Patients with Documented Penicillin Allergy at Higher Risk for MRSA, C. difficile

By Amy Orciari Herman

Edited by Richard Saitz, MD, MPH, FACP, DFASAM

Patients whose medical records list a penicillin allergy are at increased risk for methicillin-resistant Staphylococcus aureus (MRSA) and Clostridium difficile infections, a study in The BMJ finds.

Using U.K. healthcare records, researchers matched roughly 64,000 adults with a documented penicillin allergy to nearly 240,000 penicillin users without a documented allergy (controls). During 6 years' follow-up, 0.7% of patients with penicillin allergy and 0.4% of controls developed a MRSA infection, and 0.7% and 0.5%, respectively, acquired C. difficile.

After multivariable adjustment, patients with penicillin allergy had nearly a 70% increased risk for MRSA and 30% increased risk for C. difficile. The association was largely mediated by increased use of beta-lactam alternatives in those with penicillin allergy — for example, fluoroquinolones, clindamycin, and macrolides.

Infectious disease specialist Dr. Paul Sax comments, "This study adds to a substantial body of evidence that documents the harm associated with having a penicillin allergy, which limits antibiotic options. That the vast majority of people with a listed allergy to penicillin either have outgrown it or never had it at all makes taking a careful history (or referring for penicillin skin testing) a high priority in these patients." Dr. Richard Ellison, editor-in-chief of NEJM Journal Watch Infectious Diseases, concurs, noting: "It is important for patients' wellbeing to correct the medical record if it can be shown that the information is inaccurate."