An antibiotic-resistant “super-bacteria” that can cause life-threatening infections is worsened by cigarette smoke, according to a UC San Diego study released Thursday.
In a report in the journal Infection and Immunity, UCSD researchers said that methicillin-resistant Staphylococcus aureus that’s exposed to cigarette smoke becomes even more resistant to the immune system.
MRSA is a sometimes deadly staph infection that can afflict patients at hospitals or other healthcare settings such as nursing homes or dialysis centers, according to the Mayo Clinic.
Another form can be spread by skin-to-skin contact — with occasional breakouts among athletes.
“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 Dr. Laura Crotty Alexander, assistant clinical professor of medicine at UCSD and staff physician at the Veterans Affairs San Diego Healthcare System.
The pulmonologist said she sees a lot of patients who smoke, and also a lot of MRSA cases, which made her wonder about a possible connection.
Her team infected white blood cells that attack infections with MRSA, and grew some with cigarette smoke extract. All of the cells, called “macrophages,” attacked the MRSA, but the ones with the extract proved harder to kill.
Upon further inspection, they found the MRSA boosted with cigarette smoke were more resistant to the chemical bursts the macrophages use to kill infections, according to UCSD.
The study also found 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 MRSA becomes even more resistant when higher doses of smoke extract were used.
“Cigarette smokers are known to be more susceptible to infectious diseases,” Crotty Alexander said. “Now we have evidence that cigarette smoke- induced resistance in MRSA may be an additional contributing factor.”
The research was funded, in part, by the U.S. Department of Veterans Affairs.
