OSU research opens door to new ways to fight antibiotic-resistant 'superbug' gonorrhea

Microscopic image of the bacteria that causes gonorrhea (image provided by Aleksandra Sikora, OSU/OHSU College of Pharmacy).

CORVALLIS, Ore. - Researchers at Oregon State University may have found a new way to attack a "superbug" resistant to all known antibiotics.

The microbe in question - Neisseria gonorrhoeae - causes 78 million new gonorreha infections each year.

Gonorrhea, a sexually transmitted diesease, can lead to endometritis, pelvic inflammatory disease, ectopic pregnancy, epididymitis and infertility, according to OSU.

And babies born to mothers infected with gonorrhea have an increased risk of blindness, according to OSU.

“The infections very often are silent,” said OSU 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.”

But the disease is proving difficult to stop: strains of Neisseria gonorrhoeae have emerged that are resistant to the last known treatment options, OSU said.

Sikora and her team at the OSU/OHSU College of Pharmacy worked with Ann Jerse’s lab at the Uniformed Services University of the Health Sciences in Bethesda, Maryland, "to discover a novel lipoprotein that N. gonorrhoeae uses to defeat the body’s first line of innate immune defense," OSU said.

Here's why that's important in the fight against gonorrhea:

The body relies on enzymes known as lysozymes that, as their name suggests, thwart bacteria by causing their cell wall to lyse, or break apart. Lysozymes are abundant both in epithelial cells, which make up the tissue on the outside of organs and the inside of body cavities, and in the phagocytic cells that protect the body by ingesting foreign particles and bacteria.
In turn, many gram-negative bacteria – characterized by their cell envelope that includes a protective outer membrane – have developed ways of defeating lysozymes.
Prior to the work by Sikora’s team, however, only one lysozyme-fighting protein had been discovered in the Neisseria genus.
Now that new targets have been identified, they can be explored as bullseye candidates for new antibiotics or a vaccine – if the lysozyme inhibitor can itself be inhibited, then the bacteria’s infection-causing ability is greatly reduced.

The researchers have named the new protein SliC, short for surface-exposed lysozyme inhibitor of c-type lysozyme.

Their research included both bacteria cultures and mice infected with N. gonorrhoeae..

“This is the first time an animal model has been used to demonstrate a lysozyme inhibitor’s role in gonorrhea infection,” Sikora said. “Together, all of our experiments show how important the lysozyme inhibitor is. This is very exciting.”

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