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July 2018

Penicillin allergy linked to increased risk of ‘superbug’ infections

Patients who have a recorded penicillin allergy are at an increased risk of developing the drug resistant ‘superbug’ infection MRSA and healthcare-associated infection C. difficile, according to a study in the BMJ earlier this month.

The risk is largely due to the use of more ‘broad spectrum’ antibiotics as alternatives to penicillin, which may be fuelling the development of drug resistant bacteria.

The researchers argue that addressing penicillin allergies ‘may be an important public health strategy to reduce the incidence of MRSA and C. difficile among patients with a penicillin allergy label.’

Penicillin allergy is the most commonly documented drug allergy, reported by about 10% of patients. However, previous studies have shown that more than 90% of patients with listed penicillin allergies can be safely treated with penicillins.

Researchers at Massachusetts General Hospital in Boston, USA examined data from the Health Improvement Network (THIN), an electronic medical record database of 11 million UK patients, and identified 64,141 adults with a documented penicillin allergy and 237,258 matched adults of similar age and sex, with recent penicillin exposure but without a penicillin allergy.

None of the participants had any history of MRSA and C. difficile infection. Over a 6-year follow-up period, a total of 1,345 participants developed MRSA and 1,688 developed C. difficile.

A penicillin allergy label was associated with a 69% increased risk of MRSA and a 26% increased risk of C. difficile.

The results show that increased use of broad spectrum antibiotics accounted for more than half (55%) of the increased MRSA risk and more than one third (35%) of the increased C. difficile risk among patients with a listed penicillin allergy.

Blumenthal KG, et al. BMJ 2018;361:k2400

July 2018