McGill breakthroughs help fight virulent bacteria on two different fronts
The bug is Clostridium difficile, also known as C. difficile. In one year in Quebec, it killed almost 10 times more people than died during the SARS epidemic in Toronto. It’s extremely contagious because it can live on surfaces and be passed easily through casual human contact. In its mildest form, the bacterium causes diarrhea and stomach pain. Its most toxic form can be fatal.
Now, there are new weapons in the fight against the infection. In December 2005, researchers at McGill and affiliated hospitals announced back-to-back breakthroughs to combat the dramatic increase in highly toxic strains of the bacterium in Quebec and around the world.
C. difficile—so named for the difficulty researchers had growing it in a laboratory setting— has been known since at least the 1930s, and was generally considered a nuisance illness affecting patients during lengthy hospital stays. However, dangerous new variants recently emerged in Canada, the US, England and the Netherlands. The Quebec strain—a nasty bug that is resistant to antibiotics, spews out 20 times more toxins than its more common cousins and is more easily spread—kills about eight per cent of those infected. C. difficile caused or contributed to the deaths of more than 400 Quebecers between August 2004 and August 2005 alone.
On December 12, 2005, researchers at the McGill University and Génome Québec Innovation Centre, McGill University Health Centre (MUHC) and the Jewish General Hospital announced they had cracked the genomic code of a virulent strain of C. difficile prevalent in Quebec since 2003. The significant breakthrough marks the first time this variant of C. difficile has been sequenced. The team was led by Ken Dewar, Assistant Professor of Human Genetics at McGill and an investigator at the MUHC Research Institute, and André Dascal, Associate Professor of Medicine, Microbiology and Immunology at McGill and Senior Infectious Disease Physician at the Jewish General Hospital.
Unravelling the genetic code for the microbe paves the way for faster diagnostic tests, and should lead to new treatment and prevention strategies for a strain of C. difficile responsible for more than three-quarters of the cases in Quebec studied to date.
A week after this genetic breakthrough was announced, a team led by Sandra Dial, Assistant Professor of Medicine at McGill and critical care physician at the Jewish General and MUHC, published research showing that drugs that reduce gastric acidity—such as heartburn medications—increase the risk of contracting C. difficile infections. The researchers, including Samy Suissa, Director of Clinical Epidemiology at the MUHC and James McGill Professor of Epidemiology, Biostatistics and Medicine at McGill, Alan Barkun, Chief of Gastroenterology at the MUHC, and epidemiology PhD student Chris Delaney, believe that the lower gastric acidity provides a more hospitable environment in the stomach for the bacteria to grow. In 2004, Dial and her team had shown that heartburn drugs in combination with certain types of antibiotics increased the risk of developing the bacterial infection. Antibiotics had been the only medication found to be a factor previously.
Dial’s study, published in the Journal of the American Medical Association, was the first to show a significant increase in C. difficile-associated infections acquired outside a hospital setting. More than 70 per cent of people in the community with these infections had not been admitted to hospital in the past year. Surprisingly, they also found that patients in the community who develop C. difficile are less likely to have been exposed to antibiotics than patients in hospitals. Until the publication of the findings, C. difficile infections had been thought to be acquired almost exclusively in a hospital setting.
The sequencing of C. difficile was supported by funding from Génome Québec and Genome Canada, the Lady Davis Institute for Medical Research and the Jewish General Hospital Foundation, and the Genome Sequencing Center at the Washington University School of Medicine. Research on C. difficile and heartburn medications was funded by the Canadian Institutes of Health Research (CIHR), the Canada Foundation for Innovation (CFI) and the Fonds de la recherche en santé du Québec (FRSQ).