A common bacterium’s ability to spread from the colon is revealed by research
Researchers from Weill Cornell Medicine have discovered that a common gut bacterium that can spread throughout the body and result in a serious infection resists both the body’s own immune mechanisms and medications by strengthening its outer, protective layer, known as the cell envelope. The discovery raises the prospect of fresh approaches to combat these bacterial illnesses.
The study, which was released on Nov. 10 in the journal mBio, sheds light on some of the underlying changes that could take place when Enterococcus faecalis (E. faecalis) populations pass through the epithelial cells lining the colon and escape to reach other body regions.
Dr. Diana K. Morales, principal investigator, is an assistant professor of microbiology and immunology in the department of obstetrics and gynecology at Weill Cornell Medicine. She explained that systemic infections with E. faecalis can be fatal because this microbe has a remarkable ability to adapt to different environments and resist treatments.
Antibiotic use and weakened immune systems, which promote E. faecalis overgrowth in the intestine, put some people at risk for contracting these infections. It may one day be possible for researchers to develop tiny compounds that block the transmission of E. faecalis outside of the gastrointestinal tract, hence reducing the risk of infectious diseases.
It is still entirely unknown how the bacterium can spread from the intestine to other organs. However, Dr. Morales noted that scientists have discovered the existence of two distinct populations of the same kind of bacterium. One population acquires characteristics that enable it to cross the intestinal barrier and gain a beneficial resistance to antimicrobials, whereas the other population remains stationary.
In a number of earlier lab investigations on the bacteria, the researchers discovered that motile E. faecalis creates polysaccharides, molecules made of sugar chains that enable the bacterium to congregate or clump together. According to Dr. Morales, these bacteria seem to gain an ability to move as they aggregate.
Researchers observed that the motile form of E. faecalis has a cell membrane that contains more glycolipids, which are fat molecules connected to a carbohydrate. The lead author of the study, Dr. Yusibeska Ramos, is a research associate in obstetrics and gynecology.
The bacteria appears to be able to withstand external stresses thanks to increased synthesis of cell membrane glycolipids. These stressors include the antibiotic daptomycin, which is frequently used to treat E. faecalis infections, and β-defensins, which are tiny molecules produced by intestinal epithelium to ward off infection.
The researchers also discovered that E. faecalis was more vulnerable to various stressors and had less ability to cross intestinal epithelial cells and cell surfaces due to genetic alterations that prevent glycolipid synthesis.
The researchers’ next step is to assess other in vivo models to see whether the molecular pathways discovered in the present study are required for the bacterium to leave the intestine. In order to assist patients fight infections caused by this gut bacteria more effectively in the future, the researchers are also interested in identifying pharmacological treatments that can target these specific pathways.
Yusibeska Ramos et al. (2022). Remodeling of the Enterococcal Cell Envelope during Surface Penetration Promotes Intrinsic Resistance to Stress, mBio. DOI: 10.1128/mbio.02294-22
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