BACTERIA _ VIRUSES

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					                                                                                 Biology Fall 2009--Rozema

                        BACTERIA & VIRUSES
                             Readings
Antibiotic Resistance Clue Found
US scientists have uncovered a defense mechanism in bacteria that
allows them to fend off the threat of antibiotics.

It is hoped the findings could help researchers boost the effectiveness of
existing treatments. The study published in Science found that nitric oxide
produced by the bacteria eliminates some key effects of a wide range of
antibiotics. One UK expert said inhibiting nitric oxide synthesis could be an
important advance for tackling tricky infections.                               MRSA highlights the problem of
                                                                                antibiotic resistance
Antibiotic resistance, for example with MRSA, is a growing problem and experts have long warned of the
need to develop new treatments. The latest research, done by a team at New York University, showed that
in bacteria the production of nitric oxide - a small molecule made up of one nitrogen and one oxygen atom
- increased their resistance to antibiotics. They found the enzymes responsible for producing nitric oxide
were activated specifically in response to the presence of the antibiotics. They also showed that nitric oxide
alleviates damage caused by the drugs as well as helping to neutralise many of the toxic compounds within
the antibiotic.

The researchers then showed that eliminating nitric oxide production in the bacteria allowed the antibiotics
to work at lower, less toxic doses.

More effective
Study leader, Dr Evgeny Nudler, said developing new medicines to fight antibiotic resistance, such as that
seen with MRSA is a "huge hurdle". "Here, we have a short cut, where we don't have to invent new
antibiotics. "Instead we can enhance the activity of well-established ones, making them more effective at
lower doses.

Dr Matthew Dryden, consultant in microbiology and communicable disease at Royal Hampshire County
Hospital and general secretary of the British Society for Antimicrobial Chemotherapy, said if the enzyme
which creates nitric oxide could be inhibited, it could suppress the ability of the bacteria to counteract
antibiotics.

"This would be a useful therapeutic advance, especially as we are running out of new classes of antibiotics
and there is less antibiotic development in general."
                                                                                Biology Fall 2009--Rozema
What Scientists Know About Swine Flu
Preliminary analysis of the swine flu virus suggests it is a fairly mild
strain, scientists say.

It is believed that a further mutation would be needed in order for the H1N1
virus to cause the mass deaths that have been estimated by some. But at this
point, it is impossible to predict with any accuracy how the virus will
continue to evolve. UK experts at the National Institute for Medical
Research outlined on Friday the work they are due to start on samples of the
virus sent from the US.

The research, being done at the World Influenza Centre in Mill Hill, will be
vital for working out the structure of the virus, where it came from, how    Influenza viruses are able to swap
quickly it is capable of spreading and its potential to cause illness.       genetic material

Structure
Analysis done so far suggests what they are dealing with is a mild virus and nowhere near as dangerous as
the H5N1 avian flu strain that has caused scientists so much concern over the past decade. Influenza A
viruses are classified according to two proteins on the outer surface of the virus - hemagglutinin (H) and
neuraminidase (N).

                 FLU STRAINS COMPARED




                 H1N1 (seasonal flu/swine flu)    H5N1 (avian flu)
                 Spreads easily through           Can mutate rapidly
                 coughing and sneezing            Causes severe illness and can
                 Less severe symptoms, but can    trigger pneumonia
                 be deadly                        Spreads easily between birds
                                                  but human transmission rare



The swine flu strain is a H1N1 virus, the same type as seasonal flu which circulates throughout the world
every year, and kills roughly 0.1% of those infected or higher in an epidemic year. Professor Wendy
Barclay, chair in influenza virology at Imperial College London says initial indications suggest there is
nothing about the genetic make-up of the new virus which is a cause for particular concern.
                                                                                    Biology Fall 2009--Rozema
The key to its potential lies largely in the H1 protein.

"There are two aspects - one is which receptors the virus tends to bind to and                  H1N1
what we see is that it is binding to the upper respiratory tract rather than deep   Can spread between humans
in the lungs."                                                                      Attaches to receptors in the
                                                                                   upper respiratory tract causing
When a flu virus binds to the upper respiratory tract, it tends to cause mild                mild illness
illness but can be easily spread as people cough and sneeze, Professor Barclay      A pandemic is thought to be
explains. If a virus binds further down in the lungs, it tends to cause much                  imminent
more severe illness, as in the case of the H5N1 avian flu virus which has caused concern in recent years.

"With the H1 gene we also look at the cleavage site," she adds.

"The virus has to be cut into two pieces to be active and it uses an enzyme in the host to do that.

"Most influenza viruses are restricted to the respiratory tract because they use enzymes in the lungs.

"But some, like H5 viruses can evolve to cut into two pieces outside the lungs, so they can replicate outside
the respiratory tract."

Predictions
Scientists have also played down concerns that the milder H1N1 virus, could combine with the more
dangerous H5N1 avian flu virus, causing a super virus that has the ability to both spread easily between
humans and cause severe illness. This is unlikely - or at least just as unlikely as it ever was and the H5N1
virus has been around for a decade without combining with normal seasonal flu. Professor Jonathan Ball,
an expert in molecular virology at the University of Nottingham said: "The chance of swine H1N1
combining with H5N1 is as likely as any other strain recombining.

"What this outbreak does highlight is how difficult it is to predict new pandemic strains.”

"Many people suspected that H5N1 was the most likely candidate for the next pandemic strain, but now it
appears that this was a mistake - but that's not to say H5N1 or another reassortment containing parts of
H5N1 may not happen in the future. “

"That's the trouble - you can't predict."

				
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