AUTHOR=Huang Xianhui , Yu Linfeng , Chen Xiaojie , Zhi Chanping , Yao Xu , Liu Yiyun , Wu Shengjun , Guo Zewen , Yi Linxian , Zeng Zhenling , Liu Jian-Hua 

TITLE=High Prevalence of Colistin Resistance and mcr-1 Gene in Escherichia coli Isolated from Food Animals in China

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.00562

DOI=10.3389/fmicb.2017.00562

ISSN=1664-302X

ABSTRACT=<p>The objective of this study was to determine the minimal inhibitory concentration of colistin for <italic>Escherichia coli</italic> from food animals and the possible underlying colistin resistance mechanisms. During 2007–2014, 4,438 <italic>E. coli</italic> isolates of food animal origins were collected. The susceptibility of colistin was tested by the agar dilution method. Mutations in <italic>pmrA, pmrB</italic>, and <italic>mgrB</italic> and the presence of <italic>mcr-1</italic> gene were determined by PCR and DNA sequencing. Complementation experiments were carried out to evaluate the contribution of the mutations to colistin resistance. There was a high frequency of colistin resistance in <italic>E. coli</italic> from pigs on farm (24.1%) and at slaughter (24.3%) in 2013–2014, followed by chickens on farm (14.0%) and at slaughter (9.5%). The resistance frequency of <italic>E. coli</italic> in cow isolates was the lowest (0.9%). MIC distribution for colistin showed that most isolates (75.2%) were distributed at 0.25 mg/L–0.5 mg/L, followed by 4 mg/L–8 mg/L (16.8%). Compared with the isolates from pigs and chickens recovered during 2013–2014, <italic>E. coli</italic> isolates collected during 2007–2008 (5.5%) and 2010–2011 (12.4%) showed significantly lower frequency of colistin resistance (<italic>P</italic> &lt; 0.05). DNA sequencing and complementation experiments failed to detect any insertion inactivation or mutation in <italic>pmrA, pmrB</italic>, and <italic>mgrB</italic> associated with colistin resistance. However, 91.0% colistin-resistant isolates were positive for <italic>mcr-1</italic>. The high frequency of colistin resistance and <italic>mcr-1</italic> gene among <italic>E. coli</italic> isolates from food animals in China urged the need to minimize potential risks of colistin resistance development and the spread of <italic>mcr-1</italic> gene.</p>