APR 14, 2017 2:56 PM PDT

New insights into gonorrhea

WRITTEN BY: Kerry Evans

Researchers at the University of Maryland figured out why some Neisseria gonorrhoeae infections become invasive, while others don’t. More invasive strains cause the epithelial layer of the endocervix (in the female genital tract) to shed, giving the bacteria access to deeper tissues.

N. gonorrhoeae, as the name suggests, is the bacterium that causes gonorrhea. Gonorrhea is a common sexually transmitted infection, and it is becoming a serious public health issue because many strains of the bacterium are resistant to antibiotics.

Electron micrograph of N. gonorrhoeae

Gonorrhea has been difficult to study because the bacteria only infect humans - this means that other animal models aren’t particularly useful (and no humans are volunteering as guinea pigs). Here, the University of Maryland researchers, led by Liang-Chun Wang, developed an explant culture model that uses human endocervical tissue.

The group found that the bacteria cause epithelial cells lining the endocervix to shed off. The bacteria also disrupt the junctions between epithelial cells by activating myosin. This is a pretty surprising finding because researchers have always thought that this “epithelial exfoliation” helped to prevent infection.

They started their experiments by testing out their new explant model and comparing it to a monolayer of T84 colonic epithelium cells. They incubated the two cell cultures with bacteria, and by 24 hours both cultures showed bacteria-induced exfoliation. Importantly, both the endocervical explants and the T84 cells behaved similarly, indicating that both models could be useful for studying gonorrhea.

Next, the researchers investigated the N. gonorrhoeae cell-surface protein called Opa because previous studies indicated that it is especially important for the pathogenesis of gonorrhea. Opa is also important because it undergoes phase variation - the bacteria only express it under certain environmental conditions.

They incubated the endocervical and T84 cells with a mutant strain of bacteria that did not produce Opa. Surprisingly, cells that lacked Opa showed more exfoliation in response to the bacteria. The percentage of exfoliation increased in the endocervical cells from 32.3% to 66.3% and in the T84 cells from 31.2% to 55.8%. Thus, it appears that cells that do not express Opa are able to establish a more productive infection (from the bacterial point of view, of course).

Their next goal was to better understand the mechanism behind the bacteria-induced epithelial exfoliation. They suspected that non-muscle myosin II was involved in the process and tested whether small chemical inhibitors of myosin affected bacteria-induced exfoliation. Sure enough, two of the inhibitors (one that inhibited calcium-dependent and another that inhibited ROCK-dependent myosin activation) reduced exfoliation.

Thus, N. gonorrhoeae activates myosin in host cells to induce exfoliation. This, along with the absence of Opa, allows the bacteria to produce a more invasive infection.

Sources: PLOS Pathogens, Science Daily

 

About the Author
  • Kerry received a doctorate in microbiology from the University of Arkansas for Medical Sciences.
You May Also Like
JAN 22, 2020
Microbiology
JAN 22, 2020
Tuberculosis Pathogen Can Survive in Soil Amoebae
Researchers have learned that the bacterium that causes bovine tuberculosis is able to survive and grow inside of amoeba that live in soil....
JAN 28, 2020
Immunology
JAN 28, 2020
Infectious Parasite Manipulates the Immune System to Survive
Toxoplasma gondii suppresses the immune system of the hosts it infects – human or otherwise – just enough to survive, thrive, and move on to mo...
FEB 04, 2020
Microbiology
FEB 04, 2020
Revealing How a Common Virus Evades the Immune System
The human metapneumovirus (HMPV) might now be well-known, but it is the second biggest cause of respiratory infections....
FEB 14, 2020
Microbiology
FEB 14, 2020
CDC Director Expects Coronavirus to Find a "Foothold"
The novel coronavirus that emerged in Wuhan, Hubei Province, China has now infected over 64,000 people....
FEB 23, 2020
Immunology
FEB 23, 2020
New discovery could help preterm babies breathe easy
Babies born more than three weeks before full term are met with complicated and often life-threatening health challenges. Most notably, these tiny preterm...
MAR 03, 2020
Microbiology
MAR 03, 2020
Understanding an Antiviral Drug, as COVID-19 Cases Rise in the US
There have now been nine deaths in the United States, all in Washington state from COVID-19, the illness caused by the novel coronavirus SARS-CoV-2....
Loading Comments...