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MOLECULAR CHARACTERISTICS OF ESCHERICHIA COLI HARBORING MCR-1 STRAINS ISOLATED FROM HEALTHY RESIDENTS IN THAI BINH
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Abstract
The study was conducted in order to analyse several molecular characteristics of Escherichia coli harboring mcr-1 isolated from stool samples of healthy residents in Thai Binh during the period 2013 - 2016. The subject consisted of 31 Escherichia coli strains previously determined to carry the mcr-1 gene and have a colistin-resistant phenotype (MIC ≥ 4 mg/L). The presence of ESBL coding genes, mcr-1 gene, ISAp11 sequence and plasmid replicon types in E. coli were all determined by PCR methods. The genetic relationship among E. coli harboring mcr-1 isolates was assessed by PFGE assay. The result indicated that most of E. coli harboring mcr-1 strains (96.8%) also harbored ESBL-coding gene(s), of which the two genotypes accounted for the highest rates were CTX-M-9 (48.4%) and CTX-M-9/TEM (25.8%). Each of E. coli harboring mcr-1 strains was capable of carrying from 1 to 6 different types of 14 plasmid replicon types detected in these strains. Three most common plasmid replicon types were HI2 (54.8%), FIB (48.4%) and N (41.9%). The ISApl1 sequence was detected in 83.9% of these isolates. Result of PFGE analysis showed that there were 4 strains forming two genetic groups where two strains in each group had a genetic similarity rate of 100%. The study showed that E. coli harboring mcr-1 and ESBL-coding genes was widely spread among healthy residents in Thai Binh. The diversity of plasmid replicon types and the high rate of ISApl1 sequence detected in E. coli may facilitate the transmission of the mcr-1 gene among E. coli bacteria in healthy residents in Thai Binh.
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Keywords
E. coli, ESBL, colistin-resistance, mcr-1
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