Will cephalexin (Cephalexin) effectively treat Group B Streptococcus (GBS)?

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Last updated: May 12, 2025View editorial policy

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From the Guidelines

Cephalexin is not recommended for the treatment of Group B Streptococcus (GBS) infections, as it is not listed as a preferred agent for GBS intrapartum prophylaxis in the guidelines. According to the guidelines from the CDC in 2010 1, the recommended regimens for intrapartum antibiotic prophylaxis for prevention of early-onset GBS disease include penicillin G, ampicillin, cefazolin, vancomycin, and clindamycin, but not cephalexin. The guidelines suggest that cefazolin, a first-generation cephalosporin, can be used as an alternative for patients with a history of anaphylaxis to penicillin, but cephalexin is not mentioned as an option. Key points to consider when treating GBS infections include:

  • The use of penicillin G or ampicillin as the first-line treatment for GBS infections when possible
  • The consideration of cefazolin as an alternative for patients with a history of anaphylaxis to penicillin
  • The importance of completing the full course of antibiotics as prescribed by a healthcare provider to effectively eliminate the infection and prevent complications or recurrence.

From the Research

Antibiotic Susceptibility of Group B Streptococcus

  • Group B Streptococcus (GBS) is generally susceptible to beta-lactam antibiotics, including penicillin and ampicillin 2, 3.
  • However, there have been reports of reduced susceptibility to beta-lactams in some countries 3.
  • Resistance to second-line antibiotics, such as erythromycin and clindamycin, remains high amongst GBS 2, 3, 4.
  • Cefazolin, a first-generation cephalosporin, has been used as an alternative for patients with penicillin allergy, but its effectiveness against GBS is not well-established 5, 6.

Effectiveness of Cephalexin against Group B Streptococcus

  • There is limited information available on the effectiveness of cephalexin, a first-generation cephalosporin, against GBS.
  • Cephalexin is not specifically mentioned in the studies as a recommended treatment for GBS infections 2, 3, 5, 4.
  • However, cefazolin, a related first-generation cephalosporin, has been used as an alternative for patients with penicillin allergy 5, 6.
  • It is unclear whether cephalexin would be effective against GBS, and more research is needed to determine its efficacy 6.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Antibiotic resistance and penicillin tolerance in ano-vaginal group B streptococci.

The journal of maternal-fetal & neonatal medicine : the official journal of the European Association of Perinatal Medicine, the Federation of Asia and Oceania Perinatal Societies, the International Society of Perinatal Obstetricians, 2009

Research

Antibiotic Prescribing Practices in Group B Streptococcus Positive Obstetric Patients with Penicillin Allergy.

South Dakota medicine : the journal of the South Dakota State Medical Association, 2022

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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