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bacteria shizz > IC14 SSTI > Flashcards

IC14 SSTI Flashcards

1
Q

How do SSTIs come about? (Pathogenesis)

A

Disruption of normal host cell defenses (eg. skin break) –> allows overgrowth & invasion of skin and soft tissue by pathogenic microorganisms

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2
Q

What are the risk factors for SSTIs?

A
  1. disruption of skin barrier
    - traumatic causes (lesions, abrasions, burns, surgery, bites from humans/animals/insects, IV drug use)
    - nontraumatic causes (ulcers, tinea pedis, dermatitis, chemical irritants)
    - impaired venous & lymphatic drainage
    - peripheral artery disease
  2. conditions that predispose to infection
    - DM, cirrhosis, neutropenia, HIV, transplant, immunosuppression
  3. history of cellulitis
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3
Q

How do you prevent SSTIs?

A
  1. management of risk factors
  2. good wound care
  3. treat tinea pedis
  4. prevent dry, cracked skin
  5. good foot care for DM patients to prevent wounds & ulcers
  6. removal of foreign objects, irrigation, tissue debridement
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4
Q

How do you diagnose a SSTI?

A

physical exam & patient history

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5
Q

Where should you and should you NOT take samples for cultures for SSTIs from?

A

do NOT take cultures from:
- open, draining wounds (v likely contaminated)
- wound swabs

take cultures from:
- deep in the wound after surface cleansed
- base of closed abscess
- curettage > wound swab/irrigation (debridement of top layers before taking tissue sample)

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6
Q

Do you need to take blood samples for SSTIs?

A

Only for severe SSTI or immunocompromised patients

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7
Q

Describe impetigo

A

erythematous papules that develop into vesicles and pustules that rupture, with the dried discharge forming a honey-colored crust on a erythematous base

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8
Q

Describe ecthyma

A

ulcerative form of impetigo that occurs in deeper skin layers (not a progression of impetigo; they are diff SSTIs)

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9
Q

Describe furuncles and carbuncles

A

furuncle (boil) - infection of hair follicle
carbuncle - group of furuncles

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10
Q

Describe skin abscesses

A

collection of pus within dermis and deeper skin tissue; painful, tender and red nodules

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11
Q

Describe erysipelas

A

fiery red painful plaque (raised above surrounding skin) with well-demarcated edges; common on face and lower extremities

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12
Q

Describe cellulitis

A

involves deeper and subq fats; acute, diffuse, spreading, non-elevated, poorly demarcated area of erythema, mostly unilateral (on one limb); typically in lower extremities

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13
Q

What are the likely pathogens for each SSTI?

A
  • impetigo: Staph, strep pyogenes
  • ecthyma: Strep pyogenes (GAS)
  • nonpurulent (cellulitis, erysipelas): Strep pyogenes
  • purulent (purulent cellulitis, furuncles, carbuncles, skin abscesses): Staph aureus, Strep pyogenes
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14
Q

What are the two kinds of MRSA that can cause SSTIs?

A

community-acquired MRSA
healthcare-associated MRSA

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15
Q

How are the two MRSAs different?

A

CA-MRSA and HA-MRSA are genetically different
1. PVL (Panton-Valentine leucocidin) [cytotoxin]
2. SCCmec (CA: IV, HA: II) [mobile genetic element for novel specific PBP2a]

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16
Q

Describe the prevalence of the two MRSAs involved in SSTIs

A

CA-MRSA: More common in USA
HA-MRSA: Usually almost always HA-MRSA in SG, so have to treat as long as patient has MRSA risk factors

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17
Q

Define HA-MRSA

A

patient develops MRSA infection within
1. 2 days of being in hospital
2. 12 months of being discharged from hospital

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18
Q

What are the risk factors for HA-MRSA?

A
  • antibiotic use
  • recent hospitalization/surgery (for a decent duration; doesn’t count if just visiting etc)
  • prolonged hospitalization
  • ICU
  • hemodialysis
  • MRSA colonization
  • close proximity to MRSA colonized/infected people
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19
Q

Describe the treatment for mild impetigo (limited lesions)

A

Likely pathogen: Staph (MSSA), strep

THEORY: Topical mupirocin BD x 5/7
NOT recommended; reserved for MRSA decolonization in hospitals

IN PRACTICE: no need to treat as self-limiting

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20
Q

Describe the EMPIRIC treatment for impetigo/ecthyma (multiple lesions)

A

Likely pathogens:
impetigo: Staph (MSSA), strep
ecthyma: grp A strep

  1. PO beta lactams
    - Cloxacillin
    - Cephalexin
  2. PO Clindamycin (penicillin allergy)
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21
Q

Describe the CULTURE-DIRECTED treatment for impetigo/ecthyma (multiple lesions) if it is caused by
1. Strep pyogenes (Grp A strep)
2. MSSA

A

Strep pyogenes:
1. PO penicillins
- Pen V
- Amoxicillin

MSSA:
1. PO beta lactams
- Cloxacillin
- Cephalexin

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22
Q

What is the typical treatment duration of impetigo & ecthyma for
1. mild infection
2. moderate to severe infection

A
  1. 5-7 days
  2. moderate to severe: 10-14 days
23
Q

What is the main treatment for purulent SSTIs (purulent cellulitis, furuncles, carbuncles, skin abscesses)?

A

incision & drainage (source control)

24
Q

When do we use antibiotics for purulent SSTIs?

A
  1. unable to drain completely
  2. lack of response to I&D
  3. extensive disease involving many sites
  4. extreme ages (v young/old)
  5. immunosuppressed
  6. signs of systemic illness (2/4 of SIRS criteria)
  7. IV abx for severe disease state
25
Q

Describe the SIRS criteria

A

SIRS = systemic inflammatory response syndrome
1. temp (>38 or <36)
2. WBC (>12 or <4)
3. HR (>90)
4. RR (>24)

26
Q

Describe the treatment to be given for purulent SSTIs that are
1. mild
2. moderate
3. severe

A

Likely pathogens: Staph aureus (MSSA)

  1. I&D + warm compress
  2. I&D + PO abx
    - Cloxacillin
    - Cephalexin
    - Clindamycin (Penicillin allergy)
  3. I&D + IV abx
    - Cloxacillin
    - Cefazolin
    - Clindamycin
    - Vanco
27
Q

Describe the empiric treatment to be given for purulent SSTIs that involve MRSA

A

PO
- co-trimoxazole
- doxycyline
- clindamycin

IV
- vanco
- daptomycin
- linezolid
(daptomycin & linezolid reserved for VRE/vanco allergy)

28
Q

What happens if purulent SSTI occurs near perioral/perirectal/ vulvovaginal areas?

A

add G(-) anaerobic coverage

29
Q

Describe the empiric treatment to be given for purulent SSTIs that involve G(-) anaerobes

A

amoxicillin-clavulanate (Augmentin)
pip-tazo (if risk of resistant strain)
carbapenem (if super duper sick)

30
Q

What is the typical treatment duration for purulent SSTIs?

A

5-10 days

31
Q

Describe the treatment to be given for nonpurulent SSTIs that are
1. mild
2. moderate
3. severe

A

Likely pathogen: Grp A strep

  1. PO abx
    - Pen V
    - Amoxicillin
    - Cloxacillin
    - Cephalexin
    - Clindamycin (penicillin allergy)
  2. moderate = signs of systemic ifxn + some purulence; IV abx
    - Ampicillin
    - Cloxacillin
    - Cefazolin
    - Clindamycin (penicillin allergy)
  3. severe = signs of systemic ifxn/failed oral therapy/immunocompromised; broader coverage + possibility of necrotizing fasciitis
    IV
    - Pip-tazo
    - Cefepime (4th gen)
    - Meropenem
    if MRSA risk factors
    - Vanco, daptomycin, linezolid
32
Q

Describe the treatment to be given for non-purulent SSTI in a patient with a history of water exposure

A

+ Cipro to cover Aeromonas, Vibrio & Pseudomonas

33
Q

What is the typical duration of treatment for nonpurulent SSTIs?

A

5-10 days
14 days for immunocompromised

34
Q

What are some other things to do when treating nonpurulent SSTIs?

A
  1. rest
  2. limb elevation to promote drainage of edema
  3. treat underlying conditions (eg. tinea pedis, skin dryness, limb edema)
35
Q

What are the monitoring parameters when monitoring for therapeutic response of SSTI treatment?

A
  • improvement within 2-3 days (won’t resolve so fast)
  • no progression of lesions/development of complications
  • reassess indication/choice of abx if no improvement within 2-3 days
36
Q

How do DFIs (diabetic foot infections) come about? (Pathogenesis)

A
  1. risk factors
    - neuropathy (loss of sensation)
    - vasculopathy (poor circulation)
    - immunopathy
  2. ulcer formation/wound
  3. bacterial colonize, penetration, proliferation
  4. DFIs
37
Q

What constitutes DFIs?

A
  • wounds
  • ulcers
38
Q

When do we treat wounds and ulcers found in diabetic patients?

A

if infected (ie. true DFI)

criteria for infection:
1. purulent discharge, or
2. at least 2 signs of inflammation
- erythema
- warmness
- tender
- pain
- induration (thickening/hardening of skin)

39
Q

What are the microbes involved in DFIs?

A

typically polymicrobial

G(+)
- Staph, Strep

G(-) (for wet/chronic wounds)
- Proteus, Klebsiella, E Coli

Anaerobes (for deep/ischemic/necrotic wounds)
- Peptostreptococcus (Finegolda magna in SOA table)
- Veillonella
- Bacteroides

40
Q

When and how do we take cultures for DFIs?

A

no need for mild DFI

need for moderate to severe DFI

take deep tissue cultures after cleansing + before starting empiric abx
- avoid skin swabs
- do not culture uninfected wounds

41
Q

What is the criteria for mild DFI?

A
  • involves skin + SQ tissue, AND
  • erythema ≤2cm, AND
  • no signs of systemic infection
42
Q

What are the organisms to cover for mild DFI?

A
  • Staph aureus
  • Strep species
43
Q

What are the antibiotics to use for mild DFI?

A

PO abx
- Cloxacillin
- Cephalexin
- Clindamycin

if MRSA risk factors (PO)
- Co-trimoxazole
- Doxycyline
- Clindamycin

44
Q

What is the criteria for moderate DFI?

A
  • involves deeper tissues (eg. bones, joints), OR
  • erythema >2cm
  • no signs of systemic infection (compulsory)
45
Q

What are the organisms to cover for moderate DFI?

A

G(+)
- Staph
- Strep

G(-)
- +/- PA

anaerobes

46
Q

What are the antibiotics to use for moderate DFI?

A

IV abx
- Amox/clav (Augmentin)
- Cefazolin/Ceftriaxone + Metronidazole

if MRSA risk factors (IV)
- Vanco
- Daptomycin
- Linezolid

47
Q

What is the criteria for severe DFI?

A
  • involves deeper tissues (eg. bones, joints) OR
  • erythema >2cm
  • signs of systemic infection (compulsory)
48
Q

What are the organisms to cover for severe DFI?

A

G(+)
- Staph, strep

G(-)
- PA

anaerobes

49
Q

What are the antibiotics to use for severe DFI?

A

IV abx
- Pip-tazo
- Cefepime + metronidazole
- Meropenem
- Cipro + clindamycin

if MRSA risk factors (IV)
- Vanco
- Daptomycin
- Linezolid

50
Q

What is the recommended duration of therapy for DFIs
1. not involving bones (mild, moderate, severe)
2. involving bones
A: surgery - infected tissue completely removed, residual infected tissue left, residual viable bone left
B: no surgery

A

Not involving bones
* mild: 1-2 wks
* moderate: 1-3 wks
* severe: 2-4 wks

Involving bone
* surgery, complete removal: 2-5 days
* surgery, residual infected tissue: 1-3 wks
* surgery, residual viable bone: 4-6 wks
* no surgery: ≥3 months

51
Q

What are some adjunctive measures for DFIs?

A
  • wound care
  • foot care
  • glycemic control
52
Q

What are some risk factors for pressure ulcers?

A
  1. reduced mobility
  2. impaired immunity
53
Q

When do we treat pressure ulcers with antibiotics?

A

when it becomes infected, meaning
1. purulent discharge
2. ≥2 signs of inflammation (erythema, warmness, tender, pain, induration)

54
Q

What are some adjunctive measures for pressure ulcers?

A
  1. debridement of infected/necrotic tissue
  2. local wound care
  3. relief pressure

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