TABLE 2

Abundance of ampicillin-, cefoxitin-, and sulfamethazine-resistant coliforms recovered from soil suspensions following 3 days of incubation in presence or absence of bacteriophage enriched from biosolidsa

Drug concnb during incubationBacteriophage supplementationDrug-resistant coliform count/total coliform count
AmpicillinCefoxitinSulfamethazine
00.000337 ± 0.0000520.00724 ± 0.009170.245 ± 0.145
+0.00101 ± 0.000990.00335 ± 0.002730.129 ± 0.037
1:1000.00143 ± 0.001420.00315 ± 0.000440.00326 ± 0.00291
+0.00252 ± 0.014800.00168 ± 0.00067*0.0207 ± 0.0132*
1:100.411 ± 0.3230.0512 ± 0.02390.0342 ± 0.0459
+0.116 ± 0.0310.192 ± 0.060*0.243 ± 0.098*
  • a Suspensions were incubated without the addition of antibiotics or with one of the antibiotics at either a 1:100 or a 1:10 clinical breakpoint concentration. Data represent the mean ± standard deviation (n = 3) of the count of resistant coliforms (in numbers of CFU per milliliter) normalized to the total coliform count (in numbers of CFU per milliliter). *, statistically significant differences between phage treatment and no phage treatment.

  • b 1:100 and 1:10, final concentrations 100-fold and 10-fold, respectively, below the breakpoint concentrations of the indicated antibiotics (ampicillin, 32 μg/ml; cefoxitin, 32 μg/ml; sulfamethazine, 512 μg/ml).