Infections involving multi-drug resistant bacteria are a major concern. Colistin is used as the "last-resort antibiotic" for dreaded
multidrug-resistant pathogens, especially in hospitals. However, gut
bacteria that have become insensitive to colistin now exist - owing to
the mobile resistance gene mcr-1.
In early 2016, bacteria carrying this
resistance gene were detected in Germany for the first time. Since then,
there has been growing concern that it may develop into a "superbug"
against which even emergency antibiotics are no longer effective.
‘A rapid genotypic resistance test for colistin is the only way with which mobile resistance can be differentiated from common resistance, because phenotypically they are the same.’
risk of a further spread of this colistin resistance is high because it
takes place through so-called mobile genetic elements (plasmids) which
are transferred between different types of bacteria relatively easily.
"Confirming the mobile mcr-1 resistance gene as rapidly as possible
is important, so as to prevent its further spread," emphasizes Linda
Falgenhauer, DZIF scientist at the Justus Liebig University Giessen and
one of the first authors of this study.
Together with her colleagues
from Giessen University and scientists from the research association
RESET, she tested a rapid genotypic resistance test for colistin that is
already commercially available.
"This is the only way with which mobile
resistance can be differentiated from common resistance, because
phenotypically they are the same," explains Can Imirzalioglu, who is
also first author of the study and DZIF scientist at the Giessen
Getting results rapidly
For the evaluation of this rapid test, the scientists worked together
with the company AmplexBiosystems GmbH which provided the testing kits
free of charge. 104 bacterial isolates from animals, humans and the
environment underwent testing with the molecular rapid test: the rapid
test results were compared to those from complete genome sequencing or
PCR, and demonstrated 100% sensitivity and specificity.
The test could clearly differentiate between common colistin
resistance and mobile resistance located on plasmids. "The test results
become available in only twenty minutes," explains Judith Schmiedel from
the Giessen Team. "With the conventional procedure, it takes several
hours to get results.
Additionally, the system is very uncomplicated, so
it should be developed further for future use in hospitals as well as
for livestock farming and food production." However, the rapid test is
still limited because applying it directly to samples has not yet been
evaluated. Up to now, the test has been only applied to bacterial
cultures, but the scientists are certain that it is only a matter of
time before it is developed further.