FIG 4.

Total and internalized counts for E. coli O157:H7 in planta. (A and B) The number of E. coli isolate ZAP1589 bacteria recovered from inoculation (10⁷ CFU ml⁻¹) of spinach (var. Amazon) (A) or lettuce (var. All Year Round) (B) roots at 0, 5, 10, and 14 dpi. (C to F) The number of E. coli isolate ZAP1589 bacteria recovered from alfalfa (C) or fenugreek (D) and E. coli isolate Sakai bacteria recovered from alfalfa (E) or fenugreek sprouts (F) after inoculation at 10³ CFU ml⁻¹. Samples were recovered at 0, 1, and 2 dpi. Averages (lines) and individual sample counts are shown for the total population (black) or the internalized population (gray) (n = 15; ∼1.5 g per sample for sprouts, individual plants for spinach and lettuce). Sprout day 0 data were assessed by the MPN method (level of detection = 0); otherwise, minimum counts were manually leveled to the direct plating detection limit of 10 CFU g⁻¹ on day 1.