Chapter 130. Streptococcal and Enterococcal Infections (Part 7)

Erysipelas is a streptococcal infection of the superficial dermis and consists of well-demarcated, erythematous, edematous, warm plaquesClassic cases of erysipelas, with typical features, are almost always due to β-hemolytic streptococci, usually GAS and occasionally group C or G. Often, however, the appearance of streptococcal cellulitis is not sufficiently distinctive to permit a specific diagnosis on clinical grounds. The area involved may not be typical for erysipelas, the lesion may be less intensely red than usual and may fade into surrounding skin, and/or the patient may appear only mildly ill. In such cases, it is prudent to broaden the spectrum...
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Chapter 130. Streptococcal and Enterococcal Infections (Part 7) Chapter 130. Streptococcal and Enterococcal Infections (Part 7) Erysipelas is a streptococcal infection of the superficial dermis andconsists of well-demarcated, erythematous, edematous, warm plaques Classic cases of erysipelas, with typical features, are almost always due toβ-hemolytic streptococci, usually GAS and occasionally group C or G. Often,however, the appearance of streptococcal cellulitis is not sufficiently distinctive topermit a specific diagnosis on clinical grounds. The area involved may not betypical for erysipelas, the lesion may be less intensely red than usual and may fadeinto surrounding skin, and/or the patient may appear only mildly ill. In such cases,it is prudent to broaden the spectrum of empirical antimicrobial therapy to includeother pathogens, particularly S. aureus, that can produce cellulitis with the sameappearance. Staphylococcal infection should be suspected if cellulitis developsaround a wound or an ulcer. Streptococcal cellulitis tends to develop at anatomic sites in which normallymphatic drainage has been disrupted, such as sites of prior cellulitis, the armipsilateral to a mastectomy and axillary lymph node dissection, a lower extremitypreviously involved in deep venous thrombosis or chronic lymphedema, or the legfrom which a saphenous vein has been harvested for coronary artery bypassgrafting. The organism may enter via a dermal breach some distance from theeventual site of clinical cellulitis. For example, some patients with recurrent legcellulitis following saphenous vein removal stop having recurrent episodes onlyafter treatment of tinea pedis on the affected extremity. Fissures in the skinpresumably serve as a portal of entry for streptococci, which then produceinfection more proximally in the leg at the site of previous injury. Streptococcalcellulitis may also involve recent surgical wounds. GAS is among the fewbacterial pathogens that typically produce signs of wound infection andsurrounding cellulitis within the first 24 h after surgery. These wound infectionsare usually associated with a thin exudate and may spread rapidly, either ascellulitis in the skin and subcutaneous tissue or as a deeper tissue infection (seebelow). Streptococcal wound infection or localized cellulitis may also beassociated with lymphangitis , manifested by red streaks extending proximallyalong superficial lymphatics from the infection site. Streptococcal Cellulitis: Treatment See Table 130-3 and Chap. 119. Deep Soft-Tissue Infections Necrotizing fasciitis (hemolytic streptococcal gangrene) involves thesuperficial and/or deep fascia investing the muscles of an extremity or the trunk.The source of the infection is either the skin, with organisms introduced into tissuethrough trauma (sometimes trivial), or the bowel flora, with organisms releasedduring abdominal surgery or from an occult enteric source, such as a diverticularor appendiceal abscess. The inoculation site may be inapparent and is often somedistance from the site of clinical involvement; e.g., the introduction of organismsvia minor trauma to the hand may be associated with clinical infection of thetissues overlying the shoulder or chest. Cases associated with the bowel flora areusually polymicrobial, involving a mixture of anaerobic bacteria (such asBacteroides fragilis or anaerobic streptococci) and facultative organisms (usuallygram-negative bacilli). Cases unrelated to contamination from bowel organismsare most commonly caused by GAS alone or in combination with other organisms(most often S. aureus). Overall, GAS is implicated in ~60% of cases of necrotizingfasciitis. The onset of symptoms is usually quite acute and is marked by severepain at the site of involvement, malaise, fever, chills, and a toxic appearance. Thephysical findings, particularly early on, may not be striking, with only minimalerythema of the overlying skin. Pain and tenderness are usually severe. In contrast,in more superficial cellulitis, the skin appearance is more abnormal, but pain andtenderness are only mild or moderate. As the infection progresses (often overseveral hours), the severity and extent of symptoms worsen, and skin changesbecome more evident, with the appearance of dusky or mottled erythema andedema. The marked tenderness of the involved area may evolve into anesthesia asthe spreading inflammatory process produces infarction of cutaneous nerves. Although myositis is more commonly due to S. aureus infection, GASoccasionally produces abscesses in skeletal muscles (streptococcal myositis), withlittle or no involvement of the surrounding fascia or overlying skin. Thepresentation is usually subacute, but a fulminant form has been described inassociation with severe systemic toxicity, bacteremia, and a high mortality rate.The fulminant form may reflect the same basic disease process seen in necrotizingfasciitis, but with the necrotizing inflammatory process extending into the musclesthemselves rather than remaining limited to the fascial layers.