Researchers in the United Kingdom used a population based matched cohort study to investigate the association between penicillin allergy and development of meticillin resistant Staphylococcus aureus (MRSA) and Clostridium difficile. The subjects of the the study were 301,399 people, 64,141 adults who had a penicillin allergy and 237,258 comparators who were matched on several variables. Over a mean 6-year follow-up, MRSA was observed in 442 participants with a penicillin allergy and 923 comparators, while C. difficile was observed in 442 participants with a penicillin allergy and 1246 comparators. For participants with a penicillin allergy, adjusted hazard ratios for MRSA and C. difficile were 1.69 (95% CI: 1.51-1.90) and 1.26 (95% CI: 1.12-1.40), respectively. Antibiotic use was also studied among those with a penicillin allergy and adjusted incidence rate ratios for macrolides, clindamycin and fluoroquinolones were 4.15 (95% CI: 4.12-4.17), 3.89 (95% CI: 3.66-4.12) and 2.10 (95% CI: 2.08-2.13), respectively. 55% of increased MRSA risk and 35% of increased C. difficile risk was linked to increased use of alternative antibiotics instead of β lactam derivatives. The study, published in the BMJ, reports an association between penicillin allergy, β lactam-alternative antibiotics and development of MRSA and C. difficile. This highlights the need for a systematic approach towards assessing penicillin allergies in public health and the management of infectious diseases among these people, as a means to reduce the incidence of MRSA and C. difficile. The original research can be accessed here.

Contributed by Australian Medication Safety Services Associate – Isabella Singh