From the Guidelines
For a urinary tract infection caused by Group B Streptococcus (Streptococcus agalactiae), the first-line antibiotic treatment is penicillin or ampicillin, as recommended by the most recent guidelines 1. A typical regimen would be ampicillin 500 mg orally four times daily for 7 days, or penicillin V 500 mg orally four times daily for 7 days. For patients with penicillin allergy, alternatives include cephalexin 500 mg orally four times daily for 7 days (if not anaphylactic to penicillin) or clindamycin 300 mg orally four times daily for 7 days (for severe penicillin allergy). Some key points to consider when treating Group B Streptococcus infections include:
- The bacterium produces beta-hemolysin and can invade the urinary tract, particularly in pregnant women, elderly patients, and those with diabetes or immunocompromise.
- Treatment should be guided by susceptibility testing when available, and patients should complete the full course of antibiotics even if symptoms resolve earlier.
- For complicated infections or pyelonephritis, consider intravenous therapy with ampicillin 2g IV every 6 hours or ceftriaxone 1-2g IV daily.
- Group B Streptococcus remains highly susceptible to beta-lactam antibiotics, which is why penicillins are the preferred treatment, as stated in the guidelines 1. However, the most recent and highest quality study 1 should be prioritized when making a definitive recommendation. In this case, the study recommends penicillin G and ampicillin for intrapartum antibiotic prophylaxis, and cefazolin for women allergic to penicillin who are at low risk of anaphylaxis. For women allergic to penicillin who are at high risk of anaphylaxis, clindamycin should be administered to those colonized with GBS that is known to be susceptible to clindamycin. Vancomycin is recommended for women colonized with clindamycin-resistant GBS isolates who are allergic to penicillin and at high risk of anaphylaxis. It's essential to follow the most recent guidelines and consider the specific circumstances of each patient when making treatment decisions.
From the FDA Drug Label
Infections of the gastrointestinal and genitourinary tracts (including those caused by Neisseria gonorrhoeae in females) Penicillin G is highly active in vitro against streptococci (groups A, B, C, G, H, L, and M)
Ampicillin (IV) or Penicillin G (IV) can be used to treat a patient with a urine culture showing growth of Streptococcus agalactiae Group B.
- The dosage of Ampicillin (IV) for infections of the genitourinary tracts is 500 mg every 6 hours for patients weighing 40 kg (88 lbs) or more, and 50 mg/kg/day in equally divided doses at 6- to 8-hour intervals for patients weighing less than 40 kg (88 lbs) 2.
- Penicillin G (IV) is highly active in vitro against Streptococcus agalactiae Group B 3.
From the Research
Antibiotic Treatment for Streptococcus agalactiae (Group B)
- The recommended antibiotic treatment for Streptococcus agalactiae (Group B) is Penicillin G 4, 5, 6, 7.
- For patients allergic to penicillin, alternative antibiotics such as Erythromycin, Vancomycin, and Clindamycin can be used 4, 7.
- However, resistance to Erythromycin and Clindamycin has been reported, with 25% and 13% resistance rates, respectively 4.
- Vancomycin is also an effective option, with no reported resistance in some studies 4.
- Ampicillin is also effective against Streptococcus agalactiae, with all strains being sensitive in some studies 4, 5, 7.
Considerations for Urinary Tract Infections
- Group B Streptococcus can cause urinary tract infections in nonpregnant adults, especially those with underlying conditions such as urinary tract abnormalities and chronic renal failure 8.
- The clinical outcome of these infections can be poor despite treatment, highlighting the need for prompt and effective antibiotic therapy 8.
- All isolates of Group B Streptococcus from urinary tract infections were sensitive to all antibiotics tested except gentamicin in one study 8.