Bacterial_Skin_Infection by xiuliliaofz


Prof. Ashraf Al-Sawy MD
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
   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.
   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.
 Acute   contagious skin infection
  caused mostly by staph. Aureus and
 Affects children mainly esp. in
  summer times.
   1- Non-bullous impetigo:
    ◦ Caused by staph., strept. or both organisms.

   2- Bullous impetigo:
    ◦ Caused by staph aureus.
•   Staph. aureus or gp A stretp. (GAS) or both “mixed
•   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
•   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.
   Sites: Exposed parts eg.
    face & extremities. Scalp
    (in pediculosis). Any part
    could be affected except
    palms & soles.
   Complications: Post-
    streptococcal acute
    “AGN” especially in
    cases due to strepto.
    pyogenes M. type 49.
•   Circinate impetigo:
    with peripheral
    extension of lesion &
    healing in the center.
   Crusted impetigo:
   on the scalp
    pediculosis. Occipital
    & cervical LNs are
    usually enlarged &
•   Ecthyma (ulcerative
    impetigo): adherent
    crusts, beneath which
    purulent irregular ulcers
    occur. Healing occurs
    after few wks, with
   Site: more on distal
    extremities (thighs &
   Age: all ages, but
    commoner in
    childhood & newborn
   Site: face is often
    affected, but the
    lesions may occur
    anywhere, including
    palms & soles.
   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.
   Treatment of predisposing causes: e.g.
    pediculosis & scabies.
   Remove the crusts: by olive oil or hydrogen
   Topical antibiotic: e.g. tetracycline, bacitracin,
    gentamycin, mupiracin (Bactroban®), Fusidic acid
•   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.
   inflammatory disease of the hair follicles,

    which may be infectious or non-infectious.
Superficial Folliculitis
(Bockhart’s Impetigo)
   a dome-shaped
    pustule at the orifice
    of a hair follicle that
    heals within 7-10
   Caused by staph
    aureus and affects
    mainly extremities
    and scalp.
   Topical steroids are a
    common predisposing
Sychosis Vulgaris
•   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.
   from penetration into
    the skin of sharp tips
    of shaved hairs.
•   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
   Cellulitis is an infection of subcutaneous
   Ersipelas: It’s 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.
   Erythema, heat,
    swelling and pain or
   Fever and malaise
    which is more severe in
   In erysipelas: blistering
    and hemorrhage.
   Lymphangitis and
    lymphadenopathy are
   Edge of the lesion:
    well demarcated and
    raised in erysipelas
    and diffuse in
•   Recurrences may lead to lymphedema.

•   Subcutaneous abscess.

•   Septicemia.

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

•   Rest, analgesics.
•   It is mild, chronic,
    localized superficial
    infection of skin by
    Coryn. Minutissimum.
•   Clinically: sharply-
    defined but irregular
    brown, scaly patches
•   usually localized to
    groins, axillae, toe clefts
    or may cover extensive
    areas of trunk & limbs.
    Obesity & DM may
•   Coral red fluorescence
    under wood’s light.
•   Topical treatment with azole antifungal agents

    for 2 weeks or topical fucidin.

•   Erythromycin orally.
Thank You

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