What is the recommended treatment for Streptococcus salivarius bacteremia?

Treatment of Streptococcus salivarius Bacteremia

For clinically significant Streptococcus salivarius bacteremia, treat with penicillin G or ampicillin as first-line therapy, but be aware that up to 31% of isolates may be penicillin-resistant, necessitating susceptibility testing and potential use of vancomycin or ceftriaxone for resistant strains. 1

Initial Assessment and Clinical Significance

• Not all positive blood cultures represent true infection: Only 32% of S. salivarius isolates from blood cultures are clinically significant, with the remainder representing contamination 1
• True bacteremia occurs primarily in patients with mucosal disruption (gastrointestinal procedures, oral trauma) and/or serious underlying diseases, particularly non-colon malignancies (53% of cases) 2, 1
• Obtain blood cultures before initiating therapy to confirm the diagnosis and guide antimicrobial selection 3

Antibiotic Selection Based on Susceptibility

First-Line Therapy (for susceptible isolates):

• Penicillin G (2-4 million units IV every 4-6 hours) is the preferred agent when susceptibility is confirmed 4
• Ampicillin or amoxicillin are effective alternatives, with 84% susceptibility rates for S. salivarius 4

For Penicillin-Resistant Isolates (31% resistance rate):

• Vancomycin (30-60 mg/kg/day IV in 2-4 divided doses, targeting trough 15-20 µg/mL for severe infections) provides 100% susceptibility 3, 4
• Ceftriaxone shows 94% susceptibility and can be used as an alternative 4
• Clindamycin (600-900 mg IV every 6 hours) demonstrates 100% susceptibility in S. salivarius isolates 4

Alternative Agents with High Activity:

• Levofloxacin, quinupristin/dalfopristin, and rifampin show excellent activity against all viridans streptococci, including S. salivarius 4

Treatment Duration

• Standard duration is 7-14 days for uncomplicated bacteremia without endocarditis 3
• Extend therapy for complicated infections: Endocarditis occurs in 18% of S. salivarius bacteremia cases and requires prolonged treatment 1
• Monitor clinical response closely: The bacteremia can be prolonged rather than transient, particularly following gastrointestinal procedures 2

Critical Pitfalls and Special Considerations

Do Not Dismiss as Contamination:

• Clinical context is paramount: While often considered a contaminant, S. salivarius bacteremia in patients with mucosal disruption, underlying malignancy, or persistent positive cultures represents true infection requiring treatment 2, 1

Endocarditis Risk:

• Evaluate for endocarditis in all cases of sustained bacteremia, though the rate (18%) is lower than with S. bovis I (74%) 1
• Obtain repeat blood cultures to document clearance and identify persistent bacteremia suggesting endocarditis or undrained foci 3

Resistance Patterns:

• Always obtain susceptibility testing: The 31% penicillin resistance rate for S. salivarius is significantly higher than other viridans streptococci and mandates testing before narrowing therapy 1
• Gentamicin is not effective as monotherapy against viridans streptococci, though combination therapy may provide additive effects in severe cases 5

Age and Underlying Disease:

• Patients with S. salivarius bacteremia are typically younger (mean age 57 years) than those with S. bovis bacteremia 1
• Screen for non-colon malignancies (53% association) rather than colon tumors (0% association), which distinguishes this from S. bovis I bacteremia 1