Community-Associated Methicillin-Resistant Staphylococcus Aureus (CA-MRSA)

Background

• Two kinds:
  • Hospital acquired (see MRSA)
    • Multi-drug resistant, most commonly seen in ventilator associated pneumonia, post operative infections, and catheter associated infections
  • Community acquired (CA-MRSA)
    • Tends to be resistant to beta-lactams, most commonly seen in Skin and Soft Tissue Infections and rarely in necrotizing pneumonia

Risk Factors

1. multiple skin sites
2. recurrent infection
3. pt who has been in close contact of person with Hx of MRSA
4. infection showing early necrosis

Treatment

1. Antibiotics
   1. Cephalexin + Bactrim DS
      1. Estimated 95-100% sensitivity of CA-MRSA
   2. Clindamycin
      1. Approximately 50% sensitivity to CA-MRSA
      2. Inducible resistance by erythromycin in laboratory, unclear significance
   3. doxycycline
      1. Contraindicated in pregnant females and children due to deposition in teeth and bones
   4. Vancomycin IV if severe infection/sepsis
   5. Linezolid
      1. Indicated in severe soft tissue infections and pneumonia thought to be caused by CA-MRSA or HA-MRSA
2. I&D if abscess
   1. (antibiotics not needed if no e/o cellulitis)

Antibiotic Sensitivities

Organisms	'	Staph. aureus (CA-MRSA)
Penicillins	Penicillin G	0
	Penicillin V	0
Anti-Staphylocccal Penicillins	Methicillin	0
	Nafcillin/Oxacillin	0
	Cloxacillin/Diclox.	0
Amino-Penicillins	AMP/Amox	0
	Amox/Clav	0
	AMP-Sulb	0
Anti-Pseudomonal Penicillins	Ticarcillin	0
	Ticar-Clav	0
	Pip-Taxo	0
Carbapenems	Piperacillin	0
	Doripenem	0
	Ertapenem	0
	Imipenem	0
	Meropenem	0
	Aztreonam	0
Fluroquinolones	Ciprofloxacin	+/-
	Ofloxacin
	Pefloxacin
	Levofloxacin	+/-
	Moxifloxacin	+/-
	Gemifloxacin	+/-
	Gatifloxacin	+/-
1st G Cephalosporin	Cefazolin	0
2nd G. Cephalosporin	Cefotetan	0
	Cefoxitin	0
	Cefuroxime	0
3rd/4th G. Cephalosporin	CefoTAXime	0
	Cefizoxime	0
	CefTRIAXone	0
	Ceftobiprole	+
	Ceftaroline	+
	CefTAZidime	0
	Cefepime	0
Oral 1st G. Cephalosporin	Cefadroxil	0
	Cephalexin	0
Oral 2nd G. Cephalosporin	Cefaclor/Loracarbef	0
	Cefproxil	0
	Cefuroxime axetil	0
Oral 3rd G. Cephalosporin	Cefixime	0
	Ceftibuten	0
	Cefpodox/Cefdinir/Cefditoren	0
Aminoglycosides	Gentamicin
	Tobramycin
	Amikacin
	Chloramphenicol
	Clindamycin	+/-
Macrolides	Erythromycin	+/-
	Azithromycin	+/-
	Clarithromycin	+/-
Ketolide	Telithromycin	+/-
Tetracyclines	Doxycycline	+
	Minocycline	+
Glycylcycline	Tigecycline	+
Glyco/Lipoclycopeptides	Vancomycin	+
	Teicoplanin	+
	Telavancin	+
	Fusidic Acid	+
	Trimethoprim	+
	TMP-SMX	+
Urinary Agents	Nitrofurantoin	+
	Fosfomycin
Other	Rifampin	+
	Metronidazole	0
	Quinupristin dalfoppristin	+
	Linezolid	+
	Daptomycin	+
	Colistimethate	0

Key

• S susceptible/sensitive (usually)
• I intermediate (variably susceptible/resistant)
• R resistant (or not effective clinically)
• S+ synergistic with cell wall antibiotics
• U sensitive for UTI only (non systemic infection)
• X1 no data
• X2 active in vitro, but not used clinically
• X3 active in vitro, but not clinically effective for Group A strep pharyngitis or infections due to E. faecalis
• X4 active in vitro, but not clinically effective for strep pneumonia

See Also

• Microbiology (Main)
• Staph. aureus