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By: Anna Goshua and Arshia Javidan/ Meducator

Why do we get sick? Moreover, why do we get better? That essentially encapsulates the research being done by Dawn Bowdish and her team at McMaster University’s Immunology Research Centre. Bowdish is an Associate Professor in the Department of Pathology, and her research focuses on pneumonia, the most costly bacterial infection in Ontario.

The bacteria that causes pneumonia is initially found in the nose, where no symptoms are observed unless it enters the lungs, bloodstream or cerebrospinal fluid. Bowdish specifically investigates why the bacteria leaves the nose in the first place, with a focus on the aging population.

“We’re particularly focused on older adults, as they contract pneumonia at much higher rates, and the consequences can be very serious,” Bowdish said. The long-term complications of contracting pneumonia include increased risk of dementia, type II diabetes and cardiovascular disease later on in life. In order to shed light on why older individuals are more susceptible to contracting pneumonia, Bowdish researches age-related changes in the immune system that may be involved.

The data is compelling in demonstrating that as we age, our levels of inflammation increase. Inflammation is a cellular response to injury or infection that is carried out by the immune system. Many age-related diseases, such as conditions involving dementia, some forms of cancer and cardiovascular disease, are linked to inflammation.

“For reasons that we’re just beginning to understand, this increasing inflammation seems to impair white blood cell function. The bacteria is able to capitalize on these inflammatory changes in the immune system in order to thrive,” Bowdish explained.

“We think that we can target age-related inflammation as a way of improving immunity. We’re testing this in an animal model at the moment. By reducing their age-related inflammation, we can improve their outcomes from pneumonia, which is a finding we’re quite excited about,” she said.

If the preclinical testing phase determines that age-related inflammation is a viable drug target, then the next phase would be a drug-screening program that would further examine the effectiveness of anti-inflammatory drugs in improving immune function. This drug has the potential to decrease the risk of devastating illnesses such as pneumonia.

Bowdish has seen how older adults benefit younger generations. “I think grandparents are really important. There’s a lot of data to support the positive role of older adults in society. They volunteer more hours than younger people and they provide a lot of unpaid caregiving. So we want them to be as healthy as they can possibly be. Essentially, my research is about keeping grandchildren and grandparents together for many years to come.”

Photo Credit: Yung Lee/ Photo Reporter

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By: Annie Cheung

Heavy metals ions, such as gold, are toxic to many species of bacteria. It is therefore surprising to see that the bacterium, Delftia acidovorans, can thrive on biofilms that form on top of gold deposits. Researchers at McMaster University have found a novel mechanism in which this gold-resistant bacterium is able to protect itself from this toxicity.

The research team led by Dr. Nathan Magarvey at Michael G. Degroote Institute for Infectious Disease Research has discovered that D. acidovorans is able to protect itself from toxic gold ions by excreting a metabolite, delftibactin, outside of its cell wall. Delftibactin is a small molecule compound that is able to precipitate soluble gold ions into nontoxic gold nanoparticles. This defense mechanism leads to the formation of a halo of gold platelets around D. acidovorans that resemble gold nuggets one would typically find in natural geological deposits. The conversion of toxic ions into harmless gold platelets prevents gold metal ions from entering D. acidovorans cells. “This finding is the first demonstration that a secreted metabolite can protect against toxic gold and cause gold biomineralization”, states Dr. Magarvey in his paper.

The discovery of delftibactin involved genome analysis to identify the gene responsible for this unique protection mechanism. Researchers grew a colony of D. acidovorans cells lacking the gene that codes for delftibactin A, the protein responsible for delftibactin synthesis. They found that the delftibactin-deficient bacteria struggled to survive in a medium supplied with toxic gold ions, while the addition of delftibactin A to the colony enabled the bacteria’s survival. Delftibactin A may potentially be used someday to identify gold-rich streams and rivers, or to precipitate gold from water.

The study did not specifically look into the viability of using the bacteria in gold-mining applications. Instead, Dr. Magarvey is more interested in understanding the chemical properties of the metabolite. In collaboration with Dr. Bin Ma at the University of Waterloo, Dr. Magarvey has recently developed a bioinformatics method that enables the discovery of elusive bioactive metabolites, such as delftibactin, in bacteria. Dr. Magarvey hopes to use this method to further understand the function of metabolites in bacteria found in humans and their possible applications in medicine.

By: Mohsin Ali


It may be as simple as probiotics, suggests a study led by McMaster professor Dr. Bradley Johnston. His colleagues analyzed twenty randomized-controlled trials, totalling almost 4,000 patients. They asked whether the use of probiotics—‘good’ bacteria found in yogurts, powders, or capsules—influenced rates of diarrheal illness related to the bacterium Clostridium difficile. Their main finding: new cases of C. difficile–associated diarrhea in hospital patients was reduced by 66 per cent, amounting to 33 cases prevented per 1,000 patients.

This effect is significant given the burden of C. difficile on the healthcare system: it causes illness and death in hospitalized adults. In fact, almost half of all diarrheal illness in hospitals is associated with C. difficile, and it is a major concern for the Ontario Ministry of Health and Long-Term Care, too, who tracked 75 outbreaks in 47 hospitals from 2009–2011.

Dr. Johnston, who is also a clinical epidemiologist at the Hospital for Sick Children in Toronto, echoes these concerns. He noted that a 2010 University of Ottawa study found one patient for every 10 infected by C. difficile died of the infection, and therefore “[m]inimizing or even preventing C. difficile among vulnerable patients is a high priority for making every hospital as safe as possible for all patients. It’s an important public health issue.”

Dr. Mark Loeb, division director of Infectious Diseases in the Michael G. DeGroote School of Medicine at McMaster, agrees. As a co-author for the study, which was published in the Annals of Internal Medicine, both he and Dr. Johnston emphasized the importance of integrating probiotics into the diets of hospitalized patients. Older patients are especially at risk when using antibiotics, which deplete both ‘good’ and ‘bad’ bacteria, providing a niche for C. difficile to thrive.

Probiotics help reintroduce healthy bacteria, and though they are not a magic bullet, said Dr. Johnston, they are an effective, safe and relatively inexpensive approach to prevent C. difficile–associated diarrheal illness.

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