Microbiology graduate Dawn Bowdish

While most people try to avoid infectious diseases, Dawn Bowdish, B.Sc. ’00, can’t stay away from them. That’s because her lab studies deadly pathogens. But she says there’s no place she’d rather be.

“We study Streptococcus pneumoniae, which normally lives in the sinuses, but if it leaves the sinuses, it can become a deadly form of pneumonia,” says Bowdish, assistant professor in pathology and molecular medicine at McMaster University. “A lot of the bacteria that live in our upper respiratory tract have the potential to become pathogens.” When these bacteria get out of control, the body’s immune system kicks in.

White blood cells, also known as macrophages, are the body’s first line of defence against bacterial invaders. During a process called phagocytosis, macrophages go on a feeding frenzy, consuming many times their own body mass in bacteria and killing them with their acid-filled vacuoles.

“The inside of a macrophage is a very nasty place to be,” says Bowdish. “We’re interested in how macrophages recognize bacteria and how they respond to them.” Understanding how macrophages attack bacteria could lead to therapies that help boost the body’s response to infection.

Pneumonia poses the greatest threat to children under 2 and adults over 65 because their immune systems aren’t strong enough to fight off the infection. According to the Public Health Agency of Canada, the disease kills almost 1.6 million children under 5 annually worldwide, more than AIDS, malaria and measles combined. Even healthy adults can be susceptible if their immune system is compromised by another infection like influenza.

Bowdish’s research is focusing on why the elderly are particularly vulnerable to pneumonia. “We know there are generalized defects in the immune response, but we don’t really understand why the susceptibility becomes so great,” she says. “There’s a lot we know, but more that we don’t know.”

Antibiotics are often used to treat infectious diseases, but the abuse and misuse of these drugs are contributing to the rise of antibiotic-resistant bacteria. That’s why Bowdish’s lab is trying to develop new therapies that strengthen the body’s own natural defence mechanisms.

“Antibiotics work by killing the bacteria directly; what we want to develop are therapies that help the body use the natural process of recognizing and killing the bacteria,” she says.

Vaccines help protect the body from infectious diseases, but since most vaccines are delivered through injections, they’re not the best choice for children and the needle phobic. Nasal spray vaccines are more effective than a shot in the arm, not only because they’re painless, but they stimulate the body’s immune response where the infection is most likely to start.

Nutrition also plays a role in the body’s ability to combat bacteria. “The healthier the hosts are, the more likely they are able to fight off infection,” says Bowdish.

One of the biggest risk factors to getting sick is exposure to young children. “There’s no cure for that,” says Bowdish with a laugh. “People like me who have kids are constantly assaulted, and that’s often how the elderly get sick ─ through exposure to their grandkids.” Since washing your kids’ hands every two seconds isn’t very practical, researchers are looking at other ways to keep both children and adults healthy.

Bowdish says she received a “spectacular microbiology education” at the University of Guelph, which helped build the foundation for her career, and she still collaborates with some of her former professors. Making a difference with her research keeps her motivated. “I think there’s a real opportunity to do good scientifically by making important discoveries, but also do good for the public.”

Bowdish will give a talk on “Mechanisms of Immune Control of Streptococcus pneumoniae in the Upper Respiratory Tract” on Jan. 14 at 11 a.m. in OVC Pathobiology, Room 1810.