Cigarettes contain hundreds of different strains of bacteria, including many human pathogens that may play a role in lung diseases and respiratory infections, new research shows.
Most health research has focused on the impact of chemicals in cigarettes and the particulates that are produced when tobacco is burned. But a new study, published in the journal Environmental Health Perspectives, paints the most complete picture to date of the bacteria in tobacco, suggesting that the germs could be another potential source of infection and disease.
The research--which shows that smokers are inhaling live bacteria--is the first time cigarettes have been implicated as a source of potentially pathogenic microbes.
"We thought it was a crazy idea to look at commercially available cigarettes to understand bacterial diversity," said Amy Sapkota, an epidemiologist at the University of Maryland, who led the research. "We were surprised to find that within a broad array of bacterial species that we found human pathogens were present as well."
Researchers are grappling with the public health implications of the findings.
Smoking cigarettes harms almost every organ system in the human body. The chemicals and heavy metals found in cigarettes--there are nearly 3,000 of them—and the particulates get most of the blame for the harmful effects of cigarettes, such as lung cancer and chronic obstructive pulmonary disease (COPD). However, emerging research points to smoking as a risk factor for respiratory illnesses such as the common cold, influenza, asthma, bacterial pneumonia and interstitial lung disease.
The discovery of pathogens “makes this story very exciting because it's a new mechanistic explanation to help us understand the variety of different diseases from cigarette smoking," said John Pauly, a cancer research scientist at the Roswell Park Cancer Institute in Buffalo, New York, who studies tobacco bacteria but was not involved in the new study.
With 1.2 billion smokers over the age of 15 worldwide, studying the bacterial diversity of tobacco is critical, according to scientists.
Bacteria have been known to be present in tobacco leaves, but only a few studies have looked into the contamination, and no research until now has attempted to catalog the bacteria diversity of cigarettes in order to investigate how these bugs may affect smokers or people exposed to second-hand smoke.
Sapkota became curious about bacteria living on tobacco while studying antibiotic-resistant genes in genetically modified tobacco plants. She was troubleshooting contamination problems when she realized the plants were full of bacteria. She remembers thinking that "if fresh tobacco leaves are loaded themselves, what is happening when the tobacco is harvested and produced to make cigarettes?"
The answer is that tobacco, too, was contaminated with bacteria.