Is Macrobid (nitrofurantoin) effective against Enterococcus faecalis?

Nitrofurantoin (Macrobid) Coverage of Enterococcus faecalis

Yes, nitrofurantoin (Macrobid) has good in vitro activity against Enterococcus faecalis and is FDA-approved for lower urinary tract infections caused by this organism. 1

Microbiological Activity

• Nitrofurantoin demonstrates excellent activity against E. faecalis, with susceptibility rates of 88-91% in clinical isolates, including those with vancomycin resistance 2, 3, 4

• The drug maintains activity against vancomycin-resistant enterococci (VRE), with 80.76% of VRE isolates remaining susceptible to nitrofurantoin 2

• No resistance was detected (MIC ≥128 μg/mL) in a study of 300 enterococcal isolates, including vancomycin-resistant E. faecalis strains 5

Clinical Indications and Limitations

Appropriate Use:

• Lower urinary tract infections (cystitis) caused by E. faecalis - this is the FDA-approved indication 1

• Chronic bacterial prostatitis caused by resistant E. faecalis when combined with rifampin (100 mg PO every 6 hours) per American Urological Association recommendations 6

Critical Limitations:

• Nitrofurantoin achieves poor plasma concentrations and should NOT be used for:

  • Bacteremia or bloodstream infections 1
  • Endocarditis 1
  • Pyelonephritis or upper urinary tract infections 1
  • Any systemic enterococcal infection 1

• Clinical efficacy data is limited - while in vitro activity is well-documented, clinical outcome data for treating VRE infections is rarely reported 1

Comparative Effectiveness

• Nitrofurantoin shows superior activity compared to other oral agents for enterococcal UTIs, with higher susceptibility rates than doxycycline (11%), co-trimoxazole (13%), and comparable to vancomycin (99%) 3

• Among ampicillin-resistant strains, 50-88% remain susceptible to nitrofurantoin 3

Monitoring and Safety

• Monitor for adverse effects including pulmonary reactions, hepatic toxicity, and gastrointestinal disturbances 6

• Complete the full prescribed course to ensure eradication and prevent relapse 6

Alternative Agents for Systemic E. faecalis Infections

When nitrofurantoin is inappropriate (systemic infections, bacteremia, endocarditis):

• Ampicillin remains the drug of choice for susceptible E. faecalis, typically combined with gentamicin for synergy in serious infections 1

• For vancomycin-resistant E. faecalis: linezolid or daptomycin (8-12 mg/kg) are preferred for serious infections 1

• Fosfomycin is FDA-approved for UTI caused by E. faecalis and has activity against VRE 1