Cigarette Smoke Makes Superbugs More Aggressive

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.

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.

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8 thoughts on “Cigarette Smoke Makes Superbugs More Aggressive”

  1. There are about 7357 chemical compound in a cigarette and 70 of them are known to have carcinogenic activity. Most of these compounds cause irritation to the skin, eyes, respiratory tract and nasal passages, but to name a few, Acrolein and Polyaromatics are DNA mutagens that can stimulate the aggressiveness of MRSA. The aggressiveness of the MRSA can decrease but not by reduced exposure to cigarettes directly. Reduced exposure to cigarettes can reduce the rate at which its DNA mutates but will also give your immune cells time to recover and “fight” the MRSA superbug and that can reduce the superbug’s aggressiveness or I could suggest experimental medicine but I not sure if that will work.

  2. We knew that smoking cigarettes harms human respiratory and immune cells, and now it superbugs(MRSA). i strong believe that smoking cigarettes has more harm than this we already known. Since it damages immune cells, such piece of work need to spread out there. Because such issues we face everyday in our community were by people have no idea what damages smoking can real cause..

  3. We tend to focus our attention mainly on the negative effects that smoking cigarettes have on harming human respiratory and immune cells. This peace was a refreshing take on the subject. I was also wondering if different types of cigarettes with the wide variety of substances they contain can have an effect on the aggressiveness of the Methicillin-resistant Staphylococcus aureus (MRSA) -Superbug ?

    Is there a way to reduce the aggressiveness of the “Superbug” once constant exposure to cigarette smoke is reduced?


  4. Thank you Mehan, I was wondering the exact same thing as 15025366. I think is would be a plausible assumption as well that cigarettes aggravate a lot of those that suck on them (Suckers) or also referred to as smokers.

  5. Dear Janse van Rensburg, L 15025366

    Interestingly enough there are no direct indications to the origin of the Methicillin-resistant Staphylococcus aureus (MRSA). This “Superbug’s” clones and related other clones differ from country to country. This naturally causes major difficulty for doctors and scientist to find a cure and predicts its future. Little knowledge, along with the ability for more and more bacteria to resist antibiotics makes the bug a serious threat to all.

    Due to easy accessibilities of hosts in a hospital or health care clinic this superbug infects its next victims with ease. Combing smoking and other health detrimental activities, the bacteria will continue to thrive and infect other innocent individuals.

    Mehan van Huyssteen, u15035647

  6. Smoking is commonly known as a health risk and this takes it to a more serious level. What I would like to know is how does one become infected with this superbug? Is it only present in certain regions or areas?

  7. Wow! But, how is it possible to say that these diseases are connected to smoking? Can’t anyone get it?

  8. What an interesting and enlightening piece. Bacterial diseases are commonly made more aggressive by smoking, but does the content of cigarettes also effect this? Different cigarettes are composed of different amounts of certain substances, such as tar and nicotine. I would like to know if certain cigarettes make this bacteria more aggressive than other cigarettes.

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