Purulent and Non-Purulent SSTIs

risk factors for community-acquired MRSA infections:

children, health care professionals, military personnel

risk factors for necrotizing fascitis:

alcohol abuse, sports participation, trauma (including surgery), poor nutrition

risk factors for hospital-acquired MRSA infections:

DM, dialysis, long-term care, long-term intravascular access, prolonged hospitalization

which bacteria cause most SSTIs?

S.aureus and b-hemolytic streptococcus

what organisms less frequently cause SSTIs?

gram-negative organisms, anaerobes, yeast and mixed infections

which infections effect the epidermis?

erysipelas, impetigo, folliculitis

which infections effect the dermis?

ecthyma, furunculosis, carbunculosis

which infections effect superficial fascia

cellulitis

which infections effect subcutaneous tissue

necrotizing fasciitis

which infections effect deep fascia (muscle)?

myonecrosis (clostridial and nonclostridial)

clinical presentations of SSTIs

erythema, swelling, warmth, induration, pain/tenderness to palpation, draining wound

signs and symptoms of systemic SSTI infections

fever/chills, diaphoresis, malaise, and elements of SIRS criteria

how to treat severe nonpurulent infections

emergent surgical inspection/debridement and empiric antibiotics (vancomycin + piperacillin/tazobactam)

how to treat severe nonpurulent infections after culture and sensitivities have been determined?

defined antibiotics (necrotizing infections)

antibiotic for severe nonpurulent SSTIs caused by monomicrobial streptococcus pyogenes

penicillin + clindamycin

antibiotic for severe nonpurulent SSTIs caused by clostridial sp.

penicillin + clindamycin

antibiotic for severe nonpurulent SSTIs caused by vibrio vulnificus

doxycycline + ceftazidime

antibiotic for severe nonpurulent SSTIs caused by aeromonas hydrophila

doxycycline + ciprofloxacin

antibiotic for severe nonpurulent SSTIs caused by polymicrobials

vancomycin + piperacillin/tazobactam

treatment for moderate nonpurulent SSTIs

intravenous antibiotics

antibiotic options for moderate nonpurulent infections

penicillin or ceftriaxone or cefazolin or clindamycin

treatment for mild nonpurulent SSTIs

oral antibiotics

oral antibiotic options for mild nonpurulent infections

penicillin VK or cephalosporins or dicloxacillin or clindamycin

empiric treatment for severe purulent SSTIs

vancomycin or daptomycin or linezolid or telavancin or ceftaroline

defined MRSA treatment for severe purulent SSTIs

vancomycin or daptomycin or linezolid or telavancin or ceftaroline

defined MSSA treatment for severe purulent SSTIs

nafcillin or cefazolin or clindamycin

empiric treatment for moderate purulent SSTIs

TMP/SMX or doxycycline

defined treatment for moderate purulent SSTIs caused by MRSA

TMP/SMX

defined treatment for moderate purulent SSTIs caused by MSSA

dicloxacillin or cephalexin

what should be done for all severities of purulent SSTIs

incision and drainage

what should be done for severe and moderate purulent SSTIs

culture and sensitivities

what is a cutaneous abscess

collection of pus within the dermis and deeper skin tissues

clinical presentation of cutaneous abscesses

painful, fluctuant red nodules, often topped with pustule, rim of erythematous swelling

define furuncle (boils)

infection of single hair follicle

define carbuncle

collection of infected follicles

diagnostic methods for purulent SSTIs

gram stain and culture of pus/exudates are recommended but not required for treatment.

when are gram stains and cultures of pus highly recommended

in impetigo

the majority of purulent SSTI infections are caused by:

staphylococcus aureus (MSSA, MRSA)

which type of purulent SSTI may spontaneously rupture and drain?

furuncles

which purulent SSTIs require incision and drainage?

cutaneous anscesses, large furuncles and carbuncles

T/F: gram stain and culture of pus are recommended if incision and drainage is performed

true

when do purulent SSTIs need antiobiotics?

if patient has systemic signs of infection, is immunocompromised, has multiple abscesses, or does not respond to incision and drainage

duration of therapy for purulent SSTIs

5-10 days of therapy following I & D

define mild purulent SSTIs

no systemic signs of infection.de

define moderate purulent SSTIs

systemic signs of infection but hemodynamically stable

define severe purulent SSTIs

failed incision/drainage + PO antibiotics or has multiple systemic signs and acute hypotension/organ dysfunction or is immunocompromised

systemic signs of infection:

temperature (> 38 degrees Celsius), tachycardia (HR > 90 beats/min), tachypnea (RR > 24 breaths/min), abnormal white blood cell count (>12,000 or < 400 cells/microliter)

what does SIRS stand for

systemic inflammatory response syndrome

SIRS criteria

temp > 38 degrees celsius or < 36 degrees celsius, tachypnea > 24 breaths/min, tachycardia > 90 beats/min, or WBC > 12,000 or < 4,000 cells/microliter)

severe purulent SSTI diagnosis based on SIRS criteria

at least 2 of the criteria or an extreme of one

moderate purulent SSTI diagnosis based on SIRS criteria

substantial inflammation (pain ± edema) ± borderline SIRS criteria

IV antibiotics for MRSA (empirically)

vancomycin, daptomycin, ceftaroline, dalbavancin/oritavancin

oral antibiotics for MRSA (empirically)

TMP/SMX, doxycycline, linezolid

IV antibiotics for MSSA (de-escalate)

ampicillin/sulbactam, nafcillin/oxacillin, cefazolin

oral antibiotics for MSSA (de-escalate)

amoxicillin/clavulanate, dicloxacillin, cephalexin, clindamycin (also IV)

which antibiotics are useful but not always reliable for MRSA empirically?

clindamycin and levofloxacin

which antibiotic is usually the first line empiric antibiotic for severe purulent SSTIs

vancomycin IV

dosing points of vancomycin

dosing range based on institutional guidelines, generally ends up being 15 mg/kg q12h (interval adjusted based on CrCl), and round dose to the nearest 250 mg increment

monitoring for vanco IV

trough level if therapy expected to be greater than 3-5 days, assess trough (10-15 mcg/ml) generally adequate for SSTIs, target of 400-600 AUC/MIC

ADRs for vanco

infusion related reactions and renal dysfunction (nephrotoxicity)

which infections are non-purulent SSTIs

cellulitis/erysipelas

classic signs of non-purulent SSTIs

red, warm, swollen, painful

erysipelas meanings:

limited more so to upper dermis, cellulitis of face only, and synonym to cellulitis

risk factors for non-purulent SSTIs include

dry skin, fragile skin, obesity, previous skin trauma, previous cellulitis edema from venous insufficiency, tinea pedis (athlete’s foot)

when do non-purulent SSTIs occur?

when bacteria invades the deeper skin tissues

the majority of non-purulent cellulitis is caused by

streptococcus species (Group A “flesh-eating bacteria,” Groups B,C,F, and G)

a subset of severe cellulitis (including hospitalized) can be caused by:

S. aureus

non-purulent SSTI treatment:

antibiotics

T/F: drainage and cultures are recommended for typical cases of cellulitis

false

when would cultures/drainages be used for non-purulent SSTIs?

immunodeficiency or cancer/chemotherapy

when are blood cultures recommended even though they rarely grow

for non-purulent SSTIs - can be significant if there is growth

define severe non-purulent SSTI classification

failed PO antibiotics or multiple systemic signs + acute hypotension/organ dysfunction or immunocompromised or signs of deeper infection (i.e. bullae, skin sloughing)

oral antibiotic options for streptococcus

penicillin VK, amoxicillin, amox/clav, cephalexin, clindamycin (for beta lactam allergies)

which antibiotics are not reliable for strep?

doxycycline and bactrim

IV options for strep

penicillin G, cefazolin, ceftriaxone, and clindamycin (BL allergies)

IV options for strep if patient has severe penicillin allergies

clindamycin, vancomycin, linezolid, or daptomycin

duration of therapy for mild cellulitis

5 days usually sufficient as long as patient responds

duration of therapy for moderate to severe cellulitis (hospitalized)

10-14 days - possibly longer in difficult to treat cases

what is necrotizing fascitis

deep infection involving the superficial fascia comprising all tissue between skin and muscles

what is Fournier’s Gangrene?

necrotizing infection of genitalia, involves the scrotum and penis or vulva, and diabetes is a strong risk factor

monomicrobial causing agents in necrotizing fascitis

S.pyogenes (group A “flesh eating” strep), S. aureus, and clostridium spp.

polymicrobial causing agents in necrotizing fascitis

mixed aerobic/anaerobic flora

what are the 4 clinical settings most often associated with polymicrobial necrotizing fascitis?

abdominal trauma/surgery, decubitus ulcers, IVDU (injection sites), and spread from genital site

how does microbial invasion of subcutaneous tissues occur in NF?

external trauma, direct spread from a perforated viscus, or from a hetergenous source

how to symptoms progress in NF?

Skin becomes more tense and red with indistinct margins, local pain is replaced by numbness, skin then becomes pale, then mottled/purple looing, and finally gangrenous. If there are gas-forming bacteria present, air under the skin (crepitus) may be palpitated

what are the most important factors impacting patient survival of NF?

early diagnosis and adequate debridement

clinical presentation of NF

severe systemic symptoms (fever, altered mental status), ast temporal progression, pain out of proportion, edema and tenderness beyond the redness, “wooden-hard induration” of subcutaneous tissue, crepitus, and skin necrosis

what would CT scans or MRIs show for NF

may show gas in soft tissues, edema along fascia

T/F: NF is a surgical emergency

true

treatment for NF

SURGERY!!!! blood cultures should also be sent as well as deep tissue cultures taken at the time of surgery, broad spectrum antibiotics empirically started and can be de-escalated based on culture results, multiple surgical interventions often required

broad spectrum regimens for NF

vanco + P/T, vanco + meropenem or imipenem or doripenem, vanco + cefepime + metronidazole or clindamycin, vanco + ciprofloxacin + metronidazole or clindamycin

which antibiotics used in NF cover gram negatives

P/T, meropenem, imipenem, doripenem, cefepime, and ciprofloxacin

which antibiotics used in NF cover anaerobes

P/T, meropenem, imipenem, doripenem, metronidazole, and clindamycin

how long should antibiotics be used for NF?

continue until debridement is no longer needed, patient is clinically improved, and afebrile for 48-72 hours