Cutaneous Bacterial Infections

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

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 infection
Early scalded skin syndrome
In older children:
Allergic contact dermatitis
Burns
Erythema multiforme
Pemphigus
Bullous 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

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Cutaneous Bacterial Infections

by Nargess Tavakoli on Dec 31, 2008

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