How Should Practitioners Test for the Colistin-Resistant mcr-1 Gene?

Prof. Andrea Endimiani, MD, PhD, from the Institute of Infectious Diseases at the University of Bern, Switzerland, discusses how practitioners should test for colistin-resistant pathogens.

Interview Transcript (slightly modified for readability)

“We have to distinguish two situations, infection, and colonization. In the case of [an] infection, we are able to detect these mechanisms, or at least we have a suspicion of these mcr-1 mechanism of resistance, because when we detect an isolate, an Escherichia coli [or] a Klebsiella in the clinical laboratory, we preform the antibiotic susceptibility test, and usually we [also] test [for] colistin [resistance], so we can see that the bacteria are resistant to colistin.

A major problem is the second situation, when the patients are only colonized at [the] intestinal level. Since we don’t have a lot of these bacteria [at] the intestinal level, there is a tiny quantity, we need to use [specific] systems to detect them. We can use culture-systems, selective plates that contain colistin to see if [the bacteria] grow in the plates, and then we can [molecularly characterize] them. [As an alternative mechanism of detection], we can [test] the stools of patients, through a rectal swab, with molecular tests. For example, [we can use] real-time PCR that is already described in the literature, to detect the mcr-1 gene. [It is] very [probable that] the performance of the real-time PCR is a little bit better than the culture approach.”