Impact of Reported β-Lactam Allergy on Management of Methicillin-Sensitive Staphylococcus aureus Bloodstream Infections

Background: Antistaphylococcal β-lactams antibiotics are the preferred treatment for methicillin-sensitive Staphylococcus aureus (MSSA) infections. Patient-reported β-lactam allergies may complicate antibiotic decision-making and delay optimal therapy, with potential implications on patient outcomes.

Objective: To determine the impact of reported β-lactam allergies on the receipt of optimal therapy and outcomes for MSSA bloodstream infections (BSI).

Methods: Retrospective, matched cohort of MSSA BSI patients with and without a reported β-lactam allergy. The primary end point was receipt of optimal therapy, defined as an antistaphylococcal β-lactam.

Results: Two hundred twelve patients were included: 53 with reported β-lactam allergy and 159 without β-lactam allergy. Commonly reported β-lactam allergies were 26 (49%) immune-mediated reaction and 8 (15%) intolerance, with 19 (36%) having no documented reaction. Optimal antibiotics were given to 135 patients without a β-lactam allergy and 37 patients with a reported β-lactam allergy (85% vs 70%, P = .015). Among reported β-lactam allergy patients, those without a documented reaction were less likely to receive optimal therapy (47% vs 79%, P = .042). Reported β-lactam allergy was not associated with clinical response (P = .61) or MSSA-related mortality (P = .83). When adjusting for immunosuppression, variables independently associated with optimal therapy were β-lactam allergy (adjusted odds ratio [adjOR], 0.3; 95% confidence interval [CI], 0.1-0.6) and infectious diseases consultation (adjOR, 6.1; 95%CI, 2.7-13.9). Optimal antibiotic use was associated with decreased all-cause 90-day mortality (adjOR, 0.23; 95%CI, 0.09-0.54).

Conclusions: Patients with reported β-lactam allergies, particularly those without a documented reaction, were less likely to receive optimal antibiotics for MSSA BSI. Patient outcomes may be improved with enhanced quality of allergy history and routine infectious disease consultation.