TABLE 2.

Characterization of CTX-resistant E. coli isolates recovered on days 0 and 25 from pigs treated with the β-lactam drugs amoxicillin, cefquinome, and ceftiofur and the untreated controls

Treatment group or strainAnimal no.Day 0Day 25
CTX-M typeaE. coli phylogenetic groupbPFGE typeCTX-M typeE. coli phylogenetic groupPFGE type
Control11B1I1AXVI
21B1II1AXVIIa
31AIII1AXVIII
41scAIII1sAXVIII
51AIII1AXVIII
Amoxicillin114DIV1AXIX
214sDVa1AXIX
314sDVa1AXIX
4d, e1sAXIX
514sDVa1AXX
Ceftiofur11AVI1sAXXI
21sAVII1AXXII
214sDVIII14DNDf
31B1IX1AXVIIb
41AX1AXVIIb
51AXI14sDXXIII
51AND
Cefquinome11sAXII1sAXXIV
21AXIII1AXXVa
214sDND
314DVa1AXXVb
41AXIV1AXXVI
414sDVa
514DVb1AXXVII
51AXV
Inoculated KV7 NALr strain1sDXXVIII
  • a The CTX-M type was determined by general PCR, group PCR, and sequencing of selected amplicons (13).

  • b The E. coli phylogenetic group was determined by multiplex PCR, as described by Clermont et al. (6).

  • c s, sequenced.

  • d —, not tested.

  • e CTX-resistant coliforms were not detected at day 0 in this animal.

  • f ND, not determined.