SSTI Flashcards
Normal protecting factors of skin
1) Dry surface - Inhibits bacterial growth
2) Fatty acids
3) Acidic pH (~5.6)
4) Renewal of epidermis - Dead skin cells & bacteria removed from skin surface
5) Low temperature
–> Inhibits excessive bacterial growth & entry into deeper layers
Pathophysiology of SSTIs
1) Penetration of normal skin bacteria into deeper layers
2) Introduction of other bacteria
3) Excess bacteria growth
Predisposing factors
- High bacteria innocula
- Excessive moisture
- Reduced blood supply
- Presence of bacterial nutrients
- Poor hygiene
- Sharing of personal items
How are SSTIs classified?
- Severity/extent
- Depth of infection
- Presence/absence of pus discharge
- Microbiology
- Anatomical site
Impetigo & Ecthyma classification
- Usually managed as outpatient
Severity: Mild
Depth: Uncomplicated
Discharge/ Purulent/Non-purulent
Micriobiology: Primary
Clinical presentation of Impetigo & Ecthyma
Impetigo: Most common in children/face/extremities as fluid-filled vesicles
Ecthyma: Deeper than impetigo, scarring common
Microbiology of Impetigo & Ecthyma
Causative microbes & cultures
Causative microbes:
i) Staph aureus - bullous form caused by S.Aureus
ii) B-hemolytic Streptococci (eg. Strep pyrogens)
Culture:
- Usually treated w/o but can culture if have pus
Impetigo treatment
Topical Mupirocin BD x 5days
Oral antibiotic only if severe cases
Ecthyma treatment
Empiric:
i) Cephalexin/Cloxacillin
ii) Clindamycin (penicillin allergy)
Culture-directed:
i) Pen VK (S. pyrogens)
ii) Cephalexin/Cloxacillin (MSSA)
Duration: x 7days
Risk factors for purulent SSTIs
Close physical contact
Crowded living conditions
Poor personal hygiene
Sharing personal items
Microbiology of Purulent SSTIs
Causative microbes & cultures
Causative microbe: Staph aureus
(Cutaneous abscess may be polymicrobial)
Usually treated w/o culture
Treatment of Purulent SSTIs
I&D
Adjunctive systemic antibiotics if:
- Unable to drain completely/ lack of response
- Extensive disease involving several sites
- Extremes of age
- Immmunosupressed
- Signs of SIRS
Criteria for SIRS
Temp > 38C or < 36C
HR > 90 beats/min
RR > 24 beats/min
WBC > 12 X 10^9 or < 4 x 10^9
Antibiotics Treatment for Purulent SSTIs
Furuncles, carbuncles
MSSA only:
- PO Cloxacillin
- PO Cephelaxin
- IV Cefazolin
MSSA, MRSA:
- PO Clindamycin
- PO Cotrimoxazole
- PO Doxycycline
Duration: 5-7 days (outpatient)
7-14 days (inpatient)
Clinical presentation of Cellulitis vs Erysipelas
Cellulitis: Poorly demarcated area, purulent/non-purulent
- Acute inflmm of epidermis, dermis & sometimes superficial fascia
- Bacteria can invade lymphatic tissue & blood
Erysipelas: Sharply demarcated area with raised border
- Affects up to superficial dermis & lymphatic tissue
Complications of Cellulitis vs Erysipelas
- Bacteremia
- Endocarditis
- Toxic shock
- Glomerulonephritis
- Lymphedema (Buildup of fluid due to blockage of lymphatic system)
- Osteomyelitis (Inflmm/swelling in bone)
- Necrotizing soft-tissue infections
Microbiology of Cellulitis vs Erysipelas
Causative microbes & cultures
Causative microbe:
i) Staph aureus (purulent)
ii) B-hemolytic strep (for Erysipelas)
Cultures:
- Not routinely recommended
- Reasonable if purulent infections after I&D/ immunosuppressed/ SIRS
- -> tissue sample valuable
Treatment of non-purulent Cellulitis/ Erysipelas
Mild: Treat for Streptococcus spp
i) PO Penicillin VK
ii) PO Cloxacillin
iii) PO Cephalexin
iv) PO Clindamycin
Moderate: Treat for Strep/ S.Aureus
1 SIRS criteria –> Treat like mild
2 SIRS criteria
i) IV Cefazolin
ii) IV Pen G
iii) IV Clindamycin
Severe: Treat for Strep/ S.Aureus/ Gram(-)
2 SIRS + hypotension/rapid progression/immunosupressed/comorbidity
i) IV Pip/Tazo
ii) IV Cefepime
iii) IV Meropenem
if MRSA risk factors, add:
- IV Vancomycin
- IV Daptomycin
- IV Linezolid
MRSA Risk factors
i) Immunosupression
ii) Critically ill
iii) Previously failed antibiotics w/o MRSA activity
Treatment of purulent Cellulitis/ Erysipelas
Mild: Streptococcus spp/S. Aureus
i) PO Cephalexin
ii) PO Cloxacillin
iii) PO Clindamycin
if MRSA risk factors, add:
- PO Cotrimoxazole
- PO Clindamycin
- PO Doxycycline
Moderate: Streptococcus spp/S. Aureus
1 SIRS criteria –> Treat like mild
2 SIRS criteria
i) IV Cloxacillin
ii) IV Cefazolin
iii) IV Clindamycin
if MRSA risk factors, add:
- IV Vancomycin
- IV Daptomycin
- IV Linezolid
Severe: Treat for Strep/S.Aureus/Gram(-) including P. aeruginosa
2 SIRS + hypotension/rapid progression/immunosupressed/comorbidity
i) IV Pip/Tazo
ii) IV Cefepime
iii) IV Meropenem
if MRSA risk factors, add:
- IV Vancomycin
- IV Daptomycin
- IV Linezolid
Organism for animal bite wounds
Pasteurella multocida
Organism for human bite wounds
Eikenella corrodens
Organism for oral anaerobes
Prevotella spp, Peptostreptococcus spp
Treatment of cellulitis from bite wounds?
i) Augmentin
ii) Ceftriaxone/Cefuroxime + clindamycin/metronidazole
iii) Ciprofloxacin/Levofloxacin + clindamycin/metronidazole
Pathophysiology of DFI
1) Neuropathy
- Peripheral: Decreased pain sensation & response
- Motor: Motor imbalance
- Autonomic: Increased dryness, cracks & fissures
2) Vasculopathy
- Early artherosclerosis
- PVD
- Worsened by hyperglycemia & dyslipidemia
3) Immunopathy
- Impaired immune response
- Increased susceptibility to infections
- Worsened by hyperglycemia
- -> Ulcer/wound formation
- -> Bacterial colonization/ proliferation/ penetration
- -> DFI
Causative organism of DFI/PU
- Typically polymicrobial
i) Staph aureus & Strep Most common
ii) Gram (-) [Chronic wounds/ Previously treated]
- E.coli, Klebsiella, Proteus
iii) Anaerobes [Ischaemic/ Necrotic wounds]
- Peptostreptococcus spp, Veilonella spp, Bacteriodes spp
Cultures for DFI
Mild: optional
Moderate: Deep tissue cultures after cleansing & before starting antibiotics. Avoid skin swabs
Do not culture uninfected wounds
Treatment of DFI/PU
Mild x 1-2 weeks: Streptococcus spp/S. Aureus (Erythema < 2cm) i) PO Cephalexin ii) PO Cloxacillin iii) PO Clindamycin
if MRSA risk factors, add:
- PO Cotrimoxazole
- PO Clindamycin
- PO Doxycycline
Mod x 1-3weeks
: Strep/S. Aureus/Gram -ve (+- P. aeruginosa)/Anaerobes
(Erythema > 2cm + No signs of systemic infection)
i) IV Augmentin
ii) IV Ceftriaxone ** ( + Clindamycin/Metronidazole)
if MRSA risk factors, add:
- IV Vancomycin
- IV Daptomycin
- IV Linezolid
Severe x 2-4weeks:
Strep/S. Aureus/Gram -ve (P. aeruginosa)/Anaerobes
(Signs of SIRS)
i) IV Pip/Tazo
ii) IV Mereopenem
iii) IV Cefepime ** ( + Clindamycin/Metronidazole)
if MRSA risk factors, add:
- IV Vancomycin
- IV Daptomycin
- IV Linezolid
Adjunctive measures for DFI
Wound care
- Debridement
- “Off-loading” [Supportive shoes]
- Apply dressings that promote a healing environment & control excess exudation
Foot care
- Daily inspection
- Prevent wounds & ulcers
How does Pressure Ulcers come about?
- Moisture
- Pressure (Amount & duration)
- Shearing force
- Friction
Risk factors for pressure ulcers
- Reduced mobility
- Debilitated by severe chronic disease
- Reduced consciousness
- Sensory & autonomic impairment
- Extremes of age
- Malnutrition
Cultures for PU?
- Recommend deep tissue cultures/biopsy specimens
- Avoid skin swabs
Adjunctive measures for pressure ulcers
- Debridement of infected or necrotic tissue
- Local wound care (Normal saline preferred)
- Relief of pressure
(Turn or reposition every 2hrs, also impt for prevention)
