SSTI Part 1 Flashcards
MRSA is resistant to all _______ antibiotics, except for _______.
Beta-lactam; ceftaroline
Why is MRSA methicillin resistant?
It harbors the mecA gene, which encodes PBP2a
PBP2 is the usual target on staph aureus; drugs bind to PBP2a with less affinity so they’re less effective
What are the risk factors for SSTI?
Injury Obesity Poor hygiene Diabetes Vascular disease Immune deficiency Steroids Problems with venous/lymphatic drainage IV drug use
What is Folliculitis? What are the likely pathogens?
Inflammation of the hair follicle, limited to the epidermis
Pruritic, erythematous papules
Likely pathogens: Staph aureus, P aeruginosa (hot tub folliculitis)
How do you treat Folliculitis?
Moist, heated compress
Topical therapy: Clindamycin, Mupirocin, Benzoyl perxocide
What are the types of purulent SSTI’s?
Cutaneous abscess: Collection of pus within the dermis and deeper layers
Furuncle: Abscess originating in hair follice, extended through dermis
Carbuncle: Adjacent furuncles
How do you treat purulent SSTI’s?
1: I & D
#2: Antibiotics, but only sometimes:
When there are systemic signs of infection
Immunosuppressed patients
Multiple/extensive abscesses
Extremes of aging (young and old)
Non-response to I&D (infection still strong after I&D)
C&S is generally recommended
Treatment options for purulent SSTI’s?
Empiric MRSA coverage!
Mild to moderate: Doxycycline/minocycline or TMP/SMX
Severe or immunocompromised patients: Vancomycin IV, goal trough 10-15 mcg/mL if not bacteremic
Duration: 5-10 days
What is Impetigo? Likely pathogens?
Superficial skin infection caused by S aureus or B-hemolytic streptococci
Usually occurs in children, on the face
Most common in the summer and it is contagious
How to treat Impetigo?
Treat for staph and strep unless only streptococci grow in the culture
Topical: Mupirocin or retapamulin BID for 5 days
Oral therapy: Preferred if there are multiple lesions or in an outbreak setting
Dicloxacillin or cephalexin for 7 days (usually MSSA)
If pt has a penicillin allergy, use Clindamycin
What is Lymphangitis? Most likely pathogen?
Inflammation of subcutaneous lymphatic system
Usually occurs secondary to puncture wounds or other skin lesions
S pyogenes most common
Treatment for Lymphangitis?
Initial therapy with IV penicillin G 2-4 million units every 4-6 hours for 48-72 hours
Step down to penicillin VK oral therapy
If they have a penicillin allergy, use clindamycin
Total duration: 7-10 days
Also elevate the affected extremity and soak in warm water every 2-4 hours
What is Erysipelas? Most likely pathogen?
Infection of superficial skin and lymphatic system
Painful, bright red, indurated, raised and well demarcated borders
Almost always caused by B-hemolytic strep, S pyogenes is the most common
What cultures do you get for Erysipelas?
Generally nothing to culture
Get blood cultures if there are severe systemic symptoms, patient is immunocompromised, and there are unusual pre-disposing factors such as animal bites or water immersion
Treatment for Erysipelas?
Penicillin is the drug of choice:
Penicillin G 2-4 million units IV q4-6h
Penicillin VK 500 mg PO QID
If they have a penicillin allergy, just clindamycin
Duration: 5-10 days
What is cellulitis? Most likely pathogen?
Diffuse, spreading, superficial skin infection involving the dermis and subcutaneous fat
Painful, erythematous, warm, non-elevated, poorly demarcated borers
Usually secondary to wound, trauma
Most common pathogen is B-hemolytic strep; consider S aureus if it’sa penetrating wound, purulent focus, or there’s illicit drug use
Gram negatives are Uncommon but considered if the patient has neutropenia, is a transplant patient, has cirrhosis, or diabetes
What cultures do you get for Cellulitis?
Generally not cultured unless there is an associated site of purulence
Blood cultures if:
- Severe systemic symptoms
- Immunocompromised patient
- Unusual predisposing factors (animal bites, water immersion)
Treatment for cellulitis?
Elevate the affected limbs
Mild infection: B-lactam preferred
- Cephalexin 500 mg PO QID x 5 days
- Dicloxacillin 500 mg PO QID x 5 days
- Clindamycin (if there’s a PCN allergy)
If concern for MRSA:
- Clindamycin, a tetracycline, or TMP/SMX
Moderate/severe infection:
Non-purulent: Cefazolin 1 g IV q8h if not septic
Purulent: IV vancomycin
Convert to oral therapy once improved/stabilized
Duration 5-10 days
Risk factors for Necrotizing infections?
Diabetes
Recent trauma
Surgery
Describe the two types of necrotizing fasciitis
Type 1 (80%): Often after trauma/surgery, polymicrobial with aerobes and anaerobes, includes Fournier’s gangrene
Type 2: S pyogenes (maybe S aureus), more skin destruction with more rapid progression; usually monomicrobial
What is Clostridial myonecrosis? Likely pathogens?
Gas gangrene
Gas production and muscle necrosis
Causes:
Trauma: C perfringens
Spontaneous: C septicum (from GI)
Treatment for Necrotizing infections (before medications)?
Surgical debridement is absolutely necessary
Urgent surgical consultation is needed in certain instances: Clinical suspicion, progression of cellulitis despite antibiotics, profound toxicity/shock, presence of gas in soft tissues
Antibiotics for Necrotizing infections?
Empiric antibiotics: MRSA coverage (vancomycin), Gram negative/anaerobic: Piperacillin/tazobactam OR cefepime or ceftriaxone + metronidazole OR carbapenem
Confirmed strep or clostridial monoinfection: Penicillin G + IV clindamycin (clindamycin used to reduce toxin production)
Duration considerations: No further debridement needed, clinically improved/afebrile for 48-72 hours
What infections are caused by oyster consumption/salt water exposure? Treatment?
Vibrio Vulnificus
Risk factors: Liver disease, alcohol consumption, diabetes, or other immunocompromising conditions
May cause necrotizing infections and septicemia
Treatment: Doxycycline 100 mg IV q12h PLUS ceftriaxone 1-2 g IV q24h
What infections are caused by fresh water exposure? Treatment?
Aeromonas hydrophilia
May cause necrotizing infections and septicemia
Treatment: Doxycycline 100 mg IV q12h PLUS ceftriaxone or ciprofloxacin
What infections are caused by dog and animal bites? Treatment?
Usually polymicrobial, aerobic/anaerobic
P Multocida
Therapy should cover P multocida and anaerobes
Amox-clavulanate/Ampicillin-sulbactam (IV)
2nd or 3rd gen cephalosporin PLUS clindamycin or metronidazole
What infections are caused by human bites and closed fist wounds? Treatment?
Mixed aerobic and anaerobic bacteria (Strep, S aureus, E corrodens, Fusobacterium, Peptostreptococcus, Prevotella, Porphyromonas)
Treatment:
- Amox/clavulanate / Amp-sulbactam
- Ciprofloxacin plus metronidazole
Daptomycin: Dosing? Monitoring? Adverse effects?
Daptomycin 4 mg/kg IV q24h unless for bacteremia, then 6 mg/kg IV q24h
Monitor CPK
Can cause rhabdomyolsis so consider holding statins
Linezolid: Dosing? Monitoring? Adverse effects?
600 mg IV/PO BID
Weak MAO-I so check for drug interactions
Monitor platelets
Tedizolid: Dosing?
200 mg PO once daily
Oxazolidinone, similar to linezolid
Ceftaroline: Dosing? Usage?
600 mg IV q12h
Useful in mixed infections
Oritavancin: Dosing?
1200 mg IV ONCE
Half life is 393 hours
Dalbavancin: Dosing?
1500 mg IV once or 100 mg on D1 and 500 mg on day 7
Half life is 346 hours
What are the two long acting antibiotics?
Oritavancin (half life 393 hours)
Dalbavancin (half life 346 hours)
