Treatment of Pelvic Inflammatory Disease Caused by Streptococcus agalactiae in Non-Pregnant Women
For non-pregnant women with PID caused by Group B Streptococcus (GBS), treat with ampicillin 2 g IV every 6 hours or penicillin G 5 million units IV initially followed by 2.5 million units IV every 4 hours, combined with appropriate coverage for other typical PID pathogens including anaerobes and Chlamydia. 1
Understanding the Clinical Context
GBS is increasingly recognized as a pathogen in non-pregnant adults, particularly in elderly patients and those with chronic conditions such as diabetes mellitus or immunocompromise. 2, 3 While GBS is traditionally associated with neonatal and pregnancy-related infections, invasive disease in non-pregnant adults is growing, with primary bacteremia and skin/soft-tissue infections being most common. 2
Antibiotic Selection and Regimens
First-Line Treatment
Ampicillin remains the cornerstone of GBS treatment with demonstrated in vitro sensitivity above 95% in urinary and systemic infections. 4
Penicillin G is universally effective against GBS, with 100% susceptibility documented across all studies worldwide, making it the preferred narrow-spectrum agent. 1
For PID specifically, combination therapy is essential because PID is typically polymicrobial—you must cover GBS plus the usual PID pathogens (Neisseria gonorrhoeae, Chlamydia trachomatis, anaerobes, and other facultative bacteria). 5
Recommended PID Treatment Regimen
Inpatient regimen: Ampicillin 2 g IV every 6 hours PLUS doxycycline 100 mg IV/PO every 12 hours PLUS metronidazole 500 mg IV every 8 hours. 5, 1
Alternative inpatient regimen: Cefoxitin 2 g IV every 6 hours or cefotetan 2 g IV every 12 hours PLUS doxycycline 100 mg IV/PO every 12 hours (note: cephalosporins provide GBS coverage). 5
Penicillin-Allergic Patients
For non-severe penicillin allergy: Cefazolin 2 g IV initially, then 1 g IV every 8 hours provides excellent GBS coverage. 1, 6
For high-risk anaphylaxis: Clindamycin 900 mg IV every 8 hours is effective, but resistance ranges from 3-25% among GBS isolates, making susceptibility testing mandatory. 1, 7
If clindamycin resistance is documented or unknown: Vancomycin 1 g IV every 12 hours provides reliable GBS coverage with 100% susceptibility. 1, 7
Critical Management Considerations
Identifying Infection Reservoirs
Successful GBS eradication requires identifying all infection foci, including reservoirs outside the urinary system such as the vagina, urethra, and gastrointestinal tract. 4
For recurrent or persistent infections, consider combined antibiotic therapy with local treatment measures. 4
Duration of Therapy
Complete the full prescribed antibiotic course to ensure eradication and prevent recurrence, typically 14 days for PID. 5, 1
Underdosing or premature discontinuation leads to treatment failure and recurrence. 6
Susceptibility Testing
Always obtain cultures and susceptibility testing before initiating therapy when possible, particularly for penicillin-allergic patients. 1
Erythromycin resistance is documented in 7-25% of GBS isolates, and clindamycin resistance in 3-25%, making empiric use of these agents problematic without susceptibility data. 1, 7
Common Clinical Pitfalls
Do not assume GBS is only a pregnancy-related pathogen—it causes significant invasive disease in non-pregnant adults, especially those over 65 years or with diabetes. 2, 3
Do not use fluoroquinolones as first-line therapy for GBS—while moxifloxacin has in vitro activity against Streptococcus agalactiae, beta-lactams remain superior with universal susceptibility. 8, 1
Do not forget to cover other PID pathogens—GBS may be isolated, but PID is typically polymicrobial and requires broad-spectrum coverage. 5
Do not rely on erythromycin or clindamycin empirically in penicillin-allergic patients without susceptibility testing, as resistance rates are substantial. 7
Special Populations
Patients with Diabetes or Immunocompromise
These patients are at increased risk for invasive GBS disease and may require longer treatment courses or more aggressive management. 2, 3
Consider evaluating for additional infection sites including skin/soft tissue and bloodstream. 2, 3