Coliphage are bacteriophage that infect and replicate in coliform bacteria.
This method must be done in the laboratory by a trained microbiologist. For the enrichment step, large sample volumes are supplemented with magnesium chloride, log-phase host E. coli , and tryptic soy broth and are incubated overnight. Divalent cations are included in the enrichment solution to enhance phage infectivity. After 24 hours of incubation at 35 C, samples are spotted onto a lawn of suitable host bacteria and incubated overnight. Positive results for coliphage appear as a clear halo around the spot.