Bacterial infections

Folliculitis

• Hair follicle infection.

• Commonly caused by staphylococci.

• Mechanical irritation is also a factor, such prolonged sitting (truck driver folliculitis) or tight clothes (blue jean folliculitis); exposure to cutting oils is another factor.

• Superficial Folliculitis (Bockhart impetigo)

• Clinical features:

Tiny pustules with erythematous border localized in superficial aspect (infundibulum) of follicle. In children, usually scalp; in adults, trunk, buttocks, thighs, beard area.

• Treatment

Topical antiseptics or antibiotics (fusidic acid or mupirocin). If lack of response, systemic antibiotics (penicillinase-resistant penicillins or first-generation cephalosporin for 7–10days).

Furuncle• Deep follicular infection that starts as firm

red nodule which rapidly becomes painful and then, after a few days, fluctuant. Heals with scarring over weeks.

• Neck, face, axillae, groin, upper back.

• In some individuals, chronic-recurrent. Systemic sepsis in immunocompromised.

Treatment

• Avoid manipulation; topical antiseptics, systemic antibiotics (penicillinase-resistant penicillin or first-generation cephalosporin for 7–10days).

• Solitary furuncle: Systemic antibiotics; incision and drainage after several days when fluctuant.

• Recurrent furuncles (furunculosis): Systemic antibiotics (often clindamycin 300mg q.i.d. for 7–10days), search for predisposing factors (diabetes mellitus, immunosuppression, perineal or nasal carriage of Staphylococcus aureus).

Carbuncle• Extensive infection of a group of contagious

follicles• Staph. aureus• Middle or old age• Predisposing factors

– Diabetes– Malnutrition– Severe generalized dermatoses– During prolonged steroid therapy

• Painful, hard lump

• Suppuration begins after 5-7 days

• Pus discharge from multiple follicular

orificies

• Necrosis of intervening skin

• Large deep ulcer

• Constitutional symptoms

Sycosis barbae• Exclusively in males after puberty

• Staph. aureus

• Pustules surrounded by erythema in beard region

• Trauma

• Upper lip and chin

Cellulitis and erysipelas•Cellulitis: Is an infection of

subcutaneous tissues.

•Erysipelas: Due to infection of the dermis & upper subcutaneous tissue.

•Group A β-hemolytic Streptococci.

•Erythema, heat, swelling and pain or tenderness.

•Fever and malaise which is more severe in erysipelas.

• In erysipelas: blistering and hemorrhage.

•Lymphangitis and lymphadenopathy are frequent.

•Edge of the lesion: well demarcated and raised in erysipelas and diffuse in cellulitis.

Complications:

• Recurrences may lead to lymphedema.

• Subcutaneous abscess.

• Septicemia.

• Nephritis.

Treatment

•Systemic antibiotics, especially penicillin, e.g. benzyl penicillin 600-1200 mg IV/6 hrs or cephalosporins.

•Rest, analgesics.

Impetigo •Acute contagious skin infection caused

mostly by Staph. aureus and Strept. Pyogenes.

•Affects children mainly esp. in summer times.

•Nonbullous impetigo: – Caused by staph., strept. or both organisms.Bullous impetigo:– Caused by Staph. aureus.

Nonbullous impetigo

• A thin-walled vesicle on erythematous base,that soon ruptures & the exuding serum driesto form yellowish-brown (honey-color) cruststhat dry & separate leaving erythema whichfades without scarring.

• Regional adenitis with fever may occur insevere cases.

Complication

• Post-streptococcal acute glomerulo-nephritis “AGN” especially in cases due to Strept. pyogenes M. type 49.

Bullous impetigo•Age: all ages, but commoner in childhood &

newborn (impetigo neonatorum).

•Site: face is often affected, but the lesions may occur anywhere, including palms & soles.

•The bullae are less rapidly ruptured (persist for 2-3 days) & become much larger. The contents are at first clear, later cloudy. After rupture, thin, brownish crusts are formed.

Treatment • Systemic antibiotics are indicated especially in

the presence of fever or lymphadenopathy, in extensive infections involving scalp, ears, eyelids or if a nephritogenic strain is suspected, e.g. penicillin, erythromycin & cloxacillin.

• Azithromycin 500 mg daily for 3 days in adults.

• In erythromycin-resistant S. aureus: amoxicillin + clavulanic a. 25 mg/kg/day.

Ecthyma• Streptococcal & staph• Common in children • Begin as small bullae or pustules on

erythematous base followed by formation of adherent dry crusts beneath which ulcer present

• Indurated base • Heals with scar and pigmentation• Buttocks, thighs and legs, commonly affected

Paronychia

• Acute or chronic

• Acute: Staph. aureus chronic: Infectious, allergic, dermatoses.

• Erythematous swelling of proximal and lateral nail fold

• Painful

Staphylococcal scalded skin syndrome (Ritter’s Disease)

• Exotoxin of staph (Phage Group II strains 71

and 55)

• Toxin mediated acantholysis

• Occult staph. upper respiratory tract

infection or purulent conjunctivitis

• Infants and children

• Tender red skin

• Denuded skin• Heals 7 - 14 day• Don’t grow Staph. from blister fluid• Complication 2%

– Cellulitis– Pneumonia

Treatment

• Systemic penicillins and cephalosporins.

• Topical emollients

• Fluid and electrolyte replacement.