Pathogenic
Escherichia coli
is an important cause of diarrhea, edema disease, and septicemia in swine. In Japan, the volume of antimicrobial
drugs used for animals is highest in swine, but information about the prevalence of antimicrobial-resistant bacteria is confined to apparently healthy animals.
In the present study, we determined the O serogroups, virulence factors, and antimicrobial resistance of 360
E. coli
isolates from swine that
died of disease in Kagoshima Prefecture, Japan, between 1999 and 2017. The isolates of the predominant serogroups O139, OSB9, O149, O8, and O116 possessed
virulence factor genes typically found in diarrheagenic
E. coli
. We further found five strains of third-generation cephalosporin-resistant
E. coli
that each produced an extended-spectrum β-lactamase encoded by
bla
CTX-M-14
,
bla
CTX-M-15
,
bla
CTX-M-24
,
bla
CTX-M-61
, or
bla
SHV-12
. In 218 swine with a clear history of antimicrobial drug use, we further analyzed associations between the use of
antimicrobials for the treatment of diseased swine and the isolation of resistant
E. coli
. We found significant associations between
antimicrobial use and selection of resistance to the same class of antimicrobials, such as the use of ceftiofur and resistance to cefotaxime, cefazolin, or
ampicillin, the use of aminoglycosides and resistance to streptomycin, and the use of phenicols and resistance to chloramphenicol. A significant association
between antimicrobial use and the resistance of
E. coli
isolates to structurally unrelated antimicrobials, such as the use of ceftiofur and
resistance to chloramphenicol, was also observed.