Vegetable and Fruit Products
143
soil exposure.
41 From a study of 14 apple and pear orchards throughout the United States in 1999,
coliforms were found in 74% of the fruits sampled and they were internalized in the cores of 40%
of fruits tested.
38 E. coli 0157:H7 was not recovered from any fruit samples. No E. coli 0157:H7 or
Salmonella spp. were found in 202 mushroom and 206 alfalfa sprout samples in the United States, but
one sprout sample was positive for L. monocytogenes.
52 In another study, E. coli 0157:H7 containing
a mutant of GFP (EGFP) which produced a longer wavelength than GFP was used as a marker to
determine attachment to produce, and the results revealed preferential attachment to damaged tissues
of green leaf lettuce and tomatoes, in contrast to intact tissue and stem surfaces.
53 The E. coli cells
were tracked by confocal scanning laser microscopy. The internalization of a green fluorescent proteincontaining strain of E. coli 0157:H7 from manure-contaminated soil and irrigation water in lettuce has
been demonstrated. In this study, the investigators used confocal and epifluorescence microscopy to
demonstrate the distribution of the bacterial cells throughout the root system of the edible parts of the
lettuce.
44 With seed inocula of 10
4 cfu/ml of the pathogen in soil, lettuce seedlings were not invaded,
but they were invaded by the pathogen at levels of 10
6 and 10
8 cfu/g.
A bioluminescent-labeled E. coli was assessed on growing spinach plants and the organism became
internalized in root tissue and to a lesser extent within the hypocotyls.
58 When added to soil with seeds
and cultivated for 42 days, the bacterium could be cultivated from roots and leaves. Under hydroponic
conditions, the pathogen at a level of 10
2 or 10
3 cfu/ml of solution became internalized, and this process
appeared to occur more under hydroponic conditions than in soils.
59 Using bioluminescent-labeled
strains of E. coli and S. Montevideo, both became internalized on mung bean sprouts after the initial
24 h germinating period.
59 The use of 20,000 ppm sodium hypochlorite was not successful in freeing
sprouts of the pathogens. The inner tissues and stomata of cotyledons of radish sprouts grown from
seeds inoculated with E. coli 0157:H7 were internalized by this bacterium, which was not removed
by the surface treatment of hypocotyl with HgCl 2 .
21
The incidence and prevalence of nontuberculous Mycobacterium spp. in a number of fresh produce
and juice products in the United States were studied, and from a total of 121 products, 25 or 20.7%
yielded seven different mycobacterial species.
2 The produce included mushrooms, sprouts, broccoli,
lettuce, leeks, parsley, and apple juice. The most frequently isolated species was M. avium, which
accounted for 12 of the 29 identified isolates. Three isolates each of M. simian and gordonae; and two
of M. flavescens were identified. The natural occurrence of the so-called fast growing mycobacteria
on fresh produce is not surprising since these organisms are part of the stable microbiota of farm soils.
Due to their slow growth rate relative to that of the soil zymogenous biota, their internalization of
produce or seed sprouts seems unlikely.
The internalization of S. Enteritidis in immature and ripened mangoes has been demonstrated. The
immersion of these fruits in 21
◦ C water containing the pathogen (which contained a green fluorescent
protein) revealed that it was internalized in 80% of the immature and 87% of the ripened mangoes.
34
The stem-end segment was more affected than other mango parts, and the pathogen was detected in
fruit pulp one week after incubation at temperatures of 10–30
◦ C.
A list of pathogens isolated from vegetables has been produced by Beuchat,
6 as well as a synopsis
of the model HACCP system for fresh-cut produce issued by the International Fresh-Cut Produce
Association.
Disease Outbreaks
A thorough review of outbreaks in Canada for the years 1981–1999 revealed that nine produce products were responsible for 18 outbreaks. The produce products were alfalfa sprouts (n = 5), raspberries
143
soil exposure.
41 From a study of 14 apple and pear orchards throughout the United States in 1999,
coliforms were found in 74% of the fruits sampled and they were internalized in the cores of 40%
of fruits tested.
38 E. coli 0157:H7 was not recovered from any fruit samples. No E. coli 0157:H7 or
Salmonella spp. were found in 202 mushroom and 206 alfalfa sprout samples in the United States, but
one sprout sample was positive for L. monocytogenes.
52 In another study, E. coli 0157:H7 containing
a mutant of GFP (EGFP) which produced a longer wavelength than GFP was used as a marker to
determine attachment to produce, and the results revealed preferential attachment to damaged tissues
of green leaf lettuce and tomatoes, in contrast to intact tissue and stem surfaces.
53 The E. coli cells
were tracked by confocal scanning laser microscopy. The internalization of a green fluorescent proteincontaining strain of E. coli 0157:H7 from manure-contaminated soil and irrigation water in lettuce has
been demonstrated. In this study, the investigators used confocal and epifluorescence microscopy to
demonstrate the distribution of the bacterial cells throughout the root system of the edible parts of the
lettuce.
44 With seed inocula of 10
4 cfu/ml of the pathogen in soil, lettuce seedlings were not invaded,
but they were invaded by the pathogen at levels of 10
6 and 10
8 cfu/g.
A bioluminescent-labeled E. coli was assessed on growing spinach plants and the organism became
internalized in root tissue and to a lesser extent within the hypocotyls.
58 When added to soil with seeds
and cultivated for 42 days, the bacterium could be cultivated from roots and leaves. Under hydroponic
conditions, the pathogen at a level of 10
2 or 10
3 cfu/ml of solution became internalized, and this process
appeared to occur more under hydroponic conditions than in soils.
59 Using bioluminescent-labeled
strains of E. coli and S. Montevideo, both became internalized on mung bean sprouts after the initial
24 h germinating period.
59 The use of 20,000 ppm sodium hypochlorite was not successful in freeing
sprouts of the pathogens. The inner tissues and stomata of cotyledons of radish sprouts grown from
seeds inoculated with E. coli 0157:H7 were internalized by this bacterium, which was not removed
by the surface treatment of hypocotyl with HgCl 2 .
21
The incidence and prevalence of nontuberculous Mycobacterium spp. in a number of fresh produce
and juice products in the United States were studied, and from a total of 121 products, 25 or 20.7%
yielded seven different mycobacterial species.
2 The produce included mushrooms, sprouts, broccoli,
lettuce, leeks, parsley, and apple juice. The most frequently isolated species was M. avium, which
accounted for 12 of the 29 identified isolates. Three isolates each of M. simian and gordonae; and two
of M. flavescens were identified. The natural occurrence of the so-called fast growing mycobacteria
on fresh produce is not surprising since these organisms are part of the stable microbiota of farm soils.
Due to their slow growth rate relative to that of the soil zymogenous biota, their internalization of
produce or seed sprouts seems unlikely.
The internalization of S. Enteritidis in immature and ripened mangoes has been demonstrated. The
immersion of these fruits in 21
◦ C water containing the pathogen (which contained a green fluorescent
protein) revealed that it was internalized in 80% of the immature and 87% of the ripened mangoes.
34
The stem-end segment was more affected than other mango parts, and the pathogen was detected in
fruit pulp one week after incubation at temperatures of 10–30
◦ C.
A list of pathogens isolated from vegetables has been produced by Beuchat,
6 as well as a synopsis
of the model HACCP system for fresh-cut produce issued by the International Fresh-Cut Produce
Association.
Disease Outbreaks
A thorough review of outbreaks in Canada for the years 1981–1999 revealed that nine produce products were responsible for 18 outbreaks. The produce products were alfalfa sprouts (n = 5), raspberries