Stopping Steno: The Fight to Halt a Dangerous Pathogen

Biofilm of antibiotic-resistant bacteria

It sounds like something out of a sci-fi horror film: An aggressive pathogen that kills as many as 70 percent of its victims by causing an infection in the bloodstream, bone, tissue, brain, heart, eye, skin or practically any other body part. But this is no Hollywood invention. It’s Stenotrophomonas maltophilia, a common bacterial pathogen that can be deadly for patients with compromised immune systems.

Associate Professor Joanna Brooke, a medical microbiologist and bacteriologist, wants to change that. The organism, which Brooke calls “Steno” for short, has the ability to form thick biofilms in your lungs, on the surface of surgical instruments, around sink faucets and on other living and nonliving surfaces. These biofilms are composed of bacterial cells surrounded by a matrix of macromolecules, such as protein, DNA, nucleic acids, lipids and carbohydrates. Unfortunately, the cells in the films tend to be drug-resistant, making them very difficult to eliminate.

Difficult, however, doesn’t mean impossible. In her lab, Brooke is pursuing several promising strategies to combat Steno. “We just published a paper showing it’s possible to use chemical compounds, combined with drugs, to increase the efficacy of drugs that used to be effective against Steno,” Brooke says. This was the first research study on Steno to take this approach; Brooke conceived of the idea after reading that Pseudomonas aeruginosa, a similar organism that can form biofilms with Steno, responded to chemical treatment.

In addition to the chemical route, Brooke has had some success in using a bacterial predator that can interact with Steno and kill it off. Brooke and a graduate student are also trying to determine whether a virus could eliminate drug-resistant Steno living in nature. “It’s not just found in hospitals,” Brooke notes.

Indeed, there are many different strains of the pathogen. The good news is that the chemical approach was effective against more than one strain, as Brooke and her co-authors, including five undergraduates, detail in their paper. From setting up and running experiments to analyzing data and writing and proofreading the manuscript, the undergraduates were heavily involved in all aspects of the research.

“When I take undergraduates into the lab, I don’t want them only doing menial tasks like washing dishes,” Brooke says. “I like for them to be involved in the actual benchwork, and I really like to see my students get published.” Brooke recalls getting in touch with her student researchers after they graduated but before the paper was accepted, asking, “Do you agree with what I’m saying here?” and “Could you check this?” Indeed, it was this hands-on mentoring that attracted Brooke to DePaul back in 2001; the college recognized her dedication with the inaugural CSH Faculty Mentor of the Year award in 2014.

Even after 16 years of working on Steno, Brooke concedes there’s still much to be done. “One limitation is that we grow our biofilms on plastic plates—it’s a test-tube situation, which is very different from the human body,” Brooke explains. “That’s why at the end of the paper, I say that it has potential, but it needs to be tested further.” The next few years will bring more trial and, inevitably, error, but Brooke isn’t fazed. “That’s science,” she says cheerfully. “It can be frustrating, sure, but it’s exciting at the same time.”

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