Bacterial Infections 07/02/2011

1. Bacterial Infections 07/02/2011 BY: MOHAMMED ALSAIDAN

3. Normal skin flora

4. Impetigo • It is the most common bacterial infection in children • highly contagious, spreading rapidly via direct person-to-person contact • The primary pathogen is S.aureus and, less commonly, Streptococcus pyogenes • Non Bullous : usually at site of trauma • Bullous: (considered a localized form of SSSS) elaborates several exfoliative toxins (A–D), targeting desmoglein 1 acantholysis in granular layer mimicking P.folaceus

5. Impetigo • Predisposing factors include • warm temperature, high humidity, • poor hygiene • atopic diathesis • skin trauma (chickenpox, insect bite, abrasion, laceration, burn) • S. aureus colonization

9. Impetigo work up ? • Diagnosis is usually made clinically • Exudate from beneath the crust and fluid from intact bullae can be sent for culture and sensitivity • Leukocytosis in 50%

11. Treatment • local wound care • Cleansing • removal of crusts • wet dressings • For healthy patients with a few, isolated superficial lesions and no systemic symptoms: • mupirocin 2% ointment or fusidic acid equally effective to oral antibiotics

13. Folliculitis • Folliculitis: infection localized to the hair follicle • Furuncle: entire follicle and surrounding tissue are involved • carbuncle : multiple furuncles grouped together • S. aureus is the most common infectious cause of folliculitis • Gram-vefolliculitis A.V. treated with long courses of oral antibiotics • Pseudomonasfolliculitis use of hot tubs

16. Folliculitis • Factors predisposing • occlusion • maceration and hyperhydration with hot and humid weather, • shaving, plucking or waxing hair • topical corticosteroids • diabetes mellitus • atopic dermatitis. • Obesity • Immunodeficiency • Poor hygiene

17. Folliculitis • Site: face, chest, back, axillae or buttocks • superficial folliculitis (Bockhart's impetigo) are small, 1–4 mm pustules or crusted papules on an erythematous base • Gram stain and bacterial cultures in recurrent or treatment-resistant cases

21. Folliculitis treatment • Localized: • antibacterial washes • bacitracin or mupirocin 2% may also be used for 7-10 days • Widespread or recurrent: • appropriate β-lactam antibiotics, macrolides or clindamycin • Chronic S. aureus carriage • mupirocin 2% ointment applied twice daily to the nares, axillae/groin and/or submammary area for 5 days.

22. Furuncles, Carbuncles • S. aureus is the most common causative organism • Furuncles usually begin as a hard, tender, red nodule that enlarges and becomes painful and fluctuant; rupture results in decreased pain, Systemic symptoms are usually absent

23. Furuncles, Carbuncles • Carbuncles are collections of furuncles that extend deep into the subcutaneous tissue. • The surface usually displays multiple draining sinus tracts and occasionally ulcerates. • They usually occur in areas with thicker skin (e.g. nape of neck, back, thigh) • Systemic symptoms are usually present. • Carbuncles are slow to heal  scar formation

25. Treatment • simple furuncles: • warm compresses may promote maturation, drainage and resolution of symptoms • Fluctuant lesions • incision and drainage • Systemic antibiotics should be used in four instances: • (1) furuncles around the nose, within the nares or in the external auditory canal • (2) large and recurrent lesions • (3) lesions with surrounding cellulitis • (4) lesions not responding to local care

26. MRSA • Furunculosis is the most frequently reported manifestation of community acquired MRSA • MRSA can manifest as : • abscesses or frank cellulitis • impetigo, bullous impetigo, scalded skin syndrome, nodules or pustules • bacteremia, septic shock and a toxic shock-like syndrome • The major cause of methicillin resistance is the production of an altered (i.e. reduced affinity) penicillin-βindingprotein (PBP) called PBP2a

28. Treatment • Emperical treatment with Vancomycin is indicated in : • patients with severe, life-threatening infection • in patients with a history of MRSA colonization • in intravenous drug users

29. Blistering Distal Dactylitis • children aged 2-16 years • Presents as a localized infection of the volar fat pad of a finger or a toe • Blister formation and involvement of the nail fold or more proximal portion of the digit • Darkening of the surrounding skin before blister formation

32. Blistering Distal Dactylitis • Group A β-hemolytic Streptococcus, S. aureus and, rarely, S. epiermidis are the responsible organisms DDx: • herpetic whitlow • thermal or chemical burn • acute paronychia • bullous impetigo (vesicles more superficial) • frictional bullae

33. Blistering Distal Dactylitis Treatment • Incision and drainage plus • a 10-day course of an oral antistaphylococcal antibiotic (e.g. cephalexin) can prevent development of new sites of infection as well as local extension.

34. Ecthyma • Considered as : ulcerated form of non-bullous impetigo like lesion • due to either a primary infection with Str. pyogenes or streptococcal superinfection of a pre-existing ulceration

38. Staphylococcal Scalded Skin Syndrome • Staphylococcal toxin-mediated infections includes: • ssss • bullous impetigo • toxic shock syndrome • Exfoliative toxins (ETs) ETA and ETB are serine proteases with a very high specificity for human desmoglein 1 (DG-1)

40. Staphylococcal Scalded Skin Syndrome • Increased frequency of staphylococcal scalded skin syndrome in children younger than 5 years due to : • Absence of antibodies specific for exotoxins • Immature renal function in this age group may impair clearance • The relative quantity of DG-1 in the skin differs with age

41. SSSS clinical features Clinical features: • Prodrome • Severe tenderness of the skin • Erythema • Flaccid bullae within the superficial epidermis. • In 1-2 days, the bullae are sloughed  moist skin and areas of thin, varnish-like crust.

42. SSSS clinical features • The flexural areas are the first to exfoliate. • Scaling and desquamation continue for 3-5 days • Re-epithelialization in 10-14 days, without scarring • The Nikolsky sign is positive. • The mortality rate is 3% for children, over 50% in adults, and almost 100% in adults with underlying disease

45. SSSS work up • Cultures taken from intact bullae are negative • Blood cultures are almost always negative in children, but may be positive in adults • The leukocyte count may be elevated or normal • Electrolytes and renal function should be followed closely in severe cases • PCR serum test for the toxin is available.

46. SSSS work up • Biopsy: separation of the epidermis at the granular layer. An inflammatory cell infiltrate is typically not present • Negative IF • In (TEN), inflammatory (lymphocytic) infiltrate is present, and the plane of separation is deeper, at the level of the basement membrane.

49. DDx • sunburn • drug reaction • Kawasaki disease • extensive bullous impetigo • viral exanthem, toxic shock syndrome, GVHD, TEN and pemphigusfoliaceus.

50. SSSS treatment • Localized disease : • Oral treatment with a β-lactamase-resistant antibiotic e.g.dicloxacillin, cloxacillin, for a minimum of 1 week • Emollient • Isolation • treatment of S. aureus carriers • Extensive, generalized forms of SSSS • hospitalization and parental antibiotics.