Abstract
AmpC is a class C Ambler β-lactamase that confers resistance to cephamycins. Globally reported AmpC-producing Enterobacterales are clinically important due to their therapeutic restrictions and epidemiology. Between April 2021 and May 2021, an outbreak of AmpC beta-lactamase-producing Escherichia coli occurred at Showa University Hospital. Because of this outbreak, plasmid typing, enterobacterial repetitive intergenic consensus-polymerase chain reaction （ERIC-PCR） analysis, conjugation experiments, and pulsed-field gel electrophoresis （PFGE） were performed to study the molecular epidemiological characteristics of these E. coli strains. ERIC-PCR and conjugation experiments detected IncFrepB＋, IncFIA＋, and IncFIB＋ multiple-replicon conjugative plasmids carrying the AmpC gene （blaDHA-1）. Five of eleven isolates showed the same PFGE banding pattern in the XbaI-digested genomic DNA, whereas the remaining six strains displayed minor variants. These data highlight the need for improvements to infection control and surveillance measures to prevent the spread of blaDHA-1-carrying E. coli strains.
