Lecture 17 Skin And Soft Tissue Infections Flashcards
What are different types of SSTIs and the parts of the skin they affect?
Epidermis: erysipelas, impetigo, folliculitis,
Dermis: ecthyma, furuncles, carbuncles,, Superficial Fascia: cellulitis,
SC Tissue: necrotizing fasciitis,
Muscle: myonecrosis
What is cellulitis?
is a rapidly spreading diffuse skin infection, that involves the deeper dermis and SC fat,
infection arises through breaks in the skin,
Predisposing Factors: ones that make skin more fragile or host defense less effective such as edema from venous insufficiency or lymphatic obstruction, pre-existing skin infections, obesity,
most commonly caused by: Group A streptococci, S. aureus, or other streptococci, if non-purulent mostly caused by strep, if purulent S. aureus is more likely,
S&S: systemic sx mild, may have fever, tachycardia, confusion, hypotension, leukocytosis, borders of area aren’t elevated nor sharply demarcated
What is erysipelas?
rapidly spreading diffuse skin infection, affects upper dermis,
infection arises through breaks in the skin,
Predisposing Factors: ones that make skin more fragile or host defense less effective such as edema from venous insufficiency or lymphatic obstruction, pre-existing skin infections, obesity,
most commonly caused by: Group A streptococci,
S&S: edema/swelling, pain, heat, systemic sx mild, may have fever, tachycardia, confusion, hypotension, leukocytosis,
has 2 distinguishing features ⇒ lesions are raised above level of surrounding skin, and there is clear demarcation between involved and uninvolved tissue
What does typical erysipelas treatment look like?
oral tx x 5 days,, active agent against Group A strep, many may cover for MRSA if nasal carriage, purulent drainage, injection drug use, SIRS,
if pt severely compromised with severe infection broad coverage can be used,
if no/Mild systemic sx: Pen VK 300-600 mg QID OR amoxicillin 500 mg TID,
if allergic ⇒ cefuroxime 500 mg BID OR clindamycin 300 mg QID,
Moderate-Severe systemic sx: Pen G 2-4 MU IV Q4-6H OR ampicillin 2 g IV Q6H,
if allergy ⇒ cefazolin 1-2 g IV Q8H OR ceftriaxone 1 g IV QD OR clindamycin 600 mg mg IV Q8H OR vancomycin,
if minimal response at 3 days tx may need to be 7-10 days, reassess for potential switch to oral tx,, *elevation of affected limb very important ⇒ if in leg, elevate higher than hip,
if arm, elevate higher than shoulder
What does typical cellulitis (as well as diabetic foot infections) tx look like?
oral tx x 5 days,
Mild: cloxacillin 500 mg QID OR cephalexin 500-1000 mg QID,
if allergy ⇒ cefuroxime 500 mg BID OR clindamycin 300 mg QID,
Moderate-Severe: cloxacillin 2 g IV Q6H x 5-10 days OR cefazolin 1-2 g IV Q8H x 5-10 days,
if allergy ⇒ ceftriaxone 2 g IV QD OR clindamycin 600 mg IV Q8H or 300 mg QID,
if minimal response at 3 days tx may need to be 7-10 days, reassess for potential switch to oral tx,
*elevation of affected limb very important ⇒ if in leg, elevate higher than hip,
if arm, elevate higher than shoulder
What does tx of recurrent cellulitis look like?
pt with previous attack especially in legs have recurrence rates of 8-20% per year (usually in same area),
attempt to resolve predisposing factors - edema, obesity, toe fissures, venous insufficiency,
prophylactic antibacterials may be considered if 3-4 episodes per year despite attempt to tx predisposing factors ⇒ Pen VK 300 mg BID x 4-52 weeks OR IM benzathine penicillin 1.2 MU Q4W,
if allergy ⇒ azithromycin 250 mg QD OR clarithromycin 500 mg QD OR other
What are risk factors for MRSA?
previous colonization or infection with MRSA, recent hospitalization (particularly if received IV antibacterials), rapid onset/progression, injection drug use,
suspect when ⇒ severe infections compatible with S. aureus, when risk fx for MRSA present, when poor response to beta-lactam tx in individuals with presumed staphylococcal infection
What is tx for MRSA in SSTIs?
Mild-Moderate: clindamycin 150-450 mg QID OR TMP/SMX 1-2 DS tabs BID OR doxycycline 100 mg BID OR linezolid 600 mg BID,
Severe: vancomycin, linezolid, or daptomycin all for 5-10 days
What does follow-up for cellulitis and erysipelas look like?
watch for improved S&S, AEs for tx, worsening S&S,
rate of resolution will depend on severity of infection/extent of damage to skin,
lesions do not have to be completely healed for antibacterials to be stopped
What are diabetic foot infections?
they are when initially uninfected ulcerations that follow minor trauma become complicated particularly when peripheral neuropathy, chronic neuropathic ulcers, or vascular insufficiency occur,
may become cellulitis, soft tissue necrosis, or osteomyelitis with a draining sinus,
prevention very important ⇒ proper foot care, glycemic control
What are organisms involved in diabetic foot infections?
S. aureus and beta-hemolytic strep frequently causative for cellulitis or mildly infected ulcers
, more chronic lesions and those previously treated with antibacterials may also have enterobacterales,, macerated lesions may contain non-enteric Gram - bacilli (ex. P. aeruginosa),
chronic refractory ulcers (especially if gangrenous) can have wide variety of organisms including S. aureus, beta-hemolytic strep, enterobacterales, non enteric Gram - bacilli (ex. P. aeruginosa), enterococci, anaerobes, sometime fungi
What is the management for diabetic foot infections?
surgical debridement (necrotic tissue) and drainage,
wound care,
Antibacterial tx: antipseudomonal coverage not always necessary (P. aeruginosa often a non-pathogenic colonizer), empiric coverage considered if ⇒ topical/warm climate, soaking of feet, failed non-antipseudomonal tx, limb threatening infection,
MRSA coverage if ⇒ current or previous (within 12 months) colonization/infection with MRSA, recent antibacterial use, recent hospitalization
What is the antibacterial management for diabetic foot infections?
Mild or simple cellulitis: tx as per cellulitis ⇒ coverage for S. aureus and GAS,
ulcer, drainage, fistula ⇒ Mild: amox/clav 875 mg PO BID,
if allergy ⇒ cefuroxime 500 mg BID OR doxycycline 100 mg BID + metronidazole 500 mg BID, all for 7-14 days (clinical response),
Moderate-Severe: cefazolin 1-2 g IV Q8H OR ceftriaxone 2 g IV QD + metronidazole 500 mg BID, for 7-14 days (clinical response),
Limb-Threatening: Piperacillin-tazobactam 3.375 g IV Q6H OR meropenem 500 mg IV Q6H + vancomycin, for 2-3 weeks
What is necrotizing fasciitis (pathogens)?
rare aggressive infection that tracks along fascial planes and extends well beyond superficial signs of infection, involves all tissue between skin and underlying muscles (SX tissue),
life threatening infection, requires prompt diagnosis and surgical intervention and antibacterials,
Predisposing Factors: DM, trauma/surgery, immunosuppression, malignancy, injection drug use,
Pathogens: toxin producing GAS, S. aureus, occasionally polymicrobial with mixed aerobic/anaerobic infection mostly from bowel
What are clinical findings in necrotizing fasciitis?
initially pain may be out of proportion to apparent skin lesion,
initial presentation is cellulitis which can advance rapidly or slowly and as progresses patient experiences high fevers with systemic toxicity, disorientation, lethargy,
skin discoloration/necrosis, hemorrhagic bullae, crepitus,
SC tissue have wooden-hard feel
What is antibacterial tx for necrotizing fasciitis?
Empiric: ceftriaxone 2 g IV QD + clindamycin 600-900 mg IV Q8H for 10-14 days,
Polymicrobial or MRSA Suspected: (morbid obesity (BMI >40), groin involvement, foul-smelling wound, recent GI/GU surgery, poorly controlled DM) ⇒ piperacillin-tazobactam 4.5 g IV Q6H x 10-14 days + vancomycin OR linezolid 600 mg IV/PO Q12H
Penicillin Allergy: imipenem 500 mg IV Q6H x 10-14 days + vancomycin OR linezolid 600 mg IV/PO Q12H
if culture proven GAS: Pen G 4 MU IV Q4H x 10-14 days + clindamycin 600-900 mg IV Q8H (clindamycin for inhibition of toxin production)
prophylaxis recommended for close/household contacts of GAS toxic shock syndrome or necrotizing fasciitis pt (or other invasive GAS disease): cephalexin 250 mg QID (or 500 mg BID) x 10 days, pediatrics ⇒ 25-50 mg/kg/day BID-QID x 10 days (max 1 g/day)
