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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

Native Valve	S. aureus Streptococci spp. Enterococcus spp. Occasional gram negative rods HACEK < 5%	Vancomycin WITH or WITHOUT* Ceftriaxone 2 g IV daily	For severe PCN allergy: Vancomycin WITH or WITHOUT* CiprofloxacinID-R: VASF 400 mg IV q12h	Narrow coverage to microbiologically confirmed pathogens *Addition of Gram-negative coverage should be considered if the patient has a sub-acute presentation.
Prosthetic Valve	S. aureus S. epidermidis	Vancomycin PLUS Rifampin300 mg PO q8h PLUS Gentamicin 1 mg/kg/dose IV q8h for initial two weeks only Single daily dose of gentamicin is not recommended		Rifampin has numerous clinically significant drug interactions.  Medication lists should be reviewed for potential drug-drug interactions with rifampin.

Spontaneous Bacterial Peritonitis (SBP)	E. coli Klebsiella spp. 'Streptococci. spp.	Ceftriaxone 1 g IV daily x 5 days	For severe PCN allergy: Vancomycin PLUS Aztreonam 2 g IV q8h
Secondary Peritonitis Mild-Moderate intra-abdominal abscess	E. coli Klebsiella  B. fragilis Streptococci spp S. aureus	Ertapenem 1g IV daily OR Piperacillin/tazobactam 3.375 g IV q6h - 4.5g IV q6h	For severe PCN allergy: Vancomycin PLUS Aztreonam 2 g IV q8h PLUS Metronidazole500 mg IV q8h
Secondary Peritonitis Severe (major peritoneal soilage, large or multiple abscesses, patient hemodynamically unstable)	E. coli  Klebsiella B. fragilis  P. aeruginosa Enterococcus spp. Streptococcus spp S. aureus	Vancomycin PLUS Piperacillin/tazobactam 4.5 g IV q6h	For severe PCN allergy: Vancomycin PLUS Aztreonam 2 g IV q8h PLUS Metronidazole500 mg IV q8h	For hemodynamically unstable health-care associated infection, consider meropenem.
Clostridium difficile-associated diarrhea	Clostridium difficile	Initial episode, mild to moderate disease (WBC ≤15K and SCr less than 1.5 times premorbid level) Vancomycin 125mg PO q6h x 10-14 days.  If unable to obtain at discharge, can complete course with Metronidazole500mg po q8h Initial episode, severe disease (WBC >15k and/or 50% increase in SCr) Vancomycin 125mg PO q6h x 10-14 days. Initial episode, severe disease with complications (Severe disease with hypotension, shock, ilios, and/or megacolon) Vancomycin 500mg PO/NG q6h x 10-14 days PLUS Metronidazole 500 mg IV q8h x 10-14 days WITH OR WITHOUT Vancomycin PR Rectal vancomycin should be considered in patients with ileus. It is given as 500 mg in 100 mL of 0.9% NaCl and instilled q6h (retain each dose for 1h) First recurrence Same therapy as initial episode, stratified by illness severity First recurrence, special population (hematologic malignancy with >30 days expected neutropenia, recent HSCT, recent treatment for GVHD, solid organ transplant <3 months) FidaxomicinID-R: UCSF SFGH  VASF 200mg PO BID x10 days Second recurrence Vancomycin with tapered or pulsed regimen PLUS Consult ID, GI PLUS Evaluate for fecal microbiota transplant	IV metronidazole alone is not indicated for treatment of C. difficile diarrhea. IV metronidazole should only be used in combination with PO vancomycin in the ICU. Recurrence in 5-30% of patients after first episode and 33-60% after second episode. ID CONSULT recommended in patients with severe disease with complications or multiply recurrent disease, and for consideration of rectal vancomycin administration.