What is the recommended treatment for a patient with group B streptococcal (GBS) bacteremia, particularly if they are allergic to penicillin, including the use of Tazocin (piperacillin/tazobactam)?

Treatment of Group B Streptococcal Bacteremia

Tazocin (piperacillin/tazobactam) is NOT recommended for Group B Streptococcal bacteremia—penicillin G or ampicillin remains the definitive first-line treatment due to universal GBS susceptibility and proven efficacy. 1, 2

First-Line Treatment Approach

Penicillin G is the preferred agent for all GBS bacteremia cases, including invasive disease, due to its narrow spectrum of activity and the fact that all GBS isolates worldwide remain universally susceptible to penicillin with no documented resistance. 1, 2, 3, 4

• Ampicillin is an acceptable alternative to Penicillin G, though it has a broader spectrum of activity. 2
• All GBS isolates tested have shown 100% susceptibility to penicillin, ampicillin, cefazolin, cefotaxime, and vancomycin. 3, 4

Treatment for Penicillin-Allergic Patients

Non-Severe Penicillin Allergy

Cefazolin is the recommended alternative for patients without severe allergic reactions (no history of anaphylaxis, angioedema, respiratory distress, or urticaria following penicillin or cephalosporin). 1, 2

• Cross-reactivity between penicillins and cephalosporins occurs in approximately 10% of patients with penicillin allergy. 1, 2
• Most patients reporting penicillin allergy are not truly allergic and may safely receive cephalosporins after careful history-taking. 5

Severe Penicillin Allergy

For patients with severe penicillin allergy, vancomycin is the recommended first-line treatment when susceptibility testing is unavailable or pending. 1

• Severe allergy is defined by history of anaphylaxis, angioedema, respiratory distress, or urticaria following penicillin or cephalosporin administration. 6, 1, 5
• If susceptibility testing is available, use clindamycin 900 mg IV every 8 hours for susceptible isolates, or vancomycin 1g IV every 12 hours for resistant isolates. 1
• Always obtain susceptibility testing for clindamycin and erythromycin when treating GBS infections in penicillin-allergic patients. 1, 2

Critical Resistance Patterns

Clindamycin and erythromycin resistance is increasing and represents a significant concern:

• Clindamycin resistance ranges from 3-15% among invasive GBS isolates and increased from 10.5% to 15.0% over surveillance periods. 1, 3
• Erythromycin resistance is 25.6% overall and increased from 15.8% to 32.8%, with resistance reaching 18% by 1994 in some series. 3, 4
• Erythromycin resistance is frequently but not always associated with clindamycin resistance. 1
• D-zone testing should be performed on isolates that are erythromycin-resistant but clindamycin-susceptible to detect inducible clindamycin resistance. 1

Why Not Tazocin?

Piperacillin/tazobactam is not mentioned in any GBS treatment guidelines because:

• GBS remains universally susceptible to narrow-spectrum penicillin, making broad-spectrum agents unnecessary. 1, 2
• Using broad-spectrum antibiotics like piperacillin/tazobactam increases selection pressure for resistant organisms without providing additional benefit. 2
• The narrow spectrum of penicillin G is specifically preferred to minimize antimicrobial resistance. 2

Common Pitfalls to Avoid

• Do not use erythromycin for GBS infections as it is no longer recommended due to increasing resistance rates exceeding 25%. 1, 3
• Do not use macrolides empirically for treatment of patients with penicillin allergies, as resistance patterns make them unreliable. 4
• Do not reserve vancomycin as a routine alternative—it should only be used when no other options exist to minimize promoting antimicrobial resistance. 2
• Do not skip susceptibility testing in penicillin-allergic patients, as clindamycin resistance can reach 15% and requires confirmation before use. 1, 3

Special Considerations for Complicated Cases

• Consider consultation with an infectious disease specialist for complicated cases or when limited treatment options are available. 1
• For patients with recent oral antibiotic step-down data (though primarily studied in uncomplicated cases), transition to oral therapy may be considered after clinical stabilization, though IV therapy remains standard for bacteremia. 7