Characterization of a Large Antibiotic Resistance Plasmid Found in Enteropathogenic Escherichia coli Strain B171 and Its Relatedness to Plasmids of Diverse E. coli and Shigella Strains.

Enteropathogenic (EPEC) is a leading cause of severe infantile diarrhea in developing countries. Previous research has focused on the diversity of the EPEC virulence plasmid, whereas less is known regarding the genetic content and distribution of antibiotic resistance plasmids carried by EPEC. A previous study demonstrated that in addition to the virulence plasmid, reference EPEC strain B171 harbors a second, larger plasmid that confers antibiotic resistance. To further understand the genetic diversity and dissemination of antibiotic resistance plasmids among EPEC strains, we describe the complete sequence of an antibiotic resistance plasmid from EPEC strain B171. The resistance plasmid, pB171_90, has a completed sequence length of 90,229 bp, a GC content of 54.55%, and carries protein-encoding genes involved in conjugative transfer, resistance to tetracycline (), sulfonamides (), and mercury, as well as several virulence-associated genes, including the transcriptional regulator and the putative calcium sequestration inhibitor (). detection of the pB171_90 genes among 4,798 publicly available genome assemblies indicates that the unique genes of pB171_90 ( and ) are primarily restricted to genomes identified as EPEC or enterotoxigenic However, conserved regions of the pB171_90 plasmid containing genes involved in replication, stability, and antibiotic resistance were identified among diverse pathotypes. Interestingly, pB171_90 also exhibited significant similarity with a sequenced plasmid from type I. Our findings demonstrate the mosaic nature of EPEC antibiotic resistance plasmids and highlight the need for additional sequence-based characterization of antibiotic resistance plasmids harbored by pathogenic .