SKIN INFECTIONS
meduploader - 05-12-09 06:01

Impetigo : superficial bacterial infection – up to epidermis – honey colored crusted lesions
So superficial  weeping, crusting, oozing.
Strep . pyogens & Staph. Aureus ( bullous impetigo )
Specific microbiological diagnosis is rarely made to necessary.
Tx : topical Mupirocin or bacitracin . Mupirocin  better activity against MRSA
Severe disease: oral dicloxicillin or cephalexin
Community acquired MRSA: TMP/SMX, clindamycin is sometimes useful.
Penicillin allergy: Rash: cephalosporin are safe
Anaphylaxis: macrolides (azithro, clarithro) or clindamycin
Severe infection with anaphylaxis: vancomycin, linezolid, daptomycin.

Erysipeal s : both dermis & epidermis involve – bilateral , shiny red , edematous Tender lesion , fever , chills , bacteremia.
Strep. Pyogens . Specific microbiological diagnosis is rarely made.
Tx : oral dicloxacilin or cephalexin. Topical antibiotics are useless.
If organism confirmed GABH Streptococci  penicillin VK

Folliculitis , Furuncles , Carbuncles :
Staphylococcus
Folliculitis  infection of hair follicle
Furuncles  collection of infected material around hair follicle
Carbuncles  several furuncles become confluent in to a single lesion
- Hot tub folliculitis  Pseudomonas
Treatment : Folliculitis  mupirocin .
Furuncle & carbuncles  Systemic anti-staphylococcal antibiotics .

Dermatophyte Infection :
Microsporum ,Trichophyton , Epidermophyton .
Microsporum – Skin , Hair , Nail
Trichophyton - Hair , Nail
Epidermophyton – Skin , Nail
Best initial test: 10 % KOH preparation
Most accurate test: Culture
Usually annular lesions expand peripherally and clear centrally .
Treatment: only skin ( curis , pedis , corporis )  Topical ( Miconazole ) .
Hair / Nail (capitis , unguium)  Oral Terbinafine / Itraconazole
Finger nail  6 weeks oral Tx . - Toe nail  12 weeks oral Tx
Gresiofulvin is used in pediatric population. (Terbinafine is not approved by FDA in pediatric population)

Cellulitis
Inflammation of skin and underlying subcutaneous tissues – can be infectious or non infectious.
Commonest causes – group A streptococci (S.pyogenes) and S.aureus.
Rx – usually a cephalosporin such a cephalexin can be used.
If allergic to penicillin, use clindamycin.
If MRSA is suspected, use oral drugs for mild/ moderate cellulitis such as Bactrim, Doxycycline, Clindamycin or quinolone. For severe MRSA cellulitis, use Vancomycin or Tigecycline IV.
If resistant to Vanco, use Linezolid
Emperically, treat patients with moderate to severe cellulitis with risk factors for MRSA infection:
Recent antibiotic use
Recent hospitalization
Hemodialysis
IV drug use
Diabetes
Previous MRSA infection or colonization
In patients with recurrent MRSA soft tissue infections, consider NASAL CARRIAGE
Culture the nares of patients with recurrent infection who are suspected of carrying MRSA.
Treat nasal carriers with mupirocin to the nares twice a day for 7 days
Cellultis from Bites
Pasteurella multocida – etiology in cat bites and rarely, dog bites. Rx – Amoxicillin/clavulanate
Eikenella cordans – human bites
Capnocytophaga tonsurans – cellulitis, disseminated infection seen in asplenic patients after Dog bites.

Necrotizing Fascitis
- Infection of the fascial planes resulting in the death of the affected tissues.
Skin color – blue-black (Black necrotic eschar may be seen at the borders of the affected areas). Crepitance at the site, Fever, malaise and leucocytosis can be seen
Common bugs – Group A strep, S.aureus, C.Perfringens Rx – Aggressive debridement + Clindamycin.
Rare causes – Vibrio vulnificus ( clue : necrotizing fascitis after immersion in warm salt water) Rx - Tetracycline
Diagnosis – mainly clinical, however in early cases CT may be obtained. Finding of gas or inflammatory stranding on CT is very suspicious of necrotizing fascitis.

Differentiate simple cellulitis from skin changes associated with a deeper infection, such as necrotizing fasciitis or gas gangrene, in patients with:
A rapid increase in lesion size
Evolution of bullous lesions
Reddish-purple coloring of the skin
Systemic toxicity (Hypotension, altered mental status)
Pain out of proportion to the clinical findings (extreme local tenderness)

Ecthyma Gangrenosum
Caused by P.aeruginosa/ can be associated with pseudomonas septicemia ( obtain blood cultures and local cultures).
Usually affects critically ill and immunocompromised hosts – AIDS, Steroid use, Cancer, Chemotherapy.
Characteristic lesions ? hemorrhagic pustules or infracted-appearing areas with surrounding erythema that evolve into necrotic ulcers surrounded by erythema
Rx with antipseudomonal antibiotic