Does Macrobid Cover E. coli?
Yes, Macrobid (nitrofurantoin) is highly effective against E. coli and is recommended as a first-line treatment for uncomplicated urinary tract infections caused by this pathogen. 1
Microbiological Efficacy
Nitrofurantoin demonstrates excellent activity against E. coli, with susceptibility rates of 95.6% and resistance rates as low as 2.3% in community isolates. 2
The WHO and major guidelines recommend nitrofurantoin as a first-choice antibiotic for lower urinary tract infections, achieving clinical and microbiological cure rates of 90-92%. 1, 3
Nitrofurantoin retains activity even against multidrug-resistant (MDR) E. coli strains, with only 2.1% resistance in isolates resistant to three other antimicrobial agents, compared to 62.6% resistance to trimethoprim-sulfamethoxazole and 48.9% resistance to ciprofloxacin in the same MDR population. 4
Clinical Guidelines and Recommendations
The AUA/CUA/SUFU guidelines designate nitrofurantoin as first-line therapy for symptomatic UTIs in women, alongside trimethoprim-sulfamethoxazole and fosfomycin, with treatment duration generally no longer than seven days. 1
The WHO Expert Committee specifically lists nitrofurantoin as an Access antibiotic for lower urinary tract infections in both adults and children, noting that E. coli susceptibility to nitrofurantoin remains generally high. 1
Nitrofurantoin is cost-effective when fluoroquinolone-resistant E. coli exceeds 12%, making it an excellent fluoroquinolone-sparing alternative in areas with high resistance. 1
Important Clinical Limitations
Do NOT use nitrofurantoin for pyelonephritis or systemic infections because it does not achieve adequate serum concentrations—it is only effective for lower urinary tract infections (cystitis). 3
Nitrofurantoin is contraindicated in the last trimester of pregnancy due to risk of hemolytic anemia in the newborn. 3
Avoid in patients with any degree of renal impairment, as the drug requires adequate renal function for urinary concentration and efficacy. 5
Dosing and Duration
The recommended dosage is 100 mg twice daily for 5 days for uncomplicated cystitis. 3
Treatment should be as short as reasonable, generally no longer than seven days, to minimize antibiotic exposure while maintaining efficacy. 1
Resistance Considerations
The low incidence of nitrofurantoin resistance (<10%) is maintained because urine-based nitrofurantoin concentrations selectively inhibit E. coli strains carrying first-step resistance mutations. 6
Despite over 60 years of use, nitrofurantoin has retained excellent activity against E. coli and other common uropathogens like Staphylococcus saprophyticus and Enterococcus species. 5