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Bacterial Diseases

  1. Common Bacterial Diseases of Skin
    The predominant primary pathogens are the group A Streptococci or Staphylococcus aureus. The clinical pictures vary because of the host factors and the local anatomic infections.
    1. Impetigo
      Two clinical types of impetigo occur.
      1. impetigo contagiosum which is due to either Streptococci or Staph. Aureus or both. It is a disease of young children in which blisters appear on the skin around the mouth. The vesicles and pustules easily rupture, forming a thick, honey-coloured, "stuck on" crust, the hallmark of impetigo. The skin lesions may be complicated with deep cellulitis or bacteraemia. 
      2. bullous impetigo, caused by Staph. Aureus. It is characterized by rapid progression of vesicles to flaccid large bullae. The bullae eventually rupture, and form thin, light brown crusts.
      Treatment of Impetigo
      Impetigo contagiosa
      Localized → Topical antibiotics like fusidic acid or mupirocin
      Extensive → Systemic antibiotics (erythromycin group to cover staphylococcus and Streptococcus). If response is poor, oxacillin-Clavulanic acid or cephalexin can be tried.
      Bullous Impetigo
      Localized → Topical fusidic acid or mupirocin
      Extensive → Systemic anti staphylococcal antibiotics (flucloxacillin, amoxicillin clavulanic acid, methicillin or erythromycin).
      1. Ecthyma
        1. Ecthyma initially presents as a vesicle or vesicopustule on the lower extremities of children or neglected elderly patients, the skin lesion gradually enlarges to form a thick crusted lesion with an underlying ulcer. Lesion always heals with scar.
        2. Post-streptococcal glomerulonephritis is a known sequel.
      2. Erysipelas
        1. A spreading infection most commonly due to Group A and B Streptococci presenting as a characteristic brawny, edematous, indurated and well demarcated margin.
        2. The patient may be acutely ill with high fever and toxaemia.
        3. Predisposing factors include alcohol abuse, diabetes mellitus, immunosuppression, venous or lymphatic obstruction.
      3. Acute Cellulitis
        This is an acute, spreading infection of subcutaneous tissue.
        There are two main bacteriological forms.
        1. Acute pyogenic cellulitis is usually due to group A Streptococci and Staph. aureus. It presents as a markedly red, hot, infiltrated edematous skin lesion and the borders are usually ill-defined. Lymphangitis and lymphadenitis involving local draining lymph glands are frequently found.
        2. Anaerobic cellulitis which is relatively rare and is usually due to a synergistic infection with both aerobic and anaerobic bacteria. The causal organisms include aerobes (coliforms, Pseudomonas aeruginosa, staph. aureus) and anaerobes (bacteriodes, anaerobic cocci).
      4. Necrotizing Fasciitis
        1. This infection usually occurs on the lower extremities, abdominal wall, perineum and operative wounds. The infective-ischaemic process spreads along the fascial plane causing extensive necrosis while the external appearance of the skin remains normal initially. So the damage is more extensive than the extent of the overlying skin.
        2. The involved area is swollen, red, warm and painful.
        3. Crepitus is often present. The patient is severely ill with fever and septic shock may occur.
      5. Progressive bacterial synergistic gangrene
        1. This infection is a gangrenous ulceration of the skin due to a mixed bacteria flora. It usually follows abdominal or thoracic infection or trauma.
        2. A small, painful, superficial ulcer develops and gradually enlarges to form a ulcer with a rim of gangrenous skin.
      6. Furuncles and Carbuncles
        1. With the exception of carbuncles, these skin infections are uncomfortable and unsightly rather than serious. Furuncle or boil involve only a single hair follicle.
        2. The lesion is a deep-seated inflammatory nodule, it is tender, hard, red and fluctuate after several days.
        3. A carbuncle is a more extensive, deeper, infiltrated lesion and usually involve multiple adjacent hair follicles. Most common site is nape of the neck. Systemic symptoms such as fever and malaise are often present.
        4. All these lesions are caused by infection with Staphylococcus aureus.
      7. Folliculitis
        1. This is an acute, small, painful pustular eruption of hair follicles.
        2. There are two main subtypes: superficial and deep. Bockhart's impetigo is a superficial folliculitis. It usually occurs on the limbs and the scalp. Small, dome-shaped pustule develops at the opening of a hair follicle surrounded by erythema. 
        3. Deep folliculitis include sycosis barbae and lupoid sycosis. Staphylococcal is the commonest pathogen.
        4. Folliculitis can also be caused by Pseudomonas aeruginosa as it is easily contracted from poorly maintained whirlpools or jacuzzis.
    The clinical presentation is similar to staphylococcal folliculitis, however the patient may feel unwell, with a low grade fever and lymphadenopathy.
    1. Management
      1. General skin care
      2. Local measures
        1. Immobilization and elevation of the involved area to reduce local trauma.
        2. Cool, sterile saline dressing daily.
        3. Extensive debridement and grafting may be required for the necrotic areas of gangrene.
        4. Mupirocin or bacitracin ointment may be useful for its antibacterial effects and softening of crusted lesions.
      3. Specific measures
        1. In mild cases, topical antibiotics are adequate for treatment.
        2. In widespread and severe situation, systemic antibiotics are indicated. Penicillin G, Penicillin V, flucloxacillin and erythromycin are good antibiotics for both the streptococcal and staphylococcal infection. Tetracycline should best be avoided in the treatment of known streptococcal disease as resistant strain is not uncommon.
        3. Special measures should be aimed at elimination of nasal and skin carriage of Staph. aureus. This include the use of:
          1. Local antibiotic ointment such as fusidic acid ointment in the nasal vestibule.
          2. Intranasal application of mupirocin ointment.
          3. Topical application of chlorhexidine or povidone iodine to eradicate Staph. aureus harboring in body folds before bathing.
          4. Oral antibiotics such as rifampicin – 600mg X 10 days.
      4. Erythrasma
        1. Erythrasma is a superficial bacterial skin infection due to Corynebacterium minutissimum.
        2. The lesions are reddish-brown, scaly and finely wrinkled macular patches, usually involve the intertriginous areas. Axillary and genitocrural areas are commonly involved.
        3. The diagnosis is supported by the characteristic "coral-red" fluorescence under wood's lamp
    2. Treatment
      1. Oral erythromycin 250 mg QID for 1 week. The lesions usually clear within several weeks.
      2. Topical therapy includes aqueous clindamycin solution, Whitfield’s ointment or miconazole cream.

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