Does Keflex (Cephalexin) cover Group B Streptococcus (GBS) in urine during pregnancy?

Keflex (Cephalexin) Coverage for Group B Streptococcus in Pregnancy

Cephalexin (Keflex) is an acceptable alternative for treating GBS bacteriuria in pregnancy when penicillins cannot be used, as it has demonstrated effectiveness against GBS with minimal resistance patterns. 1

GBS Bacteriuria in Pregnancy: Significance and Management

Significance of GBS in Urine During Pregnancy

• GBS bacteriuria at any concentration during pregnancy is a marker for heavy genital tract colonization 2
• It is associated with increased risk for early-onset GBS disease in newborns 2
• GBS is found in the urine of 2-7% of pregnant women 2
• The presence of GBS in urine requires treatment regardless of symptoms 3

Treatment Recommendations

1. Immediate Treatment Upon Detection:

   • Any GBS bacteriuria during pregnancy should be treated promptly with antibiotics 3
   • After treatment, a test of cure urine culture should be obtained 3

2. Intrapartum Antibiotic Prophylaxis (IAP):

   • Women with GBS bacteriuria during any trimester of the current pregnancy should receive IAP during labor 2, 4
   • This recommendation applies regardless of subsequent negative cultures 3

Antibiotic Options for GBS in Pregnancy

First-Line Options

• Penicillin G: 5 million units IV initial dose, then 2.5-3.0 million units IV every 4 hours until delivery 3
• Ampicillin: 2 g IV initial dose, then 1 g IV every 4 hours until delivery 3

For Penicillin-Allergic Patients

• Cefazolin: 2 g IV initial dose, then 1 g IV every 8 hours until delivery 3

  • Studies show cefazolin may have equivalent or even superior efficacy compared to penicillin for GBS prophylaxis 5
  • In one study, cefazolin achieved a 95.2% negative culture rate post-treatment compared to 80.7% for penicillin 5

• Cephalexin (Keflex):

  • As a first-generation cephalosporin like cefazolin, cephalexin has similar activity against GBS 1
  • Studies show low resistance rates of GBS to first-generation cephalosporins (15% to cefazolin) 1
  • Can be used for oral treatment of GBS bacteriuria during pregnancy when penicillins cannot be used

Important Considerations

• All GBS isolates in recent studies showed sensitivity to penicillin and cefazolin 5
• For patients with severe penicillin allergies, susceptibility testing is essential as clindamycin resistance rates range from 14-26.6% 3

Clinical Algorithm for GBS Bacteriuria in Pregnancy

1. Detection of GBS in urine during pregnancy:

   • Treat immediately regardless of concentration or symptoms
   • For oral treatment:
     • First choice: Amoxicillin-clavulanic acid 3
     • Alternative for penicillin-allergic patients: Cephalexin (Keflex) 1
   • Obtain test of cure after treatment

2. During labor:

   • Provide IAP regardless of subsequent negative cultures
   • First choice: Penicillin G or Ampicillin
   • For penicillin-allergic patients without anaphylaxis history: Cefazolin
   • For patients with severe penicillin allergies: Use susceptibility-guided therapy

Pitfalls and Caveats

• Treating GBS colonization with oral antibiotics in the third trimester does not eliminate GBS from genitourinary tract; recolonization after treatment is common 2, 3
• Antibiotics should not be used before the intrapartum period to eradicate GBS genitorectal colonization 2
• Even low colony counts (<10^4 CFU/ml) of GBS in urine are associated with increased risk for early-onset disease 2
• For cesarean delivery performed before labor onset with intact membranes, IAP is not routinely recommended 2

In conclusion, Keflex (cephalexin) is an effective option for treating GBS bacteriuria in pregnancy, particularly in penicillin-allergic patients without history of anaphylaxis, based on its demonstrated activity against GBS and low resistance patterns.