TABLE 2

Percentage of E. coli O157:H7-positive and -enumerable samples of FSM and average percentage of E. coli O157:H7-positive leafy green samples per plota

Leafy green sample date
% of E. coli O157:H7-positive (-enumerableb) samples in feedlot surface manurecAvg % of E. coli O157:H7-positive leafy green samples per plot atd:
60 m120 m180 m
28 June 201149.0 (9.0)0 A0 A1.1 A
5 July 201181.0 (10.0)4.4 A2.2 A0 A
20 July 201167.0 (2.0)2.9 A0 A1.1 A
4 August 201194.0 (9.0)1.4 A0 A0 A
29 August 201162.0 (9.0)0 A0 A0 A
12 September 201187.0 (7.0)0 A0 A2.4 A
All dates, 201173.3 (7.7)1.5 A0.4 A0.8 A
18 June 201283.0 (7.0)4.4 A3.3 A1.1 A
2 July 201266.0 (2.0)6.6 A3.3 AB0 B
23 July 201247.0 (3.0)1.7 A1.8 A0 A
13 August 201297.0 (43.0)2.2 A1.1 A0 A
27 August 201277.0 (6.0)12.2 A2.2 B0 B
10 September 201260.0 (3.0)6.4 A12.2 B15.5 B
All dates, 201271.7 (10.7)5.6 A4.0 AB2.8 B
All dates, 2011 and 201272.5 (9.2)3.5 A2.2 AB1.8 B
  • a On each sample date, 100 feedlot pen surface samples were collected, and 270 leafy green samples were collected (30 leafy green samples from each of 9 plots, for 90 leafy green samples per plot distance).

  • b Enumerable means detectable by direct plating. The limit of detection for direct plating was 200 CFU g−1.

  • c FSM samples typically were collected on the same days that leafy greens were sampled, but on 20 July 2011, 4 August 2011, and 29 August 2011, the FSM samples were collected 1, 3, and 5 days, respectively, before leafy green samples were collected.

  • d The leafy greens were spinach for all sample dates, with the exception of 13 and 27 August 2012, when a mixture of turnip and mustard greens was sampled, and 10 September 2012, when only turnip greens were sampled. Within rows, least-squares means followed by different letters (A and B) are significantly different (P < 0.05).