Figure 2.

The host range of 15 Salmonella phages against 20 Salmonella strains were measured by spotting on soft agar overlays. Phages were plated at the routine test dilution (RTD and determined as the first tenfold serial dilution of phage lysate that formed countable plaques on lawns of its own host) and 100× the RTD. Phage were tested and scored on the following criteria: phage forming >50% of the number of plaques formed on its host strain at its RTD = 4; phage forming 5% to 50% of the number of plaques formed on its host strain at its RTD = 3; phage forming a zone of confluent lysis but no individual plaques at 100× RTD = 2; phage forming individual plaques at 100× RTD = 1; and no plaque or clearing formation at either dilution = 0. The scores from three replicate experiments were averaged. To aid the reader, cells are shaded with stronger color intensity indicating a greater score. Boxed cells indicate the initial isolation and propagation host of the phage. For clarity, all values are displayed to one significant figure unless a non-zero value is present at the first decimal place.