Sludge Watch ==> Pathogens can get inside produce - study

[Maureen Reilly]

Sludgewatch Admin:

>From the Crapper to the Crop:

Much of North America's fresh greens comes from the Salinas Valley 
California in the summer months and from Yuma Arizona in the winter months.


Here is the wastewater/sludge problem:

Salinas Valley: Some of the Salinas Valley has so overpumped its groundwater 
that salt water from the ociea has intruded a dozen miles or more into the 
groundwater - sucked inland from the ocean.  This salt water can't be used 
for irrigation.  Instead of creating a desalination plant, sewage effleunt 
from the waster water treatment plant is put through a sand filter and sent 
out as irrigation water through a pipeline 22 miles long.  We know that 
wastewater effluent can contain drugs and antibiotic resistant bacteria.  We 
know that pipelines can develop biofilms that contaminate the water flowing 
through them.  Do we want fresh produce irrigated with sewage treatment 
plant effluent?

In Yuma the sewage sludge from Los Angeles and from Imperial County is 
spread on farmlands.  Some sludge sites are scant yards from fresh lettuce 
and spinach growing fields.  Flies and other vector are a real risk to food 
safety.


..........................................................


iFSN: Pathogens in produce: a brief review
28.may.08
iFSN
Ben Chapman

http://barfblog.foodsafety.ksu.edu/2008/05/articles/food-safety-communication/pathogens-in-produce-a-brief-review/index.html


Following this morning's report of a new European study demonstrating the
potential for internalization of Salmonella in produce, Ben Chapman pulled
together the following notes on the topic.

http://barfblog.foodsafety.ksu.edu/2008/05/articles/food-safety-communication/bugs-can-enter-and-grow-in-fresh-veggies-washing-is-not-enough/

Irrigation water containing raw sewage or improperly treated effluents from
sewage treatment plants may contain hepatitis A, Norwalk viruses, or
enteroviruses in addition to bacterial pathogens such as E.coli O157:H7,
Salmonella spp. and Shigella spp. (Beuchat, 1998).
Produce can also be contaminated with pathogens due to internalization of
pathogens both through the root system and flesh or stem scars. Evidence of
infiltration of bacteria into vegetables is reported in several articles 
(Bartz
1982; Bartz and Showalter 1981; Burnett et al., 2000; Seo and Frank 1999; 
Zhuang
et al., 1995). Clear evidence exists to conclude that pathogens can be
incorporated into fresh produce. So far, this evidence is based on 
laboratory
experiments, not actual real world situations. Past research suggests that
pathogens can enter lettuce plants through its roots and end up in the 
edible
leaves. Small gaps in growing roots through which plant pathogens infect 
tissue
may also allow E. coli entry (Solomon et al, 2002b; Warriner et al., 2003a,
Warriner et al., 2003b).

The uptake of Salmonella spp. by roots of hydroponically grown tomato plants
has been shown. Within one day of exposure to a high concentration mixture 
of
Salmonella spp. pathogen cells were found in the hypocotyls, cotyledons, 
stems
and leaves of young plants; though whether fruit is affected is not known at
this time (Guo et al., 2002).

Solomon and colleagues (2002a) discovered that the transmission of E.coli
O157:H7 to lettuce was possible through both spray and drip irrigation. They
also found that the pathogen persisted on the plants for 20 days following
application and submerging the lettuce in a solution of 200ppm chlorine did 
not
eliminate all viable E.coli O157:H7 cells. This suggests that irrigation 
water
of unknown microbial quality should be avoided in lettuce production 
(Solomon et
al., 2002a). In a follow-up experiment, Solomon and colleagues (2002b) 
explored
the transmission of E. coli O157:H7 from manure-contaminated soil and 
irrigation
water to lettuce plants. The researchers recovered viable cells from the 
inner
tissues of the lettuce plants and found that the cells migrated to internal
locations in plant tissue and were thus protected from the action of 
sanitizing
agents These experiments demonstrated that E. coli O157:H7 can enter the 
lettuce
plant through the root system and migrate throughout the edible portion of 
the
plant (Solomon et al., 2002b).

The risk of contamination of produce due to Salmonella spp. was found to be
increased when soil and water were present, and that soil and water actually 
act
as reservoirs of the pathogen. Xuan and colleagues (2002) found that soil 
and
water were factors in the infiltration of salmonella into the tissues of 
tomato.
This supports the theory that preharvest contact with contaminated soil or 
water
increased the contamination potential by certain pathogens and can lead to
problems in pathogen removal and the efficacy of sanitizers.
Flesh scarring can provide a suitable environment for pathogen growth, and
decreases the value of employing sanitizers, either in the packing shed or 
by
consumers (Xuan et al., 2002).

The uptake of Salmonella spp. by roots of hydroponically grown tomato plants
has also been shown. Within one day of exposure to a high concentration 
mixture
of Salmonella spp. pathogen cells were found in the hypocotyls, cotyledons,
stems and leaves of young plants; though whether fruit is affected is not 
known
at this time (Guo et al., 2002).

In a 2006 review, Vectors and conditions for preharvest contamination of 
fruits
and vegetables with pathogens capable of causing enteric diseases, Larry 
Beuchat
of the Center for Food Safety and Department of Food Science and Technology 
at
the University of Georgia, concluded:
"Manure, manure compost, sewage, sludge, irrigation water, and runoff water
represent
avenues for introduction of pathogenic bacteria, parasites, and viruses to 
soil
in which
fruits and vegetables intended to be eaten raw are grown. Pathogens vary in
their
ability to survive in soil amendments and in soil. Inactivation rates and
persistence in
soil are also influenced by soil type, rainfall, temperature, and agronomic
practices.
Some pathogens can survive in soil for periods of time exceeding those 
needed
to grow
plants from seeds or seedlings to the point of harvest. Pathogens 
originating
from
preharvest environments may contaminate the surface of produce and evidence 
is
mounting that contamination of internal tissues can also occur. Prevention 
of
preharvest contamination of fruits and vegetables is an essential part of a
systems
approach focused on applying interventions designed to achieve delivery of
microbiologically safe produce to the consumer."
References
Bartz, J.A. 1982. Infiltration of tomatoes immersed at different 
temperatures
to different depths in suspensions of Erwinia carotovora subsp. carotovora.
Plant Disease. 66:302-305.
Bartz, J.A., and R.K. Showalter. 1981. Infiltration of tomatoes by aqueous
bacterial suspensions. Phytopathology. 71: 515-518.
Beuchat, 2006. Vectors and conditions for preharvest contamination of fruits
and vegetables with pathogens capable of causing enteric diseases. British 
Food
Journal 108 (1): 38-53.
Beuchat, L.R. 1998. Surface decontamination of fruits and vegetables eaten 
raw:
a review. WHO/FSF/FOS/Publication 98.2. World Health Organization. Geneva. 
49pp.
Burnett, S.L., Chen. J. and Beuchat, L.R. 2000. Attachment of Escherichia 
coli
O157:H7 to the surfaces and internal structures of apples as detected by
confocal scanning laser microscopy. Applied and Environmental Microbiology. 
66:
4679-4687.
Guo, X., van Iersel, M. W., Chen, J., Brackett, R. E. and Beuchat, L. R. 
2002.
Evidence of association of salmonellae with tomato plants grown 
hydroponically
in inoculated nutrient solution. Applied Environmental Microbiology. 68:
3639-3643.
Hedberg, C.W., Angulo, F.J., White, K.E., Langkop, C.W., Schell, W.L.,
Stobierski M.G., Schuchat, A., Besser, J.M., Dietrich, S., Helsel, L., 
Griffin,
P.M., McFarland J.W. and Osterholm M.T. 1999. Outbreaks of salmonellosis
associated with eating uncooked tomatoes: implications for public health.
Epidemiology and Infection 122: 385-93.
Seo, K. H., and J. F. Frank. 1999. Attachment of Escherichia coli O157:H7 to
lettuce leaf surface and bacterial viability in response to chlorine 
treatment
as demonstrated by using confocal scanning laser microscopy. Journal of Food
Protection. 62: 3-9.
Solomon, E. B., Yaron, S., and Matthews, K.R. 2002b. Transmission of
Escherichia coli O157:H7 from contaminated manure and irrigation water to
lettuce plant tissue and its subsequent internalization. Applied 
Environmental
Microbiology. 68: 397-400.
Solomon, E.B., ,Potenski, C.J. and Matthews, K.R. 2002a. Effect of 
irrigation
method on transmission to and persistence of Escherichia coli O157:H7 on
lettuce. Journal of Food Protection. 65: 673–676.
Warriner K., Ibrahim F., Dickinson M,. Wright C. and Waites W.M. 2003a.
Internalization of human pathogens within growing salad vegetables.
Biotechnology & Genetic Engineering Reviews. 20: 117-134.
Warriner K., Ibrahim F., Dickinson M,. Wright C. and Waites W.M. 2003b.
Interaction of Escherichia coli with growing salad spinach plants. Journal 
of
Food Protection. 66: 1790-1797.
Xuan, G., Jinru, C., Brackett, R.E., Beuchat, L.R. 2002. Survival of 
salmonella
on tomatoes stored at high relative humidity, in soil, and on tomatoes in
contact with soil. Journal of Food Protection. 65: 274-279.
Zhuang, R.-Y., Beuchat, L.R. and Angulo. F.J. 1995. Fate of Salmonella
montevideo on and in raw tomatoes as affected by temperature and treatment 
with
chlorine. Applied Environmental Microbiolology. 61: 2127-2131.