Ultrashort-pulse lasers kill bacterial superbugs, spores
Technique likely safe for human cells; has potential for sterilizing
wounds, blood products

Date:
November 23, 2021
Source:
Washington University School of Medicine
Summary:
Researchers at Washington University School of Medicine in St. Louis
have found that multidrug-resistant bacteria and bacterial spores
can be killed by ultrashort-pulse lasers. The findings could lead
to new ways to sterilize wounds and blood products without damaging
human cells.



FULL STORY ========================================================================== Life-threatening bacteria are becoming ever more resistant to antibiotics, making the search for alternatives to antibiotics an increasingly urgent challenge. For certain applications, one alternative may be a special
type of laser.


========================================================================== Researchers at Washington University School of Medicine in St. Louis
have found that lasers that emit ultrashort pulses of light can kill multidrug-resistant bacteria and hardy bacterial spores. The findings, available online in the Journal of Biophotonics,open up the possibility
of using such lasers to destroy bacteria that are hard to kill by other
means. The researchers previously have shown that such lasers don't
damage human cells, making it possible to envision using the lasers to sterilize wounds or disinfect blood products.

"The ultrashort-pulse laser technology uniquely inactivates pathogens
while preserving human proteins and cells," said first author Shaw-Wei
(David) Tsen, MD, PhD, an instructor of radiology at Washington
University's Mallinckrodt Institute of Radiology (MIR). "Imagine if, prior
to closing a surgical wound, we could scan a laser beam across the site
and further reduce the chances of infection. I can see this technology
being used soon to disinfect biological products in vitro, and even to
treat bloodstream infections in the future by putting patients on dialysis
and passing the blood through a laser treatment device." Tsen and senior author Samuel Achilefu, PhD, the Michel M. Ter-Pogossian Professor of
Radiology and director of MIR's Biophotonics Research Center, have been exploring the germicidal properties of ultrashort-pulse lasers for years.

They have shown that such lasers can inactivate viruses and ordinary
bacteria without harming human cells. In the new study, conducted in collaboration with Shelley Haydel, PhD, a professor of microbiology
at Arizona State University, they extended their exploration to antibiotic-resistant bacteria and bacterial spores.

The researchers trained their lasers on multidrug-resistant Staphylococcus aureus (MRSA), which causes infections of the skin, lungs and other
organs, and extended spectrum beta-lactamase-producing Escherichia
coli(E. coli), which cause urinary tract infections, diarrhea and wound infections. Apart from their shared ability to make people miserable,
MRSA and E. coli are very different types of bacteria, representing two
distant branches of the bacterial kingdom.

The researchers also looked at spores of the bacterium Bacillus
cereus,which causes food poisoning and food spoilage. Bacillus spores
can withstand boiling and cooking.

In all cases, the lasers killed more than 99.9% of the target organisms, reducing their numbers by more than 1,000 times.

Viruses and bacteria contain densely packed protein structures that
can be excited by an ultrashort-pulse laser. The laser kills by causing
these protein structures to vibrate until some of their molecular bonds
break. The broken ends quickly reattach to whatever they can find, which
in many cases is not what they had been attached to before. The result
is a mess of incorrect linkages inside and between proteins, and that
mess causes normal protein function in microorganisms to grind to a halt.

"We previously published a paper in which we showed that the laser
power matters," Tsen said. "At a certain laser power, we're inactivating viruses. As you increase the power, you start inactivating bacteria. But
it takes even higher power than that, and we're talking orders of
magnitude, to start killing human cells. So there is a therapeutic window
where we can tune the laser parameters such that we can kill pathogens
without affecting the human cells." Heat, radiation and chemicals such
as bleach are effective at sterilizing objects, but most are too damaging
to be used on people or biological products.

By inactivating all kinds of bacteria and viruses without damaging cells, ultrashort-pulse lasers could provide a new approach to making blood
products and other biological products safer.

"Anything derived from human or animal sources could be contaminated
with pathogens," Tsen said. "We screen all blood products before
transfusing them to patients. The problem is that we have to know
what we're screening for. If a new blood-borne virus emerges, like
HIV did in the '70s and '80s, it could get into the blood supply
before we know it. Ultrashort-pulse lasers could be a way to make sure
that our blood supply is clear of pathogens both known and unknown." ========================================================================== Story Source: Materials provided by
Washington_University_School_of_Medicine. Original written by Tamara
Bhandari. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Shaw‐Wei D. Tsen, John Popovich, Megan Hodges, Shelley
E. Haydel,
Kong‐Thon Tsen, Gail Sudlow, Elizabeth A. Mueller, Petra Anne
Levin, Samuel Achilefu. Inactivation of multidrug‐resistant
bacteria and bacterial spores and generation of high‐potency
bacterial vaccines using ultrashort pulsed lasers. Journal of
Biophotonics, 2021; DOI: 10.1002/jbio.202100207 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211123162812.htm

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