Macrobid is NOT an appropriate choice for Group B Streptococcus UTI in elderly patients
Nitrofurantoin (Macrobid) should be changed to penicillin-based therapy, as Group B Streptococcus requires high-dose penicillin G for serious infections, and nitrofurantoin shows concerning resistance patterns in GBS isolates. 1
Why Nitrofurantoin is Problematic for GBS
Resistance Concerns
- 18.5% of GBS urinary isolates demonstrate non-susceptibility to nitrofurantoin, which is an unacceptably high failure rate for a potentially serious infection 2
- While one older study showed 95.5% sensitivity, this conflicts with more recent genomic data showing resistance patterns 3, 2
- No known nitrofurantoin resistance genes have been identified in resistant GBS strains, making resistance unpredictable and potentially underestimated 2
Clinical Severity in Elderly
- GBS causes invasive disease with particularly high mortality in elderly patients, with the highest incidence occurring in adults over 60 years of age 1
- Common manifestations include urosepsis, bacteremia without identified source, and progression to serious infections requiring aggressive treatment 1
- The majority of elderly adults with GBS infections have underlying diseases including diabetes mellitus, malignant neoplasms, and liver disease 1
Recommended Alternative Treatment
First-Line Therapy
- High-dose penicillin G (benzylpenicillin) is the recommended treatment for serious GBS infections due to somewhat higher minimal inhibitory concentrations compared to other streptococcal species 1
- Ampicillin shows 96% sensitivity in GBS urinary isolates and is an appropriate oral alternative 3
- Treatment duration should be at least 7-10 days, with longer courses for complicated infections 4, 5
Additional Appropriate Options
- Cephalothin demonstrates 100% sensitivity to GBS urinary isolates 3
- Norfloxacin shows 96.9% sensitivity, though fluoroquinolones require mandatory renal dose adjustment in elderly patients 3, 4
Critical Considerations for Elderly Patients
Renal Function Assessment
- Calculate creatinine clearance using the Cockcroft-Gault equation rather than relying on serum creatinine alone to guide antibiotic dosing 6, 4
- Dose adjustments are essential in elderly patients with renal impairment to prevent toxicity 6
Complicating Factors
- Virtually all patients above 80 years present with complicated UTI due to general debility, diabetes, bladder outflow obstruction, or abnormal bladder function 5
- Urine culture and susceptibility testing are mandatory in elderly patients to detect multiple and/or resistant microorganisms 5
Monitoring Requirements
- Pay attention to hydration status and perform repeated physical assessments, especially in nursing home residents 7
- Be vigilant for progression to bacteremia or systemic infection, which occurs frequently with GBS 1
Common Pitfalls to Avoid
- Do not continue nitrofurantoin empirically for GBS UTI without documented susceptibility testing showing sensitivity 2
- Avoid treating asymptomatic bacteriuria, which occurs in approximately 40% of institutionalized elderly women but does not require treatment 5, 4
- Do not overlook the need for surgical management in cases of soft-tissue or bone infection that may develop from GBS bacteremia 1
- Consider polypharmacy and drug interactions when prescribing antibiotics in elderly patients 6