Occurrence of CTX-M-positive and -negative cefotaxime-resistant isolates

Visit (date)Sample type (no.a)CA-positive samplesb
No. CTX-M PCR positiveNo. CTX-M PCR negativeNo. of PFGE clonesc
1 (December 2004)Calves (48)3159 (6)
Cows (60)228
Environment (0)
2 (February 2005)Calves (34)2109 (6)
Cows (51)35
Environment (7)00
3 (July 2005)Calves (41)38318 (13)
Cows (63)1511
Environment (16)41
  • a Total number of calves, cows, or environmental samples taken at the farm.

  • b Samples positive for E. coli on CHROMagar ECC plus 1 mg/liter cefotaxime.

  • c Number of PFGE clonal groups identified among cefotaxime-resistant isolates. Numbers in parentheses indicate how many clones were found among CTX-M-positive isolates.