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Patients with penicillin allergy at increased risk of ‘superbug’ infections

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Patients who have a record of a penicillin allergy are at an increased risk of developing the drug resistant infection MRSA and healthcare-associated infection C difficile, according to researchers.

They said the risk was largely due to the use of more “broad spectrum” antibiotics as alternatives to penicillin, which may be fuelling the development of drug resistant bacteria.

“Documented penicillin allergy was associated with an increased risk of MRSA and C difficile”

Study authors

The researchers said 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.”

Writing in the British Medical Journal, they noted that penicillin allergy was the most commonly documented drug allergy, reported by about 10% of patients.

However, they highlighted that previous studies had shown that more than 90% of patients with listed penicillin allergies could be safely treated with penicillins.

To evaluate the consequences of a penicillin allergy label, researchers at Massachusetts General Hospital in Boston examined data from an electronic record database of 11 million UK patients.

They 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 had any history of MRSA and C difficile infection, and were followed up for an average of six years, during which time use of antibiotics and diagnosed MRSA and C difficile were recorded.

A total of 1,345 participants developed MRSA and 1,688 developed C. difficile over the follow-up period, said the researchers.

After adjusting for several known risk factors, they found that a penicillin allergy label was associated with a 69% increased risk of MRSA and a 26% increased risk of C difficile.

“Systematically addressing penicillin allergies may be an important public health strategy”

Study authors

Once documented, a penicillin allergy was associated with increased use of alternative “broad spectrum” antibiotics, which act against a wider range of bacteria.

The increased use of broad spectrum antibiotics accounted for 55% of the increased MRSA risk and 35% of the increased C difficile risk among patients with a listed penicillin allergy.

The researchers said patient risk “may be modifiable, to some degree, through changes in antibiotic prescribing”.

In the BMJ, they stated: “Documented penicillin allergy was associated with an increased risk of MRSA and C difficile that was mediated by the increased use of β lactam alternative antibiotics.

“Systematically 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,” they added.

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