3 - Skin & Soft Tissue Infections Flashcards
What is an abscess?
- contained
- has fluid, inflammatory cells, could have bacteria
Describe the main types of skin abscesses
- In dermis and deeper structures, painful red nodule with erythema; furuncles (boils) in hair follicle, inflammatory nodule with overlying pustule collection in dermis and deeper structures; carbuncles includes collection of furuncles
- Most commonly back in neck, face, axillae
What is the most common pathogen of Skin Abscesses?
S. aureus (75% of cases)
What is the approach for treatment of a skin abscess?
1) Drainage +/- moist heat compresses x 30 min, 3-4 x daily for small lesions or surgical incision and drainage for larger lesions
2) Antimicrobial therapy for abscesses > 2 cm, multiple lesions, extensive cellulitis, systemic signs of infection, indwelling medical device or immunocompromised
What are systemic signs of infection?
temp > 38, tachypnea > 24/min, tachycardia > 90/min, WBC > 12000 or < 4000
What are the 2 antibiotics for 1st line therapy for Skin Abscesses ?
Cloxacillin
Cephalexin
What is 2nd line therapy for Skin Abscesses if they have a severe B lactam allergy?
Clindamycin
List 2 important points about Clindamycin
- # 1 antibiotic associated with C. dif
- We are seeing increasing resistance in S. aureus
What would indicate a severe B lactam allergy?
- anaphylaxis
- severe rash
- hives
- angioedema (swelling of tongue, lips, face)
What are the risk factors for skin abscesses being MRSA?
- MRSA colonization
- close contact with MRSA infection
- previous antimicrobials or S. aureus infection particularly if treatment failure with regimen that lacked MRSA coverage
When is CA-MRSA prevalent?
CA-MRSA contagion among close contacts in sites such as childcare centres and athletic facilities.
Increasing prevalence from 13% to >30% of CA-MRSA over recent years in Canada; 75% SSTIs
When is HCA-MRSA prevalent?
HCA-MRSA with medical procedures, dialysis, hospitalization, long-term care facilities; higher antimicrobial resistance rates than CA strains
What is MRSA resistant to?
- penicillins
- cephalosporins
- carbapenems
(methicillin = penicillin, so they are resistant to anything with a B lactam ring)
What treatment do you chose for a CA-MRSA skin abscess?
- Clindamycin
- Doxycycline
- TMP-SMX
Why would you not chose clindamycin for CA-MRSA?
**If macrolide-resistant, increased risk of inducible clindamycin resistance developing during therapy
Explain an approach to managing patients with recurrent furuncles or carbuncles
S. aureus lives in the nose
- Try decolonizing the nose with:
- Mupirocin 2% 2-3 times daily x 5 days every month
GAS
Group A Strep Pyogenes
Gram positive cocci in clumps
Staph
Gram positive cocci in chains
Strep
Impetigo:
Highest incidence in ?
Children 2-5 years old
What is Impetigo?
- Superficial infection of the epidermis
- Pruritis with mild to moderate erythema
Impetigo:
___% non-bullous
90
Impetigo:
___% bullous
10
Impetigo:
Which form is more severe?
bullous
Impetigo:
What bugs cause non-bullous form?
S. aureus
S. pyogenes
Impetigo:
What bugs cause bullous form?
S. aureus
Impetigo:
Most common pathogen?
S. aureus or less common S. progenies (B-hemolytic Group A Streptococcus - GAS)
Impetigo:
Is antimicrobial therapy always indicated?
Yes:
- For sure in moderate-severe non-bullous and bullous infections - should get oral AB
- For mild, non-bullous infections often resolve spontaneously within weeks, however antimicrobial therapy reduces transmission, hastens symptoms and progression, prevents complications
Impetigo:
What is the treatment for non-bullous mild infections with limited area and number of lesions and low risk of complications?
*Hint - topical therapy
Mupirocin 2% applied twice daily x 5 days
MOA of Mupirocin?
monoxycarbolic acid inhibits RNA synthesis, more effective than alternatives (neomycin, polymyxin B, bacitracin, gentamicin) *increasing resistance to fusidic acid
What are the oral AB options for treating more serious cases of Impetigo?
Cloxacillin
Cephalexin
What is recommended if they have severe B lactam allergy?
Clindamycin
Impetigo:
Duration of oral AB therapy?
7 days
Impetigo:
What is the treatment for MSSA?
Cloxacillin or Cephalexin
Impetigo:
What is the treatment for MSSA if they have a severe B lactam allergy?
*Why don’t you use Doxy or TMP-SMX here?
Clindamycin
*Doxy and TMP-SMX do not cover Strep
Impetigo:
What is the treatment for MRSA?
- Clinda
- Doxy
- TMP-SMX
*I guess you can use Doxy or TMP-SMX here because you know for sure it’s only Staph ????
Impetigo:
What is the treatment for S. pyogenes?
- Pen V
- Amox
Impetigo:
What is the treatment for S. pyogenes if they have a severe B lactam allergy?
Clindamycin
Compare Clinda, Doxy and TMP-SMX?
Clinda:
- lower susceptibility
- highest incidence of C. dif
Doxy:
- can’t be used in children or pregnancy
- does not cover streptococcus
TMP-SMX:
- does not cover streptococcus
- high rate of adverse effects (allergy, hypersensitivity, rashes)
Compare Pen and Amox
Amox:
- broader coverage
- preferred in kids bc it tastes better than Pen
Pen:
- QID
- bitter taste
Describe Cellulitis
-Diffuse, superficial skin infection of epidermis and dermis that can extend to cutaneous lymphatics and subcutaneous fat
________ synonymous with cellulitis
erysipelas
Cellulitis:
Although purulence may be present, purulent discharge or pus is more consistent with ??
skin abscesses
Cellulitis:
Typically involves ______ (90% of cases) or upper extremities or face.
lower
Cellulitis:
Most common pathogen?
Strep pyogenes, less commonly S. aureus (typically associated with purulence, abscess, wound, trauma)
Describe the clinical presentation of cellulitis
-Orange-peel-like, vesicles, bull, petechiae or ecchymoses (discolouration of skin), phlebitis or lymphangitis (streaking)
What kind of symptoms (other than appearance) are associated with cellulitis
- local pain
- erythema
- warmth
- edema +/- systemic signs of infection (fever, chills, malaise)
Cellulitis:
How do you differentiate from contact dermatitis?
-contact dermatitis is pruritic
Cellulitis:
How do you differentiate from gout?
-gout has severe pain, single joint swelling
Cellulitis:
How do you differentiate from DVT?
-risk factors, calf pain
Cellulitis:
How do you differentiate from
stasis dermatitis?
-bilateral, venous insufficiency, pitting edema, hyper pigmentation
Cellulitis:
Risk factors?
- skin disruption (abrasion, insect bite, ulcer)
- inflammation (eczema, radiation)
- advanced age
- obesity
- DM
- Immunocompromised
- PVD
- lymphatic obstruction
Cellulitis:
Non-pharms
- immobilization
- elevation
- cool and warm dressings
_____ is used only in COMBO
Rifampin
*has a lot of SE and DI (drug interactions) too
Why is Rifampin only used in combo?
When used alone - leads to RESISTANCE
______ decrease vitamin K production and therefore increase bleeding with someone on anticoagulants
Antibiotics
_______ interacts with warfarin and and spironolactone (increases K+ levels)
TMP-SMX
What factors are considered in selecting PO versus IV antimicrobials for treating cellulitis?
- severity of cellulitis based on location, area, progression
- systemic signs of infection (fever, chills, confusion)
- PO tolerability
What is the treatment for Mild cellulitis? (remember you suspect S. pyogenes)
Pen V
Amox
What is the treatment for Mild cellulitis if they have a B lactic allergy? (remember you suspect S. pyogenes)
Clindamycin
Why is Doxy or TMP-SMX not a good choice for mild cellulitis?
they lack strep coverage !! (not effective for cellulitis at all then)
How is staph resistant to penicillin?
Staph learned very quickly to produce beta lactamses so penicillin was not effective against Staph
Why is cloxacillin effective against staph then?
Bc cloxacillin is penicillase stable (it has a stable ring)
What is the treatment for moderate-severe cellulitis?
Remember you suspect S. progenies and/or MSSA
Cloxacillin (po)
Cephalexin (po) or Cefazolin (iv)
Why can’t you give penicillin or amoxicillin for moderate-severe cellulitis?
Bc if you prescribe pen or amox and the bug turns out to be Staph, Pen/Amox will not kill it.
*in this scenario, you need something that will target strep and staph
What is the treatment for moderate-severe cellulitis if they have a severe B lactam allergy?
Clindamycin
What is the treatment for moderate cellulitis (Suspect S. pyogenes or MRSA)
- Clindamycin
- Doxy + (Pen or Amox) for strep coverage
- TMP-SMX + (Pen or Amox) for strep coverage
What are some risk factors for getting MRSA?
- MRSA colonization
- close contact with MRSA infection, previous antimicrobials or S aureus infection particularly if treatment failure with regimen that lacked MRSA coverage
What is the treatment for severe cellulitis (suspect S. pyogenes or MRSA)
Vancomycin
What is the treatment for severe cellulitis (suspect S. pyogenes or MRSA) if Vanco intolerance or treatment failure?
- Linezolid
- Daptomycin
Despite an approved indication for treating uncomplicated SSTIs, what are the potential disadvantages of using Levo or Moxi ??
- less effective than alternatives due to unreliable streptococcal and staphylococcal activity from intrinsic or acquired resistance during therapy
- unnecessarily broad GN coverage
- increasing resistance and significant concern regarding collateral resistance
What is the expected response for the treatment of uncomplicated cellulitis?
Clinical improvement within 24-48 hours, visible improvement may be delayed 72 hours
What is the duration of therapy for uncomplicated cellulitis?
5 days (to 14 days for severe infection, slow response, immunocompromised)
Necrotizing Cellulitis:
Describe Type 1 (80%)
-associated with surgery or trauma; polymicrobial mixed infection with GP, GN and anaerobes
Necrotizing Cellulitis:
Describe Type 2 (streptococcal gangrene, “flesh-eating” bacteria)
-caused by virulent S. pyogenes, very rapid progression with severe systemic signs of infection including septic shock
Necrotizing Cellulitis:
Describe Type 3 (clostridial gas gangrene - C. perfringes, myonecrosis - C. septicum)
-associated with surgery or trauma, very rapid progression with gas production and myonecrosis
What is the general treatment for necrotizing cellulitis?
1) emergency surgery for inspection, debridement and wound cultures
2) empirical broad-spectrum antimicrobial therapy (pip-tazo or meropenem + vancomycin +/- clinda)
**start broad and then once you figure out exactly what it is, use pathogen-directed therapy
3) pathogen-directed therapy
Necrotizing Cellulitis:
What is the therapy directed at S. pyogenes (necrotizing cellulitis)?
Pen G + Clinda +/- IVIG for toxic shock
Necrotizing Cellulitis:
What is the therapy directed at Clostridium?
Pen G + Clinda +/- IVIG for toxic shock
IVIG
intravenous immunoglobulin
Necrotizing Cellulitis:
What is the therapy for Aeromonas hydrophila (fresh water) ?
TMP-SMX or Cipro or Ceftriaxone or Doxy (as per susceptibilities)
Necrotizing Cellulitis:
What is the therapy for Vibro vulnificus (sea water) ?
Ceftriaxone + (Doxy or Cipro)
What is the role of adding Clinda to Pen G in treating serious SSTI involving S. pyogenes?
- it down regulates production or proteins and toxins
- it mitigates the toxin release that happens with beta lactam
20% of dog and 50% of cat bites develop infection, typically within _____ days
2-3
What is the main bug involved in dog/cat bite wounds?
Pasteurella multocida (GNCB)
- 50% of dog bites
- 75% of cat bites
What other bugs can be involved in dog/cat bite wounds?
- strep/staph in 40%
- anaerobes
What is Pasteurella multicoda typically susceptible to?
- Pen
- Doxy
- FQ
- TMP-SMX
What is Pasteurella multicoda resistant to?
- 1st GC
- Clinda
Describe the prophylactic treatment of dog/cat bite wounds
-antimicrobials for 3-5 days to prevent infection of high risk wounds from moderate-severe bite, on face, on hands involving joints, significant edema or immunocompromised
Prophylactic duration for dog/cat bite wounds
3-5 days
Treatment duration for dog/cat bite wounds
5-10 days
or
4-6 weeks for septic arthritis or osteomyelitis (involving bone or joint)
What is the 1st line for dog/cat bite wounds?
Amox-clav (po) x 5-10 days
What are some alternatives if someone has a severe B lactam allergy?
- Doxy + (Clinda or Metro)
- (Cipro/Levo/Moxi) + (Clinda or Metro)
- TMP-SMX + (Clinda or Metro)
- Macrolide/Azolide (if susceptible Pasteurella) + Clinda
What if someone has a severe infection from a dog or cat bite wound?
- pip-tazo
- ceftriax + metro
- (cipro/levo/moxi) + (clinda or metro)
What option should be given to pregnant women and children?
Macrolide/Azolide (if susceptible pasteurella) + Clinda
What are some additional considerations for someone with a dog/cat bite wound?
- Tetanus toxoid (Tdap) if not vaccinated within 10 years + tetanus immunoglobulin if <2 primary immunizations
- Risk assessment for rabies, post-exposure prophylaxis with hyper-immune globulin (40 IU/kg) infiltrated in and around wound, and serious of 5 vaccinations over 28 days
What bug is responsible for cat scratch disease
Bartonella henselae
How does Bartonella henselae present?
presents as papule or pustule with lymphadenopathy within 3-30 days
What is the treatment for cat scratch disease (Bartonella henselae)?
Azithro
______% of human bites develop infection, associated with severe infection and complications
10-50
Human Bite Wounds:
B-hemolytic streptococcus (viridans group, S. anginosus) in >___%
80
Human Bite Wounds: Eikenella corrodens (GNCB) in \_\_\_\_%
30
Human Bite Wounds:
S. aureus, oral anaerobes such as fusobacteria, prevotella, porphyromonas, peptostreptococcus in > ___%
40
What is E. corrodens susceptible to?
- Pens
- Doxy
- FQ
- TMP-SMX
What is E. corrodens resistant to?
- 1st GC
- Clinda
- Metro
Human Bite Wounds:
Describe the prophylactic treatment
-Prophylaxis with pre-emptive antimicrobials x 3-5 days to prevent infection of high risk wounds from bites that penetrate the dermis
Human Bite Wounds:
Treatment duration?
7-14 days
or 4-6 weeks for septic arthritis or osteomyelitis
What is the 1st line treatment for human bite wounds?
Amox-clav (po)
What are alternatives for human bite wounds if someone has a severe B lactam allergy?
- Doxy + (Clinda or Metro)
- (Cipro/Levo/Moxi) + (Clinda or Metro)
- TMP-SMX + (Clinda or Metro)
What are options for a severe human bite wound infection? (IV)
- Pip-tazo
- Ceftriax + metro
- (Cipro/Levo/Moxi) + (Clinda or Metro)
What are some additional considerations for human bite wounds?
- Tetanus toxoid (as Tdap) if not vaccinated within 10 years
- Risk assessment for Hepatitis, HIV transmission
DFI:
What diabetes-related factors increase the risk of diabetic foot ulcers and infections?
- Angiopathy with PVD and ischemia
- Neuropathy with sensory, motor, autonomic dysfunction
- Immune dysfunction
DFI:
List the important adjuvant (non-antimicrobial) measures for treating diabetic foot ulcers?
- glycemic control
- wound care including debridement, dressing changes
- pressure relief, off-loading, elevation
What are the clinical features of diabetic foot infections?
- erythema, swelling (edema), warmth, purulent discharge
- little to no pain or systemic signs of infection in >50%
Describe a Mild DFI
-superficial skin with erythema < 2 cm, swelling, heat or pain; no systemic signs of infection
Describe a Moderate DFI
-deep localized with erythema > 2 cm, abscess, fascitis, septic arthritis or osteomyelitis; no systemic signs of infection
Describe a Severe DFI
-significant systemic signs of infection (tachycardia, tachypnea, leukocytosis, hypotension)
What pathogen is involved in:
Superficial, acute cellulitis and/or infected ulcer not treated with antimicrobials in previous month ??
streptococci, staphylococci
*therefore here we don’t have to go very broad - use same meds that we talked about earlier in cellulitis
What pathogen is involved in:
Deep, chronic infected ulcer and/or treated with antimicrobials in previous month ?
mixed, polymicrobial with Gram positive aerobes in >40% (streptococci, staphylococci), gram positive aerobes in <20% (Proteus species, E. coli) and anaerobes in 25-40%, particularly if necrotic or gangrenous
**deep and chronic infections have a mixed amount of bugs, need broader treatment
What are the complications of DFI’s?
- 20% of diabetes-related hospitalizations
- contiguous spread to joints (septic arthritis) or bone (osteomyelitis) in 25%
- amputation in 10-20% of cases at one year and 25-50% at 5 years
What factors are considered in using antimicrobials in treating DFI’s?
- infected wound versus colonized ulcer
- adequate wound debridement and care
- severity of infection and clinical status
- bone involvement
- risk factors for antimicrobial resistance: chronic infections, repeat antimicrobial exposure, low antimicrobial concentrations at infection site, MDR pathogens that limit options for antimicrobial therapy
What is the treatment for mild, acute infection suspected Gram positives (po) ?
Cloxacillin > 1-2 weeks of therapy
Cephalexin > 1-2 weeks of therapy
+/- Doxy or TMP-SMX for MRSA coverage
What is the treatment for mild, acute infection suspected Gram positives (po) IF THEY HAVE A BETA LACTAM ALLERGY ?
CLINDAMYCIN
What is the treatment for moderate, acute or chronic infection suspected mixed, polymicrobial (po) ?
Amox-clav for > 2 weeks of therapy (may require initial IV with po step-down)
+/- Doxy or TMP-SMX for MRSA coverage
What is the treatment for moderate, acute or chronic infection suspected mixed, polymicrobial (po) ? IF THEY HAVE A BETA LACTAM ALLERGY ?
CLINDA +/- (Cipro/Levo/Moxi)
**this includes MRSA coverage
What does clavulanic acid add to amoxicillin ?
covers beta lactamase
What bugs produce beta lactase ?
E. coli, clebsiella (enteric gram negatives)
- *Clavulanic acid tremendously expands coverage of gram negatives
- *Clavulanic acid also covers anaerobes
______ has a stable ring
Cloxacillin
What is the treatment for severe, chronic, extensive infection suspected mixed polymicrobial (iv) ?
Pip-tazo
Meropenem
Ceftriazone + Metro
Ceftazadime + Metro
x > 2-4 weeks (initial broad-spectrum iv therapy with de-escalation and po step down)
What is the treatment for severe, chronic, extensive infection suspected mixed polymicrobial (iv) ?
IF THEY HAVE A SEVERE BETA LACTAM ALLERGY
Moxi (also po)
Cipro/Levo + Metro (also po)
+/- Vancomycin for MRSA coverage
