What is the recommended treatment for a Streptococcus anginosus urinary tract infection (UTI)?

Treatment for Streptococcus anginosus Urinary Tract Infection

Penicillin is the drug of choice for treating Streptococcus anginosus urinary tract infections due to high susceptibility patterns and excellent clinical outcomes. 1

Antimicrobial Options

First-line Treatment:

• Penicillin G or Ampicillin
  • Streptococcus anginosus strains show excellent susceptibility to penicillins 1
  • For uncomplicated UTI: Ampicillin 500 mg PO three times daily for 7-10 days
  • For complicated UTI: Consider parenteral therapy initially

Alternative Options (if penicillin allergy):

• Cephalosporins (except ceftazidime which shows intermediate susceptibility) 1
  • Cefotaxime or cefuroxime are good alternatives
• Clindamycin 300-450 mg PO four times daily for 7-10 days 1
• Vancomycin (for severe infections or multi-drug resistant strains) 1

Agents to Avoid:

• Tetracycline (61.4% of S. anginosus strains show resistance) 1
• Ceftazidime (54.5% of strains show intermediate susceptibility) 1

Treatment Algorithm

1. Obtain urine culture before starting antibiotics

   • Essential to confirm diagnosis and guide targeted therapy 2

2. Initiate empiric therapy while awaiting culture results

   • Use penicillin or ampicillin as first-line agents
   • Consider local resistance patterns and patient factors

3. Adjust therapy based on culture and susceptibility results

   • Narrow spectrum when possible for antibiotic stewardship 2

4. For complicated infections:

   • Consider imaging to rule out abscess formation
   • S. anginosus is known for its propensity to form abscesses 3, 4
   • If abscess is present, surgical drainage plus antibiotics is required 4

5. Duration of therapy:

   • Uncomplicated UTI: 7-10 days
   • Complicated UTI: 10-14 days
   • Longer duration may be needed with abscess formation

Special Considerations

Risk Factors for Complicated Infection:

• Diabetes mellitus
• Immunocompromised status
• Structural urinary tract abnormalities
• Advanced age
• Recent urologic procedures

Monitoring Response:

• Clinical improvement should be evident within 48-72 hours
• If symptoms persist, repeat urine culture and consider imaging to rule out abscess formation 3
• S. anginosus has a known propensity for abscess formation, which may require drainage 4

Clinical Pearls and Pitfalls

• Pearl: S. anginosus is part of the normal oral, gastrointestinal, and genitourinary flora but can cause invasive infections
• Pitfall: Failing to consider abscess formation in patients with persistent symptoms despite appropriate antibiotic therapy
• Pearl: Blood cultures should be obtained in patients with systemic symptoms to rule out bacteremia
• Pitfall: Misidentification of S. anginosus as other streptococci in laboratory testing, potentially leading to inappropriate treatment
• Pearl: Despite being part of the viridans group, S. anginosus is more invasive and pyogenic than other viridans streptococci

In cases where S. anginosus UTI leads to bacteremia, more aggressive therapy and evaluation for metastatic infection sites may be warranted 3, 4.