28
&
January 2016 | Read this issue and more at www.healthandwellnessmagazine.net |
Antibiotic Resistance
is Here Now
Gene mutation poised to
spread worldwide
By Angela S. Hoover, Staff Writer
There are already 15 different
antibiotic-resistant bacteria, with
three more rapidly evolving antibiotic
resistance, according to the Centers for
Disease Control (CDC). A new gene
mutation (mcr-1) in common bacteria
easily transfers antibiotic resistance to
other bacteria and has the potential to
do so between different bacteria species. It’s just a matter of when – not if –
this gene mutation spreads worldwide,
according to several experts.
Scientists in China accidentally
made the discovery during routine
testing of livestock animals for
the food market. An E. coli strain
(SHP45) from a pig showed resistance
to the polymyxin-class antibiotic
colistin. Lab tests demonstrated the
plasmid easily transferred the mcr-1
gene into surrounding bacteria that
did not have polymyxin resistance.
Fortunately, the plasmid had a harder
time moving between different bacterial species. The researchers could only
achieve cross-species transference of
mcr-1 via electroporation (using electrical pulse to make cell membranes
more permeable). This suggests the
plasmid may not easily move between
species naturally. Their findings
were published in the journal Lancet
Infectious Diseases.
Here are some key points about
antibiotic resistance:
• Colistin, which has been around
since 1959, is a last-resort drug
because it is toxic to the kidneys.
Antibiotic resistance had already been
seen in colistin, but only in genes
embedded in the bacterial genomes.
Therefore, it only effected an individual bacteria.
• This recent mutation of the mcr-1
gene is on the plasmids. Plasmids are
on several common bacteria, including
E. coli. Bacteria can make copies of
plasmids and share them with whatever bacteria happens to be nearby.
Such plasmid transference has been
observed before with other bacteria
and other classes of antibiotics, but
never before in polymyxins. This is
why polymyxins were the last fully
functioning class of antibiotics.
• The mcr-1 gene is widespread
in Enterobacteriaceae bacteria that is
carried by pigs and people in south
China. Enterobacteriaceae can cause a
range of diseases, including pneumonia and serious blood infections.
• Some bacteria strains with this
gene have epidemic potential. This
resistance moving between bacteria is
likely not isolated to China. Chinese
researchers and other scientists believe
this recent mutation is due to the use
of colistin in agriculture. Colistin is
heavily used in livestock feed in Asia. It
used in the United States and Europe
to a much lesser extent.
• If plasmids containing mcr-1
spread to multi-drug-resistant bacterial
strains, they would become truly “pandrug resistant” and result in untreatable infections.
Until a few years ago, carbapenumclass antibiotics were considered
the last line of defense for treating
complex hospital infections of E. coli,
Klebsiella, Acinetobacter and other
similar gut bacteria. Then several different resistance factors such as NDM,
OXA and KPC began cropping up
worldwide, making these bacteria carbapenum-resistant Enterobacteriaceae
(CREs). At this point, colistin was
truly all that was left, so it was reintroduced, despite its toxicity to kidneys.
Ever since, colistin use has increased
in agriculture, primarily because it is
an affordable addition to feed to make
animals gain muscle mass faster and
Like us
@healthykentucky
protect them from the conditions of
intensive farming. China is the most
prevalent agricultural user of colistin,
but global demand for the drug is
expected to reach 11,942 tons per
annum by the end of 2015, increasing
to 16,500 tons by 2021. In the Lancet
Infectious Diseases journal in which
the