TABLE 2.

Total and tetracycline-insensitive bacterial population levels in swine cecal contents and cecal tissue homogenates

SampleChlortetra- cycline concn (μg/ml)No. of viable bacteriaa ± SEM
Farm AFarm B
Cecal contents010.44 ± 0.06510.18 ± 0.071
410.39 ± 0.06610.18 ± 0.092
1610.17 ± 0.067A10.13 ± 0.083
649.62 ± 0.093A,B10.12 ± 0.095B
128ND10.07 ± 0.041
2567.68 ± 0.140A,B9.68 ± 0.084A,B
Cecal tissues07.24 ± 0.0607.07 ± 0.132
47.25 ± 0.1077.08 ± 0.143
166.91 ± 0.1637.11 ± 0.109
646.38 ± 0.118A,B7.07 ± 0.112B
128ND6.80 ± 0.085
2565.07 ± 0.373A,B6.40 ± 0.014A,B
  • a Values are average log10 bacterial counts for animals from each farm for cecal contents and cecal tissues. Farm A, seven swine fed a diet without tetracycline (or other antibiotics). Farm B, six swine fed a diet containing 400 g of chlortetracycline/ton. A, values are significantly (P ≤ 0.01) different from values of samples from the same farm and cultured on medium without antibiotic. B, values are significantly different between farms at the same antibiotic concentration. ND, not determined.