Content Update
July 3, 2018
Risk of Methicillin-resistant Staphylococcus aureus and Clostridium difficile Infection with Documented Penicillin Allergy: Many patients are labelled as penicillin allergic but do not have true immediate penicillin hypersensitivity. This can lead to unnecessary administration of broad-spectrum antimicrobials, which can promote emergence of antimicrobial resistance (eg, MRSA) and development of healthcare-associated infections such as C. difficile. A recent report demonstrated that patients with documented penicillin allergy have a higher risk of infections with MRSA and C. difficile. The report supports the principle of using the most narrow spectrum antimicrobial that is effective to treat an infection, and that unnecessary use of broad-spectrum antimicrobials increases the risk of bacterial resistance and emergence of superinfections. When penicillin allergy is suspected, efforts should be made to determine if the patient experienced an immediate hypersensitivity reaction.
UPDATE
Risk of Methicillin-resistant Staphylococcus aureus and Clostridium difficile Infection with Documented Penicillin Allergy
Author: Joseph T. DiPiro, PharmD, Dean and Archie O. McCalley Chair, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia
Related to: Chapter 105, Antimicrobial Regimen Selection; Chapter 113, Gastrointestinal Infections and Enterotoxigenic Poisonings
Topic: A recent report demonstrated that patients with documented penicillin allergy have a higher risk of infections with methicillin-resistant Staphylococcus aureus (MRSA) and Clostridium difficile.1
Background: Many patients are labelled as penicillin allergic but do not have true immediate penicillin hypersensitivity. This leads to patients unnecessarily receiving other antibiotics, sometimes antimicrobials with much broader spectrum. Use of broader spectrum antimicrobials can promote emergence of antimicrobial resistance, such as with MRSA, and development of healthcare-associated infections such as C. difficile.
New Information: Investigators reported a population based matched cohort study that examined the relationship between a newly recorded penicillin allergy and the risk of MRSA and C. difficile.1 An electronic medical record database of 11.1 million patients in the United Kingdom was used to identify 64,141 patients with a documented penicillin allergy and 237,258 matched comparators over 18 years of age between 1995 and 2015 with no history of MRSA or C. difficile diagnoses before study entry. Antimicrobial utilization during the follow-up period was assessed from prescription records. A total of 442 patients with penicillin allergy and 923 comparator patients developed MRSA, and 442 patients with penicillin allergy and 1246 comparator patients developed C. difficile. Hazard ratios for patients with penicillin allergy were 1.84 (95% confidence interval [CI] 1.64 to 2.06) for MRSA and 1.37 (CI 1.23 to 1.53) for C. difficile. Patients with penicillin allergy label had increased use of macrolide antibiotics, clindamycin, fluoroquinolones, tetracyclines, and sulfonamide antibiotics and had nearly a 70% increased risk of new MRSA and a 26% increased C. difficile risk.
Interpretation and Application: The report provides additional evidence in support of the principle of using the most narrow spectrum antimicrobial that is effective to treat an infection, and that more frequent use of broad-spectrum antimicrobials increases the risk of bacterial resistance and emergence of superinfections. Patients suspected of having penicillin “allergy” should undergo a thorough history to determine if the reaction was an immediate hypersensitivity. Also, penicillin skin test followed by challenge dose if negative should be used more widely to differentiate adverse reactions from immediate penicillin allergies.
References:
Blumenthal KG, Lu N, Zhang Y, Li Y, Walensky RP, Choi HK. Risk of methicillin resistant Staphylococcus aureus and Clostridium difficile in patients with a documented penicillin allergy: population based matched cohort study. BMJ 2018; 361:k2400. doi: https://doi.org/10.1136/bmj.k2400.
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