Abstract
A novel mcr colistin resistance gene was identified in a strain of Salmonella enterica, monophasic variant of serovar Typhimurium (4,5,12:i:- ), isolated from a pig at slaughter in Italy in 2013, and in Escherichia coli strains collected during routine diagnostic of post-weaning diarrhoea in pigs from Spain and Belgium in 2015 and 2016. Immediate implementation of mcr-screening including this novel gene variant is required for Salmonella and E. coli from humans and food-producing animals in Europe.
Highlights
The wide use of colistin in veterinary medicine for the control of Enterobacteriaceae infections, and for prophylaxis purposes caused a significant increase in colistin resistance, especially in Escherichia coli from pigs [1]
In 2013, one colistin-resistant (minimum inhibitory concentration (MIC) = 8 mg/L, measured by broth microdilution) [3] monophasic variant of S. enterica serovar Typhimurium (4,5,12:i:– ) isolate R3445 was obtained from the caecal content of a pig at slaughter, during a study performed by the Istituto Zooprofilattico of Umbria and Marche in Italy [2]
Whole genome sequencing (WGS) of the strain was performed by an Illumina MiSeq (2 x 300 PE), with the objective to identify the mechanism of colistin resistance
Summary
Novel plasmid-mediated colistin resistance mcr-4 gene in Salmonella and Escherichia coli, Italy 2013, Spain and Belgium, 2015 to 2016. A novel mcr colistin resistance gene was identified in a strain of Salmonella enterica, monophasic variant of serovar Typhimurium (4,5,12:i:- ), isolated from a pig at slaughter in Italy in 2013, and in Escherichia coli strains collected during routine diagnostic of postweaning diarrhoea in pigs from Spain and Belgium in 2015 and 2016. The pMCR plasmid was detected in the three genomes, but several additional plasmids were identified, belonging to the I1, I2, F, X1 and HI2 families, probably associated with the large repertoire of resistance genes in these E. coli strains (Table 1). Two IS5 copies in direct orientation flanked the complete pMCR plasmid sequence, suggesting that a
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