- WASHINGTON (Reuters) - Cholera bacteria and their cousins swapped genes
to develop stronger, new strains long before antibiotics were invented,
researchers said Thursday.
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- They said this showed antibiotics were
not the primary driving force that has caused bacteria to mutate into ever
stronger forms. Antibiotic-resistant bacteria are becoming a bigger and
bigger problem. They range from penicillin-resistant gonorrhea to super-strains
of staphylococcus that cannot be killed by vancomycin, the strongest antibiotic
available. One of the things that allows bacteria to develop resistance
to antibiotics is their habit of meeting and exchanging genes with one
another.
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- Didier Mazel and colleagues at the University
of British Columbia studied the Vibrio genus of bacteria, which include
the bug that causes cholera. They looked at samples of bacteria taken and
preserved and dating back to 1888 -- before antibiotics were discovered.
They identified a mechanism of gene-swapping called VCRs, Vibrio cholera
repeat sequence clusters, in the older bacteria. They look and act just
like integrons, which bacteria are known to use to develop resistance to
drugs. Integrons are used by cells to ``read'' new genes and convert them
into working genes. ``It is well established that integrons had a major
role in the recent spread of multidrug resistance among Gram-negative bacteria,''
they wrote in their report published in the journal Science.
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- There are two kinds of bacteria, Gram-positive
and Gram-negative. The Gram-negative strains are harder to kill because
their cell walls are stronger. Obviously the older bacteria did not use
the integrons to survive the onslaught of antibiotics, so they must have
an older purpose, Mazel's team concluded. They said it was likely other
kinds of bacteria have similar mechanisms. Studying them might shed light
on how to battle emerging new superbugs.
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