Researchers claim this is the first study to provide evidence that the number of bacteria in a cigarette may be equivalent to the number of chemicals.
Hundreds of bacterial species were present in each cigarette. Some are associated with lung and blood infections, respiratory infections and even anthrax.
Researchers believe that if the organisms can survive the smoking process, then they have the potential to contribute to both infectious and chronic illnesses in both smokers and people exposed to second-hand smoke.
"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," explained Sapkota.
The study will appear in an upcoming edition of the journal Environmental Health Perspectives.