Having a penicillin allergy increases risk of superbug infections

Having a penicillin allergy increases risk of superbug infections

Patients with a recorded penicillin allergy on their medical records are at risk of develop drug-resistant superbug infections such as MRSA, a new study published by the BMJ reveals.

The risk of developing such superbug infections has been found to be due to the use of ‘broad-spectrum’ antibiotics as alternatives to penicillin.

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

Researchers have argued that addressing allergies to penicillin “may be an important public health strategy to reduce the incidence of MRSA and C. difficile among patients with a penicillin allergy label.”

What were the consequences of penicillin allergy?

Researchers at Massachusetts General Hospital, Boston, USA, evaluated public health consequences of penicillin allergy and development of MRSA and C. difficile.

Using data from the Health Improvement Network (THIN), an electronic medical record database of 11 million UK patients, they identified over 60,000 adults with a documented penicillin allergy and over 230,000 matched adults of similar age and sex, with recent penicillin exposure but without a penicillin allergy.

How many people developed MRSA?

None of the participants had a history of MRSA and C. difficile infection and were followed up for an average of six years, during which time their use of antibiotics and cases of doctor-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.

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

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

Results show that 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.

How at risk are people with penicillin allergies?

Concluding the observational study, researchers said that patients with a documented penicillin allergy “have an increased risk of new MRSA and C. difficile that may be modifiable, to some degree, through changes in antibiotic prescribing”.

They added that as infections with resistant organisms increase, “systematic efforts to confirm or rule out the presence of true penicillin allergy may be an important public health strategy to reduce the incidence of MRSA and C. difficile”.

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