FIG. 1.

Southern blot hybridization of bacteriophage DNA isolated from reconstituted culture-positive stools containing serial dilutions of the genetically marked phage CTX-KmΦ and probed with the zot probe. Lanes 1 through 7 correspond to extracts from 5 ml of stools containing 1 × 10², 5 × 10², 1 × 10³, 1.5 × 10³, 2 × 10³, 2.5 × 10³, and 5 × 10³ phage particles, respectively. Numbers indicating the molecular sizes of bands correspond to the supercoiled DNA ladder (Bethesda Research Laboratories).