Bacterially Mediated Infections (#9)

Question 1

Impetigo

Answer 1

Etiology: Staph (temperate climates), Strep (tropical climates)

S/S: Macules, vesicles, bullae, pustules, and honey colored crusts that leave red denuded area when removed. Face and other exposed areas most commonly affected

Diagnosis: Gram stain and culture. Rule out other causes such as viral infections, contact derm

Treatment: Topical agents such as bacitracin, mupirocin, retapamamulin. Soaks and scrubs. Wide spread- use cephalexin or doxy.

Prevention: Bleach baths (1/4 to 1/2 cup per 20 liters of water) for 15 minutes. Clean house with bleach. Treat all family members

Question 2

Erysipelas

Answer 2

Usually Grp A Strep

• Superficial cellulitis, involving dermal lymphatics
• Commonly lower leg; unilateral facial
• Painful, often w/ fever, chills

Erysipelas/Cellulitis Treatment: Oral antibiotic for 7-10 days for mild localized cellulitis and erysipelas; Hospitalization and IV antibiotics (e.g.,penicillin) for more severe cases and usually in diabetics; Ceftriaxone for Hib cellulitis in infants; Consider covering for MRSA

Question 3

Cellulitis

Answer 3

Grp A Strep and S. aureus

• Commonly upper extremities in IVDA, lower extremities in adults; H. influenzae type b in infants, buccal location, violaceous
• Blood cultures are negative and no elevated WBC (except w/ Hib, 50% + blood cx, and WBC elevated)

Erysipelas/Cellulitis Treatment: Oral antibiotic for 7-10 days for mild localized cellulitis and erysipelas; Hospitalization and IV antibiotics (e.g.,penicillin) for more severe cases and usually in diabetics; Ceftriaxone for Hib cellulitis in infants; Consider covering for MRSA.

Question 4

erythrasma

Answer 4

Corynebacterium minutissimum

S/S: Intertriginous erythema without satellite lesions, vesiculation, or significant inflammation. Most commonly webspaces of toes; other intertriginous areas

Dx: Coral-red fluorescence from coproporphyrin III

Tx: AlCl 25%, topical clinda/erythromycin, miconazole cream; erythromycin PO 500 mg x 5-7 days

Question 5

pitted keratolysis

Answer 5

Etiology: Due to Corynebacterium or Micrococcus sedentKeratolysis due to enzyme-derived proteolysis of stratum corneum

S/S =

• Punched out pits in stratum corneum, 1-8 mm in diameter, Sweaty, malodorous feet; Pressure sites usually

Tx = AlCl 25%, Topical Abx or, antifungals. Per Fitzpatrick’s: Usually controlled with benzoyl peroxide wash or sanitizing alcohol gel.

Question 6

furuncles/carbuncles

Answer 6

furuncle- Acute, red, hot,tender, nodule or abcess that evolves from staph folliculitis.

Carbuncle- Deeper infection with multiple interconnecting abcesses arising from several hair follicles.

Signs/symptoms/PE: a firm, tender nodule with abcess formation with or without central pustule. A carbuncle is usually a large, inflammatory plaque with multiple pustules.

DX: Gram stain and culture

LAB: Staph Aureus (MSSA, MRSA)

TX: Incision and drainage, plus systemic ABX

Question 7

Felon

Answer 7

An abscess within the compartments of eccrine sweat glands and fat globules in the finger tips

Signs/symptoms: pain, erythema, swelling, abscess on pads of thumb, index finger.

History: penetrating injury, splint, paronychia

PE: soft tissue infection of pulp space of distal phalanx

DX/LAB: culture pus from abscess

TX: Incision and drainage

Question 8

toxic shock syndrome

Answer 8

Signs/symptoms: Rapid onset of fever >38.9, hypotension, watery diarrhea, multisystem organ failure and rash.

PE: Blanching erythema, “painless sunburn”. Diffuse macular erythematous rash and nonpurulent conjunctivitis. **Mucous membrane involvement, ulcers in mouth, esophagus, vagina.

Desquamation in recovery phase: begins one week after onset of rash. Torso, face, extremities, palms/soles, fingers/toes.

DX: based on clinical presentation.

LAB: Toxin producing S. aureus can be identified from cultures from mucosal and wound sites. blood cultures will be negative because source is the toxin.

TX: Rapid rehydration, vasopressors, Systemic abx to treat infection (UpToDate recommends IV Clindamycin plus oxacillin or nafcillin)

Question 9

Scalded Skin Syndrome

Answer 9

Signs/symptoms: Neonates and young children

PE: Localized form: Intact flaccid purulent clustered bullae in intertriginous area.

Generalized form: Macular scarlatiniform rash (sandpaper like scarlet fever), then skin gets tender. Skin resembles a wet tissue and can be removed by gentle pressure (NIKOLSKY SIGN).

****No Mucous membrane involvement

DX: Bacterial culture

LAB: S. aureus.

TX: Systemic Abx. Superficial areas heal within 3-5 days with no scarring

Question 10

Stevens-Johnson syndrome (SJS) and Toxic epidermal necrolysis (TEN)-

Answer 10

Signs/symptoms: 1-3 week onset after drug exposure.

Fever, malaise, arthralgias 1-3 days prior to eruption, skin tenderness, conjunctival burning/itching, painful mouth lesions, photophobia

PE: Initially on face and extremities. Exanthematic macular areas of necrotic epidermis that enlarge and coalesce, sheet like loss of epidermis. Raised flaccid blisters that spread with lateral pressure (NIKOLSKY SIGN). Full thickness epidermal detachment yields oozy dermis. Painful lesions on mucus membranes, 85% have conjunctival lesions.

DX: fever, distress due to pain, tachycardia, acute renal failure, sloughing of epithelium with erosions in GI and respiratory tract

LAB: Neutropenia = poor prognosis, serum urea increased, serum bicarb decreased. Sin biopsy: Necrosis of basal keratinocytes throughout epidermis.

TX: Early diagnosis and withdrawal of suspected drug. Treatment in ICU.

Replace fluids, systemic glucocorticoids if early in the disease, IV immunoglobin treat eye lesions with erythromycin ointment

Regrowth of epidermis is completed in >3 weeks.

Remember: **SJS:<10% epidermal detatchment

SJS: 50% cases associated with drug exposure, the rest are due to chemicals, mycoplasma pneumonia, viral infection, immunizations.

TEN: >30% epidermal detachment

TEN: 80% association with specific medications

TEN: higher fever than SJS