For decades, clinicians have defaulted to broader anti-staphylococcal penicillins even when bloodstream infections are caused by strains technically susceptible to narrow-spectrum benzylpenicillin — a precaution driven by fear of cryptic resistance rather than clinical evidence. A large international trial now provides the clearest answer yet on whether that caution translates into meaningfully better outcomes.
The SNAP trial enrolled adults with confirmed penicillin-susceptible Staphylococcus aureus (PSSA) bacteraemia across 67 hospitals in eight countries — Australia, New Zealand, Canada, Israel, the Netherlands, the UK, Singapore, and South Africa. Participants were randomized 1:1 to intravenous benzylpenicillin (1.8 g every 4 hours or 2.4 g every 6 hours) or to flucloxacillin/cloxacillin (2.0 g per dose). The trial was designed as a non-inferiority study embedded within the adaptive S. aureus Network Adaptive Platform (SNAP) framework, allowing rigorous comparison while preserving trial efficiency. The primary endpoint assessed clinical and microbiological outcomes sufficient to determine whether benzylpenicillin could be considered a legitimate frontline option rather than a compromise.
This result carries meaningful implications for antimicrobial stewardship. Benzylpenicillin has a narrower spectrum, generally better tolerability — particularly regarding hepatotoxicity, which is a recognized concern with flucloxacillin — and is often cheaper and more widely available in low-resource settings. If confirmed non-inferior, routine use in verified PSSA bacteraemia would represent a rational de-escalation strategy aligned with stewardship principles. However, important caveats apply: the open-label design introduces potential assessment bias, non-inferiority trials require careful scrutiny of the chosen margin, and the re-emergence of PSSA globally means institutional resistance surveillance quality will determine how safely this approach can be generalized. The trial's adaptive platform design is a methodological strength, but the practical reliability of penicillin susceptibility testing — the gating criterion for treatment allocation — remains a real-world limitation. This is an incrementally important but potentially practice-changing finding for infectious disease specialists and stewardship programs.