Sunnybrook Magazine - Spring 2018 Wellness

How bedside allergy testing could help curb antibiotic resistance

Woman looking through medicine cabinet

All her life, Marjorie Wall believed that she was allergic to penicillin, but a new allergy skin test developed at Sunnybrook proved otherwise. Photography by Meg Wallace


After breaking out in hives all over her body, following complications from a difficult pregnancy, Marjorie Wall refused to take penicillin again for 40 years.

But when a severe infection developed during recent back surgery, her doctors at Sunnybrook asked her to consider bedside allergy testing in case the allergic reaction had changed.

“They told me they really wanted to try penicillin because they had found several strains of bacteria in the incision, recalls Wall, 71. “Other kinds of antibiotics they had tried weren’t working.”

“They came in to do a scratch test on my arm, which didn’t react. Then they put me on an IV with a penicillin-based antibiotic, which I was on for the next nine weeks without any issues.

“Now I take them orally twice a day for the rest of my life. All these years, I thought I had an allergy to penicillin but [I didn’t]. It was actually penicillin that made my surgery a success.”

The bedside skin testing Marjorie received is part of a study of seriously ill patients with life-threatening infections that are best treated with penicillin, otherwise known as beta-lactam.

This study on beta-lactam allergy skin testing (BLAST) is the first of its kind. Led by Dr. Jerome Leis, medical director of Infection Prevention and Control at Sunnybrook, the BLAST study was conducted in three hospitals. It found that more than 80 per cent of patients with a penicillin allergy were able to tolerate the drug without serious complications.

Dr. Jerome Leis

Dr. Jerome Leis, medical director of Infection Prevention and Control at Sunnybrook, is leading a groundbreaking study on penicillin intolerance to address issues around antibiotic resistance, which he describes as “a major health crisis.” Photography by Kevin Van Paassen

Like Marjorie, one in 10 Canadians report having an allergy to penicillin. “At some point in their lives, they may have been misclassified as having an allergy, when in fact their reaction was due to other reasons,” says Dr. Leis. “Many people outgrow it or are now able to receive the drug without the same initial reaction.

“We’ve known for a while that patients who report an allergy to penicillin actually have worse clinical outcomes. They might have infections that are more difficult to treat, while the alternatives they get treated with are associated with more toxic side effects or a greater risk of developing more antibiotic-resistant organisms.”

The ongoing study, published last October in Clinical Infectious Diseases, is expanding to include 10 hospitals across Ontario and western Canada and is part of a larger strategy on curbing the epidemic of antibiotic resistance. BLAST is now part of standard practice at Sunnybrook.

“We are not talking about antibiotic resistance enough. This is a major health crisis,” notes Dr. Leis. “Current worldwide estimates of deaths attributed to untreatable infections directly from antibiotic resistance are at about 700,000 a year. At our current rate of antibiotic overuse and without the development of new drugs, by 2050 that number is expected to rise to 10 million deaths worldwide. This is more than what we see from cancer today.”

To effectively combat such alarming figures, Canada’s approach needs to include a strategy for safely using penicillin, says Lesley Palmay, study co-author and clinical coordinator of infectious diseases in the Pharmacy Department at Sunnybrook. “Allergies are troublesome because they limit our ability to prescribe optimal medications. For infectious diseases practitioners and pharmacists, the penicillin-based antibiotics are our workhorses,” she says.

While it’s only physicians who have historically conducted skin allergy tests, pharmacists were also trained to administer them during the study and may eventually lead this activity in hospitals as part of their expanding role in Ontario.

“As pharmacists, we are well versed in taking a thorough allergy and medication history, [and we] know what anti-microbial treatments are required and remain a core part of the team, especially in teaching hospitals where physicians rotate through regularly,” says Palmay. “In this setting, the pharmacist is the one constant member that stays on as part of the infectious diseases team.

“Our approach to being more collaborative, systematic and questioning of antibiotic allergies is crucial in our fight to combat antibiotic resistance in Canada.”

Test ahead of time

Think you may have an allergy to penicillin? Ask your family doctor to review your history and decide whether you are a candidate for allergy testing.

Over the past two years in the Drug Safety Clinic at Sunnybrook, 97 per cent of the 1,500 outpatients tested for penicillin allergies turned out to be no longer allergic.

“Patients need to know that declaring an allergy to penicillin means being denied more than 20 drugs from their arsenal of potential treatments. A lot of doctors will hesitate to give anything related to penicillin if there is even a sniff of a reaction,” says Jackie Campbell, a drug safety pharmacist at the clinic.

Testing involves surface skin testing, followed by oral administration of a penicillin antibiotic over the course of six hours in the Drug Safety Clinic at Sunnybrook.

For more information, visit drugsafety.sunnybrook.ca

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Barbara Balfour