Is Bactrim (trimethoprim/sulfamethoxazole) effective for treating viridans streptococcus infections?

Bactrim Is Not Effective for Treating Viridans Streptococcus Infections

Trimethoprim-sulfamethoxazole (Bactrim) is not recommended for the treatment of viridans streptococcus infections as it lacks reliable activity against these organisms and may potentially increase the risk of viridans streptococcal sepsis in certain populations.

Preferred Treatment Options for Viridans Streptococci

First-line treatments:

• Penicillin-susceptible isolates:
  • Penicillin/ampicillin
  • Ticarcillin
  • Piperacillin
  • Cefepime (but not ceftazidime)
  • Carbapenems (imipenem-cilastatin or meropenem) 1

For penicillin-resistant isolates:

• Vancomycin is the drug of choice 1

Evidence Against Bactrim for Viridans Streptococci

Trimethoprim-sulfamethoxazole (Bactrim) is actually considered a risk factor for developing viridans streptococcal bacteremia in neutropenic patients rather than an effective treatment 1, 2. The 2002 guidelines for neutropenic patients with cancer specifically note that prophylactic use of TMP-SMX may predispose patients to viridans streptococcal infections 1.

Several studies have identified TMP-SMX as a risk factor for viridans streptococcal bacteremia:

• Viridans streptococci are frequently resistant to TMP-SMX 3
• Prophylactic antibiotic treatments with TMP-SMX have been identified as risk factors for viridans streptococcal bacteremia 4

Clinical Considerations

Resistance patterns

• Some strains of viridans streptococci are resistant to or tolerant of penicillin 1
• Resistance to various antimicrobial agents is increasingly recognized among viridans streptococci 3
• High resistance rates of viridans group streptococci have been reported in both healthy individuals and patients with serious underlying diseases 1

Special situations

For endocarditis:

• The American Heart Association guidelines recommend penicillin or ceftriaxone for penicillin-susceptible viridans streptococci 1
• For penicillin-resistant strains, vancomycin is the preferred treatment 1, 5

For neutropenic patients:

• Viridans streptococcal bacteremia can cause serious complications including:
  • Adult respiratory distress syndrome (3-33%)
  • Shock (7-18%)
  • Mortality rates of 6-30% 4, 3
• Empirical vancomycin therapy should be used for neutropenic patients with cancer who have shock or are developing acute respiratory distress syndrome due to viridans streptococci 3

Conclusion

When treating viridans streptococcus infections, clinicians should select antibiotics with proven activity against these organisms. Bactrim (TMP-SMX) is not an appropriate choice for treating viridans streptococcal infections and may actually increase the risk of infection in certain populations. Treatment should be guided by susceptibility testing, with penicillins, cephalosporins (except ceftazidime), or carbapenems for susceptible isolates, and vancomycin for resistant strains.