20 November 2009

Popular cigarette brands loaded with bacteria

by Kate Melville

Cigarettes are "widely contaminated" with bacteria known to be harmful to humans, claims a new study in Environmental Health Perspectives. And, according to the researchers, some of the organisms identified are resilient enough to survive the burning process.

The study, conducted by a University of Maryland (UM) environmental health researcher and microbial ecologists at the Ecole Centrale de Lyon in France, is the first to show that cigarettes themselves could be the source of exposure to a wide array of potentially pathogenic microbes among smokers and other people exposed to secondhand smoke.

"We were quite surprised to identify such a wide variety of human bacterial pathogens in these products," says UM's Amy R. Sapkota, the lead researcher on the study. "The commercially-available cigarettes that we tested were chock full of bacteria, as we had hypothesized, but we didn't think we'd find so many that are infectious in humans."

But can the cigarette-borne bacteria survive the burning process and go on to colonize smokers' respiratory systems? According to Sapkota, existing research suggests that some hardy bacteria can be transmitted this way, which would account for the fact that the respiratory tracts of smokers are characterized by higher levels of bacterial pathogens.

"[The bacteria could] contribute to both infectious and chronic illnesses in both smokers and individuals who are exposed to environmental tobacco smoke," Sapkota warns. "So, it's critical that we learn more about the bacterial content of cigarettes, which are used by more than a billion people worldwide."

Previous studies have taken small samples of cigarette tobacco and placed them in cultures to see whether bacteria would grow. But Sapkota's team took a more holistic approach using DNA microarray analysis to estimate the so-called bacterial metagenome, the totality of bacterial genetic material present in the tested cigarettes.

Key findings from the analysis:

"Now that we've shown that a pack of cigarettes is loaded with bacteria, we will conduct follow-up research to determine the possible roles of these organisms in tobacco-related diseases," Sapkota said in conclusion.

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Source: University of Maryland School of Public Health