Clinical Outcomes with Penicillin Versus Alternative β-Lactams in the Treatment of Penicillin-Susceptible Staphylococcus aureus Bacteremia.

Objectives: To identify the impact of penicillin versus alternative β-lactams on clinical outcomes in patients with penicillin-susceptible Staphylococcus aureus (PSSA) bacteremia.

Design: Retrospective cohort study.

Setting: Academic medical center.

Patients: Adult patients with PSSA bacteremia treated with a β-lactam as definitive therapy.

Measurements: The primary outcome was a composite end point of 30-day clinical failure (change in PSSA therapy due to persistent or worsening signs and symptoms, PSSA bacteremia recurrence or persistence, and/or infection-related mortality) in patients treated with penicillin versus alternative β-lactams. Secondary outcomes included infection-related and hospital length of stay (LOS), 90-day recurrence, 90-day infection-related readmission, 30-day all-cause mortality, adverse drug events (ADEs), and 30-day change in PSSA therapy due to ADEs. A subgroup analysis comparing penicillin, nafcillin, and cefazolin was also conducted.

Main Results: For the 122 patients who were included, the most common definitive therapies were nafcillin (37%), cefazolin (29%), and penicillin (21%). No difference was found in 30-day clinical failure (4% vs 11%, p=0.46), infection-related LOS (12 days vs 11 days, p=0.39), hospital LOS (12.5 days vs 12 days, p=0.69), 90-day recurrence (p=1.00), 90-day infection-related readmission (p=1.00), or 30-day all-cause mortality (p=0.45) between penicillin and other β-lactams. The prevalence of ADEs was different among penicillin, nafcillin, and cefazolin (p=0.049), with nafcillin requiring more changes in therapy (p=0.005).

Conclusions: Definitive therapy with penicillin had similar efficacy compared with alternative β-lactams for the treatment of PSSA bacteremia. However, nafcillin was associated with more ADEs requiring a change in therapy.