IC14 SSTI Flashcards
Types of SSTI and their anatomical sites
epidermis - impetigo
dermis - ecthyma, erysipelas
hair follicles - furuncles, carbuncles
SC fat - cellulitis
fascia - necrotising fasciitis
muscle - myositis
protective mechanisms of skin
- continuous renewal of epidermal layer (shedding of keratocytes and skin microbiota)
- sebaceous secretion (inhibit bacteria/ fungi growth)
- normal commensal skin microbiome (prevent colonisation and overgrowth of bacteria)
best defense against SSTI
how does SSTI occur
Best defense against SSTI is intact skin
Majority of SSTIs result from the disruption of normal host defenses which allows overgrowth and invasion of the skin by bacteria
RF of SSTI
- disruption of skin barrier
- traumatic: burns, laceration, bites
- non traumatic: ulcers, tinea pedis
- impaired venous and lymphatic drainage: venectomy, obesity
- peripheral artery disease
- conditions that predispose to infection (DM, cirrhosis, neutropenia, HIV, immunosuppressed)
- hx of cellulitis
prevention of SSTI
- manage predisposing risk factors
- maintain skin integrity (good wound care, prevent dry crack skin, tx of tinea pedis)
- acute traumatic wound -> do source control (irrigate and debridement)
diagnosis of SSTI by
based on hx and physical examination
- hx taking and recognising RF
when is culture needed for SSTI?
how to collect?
- mild superficial: no need
- moderate, severe: may need
avoid wound swabs
collect deep in wound after surface cleansed
collect from base of closed abscess
collect by curettage rather than swab/ irrigation
blood culture only for very severe cases with systemic sx/ immunocompromised pt
impetigo: pathogens
staph
strep
bullous form caused by toxin producing strains of S.aureus
ecthyma: pathogens
grp A strep (strep pyrogenes)
non purulent (cellulitis, erysipelas): pathogens
beta hemolytic strep (grp A strep most common)
Staph aureus (less common)
water exposure: pseudomonas, aeromonas, vibrio
purulent (furuncles, carbuncles, skin abscess, purulent cellulitis): pathogens
Staph aureus (MSSA/ MRSA)
- HA-MRSA more common in SG
beta hemolytic strep (some)
gram negative, anerobes (skin abscess involving the perioral, perirectal or vulvovaginal areas)
is CA-MRSA related to HA-MRSA
no, genetically different
susceptible to oral non betalactams (clindamycin, cotrimoxazole, doxycycline)
RF for CA-MRSA
- contact sports, military personnel, intravenous drug abusers (IVDA), prison inmates
- overcrowded facilities, close contact and lack of sanitation
definition of HA-MRSA
MRSA infection that occurs:
- >48hrs following hospitalisation
- (outside of hospital) within 12 mths of exposure to healthcare
RF for HA-MRSA in SSTI
- antibiotic use
- recent hospitalisation or surgery
- prolonged hospitalisation
- intensive care
- hemodialysis
- MRSA colonisation
- proximity to others with MRSA colonisation or infection
abx tx for impetigo and ecthyma
(impetigo: mild, limited lesions)
topical mupirocin 2% BD x5d
(impetigo, ecthyma: multiple lesions)
PO cloxacillin
PO cephalexin
PO clindamycin
5-7 days
culture directed abx tx for impetigo and ecthyma
(S.pyrogenes)
PO pen V
PO amoxicillin
(MSSA)
PO cloxacillin
PO cephalexin
5-7 days
tx of purulent SSTI (when to give abx)
I&D
abx given when:
- unable to drain completely
- lack response to I&D
- immunocompromised
- moderate/ severe purulent SSTI with signs of systemic illness (SIRS criteria, 2 out of 4)
- temp >38, <36
- HR >90
- RR >24
- WBC >12, <4
abx for purulent SSTI (mild moderate severe)
(mild, eg stye): I&D, warm compress
(moderate, with systemic sx): I&D and
PO cloxacillin
PO cephalexin
PO clindamycin (pen allergy)
(severe) I&D and
IV cloxacillin
IV cefazolin
IV clindaymcin
IV vancomycin (if need cover MRSA)
(MRSA RF)
PO cotrimoxazole, doxycycline, clindamycin
IV vancomycin, daptomycin, linezolid
(empiric gram -‘ve, anaerobes) eg abscess
IV amoxicillin-clavulanate
IV piperacillin-tazobactam
IV carbapenems (for ESBL strains)
5-10 days
abx for non-purulent SSTI (mild moderate severe)
mild (no systemic sx of infection)
- PO pen V
- PO amoxicillin
- PO cloxacillin
- PO cephalexin
- PO clindamycin (high risk of C.difficle, avoid if possible, unless cover anaerobes or sever pen allergy)
moderate (with systemic sx, some pus, to include MSSA) -> give IV
- IV cloxacillin
- IV cefazolin
- IV clindamycin (pen allergy)
(water exposure) ADD ciprofloxacin to cover pseduomonas, vibrio, aeromonas
severe (eg necrotising infection) - broad coverage
- IV piperacillin-tazobactam
- IV cefepime
- IV meropenem
(MRSA RF) add
IV vancomycin, daptomycin, linezolid
5-10 days
why should clindamycin be avoided if possible
high risk of C.difficle
used only to cover anaerobes or severe pen allergy
non-pharmalogical management of SSTI
rest and limb elevation (drainage of edema and inflammatory substances)
treat underlying conditions
Monitoring in SSTI
- improvement after 48-72hrs after initiation of abx
- no progression of lesions or develop complications
- switch to PO if getting better
- reassess indication/ choice of abx if pt fails to respond in 2-3 days
- repeat culture not required
- no ADR and allergies
topical abx for SSTI
mupirocin 2% ointment
- controversial, for mild cases that are self limiting
- used for MRSA decolonisation
