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Cold Plasma eliminates Ehec bacteria
In first experiments with prototypes the number of these dangerous germs is reduced drastically
The next wave of infections with Ehec bacteria might be preventable: Scientists at the Max Planck
Institute for Extraterrestrial Physics in Garching and at the Munich hospital "Klinikum Schwabing"
successfully killed various strains of Ehec bacteria with cold plasma, which is a strongly ionised
gas at moderate temperatures. In the recent experiments the cold plasma now proved to be effective
against the O104:H4 strain, which had caused the outbreak with thousands of serious cases. The
scientists used prototypes of devices suitable for everyday use that could be employed in the
food industry or in private households.

A tool agains Ehec bacteria: Comsumers could use this device to eliminate dangerous germs such
as Ehec from foodsuffs in their own kitchen.
Credit: Max-Planck-Institut für extraterrestrische Physik
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The researchers at the Max Planck Institute for Extraterrestrial Physics (MPE) and the "Klinikum
Schwabing" reduced more than 100 cultures of five different Ehec strains drastically. All strains
are E.coli bacteria with the serotype O104:H4 producing the Shiga toxin, which were isolated during
the present Ehec wave from patients with the HUS-syndrome. At the microbiology department of the
hospital in Schwabing, the scientists treated the germ cultures with two prototypes producing a
cold plasma, which were developed at the MPE. "The results are very convincing from our perspective,"
says Gregor Morfill, director at the MPE, who led the study. "Even though the Ehec bacteria are
somewhat more robust than normal E.coli bacteria this did not matter for their inactivation."
One of the devices, which can be extended in a modular fashion, could be expanded to a large facility
with some further development. Companies processing foodstuffs could use these facilities to eliminate
Ehec bacteria already during production. In the current experiments, the prototype device reduced the
number of germs in 15 seconds by a factor of 10 000 - enough to ensure that fruit and vegetables can
be consumed without any concerns. The other device could be used by consumers to kill germs in their
own kitchen. With a similar size to a flashlight it could be produced to about 100 Euros. In the
experiments, this device reduced the germs in 20 seconds by a factor of 100 000. "These prototypes
just need to be brought to maturity for industry," says Gregor Morfill.
Plasmas are already used in medicine today, e.g. to sterilise chirurgical instruments, but most of these
plasmas are hot. Fresh produce cannot be treated in this way. The scientists at the MPE, however, produce
plasmas which are lukewarm. The physicists at the MPE use these kinds of plasma to study how crystals
form and how liquids flow - some experiments are even on the International Space Station. "As our plasmas
are cold, they lend themselves naturally to a medical application," says Gregor Morfill. In a currently
ongoing clinical trial, the researchers test how chronically infected wounds can be treated with cold
plasma or how the hospital staff could use it to disinfect their hands. First results indicate better
and faster healing and the new experiments now show that devices with cold plasma could also contribute
to improve hygiene when dealing with foodstuffs.
When treating food with plasma, does this affect the food's taste? Naturally there can be no comprehensive
answer to this question - all relevant foodstuffs would need to be tested. In general, however, a number of
studies show that cold plasmas do not cause substantial surface modifications (in particular on heat-sensitive
surface such as the human skin even with a plasma dose that is 100 times larger). Presumably the cold plasma
therefore should cause neither a change in taste nor in nutrients. Plasma only modifies the air
"homoeopathically" for a short time, then everything recombines "ecologically" without any residues.
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