Table 1.
Phage titer and efficiency of plating characterization of Shiga-toxigenic E. coli (STEC) by phages.
| STEC Isolate 1 | Sero-ID | Phage Cocktail Titer (log10 PFU/mL) 2 | Phage Efficiency of Plating (EOP) | ||||
|---|---|---|---|---|---|---|---|
| Phage A | Phage B | Phage C | Phage D | Phage Cocktail 4 | |||
| USDA-FSIS 380-94 | O157:H7 | 8.6 ± 0.1 | - | 0.19 3 | 1.0 | + | 1.0 |
| CDC 96-3258 | O45:H2 | 8.3 ± 0.1 | + | 0.08 | - | + | 0.5 |
| CDC 90-3128 | O103:H2 | 8.4 ± 0.5 | + | 1.0 | 0.42 | 0.25 | 1.0 |
| JB1-95 | O111:H- | 9.1 ± 0.1 | 1.0 | - | - | 0.29 | 3.3 |
| CDC 97-3068 | O121:H19 | 6.7 ± 0.1 | - | - | - | 0.08 | 0.01 |
1 STEC isolates provided by J.B. Luchansky (USDA-Agricultural Research Service, Wyndmoor, PA, USA). 2 Values depict mean ± one standard deviation (N = 3) of phages plated for corresponding STEC isolate. 3 EOP calculated as phage titer on test STEC isolate divided by phage titer on the E. coli O157:H7 isolate for phages A, B, and C. EOP for phage D was normalized to phage titer on E. coli O27:H11 isolate H30 (data not shown). -: no observed plaques or clearing zones formed at any phage dilution; +: confluent spot formation at 10−1–10−2 phage dilutions but no isolated plaques observed. 4 EOP calculated as observed phage titer on the STEC isolate divided by phage titer for E. coli O157:H7 isolate.