The bacteria injected by a cat bite can include a strain
common in animals and particularly hard to fight with
antibiotics, he says.
In the study, researchers identified 193 Mayo Clinic
patients with cat bites to the hand from January 1,
2009, through 2011. Of those, 57 were hospitalized;
on average, they were in the hospital three days. Of
those hospitalized, 38 needed to have their wounds
surgically irrigated, or flushed out, and infected tissue
removed, a procedure known as debridement. Eight
patients needed more than one operation, and some
needed reconstructive surgery.
Of the 193 patients, 69 percent were female, and the
mean age was 49. About half of the patients first
went to the emergency room, and the others went to
primary care. The mean time between the bite and
medical care was 27 hours. Patients with bites directly
over the wrist or any joint in the hand had a higher
risk of hospitalization than people with bites over soft
tissue, the study found.
Thirty-six of the 193 patients were hospitalized
immediately when they sought medical care, while
154 were treated with oral antibiotics as outpatients
and three weren’t treated. The outpatient antibiotic
treatment failed in 21 patients, a 14 percent failure
rate, and those patients needed to be hospitalized.
The bottom line: Physicians and victims of cat bites
to the hand need to take the wounds seriously
and carefully evaluate them, Dr. Carlsen says. When
patients have inflamed skin and swelling, aggressive
treatment should be pursued, he and the other
researchers say.
People tend to be more dismissive of cat bites than
dog bites, in part because cat bites often look like a
pinprick, and dog bites look much worse, Dr. Carlsen
says. That’s a mistake, he says: “Cat bites look very
benign, but as we know and as the study shows, they
are not. They can be very serious.”
Ecotoxicity: All clear for
silver nanoparticles?
It has long been known that, in the form of free
ions, silver particles can be highly toxic to aquatic
organisms. Yet to this day, there is a lack of detailed
knowledge about the doses required to trigger a
response and how the organisms deal with this kind
of stress. To learn more about the cellular processes
that occur in the cells, scientists from the Aquatic
Research Institute, Eawag, subjected algae to a range
of silver concentrations.
In the past, silver mostly found its way into the
environment in the vicinity of silver mines or via
wastewater emanating from the photo industry.
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More recently, silver nanoparticles have become
commonplace in many applications -- as ingredients
in cosmetics, food packaging, disinfectants, and
functional clothing. Though a recent study conducted
by the Swiss National Science Foundation revealed
that the bulk of silver nanoparticles is retained in
wastewater treatment plants, only little is known
about the persistence and the impact of the residual
nano-silver in the environment.
Infiltrating the energy
metabolism undercover
Smitha Pillai from the Eawag Department of
Environmental Toxicology and her colleagues from
EPF Lausanne and ETH Zürich studied the impact
of various concentrations of waterborne silver ions
on the cells of the green algae Chlamydomonas
reinhardtii. Silver is chemically very similar to copper,
an essential metal due to its importance in several
enzymes. Because of that, silver can exploit the cells’
copper transport mechanisms and sneak into them
undercover. This explains why, already after a short
time, concentrations of silver in the intracellular fluid
can reach up to one thousand times those in the
surrounding environment.
A prompt response
Because silver damages key enzymes involved in
energy metabolism, even low concentrations can cut
photosynthesis and growth rates by a half in just 15
minutes. Over the same time period, the researchers
also detected changes in the activity of about 1000
other genes and proteins, which they interpreted
as a response to the stressor -- an attempt to repair
silver-induced damage.