Bacterial Skin Infections PDF

Bacterial Infections of the Skin Clinical cases  Pyogenic diseases of the skin are mainly caused by Staph. aureus and Strept. Pyogenes. They may be the primary cause of certain skin diseases "primary pyoderma” or may cause secondary infection of other skin diseases as ecze...

Bacterial Infections of the Skin Clinical cases  Pyogenic diseases of the skin are mainly caused by Staph. aureus and Strept. Pyogenes. They may be the primary cause of certain skin diseases "primary pyoderma” or may cause secondary infection of other skin diseases as eczema, ulcers or itchy skin conditions as scabies or pediculosis “secondary pyoderma”.  Impetigo The most common bacterial infection of the skin. It is more common in the first 5-10 years of life, particularly during summer months. Causative organism: Staph. aureus or Strept. pyogenes or both.  Ordinary impetigo contagiosum Commonest form (70%). It is usually caused by Staphylococcus aureus and/or Group A beta-hemolytic Streptococci. The usual location is on the face especially periorificial -around the mouth and the nose- and also the extremities. It occurs also frequently on the scalp, complicating pediculosis.  Clinical Picture The initial lesion is a thin-walled vesicle on an erythematous base, then, the vesicles rupture so rapidly that it is rarely seen as such. The exuding serum dries to form yellowish- brown, honey-colored, stuck on crusts (hallmark of the disease) (Figure 2.1). The crusts then dry & separate, leading to erythema that fades without scarring (may leave temporary hypo- or hyperpigmentation). Regional lymphadenopathy is common. Scalp Imptigo  Bullous impetigo It is an acute blistering infection caused by Staph aureus (group II, phage 71). Affects mainly neonates & infants. The trunk is the most common affected site. It may spread & become generalized.  Clinical Picture The initial lesion is a small flaccid bulla with a faint rim of surrounding erythema containing yellow turbid fluid. The roof of the bulla tends to collapse rather than rupture, retaining the fluid content that finally desiccates and a thin flat crust is formed. Central healing and peripheral extension may form a circinate lesion. Regional lymph nodes are usually not enlarged. Bullous impetigo  Diagnosis of Impetigo 1. Based primarily on clinical presentation. 2. Gram stain and appropriate cultures are needed to isolate the specific bacterial pathogen. 3. Sensitivity testing is done to use appropriate antibiotic.  Complications Spread of infection to other sites or other individuals. Post-streptococcal glomerulonephritis (most serious) occurs 2-3 weeks after acute infection.  Treatment of Impetigo 1. Treatment of predisposing factors as pediculosis and scabies. 2. Local treatment: -Gentle removal of the crust using olive oil (hot foments). -Anti-septic solution as potassium permanganate 1/8000. -Topical antibiotic: as fusidic acid cream in localized lesions. 3. Systemic broad-spectrum antibiotics in widespread lesions (for 5-7 days): -Beta-lactamase resistant antibiotics as amoxicillin/clavulonate, ampicillin/cloxacillin or cephalexin or azithromycin.  Ecthyma (Ulcerative Impetigo) It is a deeper form of pyogenic skin infection that heals by scar formation. Mainly caused by streptococci (less by staphylococci). The most common involved site is on the lower extremities (shin of tibia).  Clinical picture It mainly affects children, neglected elderly, lymphedematous patients and immunocompromised patients. The initial lesion is a vesicle with an erythematous base and surrounding halo that enlarges to 0.5-3 cm in size and then ruptures leaving a dark adherent crust surrounded by a rim of erythematous indurated area.  Removal of the crust shows a saucer (dish) shaped ulcer with raised, indurated, violaceous margin. The base extends deeply in the dermis. It heals with scar formation. Local lymphadenopathy may be present.  Complications Cellulitis and osteomyelitis occur infrequently. Rarely systemic symptoms and bacteremia.  Treatment Treatment of predisposing factors. Appropriate antibacterial therapy (as impetigo but for 10-14 days).  Folliculitis It is an infection of the pilosebaceous apparatus mostly by staphylococci.  Classification 1. Acute folliculitis: I. Acute superficial folliculitis (Bockhart’s impetigo) II. Acute deep folliculitis (Furunculosis or boils) III. Carbuncle 2. Subacute & Chronic folliculitis: I. Sycosis barbae II. Acne keloidalis (folliculitis keloidalis)  1. Acute folliculitis I. Acute superficial folliculitis (Bockhart’s impetigo): Scalp and extremities. It can be also seen on the face. It occurs at any age (more frequent at school age). The initial lesion is thin walled yellowish-white domed pustule at the follicular orifices, pierced at its center by a hair. It heals without scarring.  Treatment Topical antiseptics. Topical antibiotics in localized lesions and systemic antibiotics in disseminated lesions. II. Acute deep folliculitis (Furunculosis or boils): Face, neck, axilla and buttocks. It occurs at any age. It affects the deeper parts of the hair follicles that ends in central suppuration and formation of the core (characteristic of the boil).  The initial lesions are single or multiple hard, tender nodules that enlarge and become painful, then pustular and necrotic. Healing after discharge of the necrotic core may be complicated by scarring and post–inflammatory hyperpigmentation.  Treatment Warm compresses: may enhance maturation, drainage and resolution of infection. Incision and drainage: of fluctuant lesions. Systemic antibiotics: for large and recurrent lesions and lesions with surrounding cellulitis. III. Carbuncle The most commonly involved sites are the back of the neck, shoulders, buttocks and thighs. Adults, mainly diabetics & immunocompromised individuals are the susceptible group.  The initial lesion is an indurated, tender circumscribed area with deep staphylococcal infection of a group of adjacent follicles with subsequent perforation of the hair follicles. Local spread of infection leads to mass necrosis of the infected tissue and expulsion of the necrotic material to the outside through multiple openings.  Treatment Surgical drainage and appropriate Topical and Systemic Antibiotics. 2. Subacute & Chronic folliculitis I. Sycosis barbae Beard area. Adult males are susceptible. The initial lesion is in the form of recurrent discrete inflammatory papules or pustules in the beard area pierced by hairs. If neighboring follicles are affected, a plaque studded with pustules may result.  Treatment: Topical antiseptic as chlorhexidine and topical antibiotics. Systemic antibiotics for resistant cases.  Differential Diagnosis Pseudofolliculitis: It is a non-infectious, inflammatory condition (foreign body reaction to hair) caused by ingrowing hairs in people who shave. It mostly affects men with curled hair. Papules and pustules commonly occur on the anterolateral aspect of the neck or on the angle of the jaw in men. It could also affect women who shave especially in the groin area. Tinea barbae A fungal infection with Inflammatory papules and pustules on beard area with loosened hair. KOH and culture are positive for fungus. II. Acne keloidalis (folliculitis keloidalis) It most commonly involves the occipital area of the scalp. It occurs mostly in adult males. The initial lesion is in the form of small pustules that are followed by firm, dome-shaped follicular papules. They slowly enlarge and coalesce and may form keloid-like plaques.  Treatment: Local or intralesional corticosteroids. Topical antibiotics as fusidic acid cream for pustular lesions. Systemic antibiotics are rarely indicated.  Erysipelas This is an infection of the dermis with significant lymphatic involvement caused by haemolytic Streptococci. The organism reaches the dermis through a wound or a small abrasion. The commonest sites are face and legs.  Clinical picture After an incubation period of 1-5 days, the disease begins with sudden onset of fever, rigors & malaise. This is followed few hours up to 1 day later by the eruption. The skin shows redness, hotness, swelling and pain. The lesion is in the form of a well-demarcated red area. The lesion has an advancing edge, and the surface may show vesicles, pustules or bullae. Erysipelas  Cellulitis Cellulitis is an acute or subacute inflammation of deep dermis and subcutaneous tissue. It is deeper than erysipelas. It occurs most commonly as a complication of a wound or skin lesion. The leg is the commonest site. Ill-defined, indurated, red, tender hot area of skin appears at the affected site. Systemic symptoms (fever, malaise). Cellulitis Erysipelas versus Cellulitis  Complications 1. Recurrent erysipelas may lead to lymphoedema. 2. Nephritis. 3. Subcutaneous abscess. 4. Septicaemia (rare).  Treatment: 1. Rest in bed and antipyretics. 2. Penicillin is the drug of choice (given for 10-14 days). Other antibiotics (e.g. Macrolides; azithromycin or erythromycin) may be used if the patient is sensitive to penicillin.  Intertrigo The term intertrigo denotes inflammation of skin folds as behind the ears, under the breasts, axillae, groin and skin folds in obese persons.  Causes 1. Streptococcal intertrigo: Longitudinal painful fissure at the angle of the skin folds. The skin around is red, moist & may be crusted. 2. Simple intertrigo due to friction. 3. Contact Dermatitis. 4. Flexural psoriasis. 5. Seborrheic dermatitis. 6. Tinea cruris. 7. Candidal intertrigo. 8. Erythrasma. Treatment of bacterial intertrigo: 1. Frequent washing with antiseptic lotion as potassium permanganate solution 1/8000. 2. Topical antibiotic cream. 3. Systemic antibiotics.  Erythrasma A mild chronic, localized, superficial infection of the intertriginous areas. Corynebacterium minutissimum. Well-defined reddish-brown patches with no active edge, covered with fine scales. It may be asymptomatic or associated with mild itching  Diagnostic methods Wood's light examination … coral red fluorescence. Treatment: Topical antifungal and topical antibiotic (erythromycin, clindamycin, fusidic acid, mupirocin). Systemic erythromycin (if widespread or recalcitrant lesions).  Paronychia Paronychia is inflammation of the nail folds. It may be acute and chronic. Acute Paronychia: Bacterial paronychia is common, especially in children and follows minor trauma. The affected digit is red, swollen and painful. Compression of the nail fold may drain pus. Chronic Paronychia: Chronic Paronychia involves the nail folds of adult women. Occupational paronychia is common in food handlers and cleaning personnel. The condition represents a contact reaction to irritants or allergens. Secondary infection by candida or bacteria is common. Treatment: 1. Drainage of pus. 2. Systemic and topical antibiotics.  Angular Cheilitis (Angular Stomatitis) Angular cheilitis (perlèche) is inflammation of the angle of the mouth. It is characterized by maceration, erythema and fissuring of the oral commissures. Angular stomatitis  Angular stomatitis Predisposing factors: 1. Excessive salivation. 2. Ill-fitting dentures. 3. Debilitating diseases and old age  Angular stomatitis Treatment 1. Correction of any predisposing factors. 2. Topical antifungal &/or topical antibiotic cream. 3. Vitamin B-complex. Thank you