="font-size: small;">Most common cause of osteomyelitis overall&nbsp;<a style="font-size: medium;" title="question" href="#211041"><img src="/images/question_sae.png" alt="" /></a></span></li>
    </ul>
    </td>
    </tr>
    <tr>
    <td align="left" valign="middle"><span style="font-size: small;">Acute endocarditis</span></td>
    <td align="left" valign="middle">
    <ul>
    <li><span style="font-size: small;">Symptoms</span>
    <ul>
    <li><span style="font-size: small;">chills</span></li>
    <li><span style="font-size: small;">myalgias</span></li>
    </ul>
    </li>
    <li><span style="font-size: small;">Physical exam</span>
    <ul>
    <li><span style="font-size: small;">fever</span></li>
    </ul>
    </li>
    </ul>
    </td>
    <td align="left" valign="middle">
    <ul>
    <li><span style="font-size: small;">There is rapid vegetation growth on the heart valve, which can cause</span>
    <ul>
    <li><span style="font-size: small;">valvular destruction</span></li>
    <li><span style="font-size: small;">embolism to the brain leading to stroke</span>
    <ul>
    <li><span style="font-size: small;">with left-heart valvular involvement</span></li>
    </ul>
    </li>
    <li><span style="font-size: small;">embolism to the lung</span>
    <ul>
    <li><span style="font-size: small;">with right-heart valvular involvement</span>
    <ul>
    <li><span style="font-size: small;">more common in intravenous drug users</span></li>
    </ul>
    </li>
    </ul>
    </li>
    </ul>
    </li>
    </ul>
    </td>
    </tr>
    <tr align="left" valign="middle">
    <td><span style="font-size: small;">Septic arthritis</span></td>
    <td>
    <ul>
    <li><span style="font-size: small;">Symptom</span>
    <ul>
    <li><span style="font-size: small;">joint pain</span></li>
    </ul>
    </li>
    <li><span style="font-size: small;">Physical exam</span>
    <ul>
    <li><span style="font-size: small;">inflamed joint with decreased range of motion</span></li>
    </ul>
    </li>
    </ul>
    </td>
    <td align="left" valign="middle">
    <ul>
    <li><span style="font-size: small;">Caused by <em>S. aureus</em>&nbsp;invasion into the synovial membrane</span></li>
    <li><span style="font-size: small;">Joint aspiration demonstrates</span>
    <ul>
    <li><span style="font-size: small;">yellow and turbid synovial fluid</span></li>
    <li><span style="font-size: small;">prominent amount of neutrophils (&gt;100,000)</span></li>
    <li><span style="font-size: small;">positive Gram stain (gram-positive cocci in clusters)</span></li>
    </ul>
    </li>
    </ul>
    </td>
    </tr>
    <tr align="left" valign="middle">
    <td><span style="font-size: small;">Skin infections</span></td>
    <td>
    <ul>
    <li><span style="font-size: small;">Impetigo&nbsp;<a style="font-size: medium;" title="question" href="#109288"><img src="/images/question_step_1.png" alt="" /></a></span>
    <ul>
    <li><span style="font-size: small;">physical exam</span>
    <ul>
    <li><span style="font-size: small;">small vesicles or pustules that crust over into honey-colored lesions</span>
    <ul>
    <li><span style="font-size: small;">typically appear in the face and especially around the mouth</span></li>
    </ul>
    </li>
    </ul>
    </li>
    </ul>
    </li>
    <li><span style="font-size: small;">Cellulitis</span>
    <ul>
    <li><span style="font-size: small;">physical exam</span>
    <ul>
    <li><span style="font-size: small;">fever</span></li>
    <li><span style="font-size: small;">the affected area is erythematous, warm, and tender to palpation</span></li>
    </ul>
    </li>
    </ul>
    </li>
    <li><span style="font-size: small;">Other skin infections include</span>
    <ul>
    <li><span style="font-size: small;">local abscess</span>
    <ul>
    <li><span style="font-size: small;">pus collection</span></li>
    </ul>
    </li>
    <li><span style="font-size: small;">furuncles</span>
    <ul>
    <li><span style="font-size: small;">infection of a hair follicle</span></li>
    </ul>
    </li>
    <li><span style="font-size: small;">carbuncles</span>
    <ul>
    <li><span style="font-size: small;">a cluster of furuncles</span></li>
    </ul>
    </li>
    </ul>
    </li>
    </ul>
    </td>
    <td>
    <ul>
    <li><span style="font-size: small;">Some skin infections can be caused by <em>Streptococcus pyogenes</em>&nbsp;or <em>S. aureus</em>; therefore, these skin infections should be treated with penicillinase-resistant penicillins (<em>e.g.,&nbsp;</em>dicloxacillin)</span></li>
    </ul>
    </td>
    </tr>
    </tbody>
    </table>
    </td>
    </tr>
    <tr>
    <td><br /></td>
    </tr>
    <tr style="background-color: #f4f4f4;">
    <td><strong>Methicillin-Resistant <em>S. aureus </em>(MRSA)</strong></td>
    </tr>
    <tr>
    <td>
    <ul>
    <li>Introduction
    <ul>
    <li>most staphylococci are penicillin resistant due to their penicillinase
    <ul>
    <li>to combat this, a number of penicillinase-resistant penicillins were developed (<em>e.g.,</em>&nbsp;methicillin and nafcillin)</li>
    </ul>
    </li>
    <li>MRSA is a strain of <em>S. aureus</em>&nbsp;that has acquired resistance against penicillinase-resistant penicillins (thus being methicillin-resistant)
    <ul>
    <li>due to altered penicillin-binding protein</li>
    </ul>
    </li>
    </ul>
    </li>
    <li>Epidemiology
    <ul>
    <li>incidence
    <ul>
    <li>typically appears in the hospital setting&nbsp;<a style="font-size: medium;" title="question" href="#101540"><img src="/images/question_step_1.png" alt="" /></a></li>
    </ul>
    </li>
    </ul>
    </li>
    <li>Microbiology
    <ul>
    <li>transmission
    <ul>
    <li>via health care workers</li>
    </ul>
    </li>
    </ul>
    </li>
    <li>Treatment
    <ul>
    <li>medical
    <ul>
    <li><strong><span style="color: #0000cc;">vancomycin</span></strong>
    <ul>
    <li>indication
    <ul>
    <li>the drug of choice for MRSA</li>
    </ul>
    </li>
    </ul>
    </li>
    <li><strong><span style="color: #0000cc;">linezolid</span></strong>
    <ul>
    <li>indication
    <ul>
    <li>can be used to treat vancomycin-resistant <em>S. aureus</em>&nbsp;(VRSA)</li>
    </ul>
    </li>
    </ul>
    </li>
    </ul>
    </li>
    </ul>
    </li>
    </ul>
    </td>
    </tr>
    <tr>
    <td style="color: #000000; font-family: Arial, Helvetica, sans-serif; font-size: medium;" bgcolor="#F4F4F4"><strong><span style="font-size: medium">Treatment</span></strong></td>
    </tr>
    <tr>
    <td>
    <ul>
    <li>Medical
    <ul>
    <li><strong><span style="color: #0000cc;">penicillinase-resistant penicillins</span></strong>
    <ul>
    <li>indication
    <ul>
    <li>drug of choice for organisms sensitive to these drugs</li>
    </ul>
    </li>
    <li>medications
    <ul>
    <li>nafcillin</li>
    <li>oxacillin</li>
    <li>dicloxacillin</li>
    </ul>
    </li>
    </ul>
    </li>
    <li><strong><span style="color: #0000cc;">vancomycin</span></strong>
    <ul>
    <li>indication
    <ul>
    <li>MRSA</li>
    </ul>
    </li>
    </ul>
    </li>
    <li><strong><span style="color: #0000cc;">linezolid</span></strong>
    <ul>
    <li>indication
    <ul>
    <li>VRSA</li>
    </ul>
    </li>
    </ul>
    </li>
    </ul>
    </li>
    </ul>
    </td>
    </tr>
    </tbody>
    </table>
Introduction
  • Classification
    • gram-positive cocci in clusters 
  • Microbiology
    • properties
      • facultative anaerobes
      • catalase positive
        • neutralizes its own hydrogen peroxide, which results in the hosts phagocytes inability to produce reactive oxygen species to combat infection (especially in patient's with chronic granulomatous disease )
      • coagulase positive
        • coagulase activates prothrombin, leading to clotting
          • leads to fibrin formation around this organism
        • differentiates S. aureus from S. epidermidis and S. saprophytic
      • β-hemolytic
        • complete hemolysis of red blood cells on an agar plate
      • appears gold in sheep blood agar
      • protein A 
        • binds to the Fc region of the IgG antibody
          • this prevents opsonization and phagocytosis
      • hemolysins
        • damages red blood cells, platelets, neutrophils, and macrophages
      • leukocidins
        • damages white blood cells
      • penicillinase
        • a secreted form of β-lactamase, which makes S. aureus resistant to penicillins
      • toxins
        • exfoliative toxin
          • causes skin sloughing, as seen in staphylococcal scalded skin syndrome
        • heat-stable enterotoxin
          • leads to food poisoning
        • toxic shock syndrome toxin (TSST) 
          • leads to staphylococcal toxic shock syndrome
Diseases
 
S. aureus Associated Diseases
Disease
Clinical Presentation
Comments
Toxic shock syndrome
  • Symptoms
    • nausea and vomiting
    • watery diarrhea
  • Physical exam
    • fever
    • diffuse erythematous rash
    • palm and sole desquamation
    • hypotension
  • Can be caused by leaving tampons in place for a long period of time
    • stimulates toxic shock syndrome toxin-1 (TSST-1) release, penetrating the vaginal mucosa, and cross-linking the β region of the T-cell receptor to MHC class II
      • leads to an overwhelming release of
        • IL-1 and IL-2
        • IFN-γ
        • TNF-α
  • Treatment
    • source control
      • removing the tampon or surgical suture that enabled the production of TSST-1
    • antibiotics
      • the choice depends on drug sensitivity testing
      • will not cure the disease but may help as it can eliminate TSST-1 producing S. aureus
Staphylococcal skin syndrome

  • Physical exam
    • fever
    • erythematous rash with skin sloughing
  • Exfoliative toxin destroys keratinocyte attachments to the stratum granulosum
  • Typically seen in newborns, children, and adults with renal insufficiency
Gastroenteritis
  • Symptoms
    • nausea
    • vomiting
    • abdominal pain
  • Physical exam
    • watery diarrhea
  • Staphylococci can produce exotoxin as it grows in food
    • ingested pre-formed toxin causes intestinal peristalsis, resulting in
      • nausea
      • vomiting
      • abdominal pain
      • watery diarrhea
Pneumonia
  • Physical exam
    • fevers
    • chills
  • Typically seen as a superinfection after an influenza upper respiratory infection
    • results in a lobar consolidation and lung parenchymal cavitations
Osteomyelitis
  • Physical exam
    • fever
    • warm and swollen tissue over bone
  • S. aureus spreads to the bone hematogenously
  • Most common cause of osteomyelitis overall 
Acute endocarditis 
  • Symptoms
    • chills
    • myalgias
  • Physical exam
    • fever
  • There is rapid vegetation growth on the heart valve, which can cause
    • valvular destruction
    • embolism to the brain leading to stroke with left-heart valvular involvement
    • embolism to the lung
      • with right-heart valvular involvement
        • more common in intravenous drug users
Septic arthritis
  • Symptom
    • joint pain
  • Physical exam
    • inflamed joint with decreased range of motion
  • Caused by S. aureus invasion into the synovial membrane
  • Joint aspiration can demonstrate
    • yellow and turbid synovial fluid
    • prominent amount of neutrophils (> 100,000 CFU/mL)
    • positive Gram stain (gram-positive cocci in clusters)
Skin infections
  • Impetigo 
    • physical exam
      • small vesicles or pustules that crust over into honey-colored lesions
        • typically appear in the face and especially around the mouth
  • Cellulitis
    • physical exam
      • fever
      • the affected area is erythematous, warm, and tender to palpation
  • Other skin infections include
    • local abscess
      • pus collection
    • furuncles
      • infection of a hair follicle
    • carbuncles
      • a cluster of furuncles
  • Some skin infections can be caused by Streptococcus pyogenes or S. aureus; therefore, these skin infections should be treated with penicillinase-resistant penicillins (e.g., dicloxacillin)

Methicillin-Resistant S. aureus (MRSA)
  • Introduction
    • most staphylococci are penicillin resistant due to their penicillinase
      • to combat this, a number of penicillinase-resistant penicillins were developed (e.g., methicillin and nafcillin)
    • MRSA is a strain of S. aureus that has acquired resistance against penicillinase-resistant penicillins (thus being methicillin-resistant)
      • due to altered penicillin-binding protein 
  • Epidemiology
    • incidence
      • typically appears in the hospital setting 
  • Microbiology
    • transmission
      • via health care workers
  • Treatment
    • medical
      • vancomycin
        • indication
          • the drug of choice for MRSA
      • linezolid
        • indication
          • can be used to treat vancomycin-resistant S. aureus (VRSA)
Treatment
  • Medical
    • penicillinase-resistant penicillins
      • indication
        • drug of choice for organisms sensitive to these drugs
      • medications
        • nafcillin
        • oxacillin
        • dicloxacillin
    • vancomycin
      • indication
        • MRSA
    • linezolid
      • indication
        • VRSA
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(M1.MC.13.104) A 14-year-old Caucasian male presents with painful erythematous and honey-colored crusted lesions around his mouth. Culture of the lesions reveals gram-positive cocci in clusters. Further analysis reveals bacteria that are beta-hemolytic, coagulase positive, catalase positive, and appear golden on the blood agar plate. Which of the following helps the bacterium in this infection bind to immunoglobulin and prevent phagocytosis when invading its host? Tested Concept

QID: 101563
FIGURES:
1

Protein A

56%

(41/73)

2

Staphylokinase

7%

(5/73)

3

Exfoliatin A

4%

(3/73)

4

Protein M

29%

(21/73)

5

Neurotoxin

0%

(0/73)

M 1 D

Select Answer to see Preferred Response

(M1.MC.12.81) A 63-year-old female recovering from a total shoulder arthroplasty completed 6 days ago presents complaining of joint pain in her repaired shoulder. Temperature is 39 degrees Celsius. Physical examination demonstrates erythema and significant tenderness around the incision site. Wound cultures reveal Gram-positive cocci that are resistant to nafcillin. Which of the following organisms is the most likely cause of this patient's condition?
Tested Concept

QID: 101540
1

Streptococcus viridans

0%

(0/48)

2

Escherichia coli

0%

(0/48)

3

Staphylococcus epidermidis

35%

(17/48)

4

Staphylococcus aureus

52%

(25/48)

5

Streptococcus pyogenes

6%

(3/48)

M 2 E

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