Bacterial survival on and in produce

There has been little work on the survival of bacteria and viruses on fruits and vegetables or the soils they grow in.
As noted in the land application section, EPA acknowledges that bacteria may survival over a year in soils and up to 6
months on crops. This is found to be the case when food contamination is blamed on manure. However, when scientist
search for the cause of the Salinas Valley foodborne outbreaks - bacteria only survive for a few days and don't
contaminate lettuce. On the other hand, the difference may be in the temperature of the tests.

1999
Potential for Infiltration, Survival and Growth Of Human Pathogens within Fruits and Vegetables
[There have only been 9 studies of human pathogens in produce and juice that FDA could find?]

Published and unpublished information relevant to the subject of microbial infiltration and survival in produce has
demonstrated that, under certain conditions, microorganisms can become internalized into fruits and vegetables,
including citrus fruits, and can survive in that  environment. Water, insects or birds, all of which may carry human
pathogens, may serve as vectors resulting in the contamination of damaged or decayed sites on the rind.
Microorganisms subsequently may infiltrate the produce through these damaged sites. In addition, fruit can become
contaminated if warm fruit is submerged into cold, contaminated water or if vulnerable external points of fruit are
immersed in contaminated water. Under certain conditions, equipment also has been shown to cross contaminate both
fresh apple and orange juice during processing.

Survival of pathogens, both plant and human, has been demonstrated in both produce and juice. In laboratory studies,
human pathogens have been found in or on tomatoes, cantaloupe, watermelon, honeydew melon, and apples. There
appears to be no published information on human pathogens in citrus fruits; however, the presence of other bacteria
internalized in citrus was noted. Numerous studies have shown that human pathogens can survive in both apple and
orange juice, despite their natural acidity.
http://thewatchers.us/1-food_bacterial_poisoning.html

2004
Persistence of enterohemorrhagic Escherichia coli O157:H7 in soil and on leaf lettuce and parsley grown in fields
treated with contaminated manure composts or irrigation water.
Outbreaks of enterohemorrhagic Escherichia coli O157:H7 infections associated with lettuce and other leaf crops have
occurred with increasing frequency in recent years. Contaminated manure and polluted irrigation water are probable
vehicles for the pathogen in many outbreaks. In this study, the occurrence and persistence of E. coli O157:H7 in soil
fertilized with contaminated poultry or bovine manure composts or treated with contaminated irrigation water and on
lettuce and parsley grown on these soils under natural environmental conditions was determined. Twenty-five plots,
each 1.8 by 4.6 m, were used for each crop, with five treatments (one without compost, three with each of the three
composts, and one without compost but treated with contaminated water) and five replication plots for each treatment.
Three different types of compost, PM-5 (poultry manure compost), 338 (dairy manure compost), and NVIRO-4 (alkaline-
stabilized dairy manure compost), and irrigation water were inoculated with an avirulent strain of E. coli O157:H7.
Pathogen concentrations were 107 CFU/g of compost and 105 CFU/ml of water. Contaminated compost was applied to
soil in the field as a strip at 4.5 metric tons per hectare on the day before lettuce and parsley seedlings were
transplanted in late October 2002. Contaminated irrigation water was applied only once on the plants as a treatment in
five plots for each crop at the rate of 2 liters per plot 3 weeks after the seedlings were transplanted. E. coli O157:H7
persisted for 154 to 217 days in soils amended with contaminated composts and was detected on lettuce and parsley for
up to 77 and 177 days, respectively, after seedlings were planted. Very little difference was observed in E. coli O157:H7
persistence based on compost type alone. E. coli O157:H7 persisted longer (by .60 days) in soil covered with parsley
plants than in soil from lettuce plots, which were bare after lettuce was harvested. In all cases,
E. coli O157:H7 in soil,
regardless of source or crop type, persisted for >5 months after application of contaminated compost or
irrigation water.
http://thewatchers.us/EPA/3/2004-E_coli-survival.pdf

Fate of Salmonella enterica Serovar Typhimurium on Carrots and Radishes Grown in Fields Treated with Contaminated
Manure Composts or Irrigation Water
Three different types of compost, PM-5 (poultry manure compost), 338 (dairy cattle manure compost), and NVIRO-4
(alkaline-pH-stabilized dairy cattle manure compost), and irrigation water were inoculated with an avirulent strain of
Salmonella enterica serovar Typhimurium at 107 CFU g−1 and 105 CFU ml−1, respectively, to determine the
persistence of salmonellae in soils containing these composts, in irrigation water, and also on carrots and radishes
grown in these contaminated soils. A split-plot block design plan was used for each crop, with five treatments (one
without compost, three with each of the three composts, and one without compost but with contaminated water applied)
and five replicates for a total of 25 plots for each crop, with each plot measuring 1.8 × 4.6 m. Salmonellae persisted for
an extended period of time, with the bacteria surviving in soil samples for 203 to 231 days, and were detected after
seeds were sown for 84 and 203 days on radishes and carrots, respectively. Salmonella survival was greatest in soil
amended with poultry compost and least in soil containing alkaline-pH-stabilized dairy cattle manure compost. Survival
profiles of Salmonella on vegetables and soil samples contaminated by irrigation water were similar to those observed
when contamination occurred through compost. Hence, both contaminated manure compost and irrigation water can
play an important role in contaminating soil and root vegetables with salmonellae for several months
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=383101

2001
Legionella: Drinking Water Health Advisory     [Amoebae also are on vegetables -- 2008 protozoa]
Currently, Legionella are known to infect a total of 13 species of amoebae and two species of ciliated protozoa (Fields
1996). Legionella also can multiply intracellularly within protozoan hosts (Vandenesch et al. 1990). Legionella strains
that multiply in protozoa have been shown to be more virulent, possibly due to increased bacterial numbers (Kramer and
Ford 1994). The ability to proliferate within these symbiont hosts provides Legionella with protection from otherwise
harmful environmental conditions. Thus, Legionella are able to survive in habitats with a greater temperature range, are
more resistant to water treatment with chlorine, biocides and other disinfectants, and survive in dry conditions if
encapsulated in cysts. Their enhanced resistance to water treatment has major implications for both disease
transmittance and water treatment procedures. ! Legionella also grow symbiotically with the aquatic bacteria attached to
the surface of biofilms (Kramer and Ford 1994). Biofilms provide the bacteria with nutrients for growth and also offer
protection from adverse environmental conditions (including during water disinfection). The concentration of Legionella
in biofilms depends upon water temperature; at higher temperatures, they can more effectively compete with other
bacteria. Because biofilms colonize drinking water distribution systems, they provide a habitat suitable for Legionella
growth in potable water, which can lead to human exposure.
http://www.epa.gov/waterscience/criteria/humanhealth/microbial/legionellaha.pdf

2005
Survival of Escherichia coli O157:H7 in soil and on carrots and onions grown in fields treated with contaminated manure
composts or irrigation water
Many foodborne outbreaks of enterohemorrhagic Escherichia coli O157:H7 infection have been associated with the
consumption of contaminated vegetables. On-farm contaminations through contaminated manure or irrigation water
application were considered likely sources of the pathogen for several outbreaks. Field studies were done to determine
the survival of E. coli O157:H7 on two subterranean crops (carrots and onions), and in soil fertilized with contaminated
manure compost or irrigated with contaminated water. Three different types of composts, PM-5 (poultry manure
compost), 338 (dairy manure compost) and NVIRO-4 (alkaline stabilized dairy manure compost), and irrigation water
were inoculated with an avirulent strain of E. coli O157:H7 at 107 cfu g−1 and 105 cfu ml−1, respectively. A split-plot
block design plan was used for each crop, with five treatments (one without compost, three with each of the three
composts, and one without compost but with contaminated irrigation water applied) and five replicates for a total of 25
plots, each measuring 1.8×4.6 m2, for each crop. Composts were applied to soil as a strip at a rate of 4.5 metric tons
ha−1 before carrots and onions were sown. Contaminated irrigation water was sprayed once on the vegetables at the
rate of 2 l per plot for this treatment 3 weeks after carrots and onions were sown.
E. coli O157:H7 survived in soil
samples for 154–196 days, and was detected for 74 and 168 days on onions and carrots, respectively.
E. coli
O157:H7 survival was greatest in soil amended with poultry compost and least in soil containing alkaline-stabilized dairy
manure compost.
Survival profiles of E. coli O157:H7 on vegetables and soil samples, contaminated either by
application of contaminated compost or
irrigation water, were similar. Hence, preharvest contamination of carrots
and onions with E. coli O157:H7 for several months can occur through both contaminated manure compost and
irrigation water.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WFP-4D5FVCK-
8&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=994928940&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=e226c88573dad91c175c8d29410303f0

2006
Quantification of contamination of lettuce by GFP-expressing Escherichia coli O157:H7 and Salmonella enterica serovar
Typhimurium
The primary objective of this study was to determine the possibility of internalization of GFP-expressing Escherichia coli
O157:H7 and Salmonella enterica serovar Typhimurium (S. Typhimurium) strains MAE 110 (multi-cellular morphology)
and 119 (wild type morphology) into lettuce seedlings (Lactuca sativa cv. Tamburo) grown in an inoculated hydroponic
and soil system. The second aim was to quantify the level of contamination with the use of a proper surface sterilization
method. Silver nitrate was superior in reducing the number of viable bacteria on leave surfaces compared to sodium
hypochlorite and ethanol. With the hydroponic system internal colonization of lettuce only occurred at high densities with
S. Typhimurium MAE 119. With the soil system E. coli O157:H7, S. Typhimurium 110 and S. Typhimurium 119 were
found at considerable densities in sterilized leaf samples (respectively, 3.95, 2.57 and 2.37 log cfu/g on average) with
prevalences of 0.29, 0.23 and 0.15, respectively. No statistical differences were observed between the Salmonella
strains. A negative correlation was observed between shoot weight and leaf contamination. The observed presence of
the pathogens in lettuce, after thorough surface sterilization, demonstrates the possible presence of human pathogens
in locations were they are unlikely to be removed by the actions of consumer washing and therefore pose a serious
threat when occurring in field situations.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WFP-4JJFV73-
1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=995094797&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=0286939ac349ba306a8c6862a32b32a3

2007
Microbiological Safety of Leafy Green Vegetables: A Bibliography
http://www.unitedfresh.org/assets/files/Leafy%20Greens%20Bibliography%20-%20Buchanan%20August%202007.pdf

2008
Interactions between Food-Borne Pathogens and Protozoa Isolated from Lettuce and Spinach
The present study revealed that certain protozoa isolated directly from produce can sequester S. enterica and E. coli
O157:H7 in expelled vesicles. It also provides the first evidence that viable human pathogens can multiply in, and exit
from, these protozoan vesicles. Most important for the microbial safety of fresh produce is the demonstration that the
process of vesicle formation and expulsion can occur directly on leaves of wet produce. Thus, protozoa may interact with
enteric pathogens on produce surfaces in a manner that may have significant implications for food safety and public
health.
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2293137

2009
FOOD SAFETY AND SALINAS VALLEY CROPS: [PR piece -- see the next USDA study]
[Land Grant Universities have a problem finding contamination]
5: Research on soil survival of E. coli in the Salinas Valley
All of our E. coli strains, inoculated to soil at high rates (106 or 108 CFU/ml), were recovered from soil for only a short
period. By 8 days after inoculation, recovery was at or near the detection limit for most plots. By 14 days, E. coli was no
longer detected from soil. -- E. coli persisted for a short period in surface water runoff. Romaine grown in the
experimental plots did not test positive for E. coli at anytime. Generic E. coli strains behaved similarly with attenuated
O157:H7 E. coli strains. Additional applied, field-oriented research is needed so that industry and regulators can
make informed decisions on growing practices and future food safety policies
http://cemonterey.ucdavis.edu/newsletterfiles/_i__b_Monterey_County_Crop_Notes__b___i_17098.pdf

USDA 2009  -- actually a 2004 study recently put on USDA website
Persistence of enterohemorrhagic Escherichia coli O157:H7 in soil and on leaf lettuce and parsley grown in fields
treated with contaminated manure composts or irrigation water.
Outbreaks of enterohemorrhagic Escherichia coli O157:H7 infections associated with lettuce and other leaf crops have
occurred with increasing frequency in recent years. Contaminated manure and polluted irrigation water are probable
vehicles for the pathogen in many outbreaks. In this study, the occurrence and persistence of E. coli O157:H7 in soil
fertilized with contaminated poultry or bovine manure composts or treated with contaminated irrigation water and on
lettuce and parsley grown on these soils under natural environmental conditions was determined. Twenty-five plots,
each 1.8 by 4.6 m, were used for each crop, with five treatments (one without compost, three with each of the three
composts, and one without compost but treated with contaminated water) and five replication plots for each treatment.
Three different types of compost, PM-5 (poultry manure compost), 338 (dairy manure compost), and NVIRO-4 (alkaline-
stabilized dairy manure compost), and irrigation water were inoculated with an avirulent strain of E. coli O157:H7.
Pathogen concentrations were 10(7) CFU/g of compost and 10(5) CFU/ml of water. Contaminated compost was applied
to soil in the field as a strip at 4.5 metric tons per hectare on the day before lettuce and parsley seedlings were
transplanted in late October 2002. Contaminated irrigation water was applied only once on the plants as a treatment in
five plots for each crop at the rate of 2 liters per plot 3 weeks after the seedlings were transplanted. E. coli O157:H7
persisted for 154 to 217 days in soils amended with contaminated composts and was detected on lettuce and parsley for
up to 77 and 177 days, respectively, after seedlings were planted. Very little difference was observed in E. coli O157:H7
persistence based on compost type alone. E. coli O157:H7 persisted longer (by >60 days) in soil covered with parsley
plants than in soil from lettuce plots, which were bare after lettuce was harvested. In all cases,
E. coli O157:H7 in soil,
regardless of source or crop type, persisted for >5 months after application of contaminated compost or
irrigation water.
http://hdl.handle.net/10113/26385
http://ddr.nal.usda.gov/handle/10113/26385?mode=full
2004-E_coli-survival.pdf