From the Research
Macrobid (nitrofurantoin) is not recommended for treating Streptococcus agalactiae (Group B Streptococcus or GBS) urinary tract infections. While nitrofurantoin is effective against many common UTI pathogens like E. coli, as shown in a study published in BJU International in 2008 1, it has poor activity against Group B Streptococcus. The most recent and highest quality study, a narrative review published in Frontiers in Cellular and Infection Microbiology in 2023 2, does not provide specific information on the effectiveness of nitrofurantoin against GBS. However, based on the mechanism of action of nitrofurantoin, which works better against gram-negative organisms than gram-positive bacteria like Streptococcus, it is unlikely to be effective against GBS.
Some key points to consider when treating UTIs include:
- The importance of choosing an antibiotic with activity against the specific causative organism
- The need for culture and sensitivity testing to guide appropriate therapy
- The potential for resistance to certain antibiotics, such as the emergence of nitrofurantoin resistance in E. coli, as reported in a study published in Microorganisms in 2020 3
- The consideration of renal function when prescribing nitrofurantoin, as highlighted in a study published in the European Journal of Clinical Microbiology and Infectious Diseases in 2017 4
For GBS UTIs, preferred antibiotics include:
- Penicillins (such as amoxicillin 500 mg three times daily for 5-7 days)
- Cephalosporins (like cephalexin 500 mg four times daily for 5-7 days)
- Clindamycin (300 mg four times daily for 5-7 days) in cases of penicillin allergy. A randomized clinical trial published in JAMA in 2018 5 compared the effectiveness of nitrofurantoin and fosfomycin in treating uncomplicated lower urinary tract infections, but did not provide specific information on the treatment of GBS UTIs.