Thursday, March 18, 2010

Germs in Tobacco

Bacteria found in major cigarette brands.

It’s not enough that smoking causes all manner of cardiopulmonary complications, or that more than 3,000 chemicals and heavy metals have been identified as additives. Now comes evidence that tobacco particles extracted from cigarettes contain markers for hundreds of known bacteria. Lung infections in some smokers may be caused by germs on shredded tobacco, rather than the act of smoking itself.

According to a report by Janet Raloff in Science News, Amy Sapkota and a team of researchers at the University of Maryland screened tobacco flakes from cigarettes for bacterial DNA using known markers. ResearchBlogging.orgIn an online paper for Environmental Health Perspectives, the scientists explored the bacterial metagenomics of cigarettes using standard cloning and sequencing processes. The team provided evidence for the presence of Campylobacter (a cause of food poisoning), E. coli, several Staphylococcus varieties, as well as a number of bacteria, such as Clostridium, which is directly associated with pneumonia and other infections. Fifteen different classes of bacteria in all, with no significant variation from one cigarette brand to another. 

The time has come, Sapkota and coworkers conclude, “ to further our understanding of the bacterial diversity of cigarettes,” given the more than 1 billion smokers worldwide.  Smoking is now recognized as a risk factor for a basketful of respiratory illnesses, including influenza, asthma, bacterial pneumonia, and interstitial lung disease. In light of this, the authors have advanced their study as solid evidence that “cigarettes themselves could be the direct source of exposure to a wide array of potentially pathogenic microbes among smokers and other people exposed to secondhand smoke.”

In 2008, researcher John Pauly and coworkers at the Roswell Park Cancer Institute in Buffalo, New York, helped provide early evidence by conducting a tobacco flake assay and publishing the results in the journal Tobacco Control. The scientists opened a package of cigarettes “within the sterile environment of a laminar flow hood. A single flake of tobacco was collected randomly and aseptically from the middle of the cigarette column and placed onto the surface of a blood agar plate. The test cigarettes included eight different popular brands, and these were from three different tobacco companies.”

And the results? “After 24 hours of incubation at 37 degrees C, the plates showed bacterial growth for tobacco from all brands of cigarettes. Further, more than 90% of the individual tobacco flakes of a given brand grew bacteria.” Pauly believes that “the results of these studies predict that diverse microbes and microbial toxins are carried by tobacco microparticulates that are released from the cigarette during smoking, and carried into mainstream smoke that is sucked deep into the lung.”

In a recent study published in Immunological Research , Pauly and others expanded on their findings, writing that “Cured tobacco in diverse types of cigarettes is known to harbor a plethora of bacteria (Gram-positive and Gram-negative), fungi (mold, yeast), spores, and is rich in endotoxin (lipopolysaccharide).” This time out, the researchers conclude that “lung inflammation of long-term smokers may be attributed in part to tobacco-associated bacterial and fungal components that have been identified in tobacco and tobacco smoke.”

Cigarette manufacturers already use antibacterial washes during the curing process in order to reduce infection by fungi and bacteria.

If the findings are sound, they could place the argument over secondhand smoke in a vastly different light—cigarettes smoke may be taking the rap for respiratory infections cause by extant bacteria. With smoking rates in the U.S. holding at a steady 21 percent of the population, the issue is not trivial.

Sapkota, A., Berger, S., & Vogel, T. (2009). Human Pathogens Abundant in the Bacterial Metagenome of Cigarettes Environmental Health Perspectives, 118 (3), 351-356 DOI: 10.1289/ehp.0901201

Pauly, J., Smith, L., Rickert, M., Hutson, A., & Paszkiewicz, G. (2009). Review: Is lung inflammation associated with microbes and microbial toxins in cigarette tobacco smoke? Immunologic Research, 46 (1-3), 127-136 DOI: 10.1007/s12026-009-8117-6

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