Cigarette Smoke Makes MRSA Bacteria Harder to Kill

cigarette smoke makes MRSA

A new study finds that cigarette smoke makes MRSA bacteria harder to kill by immune cells.

Methicillin resistant staphylococcus aureus (MRSA) is becoming a huge health issue with growing numbers of hospital acquired infections each passing year. The antibiotic resistant “super-bug” causes about 5,500 deaths in the US each year, with about 94,000 infections reported in 2005. Now a new study finds that smoking could worsen prognosis of infections by making the “super-bug” even harder to kill.

Cigarette Smoke Makes MRSA Bacteria Harder to Kill

“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,

Since cigarette smoking puts a strain on our cells, might it do the same on bacteria? To test this hypothesis researchers infected a type of immune cell, macrophages, with MRSA. The MRSA were grown either under exposure to a cigarette smoke extract or not. Bacteria grown under exposure to the smoke extract survived far better against methods employed by the macrophages, having a 4-fold higher survival than MRSA grown without the extract.

But why were they harder to kill?

Researchers took a closer look at the mechanisms employed by the macrophages to kill bacteria. After testing various mechanisms researchers found that smoke-exposed MRSA bacteria were resistant against two mechanisms macrophages use to kill pathogens; ROS and antimicrobial peptides. Reactive oxygen species are reactive chemicals that creates dangerous free radicals damaging important cell structures while antimicrobial peptides are small proteins that work by poking holes in bacterial cells and triggering inflammation.

The data suggest that the increased resistance is due to the smoke changing the bacterial cell wall making it better at repelling 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.

Image Credit: kenji aryan via flickr.com, CC BY-SA 2.0