Bacterial infections of the skin

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  • 2. Introduction Infections with pyogenic (pus forming) bacteria usually Staphylococcus aureus and/or Streptococci (usually Group A -haemolytic Streptococci - GABS)
  • 3. Factors in development of bacterial skin infection 1) the portal of entry 2) the host defences 3) the pathogenic properties of the organism
  • 4. Classification - primary infections (pyodermas) - secondary infections
  • 5. Primary infections (pyodermas) infections that are produced by the invasion of normal skin by a single species of pathogenic bacteria
  • 6. Secondary infections Infections after the integrity of the skin has been broken, or the local immune milieu is altered by the primary skin condition AD, scabies, tinea, may show mixture of organisms
  • 7. Staphylococcus - Commonly carried in nose(35%), perineum (20%), axillae and toe webs (5-10%) - Staphylococcus causes impetigo, folliculitis, and carbuncles plus deeper infections. - Staph. toxins (epidermolytic) cause bullous impetigo and SSSS( Staphylococcal scalded skin syndrome).
  • 8. Streptococcus - Rarely found on normal skin, often in throat (10%), occasionally in nose - Main pathogenic type Lancefield Group A. - Causes Erysipelas, cellulitis, lymphangitis, regional lymphadenitis - Post streptococcal state (1-3 weeks later) can produce acute GN, rheumatic fever, rheumatism, erythema nodosum, psoriasis.
  • 9. Normal Flora organisms that characteristically survive and multiply in various ecologic niches of the skin S. epidermidis is the principal staphylococcal species Candida Malasazia furfur , propionibacterium acne
  • 10. Superficial Cutaneous infections Impetigo infections in the epidermis untreated pyodermas can extend to the dermis, resulting in ecthyma
  • 11. Two clinical patterns Bullous impetigo and Non-bullous impetigo
  • 12. Non-bullous Impetigo 70% of impetigo industrialized countries -- S. aureus and less often by group A streptococcus in developing countries group A streptococcus remains a common cause Occurs in children of all ages and adults usually spreads from nose to normal skin pruritis or soreness
  • 13. Cutaneous Lesions initially a transient vesicle or pustule honey- colored crusted plaque surrounding erythema 90% of prolonged, untreated regional LAP may progress to Ecthyma
  • 14. Bullous Impetigo by phage group II S. aureus Three types of eruptions 1) bullous impetigo, 2) exfoliative disease( SSSS) 3) staphylococcal scarlet fever Extracellular exfoliative toxins ("exfoliatin") types A and B
  • 15. Cutaneous lesions more common in new-borns and infants rapid progression of vesicles to flaccid bullae bullae arises on normal skin fluid clear yellow- dark yellow turbid- collapse may crust
  • 16. Laboratory Gram stain Culture Histology
  • 17. Treatment - good hygiene removal of crusts. - Antibiotics - topical if mild - mupirocin, fusidic acid, - Systemic if severe, multiple lesions, - cloxacillin, Erythromycin, amoxi+ clavulanic acid, cephalexin
  • 18. Ecthyma usually a consequence of neglected impetigo characterized by thickly crusted erosions or ulcerations Caused by Group A Strept and/or Staph Commonest in children or debilitated adults, homeless and soldiers
  • 19. most commonly on the lower extremities ulcer has a punched out appearance Covered with dirty greyish-yellow crust heals slowly Treat as impetigo
  • 20. Folliculitis a pyoderma that begins within the hair follicle a small, fragile, dome-shaped pustule occurs at the infundibulum (ostium or opening) of a hair follicle
  • 21. Children scalp Adults - beard area, axillae, extremities, and buttocks Can complicate to Furuncles if untreated
  • 22. Furuncles boil deep-seated inflammatory nodule that develops around a hair follicle areas with friction, occlusion, and perspiration usually from a preceding, more superficial folliculitis
  • 23. Cutaneous Lesions solitary or multiple hard, tender, red folliculocentric nodule undergoes abscess formation Ruptures
  • 24. Carbuncle more extensive, deeper, communicating, lesion that develops when multiple, closely set furuncles coalesce. more serious inflammation red and indurated, and multiple pustules soon appear on the surface, draining externally around multiple hair follicles scar fever and malaise - ill
  • 25. beware of bacteremia from such lesions esp when appears on the face infection such as osteomyelitis, acute endocarditis, or brain abscess recurrent furunculosis
  • 26. Treatment a systemic antibiotic as impetigo for mild cases severe infections or infections in a dangerous areas - maximal antibiotic dosage by the parenteral route drain if abscess
  • 27. Erysipelas caused by group A - haemolytic streptococcus acute infection of skin- level of part of dermis superficial cellulitis with marked dermal lymphatic vessel involvement face or a lower extremity superficial erythema, edema with a sharply defined margin to normal tissue
  • 28. there may be portal of entry Recurrent erysipelas tinea pedis, lymphedema surgery Can cause lymphedema
  • 29. Cellulitis infection extends deeper into the dermis and subcutaneous tissue S. aureus and GAS common causes looks erysipelas but lack of distinct margins, deeper edema, surface bulla/necrosis can go deep if untreated fasciitis regional LAP portal of entry evident in half of cases
  • 30. Treatment Supportive - rest, immobilization, elevation, moist heat, analgesia. Dressings -cool sterile saline dressings for removal of purulent exudates and necrotic tissue Surgical - Drain abscess
  • 31. Antimicrobial Therapy - against Strept in erysipelas - against staph in cellulitis + /- against Strept
  • 32. THANKS