Blumenthal KG, et al. - The association between penicillin allergy and development of meticillin resistant Staphylococcus aureus (MRSA) and C difficile was evaluated in this population based matched cohort study. Researchers reported that documented penicillin allergy was correlated with an increased risk of MRSA and C difficile that was mediated by the increased use of β lactam alternative antibiotics. Among patients with a penicillin allergy label, systematically addressing penicillin allergies could be an important public health strategy to decrease the incidence of MRSA and C difficile.

Methods

• Study participants were patients registered with general practices in the United Kingdom between 1995 and 2015.
• For this analysis, 301,399 adults without previous MRSA or C difficile recruited in the Health Improvement Network database: 64,141 had a penicillin allergy and 237,258 comparators matched on age, sex, and study entry time.
• Risk of incident MRSA and C difficile were the primary outcomes.
• Use of β lactam antibiotics and β lactam alternative antibiotics were the secondary outcomes.

Results

• The study results showed that among 64,141 adults with penicillin allergy and 237,258 matched comparators, 1365 developed MRSA (442 members with penicillin allergy and 923 comparators) and 1688 developed C difficile (442 members with penicillin allergy and 1246 comparators) during a mean 6.0 years of follow-up.
• It was observed that among subjects with penicillin allergy the adjusted hazard ratio for MRSA was 1.69 (95% confidence interval 1.51 to 1.90) and for C difficile was 1.26 (1.12 to 1.40).
• Data reported that the adjusted incidence rate ratios for antibiotic use among subjects with penicillin allergy were 4.15 (95% confidence interval 4.12 to 4.17) for macrolides, 3.89 (3.66 to 4.12) for clindamycin, and 2.10 (2.08 to 2.13) for fluoroquinolones.
• According to the findings obtained, increased use of β lactam alternative antibiotics accounted for 55% of the increased risk of MRSA and 35% of the increased risk of C difficile.