SKIN AND SOFT TISSUE INFECTIONS

SKIN AND SOFT TISSUE INFECTIONS is a topic covered in the Harrison's Manual of Medicine.

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Skin and soft tissue infections are diagnosed principally by a careful history (e.g., temporal progression, travel, animal exposure, bites, trauma, underlying medical conditions) and physical examination (appearance of lesions and distribution). Treatment of common skin infections is summarized in Table 84-1; parenteral treatment is usually given until systemic signs and symptoms have improved. Types of skin lesions include the following:

TABLE 84-1: TREATMENT OF COMMON INFECTIONS OF THE SKIN
Diagnosis/ConditionPrimary TreatmentAlternative TreatmentSee Also Chap(s).
Animal bite (prophylaxis or early infection)aAmoxicillin/clavulanate, 875/125 mg PO bidDoxycycline, 100 mg PO bid27
Animal bitea (established infection)Ampicillin/sulbactam, 1.5–3 g IV q6h

Clindamycin, 600–900 mg IV q8h,

plus

Ciprofloxacin, 400 mg IV q12h, or cefoxitin, 2 g IV q6h

27
Bacillary angiomatosisErythromycin, 500 mg PO qidDoxycycline, 100 mg PO bid91
Herpes simplex (primary genital)Acyclovir, 400 mg PO tid for 10 daysFamciclovir, 250 mg PO tid for 5–10 days,99
  or 
  Valacyclovir, 1000 mg PO bid for 10 days 
Herpes zoster (immunocompetent host >50 years of age)Acyclovir, 800 mg PO 5 times daily for 7–10 days

Famciclovir, 500 mg PO tid for 7–10 days,

or

Valacyclovir, 1000 mg PO tid for 7 days

99
Cellulitis (staphylococcal or streptococcalb,c)Nafcillin or oxacillin, 2 g IV q4–6h

Cefazolin, 1–2 g q8h,

or

Ampicillin/sulbactam, 1.5–3 g IV q6h,

or

Erythromycin, 0.5–1 g IV q6h,

or

Clindamycin, 600–900 mg IV q8h

86, 87
MRSA skin infectiondVancomycin, 1 g IV q12hLinezolid, 600 mg IV q12h86
Necrotizing fasciitis (group A streptococcalb)

Clindamycin, 600–900 mg IV q6–8h,

plus

Penicillin G, 4 million units IV q4h

Clindamycin, 600–900 mg IV q6–8h,

plus

Cephalosporin (first- or second-generation)

87
Necrotizing fasciitis (mixed aerobes and anaerobes)

Ampicillin, 2 g IV q4h,

plus

Clindamycin, 600–900 mg IV q6–8h,

plus

Ciprofloxacin, 400 mg IV q6–8h

Vancomycin, 1 g IV q6h,

plus

Metronidazole, 500 mg IV q6h,

plus

Ciprofloxacin, 400 mg IV q6–8h

92
Gas gangreneClindamycin, 600–900 mg IV q6–8h,Clindamycin, 600–900 mg IV q6–8h,92
 plusplus 
 Penicillin G, 4 million units IV q4–6hCefoxitin, 2 g IV q6h 
aPasteurella multocida, a species commonly associated with both dog and cat bites, is resistant to cephalexin, dicloxacillin, clindamycin, and erythromycin. Eikenella corrodens, a bacterium commonly associated with human bites, is resistant to clindamycin, penicillinase-resistant penicillins, and metronidazole but is sensitive to trimethoprim-sulfamethoxazole and fluoroquinolones.
bThe frequency of erythromycin resistance in group A Streptococcus is currently ~5% in the United States but has reached 70–100% in some other countries. Most, but not all, erythromycin-resistant group A streptococci are susceptible to clindamycin. Approximately 90% of Staphylococcus aureus strains are sensitive to clindamycin, but resistance—both intrinsic and inducible—is increasing.
cSevere hospital-acquired S. aureus infections or community-acquired S. aureus infections that are not responding to the β-lactam antibiotics recommended in this table may be caused by methicillin-resistant strains, requiring a switch to vancomycin, daptomycin, or linezolid.
dSome strains of methicillin-resistant S. aureus (MRSA) remain sensitive to tetracycline and trimethoprim-sulfamethoxazole. Daptomycin (4 mg/kg IV q24h) or tigecycline (100-mg loading dose followed by 50 mg IV q12h) is an alternative treatment for MRSA.
  1. Vesicles: due to proliferation of organisms, usually viruses, within the epidermis (e.g., VZV, HSV, coxsackievirus, poxviruses, Rickettsia akari)
  2. Bullae: caused by toxin-producing organisms. Different entities affect different skin levels. For example, staphylococcal scalded-skin syndrome and toxic epidermal necrolysis cause cleavage of the stratum corneum and the stratum germinativum, respectively. Bullae are also seen in necrotizing fasciitis, gas gangrene, and Vibrio vulnificus infections.
  3. Crusted lesions: Impetigo caused by either Streptococcus pyogenes (impetigo contagiosa) or Staphylococcus aureus (bullous impetigo) usually starts with a bullous phase before development of a golden-brown crust. Crusted lesions are also seen in some systemic fungal infections, dermatophytic infections, and cutaneous mycobacterial infections. It is important to recognize impetigo contagiosa because of its relation to poststreptococcal glomerulonephritis.
  4. Folliculitis: Localized infection of hair follicles is usually due to S. aureus. “Hot-tub folliculitis” is a diffuse condition caused by Pseudomonas aeruginosa. Freshwater avian schistosomes cause an allergic reaction after penetrating hair follicles, resulting in “swimmer’s itch.”
  5. Papular and nodular lesions: Raised lesions of the skin occur in many different forms and can be caused by Bartonella henselae (cat-scratch disease and bacillary angiomatosis), Treponema pallidum, human papillomavirus, mycobacteria, and helminths.
  6. Ulcers, with or without eschars: can be caused by cutaneous anthrax, ulceroglandular tularemia, plague, and mycobacterial infection. Ulcerated lesions on the genitals can be caused by chancroid (painful) or syphilis (painless).
  7. Erysipelas: abrupt onset of fiery red swelling of the face or extremities, with well-defined indurated margins, intense pain, and rapid progression. S. pyogenes is the exclusive cause.

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TY - ELEC T1 - SKIN AND SOFT TISSUE INFECTIONS ID - 623645 Y1 - 2017 PB - Harrison's Manual of Medicine UR - https://harrisons.unboundmedicine.com/harrisons/view/Harrisons-Manual-of-Medicine/623645/all/SKIN_AND_SOFT_TISSUE_INFECTIONS ER -