Figure 5

Effect of zinc on ciprofloxacin-induced bacteriophage production from STEC bacteria, as assessed by a semi-quantitative “spot” assay. STEC filtrates were prepared as described in Materials and Methods from strain TSA14 and diluted to 1:10, 1:20, 1:40, 1: 80, and so on to 1:2560. Panel A, sterile filtrate of TSA14 not treated with antibiotics or zinc, showing a phage titer of 1: 10. Panel B, STEC filtrate from bacteria treated with 0.4 mM zinc; no phage plaques are visible. Panel C, spot assay from TSA14 treated with 4 ng/mL ciprofloxacin, showing a titer of 1:640. Panel D, phage titer resulting from bacteria treated with ciprofloxacin and zinc, showing a 8-fold reduction in phage plaque titer compared to ciprofloxacin alone.