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A new plasmid carrying mphA causes prevalence of azithromycin resistance in enterotoxigenic Escherichia coli serogroup O6

  • Xiang, Ying1, 2, 3
  • Wu, Feng1, 2
  • Chai, Yinghui2
  • Xu, Xuebin4
  • Yang, Lang1
  • Tian, Sai2
  • Zhang, Haoran1
  • Li, Yinxia2
  • Yang, Chaojie2
  • Liu, Hongbo2
  • Qiu, Shaofu2
  • Song, Hongbin2
  • Sun, Yansong1
  • 1 Academy of Military Medical Sciences, NO.20 Dongda Street, Fengtai District, Beijing, 100071, China , Beijing (China)
  • 2 Chinese PLA Center for Disease Control and Prevention, NO.20 Dongda Street, Fengtai District, Beijing, 100071, China , Beijing (China)
  • 3 Center for Disease Control and Prevention of Southern Theatre Command, Guangzhou, China , Guangzhou (China)
  • 4 Shanghai Municipal Center for Disease Control and Prevention, Shanghai, China , Shanghai (China)
Published Article
BMC Microbiology
Springer (Biomed Central Ltd.)
Publication Date
Aug 11, 2020
DOI: 10.1186/s12866-020-01927-z
Springer Nature


BackgroundAt present, azithromycin has become an effective treatment for severe diarrhea caused by Enterotoxigenic Escherichia coli (ETEC) infection. However, enterobacteria have begun to develop resistance to azithromycin and have attracted attention in recent years. This study conducted to described the emergence of a high proportion of azithromycin-resistant ETEC serogroup O6 strains in Shanghai and to analyzed the mechanisms of azithromycin resistance.ResultsStrains from adult diarrhea patients with ETEC serogroup O6 infections were collected by Shanghai Diarrhea Surveillance Network and the Foodborne Surveillance Network from 2016 to 2018. We tested 30 isolates of ETEC O6 serogroup, 26 of which were resistant to azithromycin. Phylogenetic analysis revealed that these ETEC serogroup O6 strains have formed an independent dominant clone. S1-PFGE and southern blotting revealed the presence of the mphA gene on the 103 kb plasmid. Illumina and Nanopore sequencing and plasmid coverage analysis further confirmed that azithromycin-resistant strains carried a novel IncFII plasmid harboring mphA and blaTEM-1 resistance genes.ConclusionsThis is the first study to report a high proportion of azithromycin resistance in a particular ETEC serogroup due to a specific plasmid carrying mphA. Our findings indicate the rapid spread of azithromycin resistance, highlighting the urgency of stringent surveillance and control measure.

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