Sludge Watch ==> Transfer of EcoliO157 through contact water from melting ice

[Maureen Reilly]

Sludgewatch Admin:

This study shows that EcoliO157 in ice used to cool romaine lettuce remains 
on the lettuce even after rinsing with chorinated water. Note that the 
pathogen is not inactivated in the ice.

We need to rethink the use of sewage effluent for spray irrigation of 
lettuce (like in the Salinas Valley) since the water, and the pathogens from 
biofilms in the irrigation pipes, may be contaminating the produce.

In Yuma, there should be no spreading of sewage sludge since flies from the 
sludge sites can deposit pathogens on the tender greens in the next field.

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Transfer of Escherichia coli O157:H7 to romaine lettuce due to contact water 
from melting ice
01.feb.08
Journal of Food Protection
Kim, Jin Kyung; Harrison, Mark A.

http://www.ingentaconnect.com/content/iafp/jfp/2008/00000071/00000002/art00001;jsessionid=anrcjs16c1l0o.henrietta


Ice can be used to chill romaine lettuce and maintain relative humidity 
during transportation. Escherichia coli O157:H7 may contaminate water used 
for ice. The objective of this study was to determine the potential for E. 
coli O157:H7 contamination of romaine lettuce from either ice contaminated 
with the pathogen or by transfer from lettuce surfaces via melting ice. In 
experiment 1, lettuce was spot inoculated with E. coli O157:H7 and chilled 
with ice prepared from uncontaminated tap water. In experiment 2, water 
inoculated with this pathogen was frozen and used to ice lettuce. Three 
heads of lettuce were stacked in each container and stored at 4 or 20°C. 
After the ice melted, E. coli O157:H7 attachment to and recovery from the 
lettuce leaves were determined. For experiment 1, the population of E. coli 
O157:H7 attached to inoculated sites averaged 3.8 and 5.5 CFU/cm2 at 4 and 
20°C, respectively. Most of the uninoculated sites became contaminated with 
the pathogen due to ice melt. For experiment 2, 3.5 to 3.8 log CFU E. coli 
O157:H7 per cm2 was attached to the top leaf on the first head. After 
rinsing with chlorinated water (200 _g/ml), E. coli O157:H7 remained on the 
surface of the top head (1.8 to 2.0 log CFU/cm2). There was no difference in 
numbers of E. coli O157:H7 recovered from each sampling site at 4 and 20°C. 
Results show that E. coli O157:H7 can be transferred onto other produce 
layers in shipping containers from melted ice made of contaminated water and 
from contaminated to uncontaminated leaf surfaces.

Affiliations: 1: Department of Food Science and Technology, University of 
Georgia, Athens, Georgia 30602, USA; Department of Food Science and Human 
Nutrition, Clemson University, Clemson, SC 29634, USA 2: Department of Food 
Science and Technology, University of Georgia, Athens, Georgia 30602, USA