What did the bacteria say to the cigarette?

Researchers at UC San Diego and the Veterans Affairs San Diego Healthcare System have found a population whose health actually improves when exposed to cigarette smoke: deadly, antibiotic-resistant "superbugs" such as Methicillin-resistant Staphylococcus aureus, commonly known as MRSA.

"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," senior study author Laura E. Crotty Alexander, MD, tells UCSD's NewsCenter.

Crotty Alexander led a team that infected groups of immune cells with MRSA, growing some samples normally and others in a cigarette-smoke extract. While the immune cells were able to surround the bacteria in both cases, they had a harder time killing the samples exposed to the smoke compound.

The smoke-exposed MRSA was also more successful at invading lab-generated human cells, and caused bouts of pneumonia that was likelier to be deadly in a study using mice.

Crotty Alexander's findings, she says, suggests that smoking strengthens the bacteria by altering its cell walls to better fight off attack by antimicrobials, or agents that kill or impede the bacteria's growth.

"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," the doctor concludes.