In the study, more than 700 bacterial species were found in well-known cigarette brands including Camels, Kool Filter Kings, Lucky Strike Original Red, and Marlboro Red. Sapkota suspects their screen actually underestimates the number of bacteria present, and thinks it could be closer to the thousands of chemicals found in cigarettes. The researchers noted that no one brand had significantly different levels of bacteria.
To create cigarettes, green tobacco, which has relatively few bacterial species, are fermented under conditions that are perfect for dense bacterial growth. Instead of removing the bacteria during process, the fermentation concentrates them to as much as 1 million bacteria per cigarette, Pauly said. And the bacteria are alive and capable of reproducing. A single tobacco flake from a cigarette, when placed on a dish with nutrients, will lead to the growth of live bacterial colonies, he said.
"It’s amazing how hearty these little critters are," said Sapkota. "We’re finding out more each day how they can survive."
The research team found 15 different classes of bacteria and a number of potentially pathogenic organisms. The most notorious organisms present were Acinetobacter, Bacillus, Burkholderia, Clostridium, Klebsiella, Pseudomonas aeruginosa, and Serratia. These bacteria were found in more than 90 percent of all cigarette samples tested. Also found in the samples were the pathogens Campylobacter, Enterococcus, Proteus, and Staphylococcus.
Sapkota said it's troubling that so many human pathogens are present in cigarette tobacco. Microbes are known to cause acute infectious illnesses and also are risk factors for chronic diseases such as cancers and neurological disorders. However, future studies are necessary to determine whether or not the bacteria in cigarettes actually play a role in those diseases.
What researchers do know is that smokers are inhaling living bacteria into their lungs, which are sterile in healthy individuals, and this could lead to certain types of lung disease such as COPD and inflammation that is associated with solid tumors.
According to Pauly, even dead bacteria produce endotoxins that can activate cells that cause inflammation. He says there is some concern that the chemicals and bacteria might work together to speed up the malignancy of cancer cells.
However, at this stage in the research, it is too early to indict the pathogens found in cigarettes for causing disease in humans. The goal of the study was simply to evaluate cigarettes’ bacterial metagenome, or all the bacteria present.
"The organisms are there. Now the question is, what are they doing?" said Sapkota.
This article originally ran at Environmental Health News, a news source published by Environmental Health Sciences, a nonprofit media company.