Bacterial Skin Infections Flashcards
Cellulitis: prevalence
very common infection
occurs in up to 3% of ppl per year
Cellulitis:
results from what?
presents how?
more commonly found where?
results from infection of dermis, (U) enters through a wound, insect bite or fungal infection (e.g. tinea pedis)
spreading erythematous, non-fluctuant tender plaque
more (C) found on LOWER LEG
streaks of lymphangitis may spread from the area to the draining of lymph nodes
risk factors for cellulitis (5)
- local trauma (bug bites, laceration, abrasion, puncture wound)
- underlying skin lesion (furuncle, ulcer)
- inflammation (local dermatitis, radiation tx)
- pre-existing skin infection (impetigo, tinea pedis)
- 2* cellulitis from blood-born spread of infection, or from direct spread of subadjacent infections (fistula from osteomyelitis) is rare
Cellulitis etiology
80%: GRAM POSITIVE
group A strep & staph aureus are most (C) causal pathogens
if unusual exposures (P): Pasteurella multocida (animal bites) Eikenella corrodens (human bites)
the next best step in management of cellulitis?
begin abx immediately w/coverage for gram positive bacteria
un-tx cellulitis may lead to
sepsis & death
Tx of outpatients w/nonpurulent cellulitis
empirically tx for beta-hemolytic streptococci (group A strep)
(some clinicians choose an agent that is also effective against S. aureus)
Tx of outpatients with purulent cellulitis (purulent drainage or exudate in the absence of a drainable abscess)
empirically tx for community-associated MRSA
Tx of cellulitis for unusual exposures
cover for additional bacterial species likely to be involved
Cellulitis tx (general)
monitor pts closely, revise tx if poor response to initial treatment
elevate the involved area
tx tinea pedis if present
for hospitalized pts: empiric therapy for MRSA should be continued
cultures from abscesses & other purulent Skin & Soft Tissue Infections (SSTIs) are recommended in patients tx with abx therapy
healthcare-associated MRSA (HA-MRSA) & community-acquired MRSA (CA-MRSA) risk factors include: (11)
- Abx use
- prolonged hospitalization
- surgical site infection
- intensive care
- hemodialysis
- MRSA colonization
- proximity to others w/MRSA colonization or infection
- skin trauma
- cosmetic body shaving
- congregated facilities
- sharing equipment that is not cleaned or laundered between users
Clindamycin:
dosage
comments
600 mg/kg IV q8h
300-450 mg PO TID
- excellent tissue & abscess penetration
- risk for C. difficile
- inducible resistance in MRSA
Trimethoprim-Sumfamethoxazole (TMP/SMX):
dosage
comments
1 or 2 double-strength tablets PO BID
unreliable for S. pyogenes (will need to combine w/amoxicillin to cover for group A strep)
Doxycycline:
dosage
comments
100 mg PO BID
unreliable for S. pyogenes (will need to combine w/amoxicillin to cover for group A strep)
DO NOT USE in KIDS <8 yo
Linezolid:
dosage
comments
600 mg IV q12h
600 mg PO BID
expensive
no cross-resistance w/other abx classes
Vancomycin:
dosage
comments
1 g IV q12h
parenteral DOC for tx of infections caused by MRSA
Erysipelas: def main pathogen distribution presentation
superficial cellulitis w/marker dermal lymphatic involvement (causing edematous or raised skin)
group A strep=main pathogen
(U) affects lower extremities & the face
pain, superficial erythema, plaque-like edema w/a sharply defined margin to normal tissue
plaques may develop overlying blisters (bullae)
may be a/w high white count
may be preceded by chills, fever, HA, V, joint pain
erysipelas: example presentation
large, shiny erythematous plaque w/sharply demarcated borders located on the leg
uncomplicated erysipelas: most appropriate tx
oral abx
immediate empiric abx therapy should be started (cover most common pathogen-Streptococcus)
monitor pts closely & revise therapy if there is poor response to initial tx
elevation of the involved area
tx tinea pedis if present
Skin Abscess:
description
&
presentation
collection of pus within the dermis & deeper skin tissues
painful, tender, fluctuant & erythematous nodules
often surmounted by a pustule & surrounded by a rim of erythematous edema
spontaneous drainage of purulent material may occur
Skin abscess: next best management
REQUIRE incision & drainage (TOC)
and
offer HIV test (to pts w/risk factors, such as IVDU)
When are abx recommended for abscesses? (8)
when a/w:
- severe or extensive dz
- rapid progression in presence of associated cellulitis
- signs & sxs of systemic illness
- associated comorbidities or immunosuppression
- extremes of age
- abscess in difficult to drain area (e.g. face, hand or genitalia)
- associated septic phlebitis
- lack of response to I&D alone
abscesses REQUIRE
INCISION & DRAINAGE
-most experts recommend irrigation, breaking or loculations & packing following I & D
-WOUND CULTURES should always be sent
recommend abx in pts with
multiple lesions, extensive surrounding cellulitis, immunosuppression, risk for MRSA or systemic signs of infection
