Skin & Soft Tissue Infections



1.  Streptococcus pyogenes (“Strep”)

2.  Staphylococcus aureus (“Staph”)
  • MRSA (“Methicillin-Resistant Staph Aureus”)
  • MSSA (“Methicillin-Sensitive Staph Aureus”)

Clues for Distinguishing Staph from Strep

Suspect Staph

  • spreads relatively slowly
  • pus present !!! (abscess, etc)
  • nearby satellite lesions

Suspect Strep

  • spreads very rapidly
  • superficial (pure cellulitis)
  • lymphangitis (red streak)

ANTIBIOTICS  (click link for Common Doses)

Drugs for MSSA also kill Strep

1.  Anti-Staphylococcal Penicillins (Methicillin class):
  • Dicloxacillin (oral)
  • Oxacillin (parenteral)
2.  1st Generation Cephalosporins
  • Cephalexin (oral)
  • Cefazolin (parenteral)  [3rd-Gen. Ceftriaxone too]

3.  Amoxicillin + clavulanate (Augmentin®)

4.  Clindamycin [see below under MRSA]

Drugs for MRSA do NOT kill Strep

1.  Trimethoprim-Sulfamethoxazole (TMP-SMX) [Septra®, Bactrim®, et al.)

2.  Doxycycline (the main tetracycline available)

3.  Clindamycin (if not a serious infection)
  • Does kill Strep,  doesn’t kill all MRSA
  • If C&S “Sens” to Clinda but “Resist” to Erythromycin, may NOT kill MRSA
  • Request an additional “D-Test” to know for sure
4.  Linezolid (at >$1,000)
  • Save for pt. discharged from hospital to complete course with p.o. Tx, when C&S not obtained

Treatment Strategies

MRSA not prevalent in community

1.  Dicloxacillin OR Amoxicillin-Clavulante

2.  Penicillin-Allergic:   Cephalexin

3.  Initial parenteral dose:   Cefazolin OR Ceftriaxone
  • For rapid onset when hope to avoid admission

MRSA common in community

1.  Make an educated diagnosis of Staph vs. Strep [see above]

2.  If think Strep, treat as above (as if MRSA not an issue)

3.  If think Staph & thus deal with MRSA:
  • Trimethoprim-Sulfamethoxazole (TMP-SMX)
  • Doxycycline
  • Clincamycin (if not a serious infection)
4.  Initial parenteral dose (if hope to avoid admission)
  • Cefazolin OR Ceftriaxone
  • plus TMP-SMA DS, 2 tabs


1.  NEVER give antibiotics for abscesses.  Drain them.
  • May Rx antibiotic if abscess with large area of surrounding cellulitis
2.  Failure to Respond can be due to several possibilities:
  • Wrong Diagnosis, e.g. rash is not an infection
  • Abscess (needs I & D)
  • Foreign body
  • Underlying osteomyelitis
  • Possibly – wrong Antibiotic

3.  Some special infections involve other microorganisms:

  • E. coli
  • Pseudomonas
  • Clostridium
  • Sporotrichosis
  • Mycobacteria
  • Pasteurella multocida    
  • Oral Anaerobic bacteria
> Debilitated pts, esp. infected decubiti
> Infected burns           
> Gangrene, fasciitis  
> Rose-bush infection (fungal)  
> Sea-water infection  
> Dog & Cat Bites  
> Human bites

See 2012 Guidlines from Infectious Disease Society of America.