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Cutaneous Bacterial Infections
Nastaran Tavakoli
Guilan University of medicine
IMPETIGO :
There are two classic forms of impetigo:
1)Nonbullous impetigo
2)Bullous Impetigo
Nonbullous impetigo:
• More than 70% of cases • Lesions typically begin on the skin of the face
or on extremities that have been traumatized • A tiny vesicle or pustule forms initially
• Rapidly develops into a honey-colored crusted plaque that is generally <2 cm in diameter
Nonbullous impetigo
differential diagnosis :
•viral (herpes simplex, varicella-zoster)
• fungal (tinea corporis, kerion)
•parasitic infestations (scabies, pediculosis capitis),
Etiology:
• Staphylococcus aureus • Group A β-hemolytic streptococci (GABHS) • Generally spread from the nose to normal
skin
Bullous Impetigo :
• This is mainly an infection of infants and young children
• Always caused by S. aureus
Ruptured bullous impetigo
Bullous Impetigo
• Flaccid, transparent bullae develop most commonly on skin of the face, buttocks, trunk, perineum, and extremities
• Rupture of bullae occurs easily
• Neonatal bullous impetigo can begin in the diaper area
Bullous Impetigo
Bullous Impetigo
Bullous Impetigo
DIAGNOSIS:
• Cultures of fluid from an intact blister or moist plaque
• Nonbullous impetigo has histopathologic findings similar to those of the bullous variant, except that blister formation is slight
• Nonbullous impetigo has histopathologic findings similar to those of the bullous variant, except that blister formation is slight
Differential diagnosis :
• In neonates:Herpetic infectionEarly scalded skin syndrome
• In older children:Allergic contact dermatitisBurnsErythema multiformePemphigusBullous pemphigoid
COMPLICATIONS: (Very rare)
•Osteomyelitis•Septic arthritis•Pneumonia•Septicemia
•Nephritogenic strains of GABHS may result in acute poststreptococcal glomerulonephritis
TREATMENT :
• Mupirocin (Applied topically 3 times daily for 7–10 days)
• Oral erythromycin ethylsuccinate (30–50 mg/kg/24 hr for 7–10 days)
• Topical fusidic acid • Systemic therapy with a β-lactamase–
resistant oral antibiotic (for patients with widespread involvement)
SUBCUTANEOUS TISSUE INFECTIONS
• The principal determination for soft tissue infections is whether it is non-necrotizing or necrotizing
CELLULITIS:
• Characterized by infection and inflammation of loose connective tissue
• With limited involvement of the dermis and relative sparing of the epidermis
• More common in individuals with lymphatic stasis, diabetes mellitus, or immunosuppression
Etiology :
• Streptococcus pyogenes and S. aureus are the most common etiologic agents
• In neonates, group B streptococci or, rarely, Escherichia coli are the causal organisms
• In patients who are immunocompromised or have diabetes mellitus, a number of other bacterial or fungal agents may be involved
Clinical Manifestations :
• An area of edema• Warmth• Erythema• Tenderness
• Regional adenopathy and constitutional signs and symptoms of fever, chills, and malaise are common
Diagnosis :
• Aspirates from the site of inflammation
• Skin biopsy
• Blood cultures
Treatment :
• Cellulitis in a neonate should prompt a full sepsis
evaluation • β-lactamase-stable antistaphylococcal antibiotic such
as methicillin (vancomycin is another choice)• Aminoglycoside such as gentamicin• Cephalosporin such as cefotaxime
STAPHYLOCOCCAL SCALDED SKIN SYNDROME:
• Occurs predominantly in infants and children younger than 5 yr of age
• Onset of the rash may be preceded by malaise, fever, irritability, and exquisite tenderness of the skin
• Scarlatiniform erythema
accentuated in flexural and
periorificial areas
• The conjunctivas are inflamed and occasionally become purulent
• Circumoral erythema
• Radial crusting and fissuring around the eyes, mouth, and nose
• Nikolsky sign• Initially in the flexures
and subsequently over much of the body surface
May lead to:
• Secondary cutaneous infection• Sepsis• Fluid and electrolyte disturbances
• The desquamative phase begins after 2–5 days of cutaneous erythema
• Healing occurs without scarring in 10–14 days
ETIOLOGY AND PATHOGENESIS :
Phage group 2 staphylococci
Foci of infection include the:
• Nasopharynx
• Less commonly, the umbilicus, urinary tract, a superficial abrasion, conjunctivae, and blood
• The clinical manifestations of staphylococcal scalded skin syndrome are mediated by:
Hematogenous spread, in the absence of specific antitoxin antibody of staphylococcal epidermolytic or exfoliative toxins A or B
DIAGNOSIS :
• Cultures should be obtained from all suspected sites of localized infection and from the blood
• Frozen biopsy specimen of the desquamating epidermis
• Tzanck preparation
TREATMENT :
• Semisynthetic penicillinase-resistant penicillin• Clindamycin (to inhibit bacterial protein (toxin) synthesis)
• The skin should be gently moistened and cleansed
• Emollient • Topical antibiotics are unnecessary
Thanks for your attention