The emergence of the plasmid-mediated colistin resistance gene mcr-1 is threatening the last-line role of colistin in human medicine.With mcr-1-positive Escherichia coli (E.coli) isolated from food animal being frequently reported in China, the prevalence of mcr-1 in food animal has attracted public attention.
In the present study, a total of 105 colistin-resistant E.coli strains were isolated from 200 fecal samples collected from six swine farms in northeastern China.mcr-PCR revealed that the prevalence of mcr-1 in colistin-resistant E.
coli was 53.33% (56/105).mcr-1-positive nitrile gloves in a bucket E.
coli showed extensive antimicrobial resistance profiles with the presence of additional resistance genes, increased expression of multidrug efflux pump-associated genes, and increased biofilm formation ability.MLST differentiated all the mcr-1-positive E.coli into 25 sequence types (STs) and five unknown ST, and the most common ST was ST10 (n = 11).
By phylogenetic group classification, the distribution of all mcr-1-positive E.coli belonging to groups A, B1, B2, and D was 46.43, 35.
71, 5.36, and 5.36%, respectively.
Conjugation experiment demonstrated that most of the mcr-1 were transferable at frequencies of 2.68 × 10–6–3.73 × 10–3 among 30 representative mcr-1-positive E.
coli.The plasmid replicon types IncI2 (n = 9), IncX4 (n = 5), IncHI2 (n = 3), IncN (n = 3), and IncP (n = 1) were detected in the transconjugants.The results of growth assay, competition experiment, and plasmid stability testing showed that acquisition of mcr-1-harboring plasmids could reduce the fitness of bacterial hosts, but mcr-1 remained stable in the recipient strain.
Due to the potential possibility of these mcr-1-positive E.coli being transmitted to bilstein shocks jeep xj humans through the food chain or through horizontal transmission, therefore, it is necessary to continuously monitor the prevalence and dissemination of mcr-1 in food animal, particularly in swine.