All symptomatic patients with Serratia infection require antimicrobial therapy. Serratia may be difficult to treat and is directed towards the site of infection. Antimicrobial therapy includes either cefipime, imipenem, or ciprofloxacin for 7-14 days. In endocarditis, treatment may continue up to 4-6 weeks, and in osteomyelitis up to 12 weeks.

• All symptomatic patients with Serratia infection require antimicrobial therapy.
• Serratia may be difficult to treat because it contains R-factors, which are virulence factors that allow Serratia to resist against antibiotics.

• Serratia marcescens^[1]

• 1. Bacteremia, pneumonia or serious infections

• Preferred regimen (1): Cefepime 1-2 g IV q8h
• Preferred regimen (2): Imipenem 0.5-1.0 g IV q6h
• Preferred regimen (3): Ciprofloxacin 400 mg IV q8h
• Alternative regimen (1): Aztreonam
• Alternative regimen (2): Gentamicin
• Alternative regimen (3): Amikacin
• Alternative regimen (4): Piperacillin-tazobactam also often effective
• Note: Duration depends on clinical response, usually 7-14 days

• 2. Endocarditis

• Note: Choice dictated by sensitivities, 4 to 6 week duration of parenteral therapy.

• 3. Osteomyelitis

• Note (1): Choice dictated by sensitivity profile, treat for 6-12 weeks depending upon response.
• Note (2): Use IV treatment until stable/clinically improved (10-14 days Minimum) then may convert to oral therapy if appropriate.

• 4. UTI

• Preferred regimen (1): Ciprofloxacin 250 mg PO bid or 400 mg IV q12h
• Preferred regimen (2): Levofloxacin 250 mg PO qd or 500mg IV q24h
• Note: Fluoroquinolones often sensitive but in seriously ill patient consider empiric coverage with two drugs (e.g.,beta-lactam and aminoglycoside or fluoroquinolones and carbapenem) until susceptibilities known.