Background: Carbapenem-resistant Enterobacterales (CRE) are a significant threat to worldwide public health, resulting in increased morbidity, death, hospitalization time and healthcare expenses. Here, the genomic and phylogenetic characteristics of a multidrug-resistant Escherichia coli isolate carrying both the new mcr-1.33 variant and bla _NDM-5 gene obtained from a urinary tract infection in China are investigated.
Methods: Antimicrobial susceptibility of E. coli 779 was evaluated by using the broth microdilution method. Short-read Illumina NovaSeq 6000 and long-read Oxford Nanopore MinION platforms were applied to sequence the bacterial whole genomic DNA and then de novo assembled. The genome sequence was annotated using the NCBI Prokaryotic Genome Annotation Pipeline and further subjected to identify the sequence type (ST), capsular type, and antibiotic resistance genes. BacWGSTdb 2.0 was used to perform the core genome multilocus sequence typing (cgMLST) analysis with other closely related E. coli isolates deposited in the public database.
Results: E. coli 779 was resistant to aztreonam, levofloxacin, fosfomycin, cefoxitin, cefepime, cefotaxime, imipenem, meropenem, polymyxin, and tigecycline. The complete genome sequence of E. coli 779 is made up of nine contigs totaling 5,667,876 bp, including one chromosome and eight plasmids. The isolate was assigned to ST101, serotype O-:H31, and phylogroup B1. The colistin resistance gene mcr-1.33 (located in a 242,460 bp IncHI2/IncHI2A plasmid) and the β-lactam resistance gene bla _NDM-5 (located in a 46,161 bp IncX3 plasmid) were among the 27 antimicrobial resistance genes discovered. The closest relative of E. coli 779, another ST101 strain (E. coli 443) obtained from a sewage sample in Shandong, China in 2015, differs by only 24 cgMLST alleles.
Conclusion: We discovered the first multidrug-resistant ST101 E. coli strain with plasmid-mediated mcr-1.33 variant and bla _NDM-5 gene in China. These findings would help us to better understanding the genomic traits, antimicrobial resistance mechanisms and epidemiological aspects of this bacterial pathogen.
Keywords: whole genome sequencing, Escherichia coli , multidrug-resistance, mcr-1.33 , bla _NDM-5, urinary tract infection