A study by University of New Mexico Health Science Center researchers was recently featured in the Journal of Immunology for their work which examines the sex bias of Methicillin-resistant Staphylococcus aureus, or MRSA. The findings indicate females are less susceptible to MRSA than males.

MRSA is a type of Staphylococcus, or staph, bacteria that is resistant to several antibiotics. About 1 in 3 people carry Staphylococcus in their nose without any illness, and 2 in 100 people carry MRSA.

MRSA is most often known for its ability to cause skin infections; however, it can also cause pneumonia and lead to sepsis if left untreated, according to the Centers for Disease Control and Prevention.



Their study titled, “Innate Sex Bias of Staphylococcus aureus Skin Infection Is Driven by Alpha-Hemolysin,” was conducted in the lab of Pamela Hall, Ph.D., an associate professor of Pharmaceutical Sciences at the UNM College of Pharmacy. Hall’s lab focuses on research-related to skin infections and the host’s innate response to Staphylococcus.

Hall said this research has been a few years in the making.

“This research was started by a graduate student in my lab back in 2014 or 2015,” she said. “It was a collaborative effort between graduate students, technicians in my lab, as well as investigators in the departments of: Cell Biology and Physiology, Internal Medicine and Emergency Medicine in the UNM School of Medicine.”

Hall’s team became interested in investigating the sex bias of Staphylococcus after noticing a difference in the way male and female cells responded to the bacteria.

“We noticed that if you take cells in the lab and test them for killing Staphylococcus, female cells are better at killing the bacteria,” she said.

In addition to the team’s interest in understanding the sex bias nature of Staphylococcus, the National Institutes of Health, which funded Hall’s work, asked researchers to conduct their study in both male and female cells, or animal models, in order to understand the differences in how they respond.

“There is a vast difference in how the innate immune system of males and females responds to things,” Hall said. “This is known epidemiologically, but we need more basic science studies to really understand the mechanisms.”

The researchers took the neutrophils — a type of white blood cell that helps fight off infections caused by bacteria — from male and female mice, Hall said. The cells were incubated with staph. Later, the living staph bacteria were counted.

“We found that there were fewer staph bacteria alive in the cells that had been incubated with the female cells,” she said. “This means that female cells were better than male cells at killing staph.”

Hall said the difference in immune response between males and females can be attributed to the presence of estrogen in females. She said she hopes future research will lead to a better understanding behind this mechanism and ultimately help advance therapies.

“We need to figure out which estrogen receptor is moderating the protection,” she said. “There are different estrogen receptors, and they can behave differently in different cells. It’s very complicated, but in the end, we would like to use this information to improve therapies.”

Hall said being published in this journal is a step in the right direction for reaching this goal and advancing future research.

“We are very happy to be published in the Journal of Immunology,” she said. “It’s a good journal that reaches a lot of people. We hope to build collaborations and advance this work as quickly as possible.”

Sex bias is important for understanding and treating MRSA, and it is also pertinent to a variety of other infections.

Kimberly Page, Ph.D., professor and chief of epidemiology, biostatistics and preventive medicine at the UNM Health Sciences Center, said understanding sex bias has been a crucial part of her research with Hepatitis C virus, or HCV.

“Sex differences can be manifested at multiple points in the natural history of infection and disease,” she said. “From my own work on HCV, we know that women may be more susceptible to acquiring HCV. This is in association with both social and biological factors.”

Page said understanding sex bias is important, but the mechanism behind it is still not understood.

“Sex differences between females and males has been seen with respect to several infections, including influenza, or flu virus...The mechanisms underlying differences in physiology and disease are not well studied. There is a growing appreciation for how females and males differentially exhibit immune responses to pathogens, not just in association with hormones, but also sex chromosome genes,” she said.

When doing research people often focus on sex differences, but Page said social and environmental factors can be at play as well.

Much like Hall, Page said she also hopes a growing understanding of sex bias will help improve the lives of patients.

“It’s always illuminating to see...how some people control infections better than others,” she said. “These differences give us clues to designing new vaccines, therapies and disease monitoring systems.”

Mikhaela Smith is a news reporter at the Daily Lobo. She can be contacted at news@dailylobo.com or on Twitter @MikhaelaSmith18.