Cefixime for UTI Caused by Streptococcus Viridans Group
Cefixime is NOT adequate for treating UTI caused by Streptococcus viridans group, as this organism demonstrates significant resistance to oral cephalosporins, with cephalexin showing 96% resistance rates and cefixime having poor activity against viridans streptococci.
Resistance Profile of Viridans Group Streptococci
The viridans group streptococci have developed substantial resistance to cephalosporins over recent decades:
- Cephalexin demonstrates 96% resistance among viridans group streptococci blood culture isolates 1
- The rank order of cephalosporin activity shows cefpodoxime and ceftriaxone are superior to other oral cephalosporins, with cephalexin being the least active 1
- Resistance to ceftriaxone ranges from 17-42% in various studies, and ceftriaxone is 2-4 times more active than cefazolin 1
- Penicillin resistance has increased from 0% (1971-1986) to 13% (1994-2002), with similar trends for other beta-lactams 1
Recommended Treatment Alternatives
For UTI caused by Streptococcus viridans group, consider these evidence-based options:
First-Line Agents
- Amoxicillin 2g orally is the preferred agent for viridans streptococci when oral therapy is appropriate 1
- Ampicillin 2g IM or IV for patients unable to take oral medications 1
- Ceftriaxone 1g IM or IV has better activity than oral cephalosporins and can be used parenterally 1
Alternative Agents (if penicillin-allergic)
- Clindamycin 600mg (though resistance ranges 13-27%) 1
- Azithromycin or clarithromycin 500mg should be used cautiously given macrolide resistance rates of 22-58% 1
Critical Clinical Considerations
Common pitfall: Assuming all cephalosporins have equivalent activity against viridans streptococci. The evidence clearly demonstrates that oral cephalosporins, particularly first-generation agents like cephalexin and likely cefixime, have unacceptably high resistance rates 1.
Antibiotic stewardship principle: While cefixime has demonstrated efficacy for typical uropathogens like E. coli in uncomplicated UTI (94-100% cure rates) 2, 3, 4, its spectrum does not adequately cover viridans streptococci, which require different therapeutic considerations 1.
For complicated UTI with viridans streptococci, infectious disease consultation is strongly recommended to optimize antimicrobial selection and avoid treatment failure 1, 5.