21
percent
Proportion of adults
who smoked in the
United States in 2008
45
percent
Proportion of smokers
who reported trying to
quit in previous year
Germs in tobacco potential source
for infections blamed on smoking
Tests find hundreds of bacterial species in major brands
By Janet Raloff
Cigarettes host a bacterial bonanza of
hundreds of different germs, including
those responsible for many human ill-nesses, a new genetics study reports.
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
Tobacco
Bacterium
Hemolysis
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.
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 bac-
teria like Bacillus subtilis can survive in a
state akin to suspended animation until
they reach a suitable environment.
Roswell Park immunologist John
Pauly agrees. In a paper last September
in Immunological Research, he and his
colleagues reviewed studies showing that
live germs inhabit all types of tobacco
products, although in most cases few
to none of the microbes had
been identified by species.
Pauly’s group also summa-
rized tests at Roswell Park
showing that about 60 per-
cent of cigarette filters they
examined — representing 11
brands — contained tobacco
particles. The tobacco also
hosted bacterial toxins. And
as a rule, the team reported,
“bacteria grew from greater than 90 per-
cent of the randomly selected flakes.”
When cultured with blood, Pauly’s
team demonstrated, “those tobacco-
derived bacteria frequently destroyed
the red blood cells.”
Bacterial contamination of tobacco
tends to occur after harvesting. “When
you place it in a curing situation, for
example —a barn with high tempera-
tures, high humidity, poor ventilation
and blocked-out sunlight —you get a
near-perfect environment for growing
bacteria and fungi,” Pauly says.
Cigarette companies have been
awarded a host of U.S. patents for killing
microbes. These include one issued six
years ago to three Virginia scientists on
behalf of cigarette maker Philip Morris. 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 fun-
gal populations.” The patent points out
that these microbes are responsible for
producing endotoxins and tobacco-spe-
cific nitrosamines. Those nitrosamines
are “the number one carcinogens found
in both smoking and smokeless tobacco
products,” Pauly says.
Markers
for known
bacteria
matched
hundreds of
bacteria from
four brands of
cigarettes.
material, protein-building elements
that read and execute instructions
encoded within a cell’s DNA. Sapkota’s
team homed in on long, species-spe-cific 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,”
