(Press-News.org) Methicillin-resistant Staphylococcus aureus (MRSA), an antibiotic-resistant superbug, can cause life-threatening skin, bloodstream and surgical site infections or pneumonia. Researchers at the University of California, San Diego School of Medicine now report that cigarette smoke may make matters worse. The study, published March 30 by Infection and Immunity, shows that MRSA bacteria exposed to cigarette smoke become even more resistant to killing by the immune system.
"We already know that smoking cigarettes harms human respiratory and immune cells, and now we've shown that, on the flipside, smoke can also stress out invasive bacteria and make them more aggressive," said senior author Laura E. Crotty Alexander, MD, assistant clinical professor of medicine at UC San Diego and staff physician at the Veterans Affairs San Diego Healthcare System.
Crotty Alexander is a pulmonologist who sees many patients who smoke cigarettes. She also sees many MRSA infections, and that got her wondering if one might influence the other. To test the hypothesis, Crotty Alexander and her team infected macrophages, immune cells that engulf pathogens, with MRSA. Some of the bacteria were grown normally and some were grown with cigarette smoke extract. They found that while the macrophages were equally able to take up the two bacterial populations, they had a harder time killing the MRSA that had been exposed to cigarette smoke extract.
To better understand why, the Crotty Alexander team tested the bacteria's susceptibility to individual mechanisms macrophages typically employ to kill bacteria. Once inside macrophages, smoke-exposed MRSA were more resistant to killing by reactive oxygen species, the chemical burst that macrophages use to destroy their microbial meals. The team also discovered that smoke-exposed MRSA were more resistant to killing by antimicrobial peptides, small protein pieces the immune system uses to poke holes in bacterial cells and trigger inflammation. The effect was dose-dependent, meaning that the more smoke extract they used, the more resistant the MRSA became.
MRSA treated with cigarette smoke extract were also better at sticking to and invading human cells grown in the lab. In a mouse model, MRSA exposed to cigarette smoke survived better and caused pneumonia with a higher mortality rate.
The data suggest that cigarette smoke strengthens MRSA bacteria by altering their cell walls in such a way that they are better able to repel antimicrobial peptides and other charged particles.
"Cigarette smokers are known to be more susceptible to infectious diseases. Now we have evidence that cigarette smoke-induced resistance in MRSA may be an additional contributing factor," Crotty Alexander said.
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Study co-authors include Elisa K. McEachern, John H. Hwang, Katherine M. Sladewski, UC San Diego and Veterans Affairs San Diego Healthcare System; Shari Nicatia, UC San Diego, Veterans Affairs San Diego Healthcare System and Utrecht University; Carola Dewitz, UC San Diego, Veterans Affairs San Diego Healthcare System and University of Veterinary Medicine, Hannover, Germany; Denzil P. Mathew, Veterans Affairs San Diego Healthcare System; and Victor Nizet, UC San Diego.
This research was funded, in part, by the U.S. Department of Veterans Affairs.
(SACRAMENTO, Calif.) -- The micro RNA miR-22 has long been known for its ability to suppress cancer. However, questions remain about how it achieves this feat. For example, which molecules are regulating miR-22, and which are miR22 targets?
Researchers at UC Davis have unraveled some of these relationships, identifying several interactions that directly impact liver and colon cancer. The work provides new insights into how miR-22 operates and could potentially lead to new cancer therapies. The study was published in the Journal of Biological Chemistry.
"There are quite ...
WASHINGTON, April 2, 2015 -- It's supposed to help keep our bodies healthy in stressful situations. But the constant stress of our everyday lives means we're getting overexposed to cortisol. Raychelle Burks, Ph.D., explains why too much cortisol is bad for you in the latest episode of the Reactions series Get To Know A Molecule. Check it out here: https://youtu.be/fPnDaRYXHs4.
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For more than 50 years, scientists thought that the horned anole lizard -- sometimes called the "Pinocchio Lizard" for its long, protruding nose -- was extinct. But it turns out this is a tall tale.
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A molecular pathway known to suppress tumors appears to also be a major player in clearing cells of damaged proteins implicated in neurodegenerative diseases such as ALS and certain types of dementia, new research in roundworms and human cells suggests.
Johns Hopkins Bloomberg School of Public Health researchers, publishing April 2 in the journal PLOS Biology, say their findings shed new light on how a cell's protein quality control mechanism works - and how this system could be harnessed one day to combat diseases caused by a buildup of proteins in cells. To function ...
