Survival of Pathogenic Escherichia Coli on Basil, Lettuce, and Spinach

Summary The contamination of lettuce, spinach and basil with pathogenic E . coli has caused numerous illnesses over the past decade. E . coli O 157: H 7, E . coli O 104: H 4 and avian pathogenic E . coli ( APEC stx‐ and APEC stx+) were inoculated on basil plants and in promix substrate using drip and overhead irrigation. When overhead inoculated with 7 log CFU /ml of each strain, E . coli populations were significantly ( P  = 0.03) higher on overhead‐irrigated plants than on drip‐irrigated plants. APEC stx ‐, E . coli O 104: H 4 and APEC stx + populations were recovered on plants at 3.6, 2.3 and 3.1 log CFU /g at 10 dpi (days post‐inoculation), respectively. E . coli O 157: H 7 was not detected on basil after 4 dpi. The persistence of E . coli O 157: H 7 and APEC stx‐ were similar when co‐inoculated on lettuce and spinach plants. On spinach and lettuce, E . coli O 157: H 7 and APEC populations declined from 5.7 to 6.1 log CFU /g and 4.5 log CFU /g, to undetectable at 3 dpi and 0.6–1.6 log CFU /g at 7 dpi, respectively. The detection of low populations of APEC and E . coli O 104: H 4 strains 10 dpi indicates these strains may be more adapted to environmental conditions than E . coli O 157: H 7. This is the first reported study of E . coli O 104: H 4 on a produce commodity.