Agriculture Reference
In-Depth Information
and others (2007) used a nontoxigenic strain to determine the effect of heap turning.
They observed that the pathogen reached almost undetectable levels in less than
2 weeks when the compost piles were turned, but the organism was still detected after
4 months if the surface did not reach higher than 50 °C and there was signifi cant
temperature stratifi cation.
Survival of Pathogenic Organisms in Soil
A thorough assessment of the ability of pathogenic organisms to survive in soil after
the soil has been amended with manure is critical to determine the likelihood of
contamination in organic produce. Recent outbreaks caused by contaminated fresh
vegetables have stressed the potential role of soil as a vehicle of transmission.
Determining the survival rates of pathogenic organisms in soil has been a very active
area of research in preharvest food safety; some of the most relevant studies are
summarized in Table 4.3. From the results of these reports, the type of soil and crop
type are factors that have an important effect on survival of pathogenic organisms.
Table 4.3.
Summary of survival studies of foodborne pathogens in soil
Soil, Manure Type,
and Conditions
Organism
Maximum
Survival (Days)
Other Findings
Reference
Soil cores in lab
E. coli
O157
130
Only 2 - log reduction
Maule 2000
Clay loam and sandy
loam, cattle slurry
E. coli
O157
28
Reduction similar to
indicator
E. coli
Ogden and
others 2001
Pig manure
S.
Typhimurium
<
21
Noted that it could
survive up to 299
days
Baloda and
others 2001
Campsite with sheep
manure
E. coli
O157
105
Outbreak - related
Ogden and
others 2002
Clay soil/ loamy
sands, cow
manure
S.
Typhimurium
63
3 - to 4 - log reduction
Natvig and
others 2002
Fallow soil and silt
loam soil, cattle
manure
E. coli
O157
41 (fallow)
92 (silt loam)
500 (frozen)
Clay increased
persistence
Gagliardi and
Karns 2002
Clay loam and
channery silt loam
Cryptosporidium
parvum
120 (90%)
164 (99%)
High variability in
survival
Kato and
others 2004
Composted dairy
and poultry
manure
E. coli
O157
154 (lettuce)
214 (parsley)
4 - log reduction after
42 days
Islam and
others 2004
Sandy loam soil,
dairy cow manure
E. coli
O157
196 (onion)
> 84 (carrot)
3 - log reduction w/
onions at 64 days
Islam and
others 2005
Cattle slurries at RT
Campylobacter
Salmonella
E. coli
O157
90
Inactivated after 30
days at 55 ° C
Nicholson and
others 2005
Garden soil
E. coli
O157
96
Natural contamination
linked to a human
case
Mukherjee
and others
2006a
Organic and
conventional soils
E. coli
O157
> 60
No difference
between soil types
Semenov and
others 2008
