What antibiotics are effective against Group B Streptococcus (GBS) in urine?

From the Guidelines

Penicillin G and ampicillin are the first-line antibiotics for treating Group B Streptococcus (GBS) in urine, as recommended by the most recent guidelines 1. For uncomplicated urinary tract infections, typical dosing of ampicillin is 500 mg orally four times daily for 3-7 days.

• The choice of antibiotic depends on the severity of the infection and the patient's allergy status.
• For penicillin-allergic patients, alternatives include:
  • Cephalosporins like cefazolin if the allergy is non-severe.
  • Clindamycin or vancomycin for those with severe penicillin allergies, with clindamycin being recommended for women colonized with GBS that is known to be susceptible to clindamycin 1.
• Nitrofurantoin can also be effective for uncomplicated GBS urinary tract infections.
• Treatment duration typically ranges from 3-7 days for uncomplicated cases to 10-14 days for complicated infections.
• GBS remains universally susceptible to penicillins, which work by inhibiting bacterial cell wall synthesis.
• It's essential to complete the full course of antibiotics even if symptoms improve quickly, and pregnant women with GBS in urine require treatment regardless of symptoms due to risks of ascending infection and neonatal transmission. The most recent guidelines from 2020 1 emphasize the importance of using penicillin G and ampicillin for intrapartum antibiotic prophylaxis, with cefazolin recommended for women allergic to penicillin who are at low risk of anaphylaxis, and vancomycin recommended for women colonized with clindamycin-resistant GBS isolates who are allergic to penicillin and at high risk of anaphylaxis.

From the FDA Drug Label

Vancomycin has been shown to be active against most strains of the following microorganisms, both in vitro and in clinical infections... Streptococcus agalactiae Vancomycin exhibits in vitro MIC's of 1 mcg/mL or less against most (≥90%) strains of streptococci listed below The bactericidal action of vancomycin results primarily from inhibition of cell-wall biosynthesis.

The antibiotics that would cover Group B Streptococcus (GBS) in urine are:

• Vancomycin 2 Note that vancomycin achieves inhibitory concentrations in urine. No other antibiotics are mentioned in the provided drug labels as being effective against GBS in urine.

From the Research

Antibiotics for Group B Streptococcus (GBS) in Urine

• Penicillin G is the preferred antibiotic for GBS, with ampicillin as an alternative 3, 4, 5
• For women allergic to penicillin, options include:
  • Cefazolin for those at low risk of anaphylaxis 3, 6
  • Clindamycin and erythromycin, but resistance rates are increasing, making them less reliable choices 7, 5, 6
  • Vancomycin for those with resistance to clindamycin and erythromycin or unknown susceptibility 3, 7
• A positive urine culture for GBS should be considered clinically equivalent to a positive vaginal or rectal sample for screening 5

Considerations for Antibiotic Resistance

• Resistance to clindamycin and erythromycin is rising, with rates of 28% and 30% respectively in one study 7
• Penicillin remains efficacious in all cases, with no reported resistance 7, 6
• Antimicrobial susceptibility testing is essential for guiding antibiotic choice, especially in cases of penicillin allergy 7, 6