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Water IrrigationWater, Irrigation,and Impacts on E. coli
Steven Koike, Mike Cahn, and Trevor Suslowand Trevor Suslow
University of California
UC Cooperative Extension: L T Obj iLong-Term Objectives
• Conduct practical field studies that• Conduct practical field studies that contribute to an understanding of how E coli and other foodborne pathogensE. coli and other foodborne pathogens exist and survive in agriculture.
• Provide guidance for minimizing risks from foodborne pathogens and forfrom foodborne pathogens and for improving metrics and regulatory guidelines.g
2007 Field Experiments2007 Field Experiments• Examine soil survival of generic E. coliExamine soil survival of generic E. coli
under field conditions.
• Evaluate irrigation methods and soil nutrient levels on generic E. colinutrient levels on generic E. coli survival.
• Develop and refine detection methods for E. coli research.for E. coli research.
Field Trial 1Field Trial 1Objective: Evaluate generic E. coli survival in
il d diff t t f i kl li dsoil under different rates of sprinkler applied water
• Replicated small plots (40-inch bed x 20 feet).• Four E. coli treatments (water, soil, plant, combo.).• Two concentrations (106, 108 cfu/ml) each.• Selected for antibiotic resistance (rif mutant).
Sprinkler irrigated e er 2 da s (5 times total)• Sprinkler irrigated every 2 days (5 times total).• Water volumes were measured.• Monitor E. coli rif survival in soil.
5B
4B
3B
2B
1B
88
5A
4A
3A
2A
1A
45B15
54B34
23B43
32B62
11B21
8
7
8
75
5A2
5
4
4A8
2
3
3A3
6
2
2A5
4
1
1A7
8
5B85
4B74
3B53
2B12
1B31
66
5
5A7
4
4A4
3
3A1
2
2A8
1
1A6
B65B
B14B
B83B
B72B
B41B
5
4
5
45A
A3
4A
A6
3A
A7
2A
A2
1A
A5
35B75
64B44
73B13
22B82
51B61
33
5
5A8
6
4
4A7
1
3
3A5
8
2
2A1
7
1
1A3
4
5B25
4B84
3B33
2B52
1B71
2
1
2
1 5
5A1
4
4A3
3
3A4
2
2A6
1
1A2
B5
B2
B6
B4
B8
11
Guard Row Applied Water Applied Water Sprinkler
A4
A5
A2
A3
A1
Field Trial 1 ResultsField Trial 1 Results
• E coli rif recovered from soil up to 8E. coli rif recovered from soil up to 8 days.
• By 14 days E coli rif no longer• By 14 days, E. coli rif no longer detected (w/ exception of two plots).Hi h t i t d ith• Higher recovery rates associated with the larger amounts of applied water.
• Applied strains were never detected in adjacent uninoculated plots.
Block A & B differences
5l 4
Block ABlock B
(North)
(South)
r of s
oil
3
g C
FU/g
r
2
log
1
CocktailPlant log 8
Water log 8Soil log 8
0
Treatment
Pl Wa S
4Applied Water at Field Trial 1
ches
)3
4
Wat
er (i
nc
2
S2-5
N2-5
App
lied
W
1S1
Distance from Sprinkler Line (feet)4 6 8 10 12 14 16 18 20
0N1
Distance from Sprinkler Line (feet)
North Side 1st irrigationSouth Side 1st irrigationNorth Side total of subsequent irrigationsNorth Side total of subsequent irrigationsSouth Side total of subsequent irrigations
Field Trial 2: Field SVR 51Objective: Compare soil survival of generic E.
coli under sprinkler/drip and withcoli under sprinkler/drip and with high/standard nutrient inputs.
• Replicated large plots (three 40-inch beds x 145 feet).• Treatments:
Irrigation: drip sprinklers• Irrigation: drip, sprinklers• E. coli rif (107): noninoculated, inoculated• Fertilizer: grower std, grower std + 350 lb N/acre + 250 lb
P/acreP/acre• Plant romaine; follow E. coli survival in soil, in runoff
water (sprinkler plots only), on plants.• Target lettuce harvest: September.
SVR 51 Results A• E. coli rif recovered from soil for only a
short period of time (up to 3 days).short period of time (up to 3 days).• Irrigation methods and nutrient levels
had no effect on E. coli survival in soil.had no effect on E. coli survival in soil.• By 6 d, E. coli rif no longer detected.• No detection of E coli rif on lettuce:• No detection of E. coli rif on lettuce:
– seedling roots and rhizosphere soil– seedling leavesseedling leaves– larger plant leaves– plants of harvestable sizeplants of harvestable size
E. coli survival in soil8 Inoculum concentration
oil
6
Day of inoculation3 days after inoc.6 days after inoc.13 days afer inoc. (5 cm)
CFU
/g d
ry s
o
4
log
C
0
2
D.L. (day 3)
noc.
ntro
l
rient
noc.
ntro
l
rient
-2
D.L. (day 6)
D.L. (day 13)
sprin
kle
unin
prin
kle
inoc
. con
rinkl
e in
oc. N
utri
drip
uni
n
drip
inoc
. con
t
drip
inoc
. Nut
ri
Treatments
sp spri
Day 0, 3 and 6. Samples were collected at the north side of each plot.Day 13. Samples consisted in a composite from 10 sub-samples distributed along the plotData only from Davis analisys
SVR 51 Results BSVR 51 Results B
• Sprinkler irrigation runoff: E coli rifSprinkler irrigation runoff: E. coli rif detected up to 12 days after inoculationinoculation.
• E. coli rif strains were not detected in adjacent uninoculated plots/lettuceadjacent uninoculated plots/lettuce.
• Coliform bacteria were recovered from ff f th d ti f th t i lrunoff for the duration of the trial.
Coliform Bacteria in Sprinkler Run-off from
105
Coliform Bacteria in Sprinkler Run off from SRV 51 field trial
104
105P
N/1
00 m
l
102
103
Control (not inoculated)i l t d / if E li
Detection limit = 24196 MPN/100 ml
MP
101
10 inoculated w/ rif E.coliinoculated w/ rif E. coli + nutrients
Days after Inoculation10 20 30 40 50 60
100
Days after Inoculation
SVR 51 Results CSVR 51 Results C• Starting from 26 days post inoculation, weStarting from 26 days post inoculation, we
recovered presumptive E. coli (growth on rif medium; fluorescence on MUG medium) from plants and runoff from inoculated plots.
• Late in experiment: found presumptive E. coli from uninoculated plots.
• However, all these isolates were later found b f l i i (ID E bto be false positives (ID= Enterobacter
species).
Presumptive E. coli in Sprinkler Run-off from SRV 51 field trial
10000
Control (not inoculated)i l t d / if E li
from SRV 51 field trial0
ml
1000inoculated w/ rif E.coliinoculated w/ rif E. coli + nutrients
MP
N/1
00 100
Detection limit = M 10 1 MPN/100 ml
10 20 30 40 50 60
1
Days after Inoculation
Summary for Generic E. coli in Fi ld S diField Studies
• Simulation of a one-time, high level , gcontamination event (w/ E. coli rif) resulted in very short persistence.I i ti th d/ t i t l l did t ff t• Irrigation method/nutrient level did not affect survival of E. coli in soil or in plant tissue.
• Presumptive E coli was detected in sprinkler• Presumptive E. coli was detected in sprinkler run-off water collected from furrows.
• Water appears to play key role in survival.ate appea s to p ay ey o e su a• Testing issue raised: positives with non-E.
coli on ECC, TSA, QuantiTray assays?
E. coli in Irrigation Run-off and Creeks
Presumptive
E. coli in Irrigation Run off and CreeksEast-side Salinas Valley (9/6/07)
Bacterial TMDL proposed for thesite description Coliform
Presumptive Generic E.Coli
MPN/100 ml1 i i ti ff hi h di t l d > 24196 1300
Bacterial TMDL proposed for the Lower Salinas Valley surface water:
1 irrigation run-off high sediment load > 24196 13002 irrigation run-off high sediment load > 24196 7703 creek (downstream from 2) > 24196 4354 irrigation run-off high sediment load > 24196 1120
target for E. coli = 126 MPN/100 ml5 irrigation run-off high sediment basin > 24196 626 road-side run-off (downstream from 5) > 24196 1357 creek > 24196 10468 Irrigation run-off (clear) > 24196 459 road-side run-off (downstream from 8) > 24196 37
10 irrigation run-off high sediment load > 24196 687
Acknowledgements:1. California Lettuce Research Board2. Grower cooperators3. Research team: Patty Ayala, Elena Castro Carol D’lima Riley Hathaway KatCastro, Carol D’lima, Riley Hathaway, Kat Kammeijer, Eric Lauritzen, Salvador Montes, Lisa Quon, Adrian Sbodio, Arnett Young
Effect of Nutrients* on native ColiformEffect of Nutrients on native Coliform Bacteria and Presumptive E.coli levels in
Creek Water (site 3)
120
140
C t l
native E. coli (presumptive)
6000
8000
Control
native coliform
MP
N/1
00 m
l
60
80
100 Control+Nutrients
MP
N/1
00 m
l
4000
6000 Control+ Nutrients
0 2 4 6 8 10
M0
20
40
0 2 4 6 8 10
M
0
2000
days0 2 4 6 8 10
days0 2 4 6 8 10
*50 ppm Nitrate-N, 10 ppm orthophosphatepp pp p p