Cellulitis is "an acute, diffuse, and suppurative inflammation of loose connective tissue, particularly the deep subcutaneous tissues, and sometimes muscle, which is most commonly seen as a result of infection of a wound, ulcer, or other skin lesions."  The condition has been known from antiquity; generations of medical students learned its signs as rubor, tumor, calor, dolor or "reddened, swollen, warm to the touch, and painful." The presence of broken skin in the inflamed area is a further warning, but there may be no obvious wound.
The most common organisms are:
If purulence is present, then stept is the cause of < 10% of cases.
Differential diagnosis to rule out life-threatening conditions, such as deep venous thrombosis, compartment syndrome and gangrene, is essential; a presentation of the common signs of cellulitis needs urgent, if not emergent, evaluation.
According to the 2014 clinical practice guidelines, antribiotics or outpatients should be "an antimicrobial agent that is active against streptococci...For patients whose cellulitis is associated with penetrating trauma, evidence of MRSA infection elsewhere, nasal colonization with MRSA, injection drug use, or SIRS (severe nonpurulent; Figure 1), vancomycin or another antimicrobial effective against both MRSA and streptococci is recommended (strong, moderate)".
According to the 2011 clinical practice guidelines, if both Methicillin resistant Staphylococcus aureus and Streptococcus pyogenes are possible causes, then "options include the following: clindamycin alone (A-II) or TMP-SMX or a tetracycline in combination with a β-lactam (eg, amoxicillin) (A-II) or linezolid alone (A-II)."
According to the 2005 clinical practice guidelines, which state that staphylococcus aureus is very uncommon: "Suitable agents include dicloxacillin, cephalexin, clindamycin, or erythromycin, unless streptococci or staphylococci resistant to these agents are common in the community." A more recent trial confirms that if purulence or diabetes are not present then coverage for staphylococcus aureus is not needed.
- Higher dose antibiotics are used:
- Anonymous (2021), Cellulitis (English). Medical Subject Headings. U.S. National Library of Medicine.
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