Bacterial Skin Infection

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Bacterial Skin Infection

• By
• Prof. Ashraf Al-Sawy MD

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Staph. Aureus Infection

1. Direct infection of skin impetigo, ecthyma,
   folliculitis, furunculosis, carbuncle, sycosis.
2. Secondary infection eczema, infestations,
   ulcers, etc.
3. Effect of bacterial toxin staph.-associated
   scalded skin syndrome (SSSS), toxic shock
   syndrome.

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strepto. Infection (GAS)(gp A streptococci)

• Direct inf. of skin or subcut. tissue Impetigo,
  ecthyma, cellulitis, vulvovaginitis, perianal
  inf., strepto. ulcers, blistering distal
  dactylitis, necrotizing fasciitis.
• 2ry inf. eczema, infestations, ulcers, etc.

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• Tissue damage from circulating toxin scarlet
  fever, toxic shock-like syndrome.
• Skin lesions attributed to allergic
  hyper-sensitivity to strepto. antigens erythema
  nodosum, vasculitis.
• Skin dis. provoked or influenced by strepto.
  inf. psoriasis especially guttate forms.

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Impetigo
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• Acute contagious skin infection caused mostly by
  staph. Aureus and strept.
• Affects children mainly esp. in summer times.

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Clinical types

• 1- Non-bullous impetigo
• Caused by staph., strept. or both organisms.
• 2- Bullous impetigo
• Caused by staph aureus.

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Non-bullous Impetigo

• Staph. aureus or gp A stretp. (GAS) or both
  mixed infections.
• May arise as 1ry inf. or as 2ry inf. of
  pre-existing dermatoses, e.g. pediculosis,
  scabies eczemas.
• An intact st. corneum is probably the most
  important defense against invasion of pathogenic
  bacteria.

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• A thin-walled vesicle on erythematous base, that
  soon ruptures the exuding serum dries to form
  yellowish-brown (honey-color) crusts that dry
  separate leaving erythema which fades without
  scarring.
• Regional adenitis with fever may occur in severe
  cases.

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• Sites Exposed parts eg. face extremities.
  Scalp (in pediculosis). Any part could be
  affected except palms soles.
• Complications Post-streptococcal acute
  glomerulo-nephritis AGN especially in cases due
  to strepto. pyogenes M. type 49.

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Varities

• Circinate impetigo with peripheral extension of
  lesion healing in the center.

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• Crusted impetigo
• on the scalp complicating pediculosis. Occipital
  cervical LNs are usually enlarged tender.

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• Ecthyma (ulcerative impetigo) adherent crusts,
  beneath which purulent irregular ulcers occur.
  Healing occurs after few wks, with scarring.

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• Site more on distal extremities (thighs legs).

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Bullous Impetigo

• Age all ages, but commoner in childhood
  newborn (impetigo neonatorum).
• Site face is often affected, but the lesions may
  occur anywhere, including palms soles.

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• The bullae are less rapidly ruptured (persist for
  2-3 days) become much larger. The contents are
  at first clear, later cloudy. After rupture,
  thin, brownish crusts are formed.

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Treatment of impetigo

• Treatment of predisposing causes e.g.
  pediculosis scabies.
• Remove the crusts by olive oil or hydrogen
  peroxide.
• Topical antibiotic e.g. tetracycline,
  bacitracin, gentamycin, mupiracin (Bactroban),
  Fusidic acid (Fucidin).

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• Systemic antibiotics are indicated especially in
  the presence of fever or lymphadenopathy, in
  extensive infections involving scalp, ears,
  eyelids or if a nephritogenic strain is
  suspected, e.g. penicillin, erythromycin
  cloxacillin.
• Azithromycin (Zithromax) 2 caps 500 mg daily
  for 3 days in adults.
• In erythromycin-resistant S. aureus amoxicillin
  clavulanic a. (Augmentin) 25 mg/kg/day.

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Folliculitis
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• inflammatory disease of the hair follicles, which
  may be infectious or non-infectious.

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• Superficial Folliculitis
• (Bockharts Impetigo)

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• a dome-shaped pustule at the orifice of a hair
  follicle that heals within 7-10 days.

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• Caused by staph aureus and affects mainly
  extremities and scalp.
• Topical steroids are a common predisposing
  factor.

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• Sychosis Vulgaris

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• Recurrent red follicular papules or pustules
  centered on a hair, usually remain discrete over
  the beard or upper lip, but may coalesce to
  produce raised plaques studded with pustules.
• DD pseudofolliculitis of the beard, T. barae.

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• Pseudofolliculitis

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• from penetration into the skin of sharp tips of
  shaved hairs.

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Frunculosis (boils)
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• It is a staphylococcal infection similar to, but
  deeper than folliculitis invades the deep parts
  of the hair folliculitis.
• Occasionally several closely grouped boils will
  combine to form a carbuncle. The carbuncle
  usually occurs in diabetic cases. The site of
  election is the back of the neck.

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Cellulitis Erysipelas
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• Cellulitis is an infection of subcutaneous
  tissues.
• Ersipelas Its due to infection of the dermis
  upper subcutaneous tissue by gp A streptococci.
  The organism reaches the dermis through a wound
  or small abrasion. It is regarded as a
  superficial dermal form of cut. cellulitis.

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• Erythema, heat, swelling and pain or tenderness.
• Fever and malaise which is more severe in
  erysipelas.
• In erysipelas blistering and hemorrhage.
• Lymphangitis and lymphadenopathy are frequent.

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• Edge of the lesion well demarcated and raised in
  erysipelas and diffuse in cellulitis.

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Complications

• Recurrences may lead to lymphedema.
• Subcutaneous abscess.
• Septicemia.
• Nephritis.

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Treatment

• Systemic antibiotics, especially penicillin, e.g.
  benzyl penicillin 600-1200 mg IV/6 hrs or
  cephalosporines.
• Rest, analgesics.

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Skin diseases related to coryneform bacteria

• Erythrasma

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• It is mild, chronic, localized superficial
  infection of skin by Coryn. Minutissimum.
• Clinically sharply-defined but irregular brown,
  scaly patches

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• usually localized to groins, axillae, toe clefts
  or may cover extensive areas of trunk limbs.
  Obesity DM may coexist.
• Coral red fluorescence under woods light.

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Treatment

• Topical treatment with azole antifungal agents
  for 2 weeks or topical fucidin.
• Erythromycin orally.

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