Plasmid-mediated fosfomycin resistance in Escherichia coli isolated from pig

Area of Science:

• Microbiology
• Genetics
• Public Health

Background:

• Plasmid-mediated fosA3 has been previously identified in Escherichia coli from human and companion animals.
• The emergence and spread of antimicrobial resistance genes in food-producing animals pose a significant public health risk.

Purpose of the Study:

• To sequence and characterize the fosA3-carrying plasmid pHK23a from a multidrug-resistant E. coli isolate of pig origin.
• To investigate the genetic elements and antimicrobial resistance genes harbored by the plasmid.
• To assess the potential public health implications of this finding.

Main Methods:

• Whole-genome sequencing of the plasmid pHK23a.
• Conjugation experiments to assess plasmid transfer efficiency.
• Sequence alignment and comparative genomics to identify homologous regions and genetic elements.

Main Results:

• The plasmid pHK23a, belonging to the IncFII incompatibility group, was sequenced (73,607 bp).
• It harbors three antimicrobial resistance genes (fosA3, Δbla(TEM-1), bla(CTX-M-3)) within a novel IS26-composite transposon-like structure.
• The plasmid readily transferred to E. coli recipients at high frequencies.

Conclusions:

• This is the first report of a fosA3-containing plasmid in an E. coli isolate of pig origin.
• The efficient spread of IncFII plasmids combined with the presence of fosA3 and bla(CTX-M) is a significant public health concern.
• The findings highlight the need for surveillance of antimicrobial resistance in food-producing animals.