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