Research

The majority of skin infections are from Staphylococcus aureus, resulting in about 1% of all hospital visits. That may not sound like a lot, but from 2001-2003, that was over 11 million visits! It is very likely that you know someone who has had a Staph infection.

Staph infections are a big problem, causing billions of dollars in healthcare costs each year, and the problem hasn’t been getting any better. With the rise of antibiotic resistance, these infections have been getting harder and harder to treat. These aren’t small, harmless infections, either! 

Staph infections are known to be very virulent, which means that they are very good at causing disease and generally being nasty. They can cause flesh to rot, serious disfigurement, and even death if they don’t get treated! 

My research focuses on one mechanism S. aureus uses to be so nasty. This mechanism is called the Type Seven Secretion System (T7SS). You can think of the T7SS as a sewage pump. S. aureus constantly makes many different virulence factors. Think of these as toxins. These virulence factors are proteins that the bacteria produces inside that need to get out to cause damage. These proteins have one job: cause chaos. 

Since these toxins, the virulence factors of the T7SS, are trapped inside of the cell, they need a way out. However, these toxins are large and chunky, and can’t just leave the cell. Since the cell can’t let everything else inside it leave along with the toxins, the cell came up with a pathway to let just the toxins out. This is the T7SS. 

As the toxins continue to build up in the cell, it will tell the T7SS to start pumping them out. Once these toxins are out, they can start causing the chaos they are designed for. Some of these toxins attack DNA, while others help fight against other bacteria for resources. My research specifically focuses on how these toxins help hide the bacteria from our immune system. 

I do this by studying how the T7SS impacts different aspects of our immune system. Specifically, I am looking at components of our innate immune system. This is the part of our immune system that are first responders. The moment you get a cut, your innate immune system jumps into action to fight any bacteria or viruses that get in. 

Fruit flies have an innate immune system that is very similar to human’s, so I infect fruit flies with our Staph infections that have the T7SS and ones that don’t (we genetically remove the T7SS from the bacteria). This lets me test how well the bacteria can survive in the innate immune environment, as well as how much the T7SS is responsible for killing the flies. 

I also look at a specific part of the innate immune system. These are cells called macrophages, which are big, angry immune cells that will eat anything that gets into our bodies that isn’t supposed to be there. However, the T7SS appears to be important for how well the bacteria can avoid the macrophages, as well as for surviving within the macrophages when if it does get eaten.

Overall, my research is focused on how the T7SS, a system that pumps toxins out of S. aureus, impacts the bacteria’s ability to survive the innate immune system. If we can figure out how the T7SS helps Staph infections hide from and fight against our immune system, we might be able to design treatments that block it–and make these infections easier to treat.

2025 Goldwater Application on T7SS Research

Cruikshank et. al, 2024