Germs in tobacco are potential source of respiratory infections blamed on smoking

Tests find hundreds of bacterial species in major cigarette brands

Cigarettes host a bacterial bonanza of hundreds of different germs, including those responsible for many human illnesses, a new genetics study reports.

GERMS RIGHT AT HOME Bacteria from tobacco, grown in the lab with blood, are surrounded by remnants of red blood cells destroyed by bacterial toxins in a process called hemolysis. J. Pauly, l. Smith, m. Rickert, a. Hutson and g. Paszkiewicz/Roswell Park Cancer Inst.

The data support findings described last September by scientists at the Roswell Park Cancer Institute in Buffalo, N.Y. They extracted tobacco particles sitting atop filters or inside cigarette packaging and placed the particles in a sterile culture medium that simulated human lungs. In most cases, the team was able to grow bacteria that had been present on the near-microscopic flakes.

Scientists have long known that smokers and people exposed to secondhand smoke experience high rates of respiratory infections, notes Amy Sapkota of the University of Maryland in College Park. The presumption has been that smoking impairs lung function or immunity — which it may, she acknowledges.

“But nobody talks about cigarettes as a source of those infections,” she says. So she and her colleagues screened leafy bits of cigarettes for bacterial DNA.

The scientists probed for ribosomal material, protein-building elements that read and execute instructions encoded within a cell’s DNA. Sapkota’s team homed in on long, species-specific regions of this material known as 16S markers and compared them with those of known bacteria.

Checking 16S markers for close to 800 known bacteria revealed matches to many hundreds of markers in the four brands of cigarettes screened: Marlboro Red, Camel, Kool Filter Kings and Lucky Strike Original Red. All were purchased in Lyon, France, where Sapkota was completing postdoctoral studies.

In a paper published online in Environmental Health Perspectives, Sapkota’s team lists many of the most prevalent bacteria present, including Campylobacter, which can cause food poisoning; Clostridium, Corynebacterium, Klebsiella, Pseudomonas aeruginosa and Stenotrophomonas maltophilia — all of which are associated with pneumonia and other infections; E. coli; and a number of Staphylococcus species that underlie serious hospital-associated infections.

Such genomic analyses can’t prove whether the DNA in unlit cigarettes came from live germs. But Alejandro Rooney of the Agricultural Research Service in Peoria, Ill., says that, based on data he published five years ago, at least some could have.

In seeking the source of severe respiratory disease in some U.S. troops in Iraq, most of whom were new smokers, “We looked at the microbes that you could culture from cigarettes and that were alive,” Rooney says. Most bacteria belonged to families that form spores. “And that makes sense,” he says, because tobacco in cigarettes is dry.

And spore-forming bacteria like Bacillus subtilis can survive in a state akin to suspended animation until they reach a suitable environment.

Clearly, he says, “it would be worthwhile to investigate further whether it [bacterial contamination of tobacco] is a health problem” and whether it extends to microbes beyond those his team was able to culture.

Roswell Park immunologist John Pauly agrees.

Several years ago, he began exploratory “surgery” on cigarettes, looking for microbes. Eighteen months ago, his group published data showing that randomly selected flakes extracted from cigarette filters and packages grew in a solution mimicking blood.

In the September 18, 2009 issue of Immunological Research, Pauly and his colleagues reviewed data showing that not only cigarettes but also cigars and smokeless tobacco (such as chewing tobacco and snuff) host live germs, although in most cases, few to none of the microbes have been identified by species.
In the paper, Pauly’s group also summarized followup tests at Roswell Park. They showed that roughly 60 percent of filters — representing 11 brands of sampled cigarettes and five companies — contained tobacco particles. The tobacco also hosted bacterial toxins. And as a general rule, they reported, “bacteria grew from greater than 90 percent of the randomly selected flakes.”

When cultured with blood, Pauly’s team demonstrated, “those tobacco-derived bacteria frequently destroyed the red blood cells.”

Ironically, he says, “You’ll see very few bacteria on freshly harvested, green tobacco.” Most microbial contamination occurs later. “When you place it in a curing situation, for example — a barn with high temperatures, high humidity, poor ventilation and blocked-out sunlight — you get a near-perfect environment for growing bacteria and fungi,” Pauly says.

Pauly notes that the tobacco industry is well aware of microbial contamination in their products, and when it occurs, even though they have yet to report it in the peer-reviewed literature. His source: a host of U.S. patents awarded to cigarette companies in recent years for killing microbes.

They include patent no. 6,755,200 B1, issued on June 29, 2004, to three Virginia scientists on behalf of Phillip Morris Inc. It covers the use of an antibacterial wash on fresh or partially cured tobacco as a cost-effective method “of reducing both the numbers and activity of bacterial and fungal populations.” The patent points out that these microbes are responsible for producing endotoxins and tobacco-specific chemicals called nitrosamines.

Preventing nitrosamine formation is the real impetus for those patents, says Pauly, because those contaminants represent “the number one carcinogens found in both smoking and smokeless tobacco products.” And they don’t arise from the burning of tobacco, he notes, “but due to microbial degradation of components in the tobacco.”
However, endotoxins are not benign. Healthy lungs are sterile, Pauly notes, so seeding the airways with microbes and these toxins could promote dangerous inflammation and “constitute a previously unrecognized health risk from smoking.” 

The Family Smoking Prevention and Tobacco Control Act, signed into law last June 22, gives the U.S. Food and Drug Administration the power to compel companies to turn over all data on constituents of tobacco products that may be harmful. This would include germs, Pauly contends. The law also instructs the FDA to publicly display and annually publish a list of potentially harmful constituents in each tobacco product, by brand and by quantity. And it directs the FDA to report to Congress on innovations and treatments that would, among other things, reduce the harm associated with tobacco use.

Pauly says that he and other tobacco researchers “are hoping FDA uses the law to start asking tobacco companies: ‘Why have you withheld this information from us for so long, and when will you start using the [antimicrobial] technologies you’re patenting to reduce the harm associated with tobacco products?’ ” 

Janet Raloff

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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