Many pathogenic microbes are gaining resistance to antibiotics, and the bacterium that causes the sexually transmitted disease gonorrhea, Neisseria gonorrhoeae, is no different. The recent rise of drug-resistant gonorrhea has caused some alarm, and the pathogen has been labeled a superbug; it cannot be treated with any class of available antibiotics. Now, researchers at OSU/OHSU College of Pharmacy and collaborators have identified a protein that underlies the microbe’s virulence, which may help develop new ways to treat the disease.
Globally, there are an estimated 78 million new cases of gonorrhea every year. The disease can cause ectopic pregnancy, pelvic inflammatory disease, epididymitis, and infertility. The risk of blindness is increased in babies born to infected mothers, who may not know they have the disease.
"The infections very often are silent," explained Oregon State University researcher Aleksandra Sikora. "Up to 50 percent of infected women don't have symptoms, but those asymptomatic cases can still lead to some very severe consequences for the patient's reproductive health, miscarriage or premature delivery."
Sikora led a research team along with the lab of Ann Jerse at the Uniformed Services University of the Health Sciences in Bethesda, Maryland; they found a new kind of protein that aids in the transport of fats, a lipoprotein, which is utilized by N. gonorrhoeae to evade the defensive powers of our immune system.
Special enzymes in the body, lysozymes, can break up fatty molecules called lipids that compose cell walls. That process is used to disrupt the walls of bacteria, killing them. The cells that make up protective barriers of our body, like skin or tissues surrounding organs, are loaded with lysozymes that can help keep foreign material out.
For pathogens, that’s meant finding a way around those lysozymes. Many bacteria have developed an outer membrane, thwarting lysozymes.
This work revealed a new protein that inhibits them. It is only the second time a protein that acts against lysozyme has been found in the Neisseria genus. The protein was named SliC, short for surface-exposed lysozyme inhibitor of c-type lysozyme. The researchers confirmed the role of the protein in bacterial growth by using a mouse model.
This new target has created new candidates for engineering a vaccine or drug. Interfering with this lysozyme inhibitor could make the bacterium vulnerable to drugs and may reign in its ability to cause infection.
"This is the first time an animal model has been used to demonstrate a lysozyme inhibitor's role in gonorrhea infection," Sikora noted. "Together, all of our experiments show how important the lysozyme inhibitor is. This is very exciting."