This is a marvelous
piece of work that totally resolves the origins of flesh eating disease. It is a progressive transformation of
opportunistic bacteria we know well. How
do we prevent this occurring commonly?
The problem
certainly came out of nowhere and it may be a true super bug that somehow interacted
with the human environment in particular.
That problem deserves deep thought and research although I am sure it is
boring.
Just hope we
never have a close encounter.
How
Harmless Bacteria Quickly Turned Into a Flesh-Eating Monster
Just four changes gave Streptococcus the
ability to cause deadly disease
Susan Brink
PUBLISHED APRIL 15, 2014
By examining decades' worth of stored
bacteria samples, researchers have determined how a benign organism evolved
into a deadly pathogen that causesnecrotizing fasciitis,
commonly known as flesh-eating bacteria disease.
Using genetic sequences from more than 3,600
strains of bacteria, scientists were able to see that it took only four steps
to create the unusual microbe that spreads rapidly and destroys the body's soft
tissue.Their
report was published Monday in the Proceedings of the National Academy of
Sciences.
Necrotizing fasciitis is caused by several
types of bacteria, most commonly group
A Streptococcus. (See
images of Streptococcus and other microbes in the "Small, Small
World" photo gallery.) An international group of researchers sequenced
the genomes of group A strep bacteria in samples that had been collected from
as early as the 1920s. Those sequences revealed that sometime in the past,
group A strep was infected with first one virus and then soon after with
another. With each infection, the bacterium gained viral genes that made group
A strep more likely to cause disease.
"The third event was a mutation of a
single letter of the genome of the organism to create an even more virulent
form," said the study's main author, James Musser, director of the Center for Molecular
and Translational Human Infectious Diseases Research at the Houston
Methodist Research Institute in Texas. That mutation probably occurred in the
late 1960s.
Then, in the early 1980s, the bacterium
acquired another piece of foreign DNA, which carried the code for two toxins
that cause necrotizing fasciitis's worst effects. "We were off and running
with a strain that had increased ability to spread in humans and to cause a
more severe form of disease," Musser said.
A Long Search for Answers
The new research would not have been
possible without the foresight of several international collaborators who saved
comprehensive samples of this kind of bacteria for many decades. That let
scientists study how the organism evolved over all that time.
"If you simply sequenced the samples from
today, you really wouldn't understand how and when it flipped from a bad
pathogen to a really bad pathogen," Musser said.
Musser has been gripped with curiosity about
the flesh-eating disease since Muppets creator Jim Henson died of
the infection in 1990. At that time a new field of research—bacterial
population genetics—was just beginning. "This has been my white whale for
almost 25 years," Musser said.
Today about 650 to 800
Americans become infected with flesh-eating bacteria each year, according
to the Centers for Disease Control and Prevention. The bacteria infect layers
of membranes and connective tissue around muscle, nerves, fat, and blood
vessels. The toxins made by the bacteria destroy the tissue they infect,
causing it to die.
Healthy people with strong immune systems
who carefully clean and care for cuts, scrapes, and insect bites are usually
able to fight off the bacteria. But people with compromised immune systems or
with conditions such as diabetes, kidney disease, or cancer are more
vulnerable.
Jacqueline
Roemmele was one such unlucky person. She became infected in 1994
after the cesarean section birth of her twins. "Before they found what it
was, my flesh was falling off in the nurses' hands," she said. Roemmele
survived and went on to found, with Donna Batdorff, theNational Necrotizing Fasciitis Foundation.
The new discovery "is very
exciting," Roemmele said. "This is the first time I've heard of
science ripping apart how this actually happens to explain: Why did this become
a supercharged bacteria? ...This gives us greater insight into why it
happens."
There is still a lot of work that needs to
be done toward finding methods to prevent, treat, and cure necrotizing
fasciitis. But this study shows that analyzing the timing of the molecular
events that lead to global epidemics can help to monitor and predict the
emergence of deadly infectious diseases.
"This is the first time we've been able
to sort out the precise events that give rise to bacterial epidemics,"
said Musser. "We need to understand the general rules in order to
understand epidemics. This is the first understanding of that."
No comments:
Post a Comment