What is the treatment for Group B strep (Streptococcus agalactiae) infection in an elderly woman presenting with confusion?

Treatment of Group B Streptococcal Infection in Elderly Women with Confusion

For an elderly woman presenting with confusion due to Group B Streptococcus infection, initiate high-dose intravenous penicillin G (12-18 million units/day divided into 4-6 doses or continuous infusion) for 4 weeks, as this represents the gold standard treatment for invasive GBS disease in adults. 1

Initial Antibiotic Selection

First-Line Therapy

• Penicillin G remains the agent of choice at 12-18 million units/day IV in 4-6 doses or continuous infusion for 4 weeks 1
• Ampicillin 100-200 mg/kg/day IV in 4-6 divided doses is an acceptable alternative for 4 weeks 1
• Ceftriaxone 2 g/day IV or IM once daily for 4 weeks offers convenient dosing, particularly if outpatient therapy is considered after stabilization 1

Critical Dosing Consideration

High-dose penicillin is specifically recommended because GBS has somewhat higher minimal inhibitory concentrations compared to other streptococci, and elderly patients with invasive disease require aggressive treatment to reduce the high mortality risk 2, 3

For Penicillin-Allergic Patients

Non-Anaphylactic Allergy

• Cefazolin 2 g IV initial dose, then 1 g IV every 8 hours 1

High-Risk Anaphylaxis History

• Vancomycin 1 g IV every 12 hours if susceptibility testing unavailable or isolate resistant to clindamycin/erythromycin 1
• Clindamycin 900 mg IV every 8 hours only if isolate confirmed susceptible (note: increasing resistance patterns make this less reliable) 1, 3

Duration and Adjunctive Therapy

Treatment Duration

• Standard duration is 4 weeks for invasive GBS disease 1
• Short-term 2-week therapy is NOT recommended for Group B streptococcal infections, as these organisms produce abscesses and carry higher complication rates 1
• If gentamicin is added for synergy, limit aminoglycoside to 2 weeks maximum (3 mg/kg/day IV once daily) 1

Surgical Evaluation

Surgical consultation may be required as Group B, C, and G streptococci characteristically produce abscesses, particularly in soft tissue and bone infections 1, 2

Special Considerations for Elderly Patients

Why This Population is High-Risk

• GBS bacteremia incidence is highest among adults over 60 years of age 2
• Mortality from invasive GBS disease is particularly high in the elderly, with overall mortality rates of 33.3% and GBS-related deaths in 25.5% of cases 3
• Elderly patients commonly have underlying conditions (diabetes mellitus, malignancies, liver disease) that worsen prognosis 2, 3

Clinical Presentation Pitfalls

• Confusion may be the only presenting symptom in elderly patients with serious bacterial infections 4
• Fever response is often blunted even with bacteremia 4
• Leukocytosis may be absent; acute phase proteins are more reliable markers than ESR 4
• Non-specific functional decline without typical infection signs is common 4

Diagnostic Workup Required

Immediate Actions

• Blood cultures before antibiotic initiation 4, 3
• Lumbar puncture if meningitis suspected (confusion is a red flag) 5
• Evaluate for primary source: urinary tract, skin/soft tissue, pneumonia, endocarditis 2, 3
• Consider imaging for abscess formation given GBS propensity for abscess production 1

Poor Prognostic Factors to Monitor

Central nervous system involvement, shock, renal failure, and consciousness impairment are associated with higher mortality 3

Antimicrobial Resistance Considerations

• All GBS isolates remain uniformly susceptible to penicillin G, ampicillin, cephalosporins, and vancomycin 3
• Macrolide resistance (erythromycin) is increasing (8% in 1992 to 18% in 1994), making erythromycin unsuitable for empiric therapy in penicillin-allergic patients 3
• Ciprofloxacin resistance has been documented and fluoroquinolones should not be used 3

Common Pitfalls to Avoid

• Do not use short-course (2-week) therapy for GBS infections as recommended for other streptococcal species 1
• Do not delay treatment waiting for culture confirmation when clinical suspicion is high in an elderly patient with confusion 4
• Do not rely on absence of fever to rule out serious infection 4
• Avoid macrolides empirically in penicillin-allergic patients due to resistance patterns 3
• Do not overlook need for source control/surgical intervention, particularly with soft tissue or bone involvement 2