Clinical Edge

Summaries of Must-Read Clinical Literature, Guidelines, and FDA Actions

Penicillin Allergy & Risk of MRSA and C. difficle

BMJ; ePub 2018 Jun 27; Blumenthal, et al

Patients with a documented penicillin allergy have an increased risk of new methicillin resistant Staphylococcus aureus (MRSA) and Clostridium difficile (C difficile) that are modifiable, in part, through changes in antibiotic prescribing. This according to a population-based matched cohort study that included 301,399 adults without previous MRSA or C difficile enrolled in the Health Improvement Network database: 64,141 had a penicillin allergy with 237,258 comparators matched on age, sex, and study entry time. The primary outcome was risk of incident MRSA and C difficile; secondary outcomes were use of β lactam antibiotics and β lactam alternative antibiotics. Researchers found:

  • Among 64,141 adults with penicillin allergy and 237,258 match comparators, 1,365 developed MRSA (442 with penicillin allergy and 923 comparators) and 1,688 developed C difficile (442 with penicillin allergy and 1,246 comparators) during a mean 6.0 years of follow-up.
  • Among patients with penicillin allergy, the adjusted hazard ratio for MRSA was 1.69 and the C difficile was 1.26.
  • The adjusted incidence rate ratios for antibiotic use among those with penicillin allergy were 4.15 for marcolides, 3.89 for clindamycin, and 2.10 for fluoroquinolones.
  • Increased use of β lactam alternative antibiotics accounted for 55% of the increased risk of MRSA and 35% of the increased risk for C difficile.


Blumenthal KG, Lu N, Zhang Y, et al. Risk of meticillin resistant Staphylococcus aureus and Clostridium difficile in patients with a documented penicillin allergy: Population based matched cohort study. [Published online ahead of print June 27, 2018]. BMJ. doi:10.1136/bmj.k2400.

This Week's Must Reads

AHA Statement: Accurate Measurement of BP, Hypertension; ePub 2019 Mar 4; Muntner, et al

Coffee Consumption & Plasma Biomarkers, Am J Clin Nutr; ePub 2019 Mar 5; Hang, et al

Is Adding Aspirin to Warfarin Therapy Beneficial? , JAMA Intern Med; ePub 2019 Mar 4; Schaefer, et al

Urinary Oxalate Excretion & Risk of CKD Progression, JAMA Intern Med; ePub 2019 Mar 4; Waikar, et al

Psychosocial Stress & CV Health in Older Women, Circulation; ePub 2019 Feb 28; Burroughs-Peña, et al

Must Reads in Immunology

Penicillin Allergy & Risk of MRSA and C. difficle, BMJ; ePub 2018 Jun 27; Blumenthal, et al

CVD Risk with LABAs and LAMAs in COPD, JAMA Intern Med; ePub 2018 Jan 2; Wang, et al

Benzodiazepine Use & Risk of Pneumonia, CHEST; 2018 Jan; Chen, Winkelman, et al

Pharmacologic Tx of Seasonal Allergic Rhinitis, Ann Intern Med; ePub 2017 Nov 28; Wallace, et al

FDA Approves Epinephrine Autoinjector for Infants, Kaléo news release; 2017 Nov 20