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Hospitalized patients

Infection		Organisms	First DOC	Alternative
Osteomyelitis	Presumed hematogenous source or contiguous without vascular insufficiency	S. aureus	Vancomycin	Vanc	If S. aureus is methicillin-susceptible then cefazolin 2 g IV q8h or nafcillin 2 g IV q4h are the antibiotics of choice. Obtain bone biopsy to determine microbiologic cause prior to initiation of antimicrobial therapy if blood cultures are negative and patient clinically stable.
	With vascular insufficiency or diabetes mellitus (e.g. severe diabetic foot ulcer)	S. aureus  Enterobacteriaceae Anaerobes	Vancomycin PLUS ONE OF: Piperacillin/Tazobactam 4.5 g IV q6-8h OR Ertapenem 1 g IV daily	For severe PCN allergy: Vancomycin PLUS ONE OF: Ciprofloxacin400 mg IV q12h OR Levofloxacin 750 mg IV daily OR Aztreonam 2 g IV q8h ALL WITH OR WITHOUT: Metronidazole500 mg IV q8h (if patient critically ill)	Other organisms are possible, esp. with hardware microbiologic diagnosis and ID consultation recommended Obtain bone biopsy to determine microbiologic cause prior to initiation of antimicrobial therapy if patient clinically stable Once stable, switch to oral antibiotics based on susceptibility results.
Septic Arthritis		S. aureus Streptococci spp. N. gonorrhoeae Enterobacteriaceae (rarely)	Vancomycin PLUS Ceftriaxone1 g IV daily	For severe PCN allergy: Vancomycin PLUS ONE OF: Ciprofloxacin 400 mg IV q12h OR Levofloxacin 500 mg IV daily OR Aztreonam g IV q8h if gonococcus is strongly suspected	Gram stain recommended to guide therapy. Narrow coverage to microbiologically confirmed pathogens.

Brain abscess	Streptococci (anaerobic or aerobic) Bacteroides spp Prevotella spp Enterobacteriacea	Ceftriaxone 2 g IV q12h PLUS Metronidazole 500 mg PO/IV q8h WITH OR WITHOUT*: Vancomycin	Aztreonam 2 g IV q8h PLUS Vancomycin PLUS Metronidazole 500 mg PO/IV q8h	Consider expanded Gram-positive coverage if patient at risk for drug-resistant streptococci or MRSA
Meningitis Community-onset	S. pneumoniae Neisseria meningitidis Listeria (especially in immuno-compromised, elderly patients, and alcoholics)	ceftriaxone 2 g IV q12h PLUS Vancomycin WITH OR WITHOUT* one of: TMP/SMX 15 mg/kg/day (in divided doses) OR 'Ampicillin' 2 g IV q4h	For severe PCN allergy: Vancomycin PLUS Aztreonam2 g IV q6h-q8h WITH OR WITHOUT*: TMP/SMX (if Listeria) 15 mg/kg/day (in divided doses)	Therapy should be guided by Gram stain. If bacterial meningitis suspected, dexamethasone 10 mg PO/IV q6h x 4 days given before or with initial dose of antibiotics.  *Coverage for Listeria with TMP/SMX or ampicillin should be added for patients who are <2 or >50 years of age or immunocompromised.
Meningitis Post-neurosurgical or device associated	S. aureus Coagulase negative Staphylococci Gram negative rods	Cefepime PLUS 'Vancomycin'	For severe PCN allergy: Aztreonam 2 g IV q6h-q8h PLUS Vancomycin