Gert van der Hoek
In Memoriam - Editor, Senior Moderator
Dissemination of the mcr-1 colistin resistance gene
Published Online:17 December 2015
In their Comment on the Article by Yi-Yun Liu and colleagues about the emergence of plasmid-mediated colistin resistance involving the mcr-1 gene from bacteria isolated in China,1 David Paterson and Patrick Harris2 referred to our finding of colistin resistance in two Escherichia coliisolates from a pig and a human being in Laos that were indistinguishable by pulsed-field gel electrophoresis.3 Our results, suggested animal to human transmission for which no known chromosomally encoded colistin resistance mechanisms were identified, raising the question of a similar mechanism of colistin resistance to that identified by Liu and colleagues. We screened for the presence of the mcr-1 gene in these isolates along with other colistin-resistant E coli isolates from several countries (Laos, Thailand, France, and Nigeria) from human beings and pigs (only in Laos)4and in poultry from Algeria using PCR and sequencing as described by Liu and colleagues (table).1We included as controls a colistin-susceptible revertant E coli strain (obtained at the 18th passage in colistin-free medium) from a pig3 and 12 colistin-susceptible E coli strains isolated from the same stool samples from which the colistin-resistant E coli strains were isolated. 12 (63%) of 19 colistin-resistant E coli strains tested were positive for the mcr-1 gene and sequences were 100% identical to that of mcr-1 gene sequence reported by Liu and colleagues (table).1 These include E coli strains from Laos (from asymptomatic people and pigs including the strain transferred from a pig to a farmer), Thailand (asymptomatic people), and from Algeria (chickens). None of the 12 colistin-susceptible E coli strains and the colistin-susceptible revertant strain (the parent resistant strain was positive formcr-1) were positive for mcr-1. The susceptible revertant isolate has probably lost the resistance by loss of a plasmid that is under investigation. We clearly show that plasmid-mediated colistin resistance has spread beyond China to the neighbouring southeast Asian countries and even further to Africa where colistin is widely used in animal production.
Published Online:17 December 2015
In their Comment on the Article by Yi-Yun Liu and colleagues about the emergence of plasmid-mediated colistin resistance involving the mcr-1 gene from bacteria isolated in China,1 David Paterson and Patrick Harris2 referred to our finding of colistin resistance in two Escherichia coliisolates from a pig and a human being in Laos that were indistinguishable by pulsed-field gel electrophoresis.3 Our results, suggested animal to human transmission for which no known chromosomally encoded colistin resistance mechanisms were identified, raising the question of a similar mechanism of colistin resistance to that identified by Liu and colleagues. We screened for the presence of the mcr-1 gene in these isolates along with other colistin-resistant E coli isolates from several countries (Laos, Thailand, France, and Nigeria) from human beings and pigs (only in Laos)4and in poultry from Algeria using PCR and sequencing as described by Liu and colleagues (table).1We included as controls a colistin-susceptible revertant E coli strain (obtained at the 18th passage in colistin-free medium) from a pig3 and 12 colistin-susceptible E coli strains isolated from the same stool samples from which the colistin-resistant E coli strains were isolated. 12 (63%) of 19 colistin-resistant E coli strains tested were positive for the mcr-1 gene and sequences were 100% identical to that of mcr-1 gene sequence reported by Liu and colleagues (table).1 These include E coli strains from Laos (from asymptomatic people and pigs including the strain transferred from a pig to a farmer), Thailand (asymptomatic people), and from Algeria (chickens). None of the 12 colistin-susceptible E coli strains and the colistin-susceptible revertant strain (the parent resistant strain was positive formcr-1) were positive for mcr-1. The susceptible revertant isolate has probably lost the resistance by loss of a plasmid that is under investigation. We clearly show that plasmid-mediated colistin resistance has spread beyond China to the neighbouring southeast Asian countries and even further to Africa where colistin is widely used in animal production.
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