Therapeutics - SSTIs Flashcards
What is retapamulin 1% oint good against? MoA? Indicated in?
S. aureus and S. pyogenes
Binds to 50S ribosome
Indicated in uncomplicated skin infections >9months of age: primarily impetigo
What is impetigo?
What is it mostly caused by?
Peak incidence is in what population group?
Well-localized multiple purulent lesions, usually on exposed areas (face and extremities)
S. auerus or S. pyogenes are the primarly cause
Mostly in children 2-5 years old
How does impetigo occur?
Microorganisms colonize unbroken skin (streptococci precedes lesions by around 10 days due to poor hygiene)
Organisms inoculate into skin by abrasions, minor skin trauma
During 2-3 weeks streptococcal strains may also be transferred to URT
In staphylococcal disease, present in nose first
Nonbullus Impetigo
- primarily caused by?
- Pathophysiology
- S. pyogenes
- Begins as papules that evolve into vesicles, then become pustules. Gradually enlarge, pop and form thick crusts. Lesions heal and leave hypo-pigmented areas
Bullous Impetigo
- primarily caused by?
- pathophys
- S. aureus that produces toxin
- initially appear as superficial vesicles that enlarge to form flaccid bullae filled with clear yellow fluid. Later become darker or purulent, may rupture to form brown crust
First line treatment for Bullous and Nonbullous Impetigo
If numerous lesions or unresponsive to first line
Why should systemic antimicrobials be used for impetigo infections during outbreaks of post-strep nephritis?
-topical mupirocin or retapamulin bid x5 days
-PO tx:
MSSA: Cloxacillin or cephalexin
MRSA: doxycycline, TMP/SMX, or clindamycin
Want to eliminate nephritogenic strains of S. pyogenes from community
Presentation of cutaneous abscesses: folliculitis, furuncles and carbuncles
What pathogens often cause this?
Collections of pus within dermis and deeper tissue
Painful, tender, fluctuant red nodules often surmounted by pustule with an erythematous rim
S. aureus is a single pathogen in most patients, often polymicrobial from skin flora
How to treat cutaneous abscesses?
What role does abx have in this?
- Incision and drainage with probing
- Cover site with dry dressing
Topical abx does not improve cure rates (even with MRSA)
Systemic abx only in immunocompromised or signs of systemic infection
What is folliculitis?
What is a furuncle?
Outbreaks caused by which pathogen?
What is often a predisposing factor?
Folliculitis: superficial infection of hair follicle with pus limited to epidermis
Furuncle (boil): infectious of hair follicle which extends through the dermis to SC tissue where a small abscess forms
MSSA or MRSA
Poor hygiene
What is a carbuncle?
In which patient population is it most common?
Carbuncle: infection extends to involve several adjacent follicles producing an inflammatory mass with pus draining from multiple follicular orifices
Common in diabetics
Which abx are used in treatment of carbuncles?
- Cloxacillin or cephalexin, only is hot compresses don’t owrk
- Severe beta-lactam allergy: Doxycycline or clindamycin
- MRSA: TMP/SMX or clindamycin
What are cellulitis and erysipelas?
What are the signs of these infections?
What feature do these infections NOT contain, helping distinguish it from other SSTIs?
Presentation (superficial and systemic)
Rapidly spreading, diffuse skin infection including dermis and SC tissues
Signs: erythema, edema and head, occasionally accompanied by lymphangitis and lymph node inflammation
NO PUS
Skin surface looks like orange peel
Systemic sx: fever, tachycardia, confusion, hypotension, leukocytosis
Predisposing factors of cellulitis/erysipelas
Factors that make skin more fragile or local host defences ineffective:
- edema from venous insufficiency or lymphatic obstruction
- cutaneous damage
- Pre-existing skin infections (ex. fissured toe webs)
- obesity
What is cellulitis?
What is erysipelas?. Name 2 distinguishing factors
Cellulitis: deeper dermis and SC fat infection
Erysipelas: upper dermis including superficial lymphatics
- lesions raised above level of surrounding skin
- clear demarcation between involved and uninvolved tissue
Which pathogens often cause cellulitis/erysipelas?
In what patient population group is it most common?
Prognosis?
Also always S. pyogenes. Rarely S. aureus.
Infants, young children, older adults
Excellent with early diagnosis and treatment
CA-MRSA:
What strain is now commonly found in Canada?
How does it confer resistance?
CMRSA10
Altered PBP 2a encoded by mecA gene
What are some clincal manifestations of CA-MRSA?
- folliculitis
- furuncles
- carbuncles
- mastitis
- cellulitis
- occasionally, severe necrotizing pneumonia
What abx can be used to treat MRSA?
- Tetracycline (95%S)
- TMP/SMX (95%S)
- Clindamycin (72%S)
- Vanco and linezolid (100%S)
Principles of treating MRSA
- Incision and drainage are most important
- Abx not used routinely unless large and complicated in patients with comorbidities
- Covering wound and hand hygiene important
- recurrent infections: decolonization with chlorhexidene washes, mupirocin oint intranasally with rifampin or doxycycline x7 days
First line treatment in:
- In mild CA-MRSA skin infection
- in moderate infection
Mild:
-Cover draining lesions, no abx necessary unless otherwise specified
Mod:
-drainage, po therapy in older child/adult: clinda, TMP/SMX, doxycycline (parenteral in young)
Severe:
- vanco and/or cloxacillin/1st gen cephalosporin
- add clindamycin if toxin mediated syndrome
What is Necrotizing Fasciitis?
-Rare SC infection that tracks along fascial planes (superficial fascia: all tissue b/t skin and underlying muscle) and extends much beyond superficial signs of infection
How does necrotizing fasciitis start? What is a telltale sign that it’s not just a simple infection?
- Extension from a simple skin infection- may not even have a lesion involved
- pain is out of proportion to the apparent skin lesion
What is the presentation of necrotizing fasciitis?
- initial presentation: cellulitis
- progression: high fevers, disorientation, lethargy (often septic shock)
- SC have wooden-hard feel
What is the most common pathogen causing Necrotizing Fasciitis?
-S. pyogenes and S. aureus
