E. Coli

Review of Literature
isolates from humans and animals are increasingly resistant to the
ESCs. In humans, infections with ESC resistant Salmonella threaten
the efficacy of ceftriaxone, the drug of choice for treating
salmonellosis in children. They examined Salmonella isolates for
susceptibility to 23 antimicrobials. Isolates resistant to ampicillin and
amoxicillin/clavulanic acid that were additionally resistant to 3rd
generation cephalosporins and/or a cephamycin were further
characterized by several methods. We assessed plasmid profiles and
PFGE patterns, used PCR and sequencing to determine the presence
of the cmy-2 and other drug resistance genes, determined the
isoelectric point of the beta-lactamases produced, and carried out
conjugation, transformation and hybridization studies. E. coli isolated
during other projects were also examined. Their results revealed that
examination of all (119) S. newport isolates among 36,841 Salmonella
isolates from 1993-2002 showed that 0.1% of the 1993-98 strains but
0.4-0.6% of the 1999-02 strains were S. Newport. More than 50% of
the strains from 1993-2002 were of bovine origin. None of the S.
newport strains isolated before 2000 were multiply resistant to
antimicrobials, whilst 32 of 33 bovine and 3 of 14 poultry S. newport
strains isolated during the 2000-02 period were resistant to more than
5 antimicrobials including the ESCs. All resistant strains possessed the
cmy-2 gene. We also found cmy-2 encoded resistance to the ESCs
among other Salmonella serovars and E. coli isolates. They concluded
that the resistance of Salmonella and E. coli isolated from animals, the
animal environment, and foods of animal origin to ESCs is increasing.
This will limit treatment options when humans become infected with
such highly drug resistant strains.
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