In
pregnant women, a normally benign bacterium emits tiny toxic balloons
that
can cause premature labor and stillbirth, a new study finds.
Called Group B Streptococcus,
the bacterium lives in the vaginas of 20 to 30 percent
of pregnant
women worldwide. Strep B doesn’t cause problems in the lower genital
tract.
But in pregnant mice, Strep B secretes protein-filled balloons
that can travel up into
researchers from India report September 1 in PLOS Pathogens.
Scientists
already knew that Strep B can be a problem during pregnancy. They
didn’t know
that it makes tiny long-range weapons. The danger is “not
just the bug alone,”
says microbiologist Lakshmi Rajagopal of Seattle
Children’s Research Institute,
“but also something the bug produces.”
Using
a scanning electron microscope, researchers from the Indian Institute
of
Technology-Bombay detected small circular orbs budding off of Strep B
bacteria.
Inside those little fluid-filled balloons, the researchers
found corrosive proteins.
The scientists also found that, in mice, the
balloons can migrate from the vagina
into the uterus. There, the orbs
trigger cell death and degrade collagen in the
amniotic sac (making it
more likely to tear), and can cause inflammation,
premature birth and
stillbirth. Almost all the pups of pregnant mice with
bacterial balloons
injected into their amniotic sacs either died in utero or
were
delivered prematurely. Researchers also found that when the toxic
proteins
were disabled by inhibitors, the balloons didn’t degrade
collagen.
Previous
work had implicated a bacterial pigment in Strep B’s ill effects,
but
the balloons are a potential second mechanism, says study coauthor
Anirban Banerjee,
a microbiologist at the Indian Institute of
Technology.
It’s
still unclear why Strep B, which normally keeps a low profile, makes
toxins
in the first place. They may be used in turf wars, Banerjee
suggests, to help Strep B
compete against other bacterial species. Strep
B isn’t the only bacterium that
makes toxic balloons, either, and many
microbiologists are working to understand
exactly how the bugs secrete
them.
In
the meantime, these new findings “emphasize the need to develop an
approved vaccine” against Strep B, says Rajagopal. Today doctors test
pregnant
women for the bacterium between 35 and 37 weeks. Strep-positive
women take
antibiotics during labor to prevent infecting newborns. But
the bacteria can quickly return,
so antibiotics aren’t a permanent fix.
Understanding how and why microbes make
these teensy weapons could help
doctors discover how to block strep infections
in the first place.
*source: ScienceNews
No comments:
Post a Comment