1. high bacteria innocula 2. excessive moisture 3. reduced blood supply 4. presence of bacteria nutrients 5. poor hygiene 6. sharing of personal items

SSTI Flashcards by vernice ang

treatment of mild impetigo

topical antibiotics eg:

- mupirocin BD x 5/7

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empiric treatment of severe impetigo/ all ecthyma

cephalexin 250-500mg PO QDS* x1/52
cloxacillin 250-500mg PO QDS x1/52
(penicillin allergy): clindamycin x1/52

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culture directed treatment of severe impetigo/ all ecthyma

S pyogenes: penicilin VK 250-500mg PO QDS x1/52

MSSA:

cephalexin 250-500mg PO QDS* x1/52
cloxacillin 250-500mg PO QDS x1/52

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mainstay of treatment for purulent SSTI

incision and drainage (I&D)

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identify and treat mild, non purulent cellulitis/erysipelas

no signs of systemic infections (SIRS)
cover: strepto spp

treatment (PO)

Penicillin VK
Cloxacillin
Cephalexin
Clindamycin

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identify and treat moderate, non purulent cellulitis/erysipelas

org to cover: strept +staph
if 1 SIRS: PO antibiotic
1. Penicillin VK
2. Cloxacillin
3. Cephalexin
4. Clindamycin

if >2 SIRS or PO Tx fail: IV

Cefazolin
Penicillin G
Clindamycin

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identify and treat severe, non-purulent cellulitis/erysipelas

org to cover: strept + staph+ gram neg (p. aeruginosa)

if >2 SIRS + BP<100-60/ rapid progression/immuno/comorbidities : IV

Pipe-Tazo
Cefepime
Meropenem

MRSA risk factor: (immuno, critically ill, previous failure to non MRSA AB)- IV Tx:

vanco (preferred- narrower)
dapto
Linezolid

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identify and treat mild, purulent cellulitis/erysipelas

organism: Strep& staph
no SIRS: PO
1. Cephalexin
2. Cloxacillin
3. Clindamycin

MRSA risk factor- (immuno, critically ill, previous failure to non MRSA AB) PO antibiotics Tx:

Trimetho-Sulfametho
Clindamycin
Doxycycline

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identify and treat moderate, purulent cellulitis/erysipelas

org: strep+staph

if 1 SIRS: treat like mild, PO

Cefalexin
Cloxacillin
Clindamycin

if >2 SIRS: IV antibiotics

Cefazolin
Cloxacillin (milder +MRSA)
Clindamycin (milder +MRSA)

MRSA risk- (immuno, critically ill, previous failure to non MRSA AB) IV antibiotics:

vanco
dapto
linezolid

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identify and treat severe, purulent cellulitis/erysipelas

indications: >2SIRS, <100/60bpm, rapid progression, immuno, comorbidities

Organism: strepo + straph + gram neg (p aeruginosa)

Tx: IV antibiotics:

Pipe-tazo
Cefepime
Meropenem

MRSA risk factors (immuno, critically ill, previous failure to non MRSA AB): IV

Vanco
Dapto
Linezolid

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identify and treat mild DFI

infection of skin and SC tissue + erythema <=2cm around ulcer + no signs of systemic infection (no SIRS)

organism: strep/staph

treatment: PO antibiotics
1. Cephalexin
2. Cloxacillin
3. Clindamycin

MRSA risk factors (immuno, critically ill, previous failed AB without MRSA coverage): PO antibiotics

Trimetho/Sulfametho
Clindamycin
Doxycycline

duration: 1-2w

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identify and treat Moderate DFI

infection of skin and SC tissue + erythema >2cm around ulcer + no signs of systemic infection (no SIRS)

organism: strep/staph + gram neg (p.aeruginosa) + anaerobes

treatment: IV antibiotics
1. Amoxi/clav (dont need anaerobic coverage)
2. ceftriaxone
3. ertapenem (not really preferred; keep for esbl)

MRSA risk: IV

vanco
dapto
linezolid

Anaerobes

metronidazole
clindamycin

duration: 1-3w

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identify and treat severe DFI

signs of systemic infection (with SIRS)

organism: strep/staph + gram neg (p.aeruginosa) + anaerobes

Tx: initial IV

pipe/tazo
cefepime
meropenem

MRSA risk: IV

vanco
Daptop
Linezolid

anaerobic: IV
1. metronidazole
2. clindamycin

duration: 2-4w

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duration of DFI tx

mild: 1-2w
moderate: 1-3w
severe: 2-4w
surgery remove all infected bone: 2-5d
surgery with residual infected soft tissues: 1-3w
surgery with residual viable bone: 4-6w
no surgery/ dead bone: >=3mth

dont continue AB until wound heals completely

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protective factors of skin

drug surface (no moisture, prevent growth)
fatty acids
Acidic pH (~5.6)
renewal of epidermis (skin shed)
low temperature (inhibit bacteria growth)

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predisposing factors

high bacteria innocula
excessive moisture
reduced blood supply
presence of bacteria nutrients
poor hygiene
sharing of personal items

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least to most deep SSTI

impetigo (epidermis)
ecthyma (dermis)
erysipelas (dermis)
furuncles (hair follicles)
carbuncles (hair follicles)
cellulitis (subcutaneous fat)
necrotising fascilitis (fascia)
myotitis (muscle)

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how is impetigo and ecthyma usually managed and classified

outpatient;
severity: mild
depth of infection: uncomplicated
discharge: purulent/ non purulent
microbiology: primary
anatomical site: epidermis/ up to the dermal-epidermal junction

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scarring is common in ecthyma or impetigo

ecythma, it is deeper than impetigo

causative agent of impetigo/ecthyma

staphlococcus aureus
B-hemolytic streptococci (pyrogenes)
bullous form caused by toxin-producing strains of S. aureus

is culture a need for ecthyma or impetigo

it is optional; may culture if pus, but usually reasonable to treat without culture

empirical coverage for ecthyma/impetigo

S. aureus and B-hemolytic streptococci (cover both since unsure which is the actual causative organism)

furuncles

infection of the hair follicles, extended through the dermis, inflammatory nodule

carbuncles

involved a few adjacent follicles; form a small abscess, , larger and deeper, multiple hair follicles may be involved

cutaneous abscesses

pus collection usually within dermis, nodule with rim of erythematous swelling, abscess may not be where hair follicles are

specific risk factors of purulent SSTI

close physical contact, crowded living quarters (dorms, camps, prison), sharing personal items, poor personal hygiene

causative organism of purulent SSTI

- staphylococcus aureus (single most common organism) | - large skin abscesses may be polymicrobial

need for culture for purulent SSTI?

usually treated without cultures since purulent causing organism are very predictable, but reasonable to culture

when to use adjunctive systemic antibiotic after I&D

1. unable to drain completely 2. lack of response of !&D 3. extensive disease involving several site 4. extreme age 5. immunosuppressed (chemo, transplant) 6. signs of systemic illness (SIRS)

SIRS criteria

1. temperature >38 degree or 36 degree 2. HR>90 beats/min 3. RR >24 bpm 4. WBC >12 or <4 x10^9/L

cellulitis

acute inflammation of epidermis, dermis and sometimes superficial fascia; bacteria can invade lymphatic tissue and blood; purulent or non-purulent, poorly demarcated area or erythema, purulent or non purulent

erysipelas

affects up to superficial dermis and lymphatic tissues; non-purulent; sharply demarcated area of erythema with raised border

complications of cellulitis or erysipelas

1. bacteremia 2. endocarditis 3. toxic shock 4. glomerulonephritis 5. lymphedema 6. osteomyelitis 7. necrotising soft-tissue infections (necrotising fasciitis)

causative organism for cellulitis & erysipelas

- staphlyococcus aureus (mainly purulent) - B-hemolytic streptococci (pyogenes)- 99% cause of erypelas - chronic liver/renal disease: vibrio, E.coli, pseudo. - immunosuppressed: strep pnuemoniae, E.coli, serratia marcescens, pseudo.

should cultures be done for cellulitis/erysipelas

usually not routinely recommended, possible if purulent infections occur after I&D, immunosuppressed (chemo, transplant), SIRS criteria

organism causing cellulitis from bite wounds

caused by 1. staphylo, strepto, 2. anaerobes (prevotella spp, peptostreptococcus spp.) 3. others (pasteurella multocida - animal; eikenella corrodens - human)

cellulitis from bite wounds Tx

1. Amoxi-Clav 2. Ceftriaxone/ cefuroxime + clinda/metronidazole 3. Cipro/levo + clinda/metronidazole (pen allergy) PO/IV based of severity

duration of cellulitis & erysipelas Tx

at least 5d, may extend if not significantly improved, | immunosuppressed may need 7-14d

DFI site of infection and its complications

soft tissue or bone infections below malleolus; areas of DFIs includes skin ulceration (peripheral neuropathy) or wound (trauma); complications would include hospitalisation, osteomyelitis which would lead to amputation

DFI Pathophysiology

1. neuropathy 2. vasculopathy 3. immunopathy

neuropathy of DFI

peripheral- reduced pain sensation and altered pain response motor- muscle imbalance autonomic- increase dryness, cracks and fissures

vasculopathy of DFI

early atherosclerosis; peripheral vascular disease; worsen by hyperglycemia and hyperlipidaemia

immunopathy of DFI

impaired immune response; increase susceptibility to infections; worsened by hyperglycemia

presentation of DFI

superficial ulcer, mild erythema; deep tissue infection, extensive erythema; infection of bone and fascia, purulent discharge

causative organism for DFI

typical polymicrobial (Staph/strep), gram neg (E. coli, Kleb, Proteus), anaerobes (ischemic or necrotic wounds- peptostrepto, veillonella, bacteriodes) is cultures needed for DFI - optional for mild D

is cultures needed for DFI

- optional for mild DFI; - moderate-severe DFI: deep tissue culture after cleansing and before starting antibiotics (if possible); avoid skin swabs - do not culture uninfected wounds