Natural and Experimental Enteric Pathogen Contamination of Insects




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Natural and Experimental Enteric Pathogen Contamination of Insects
(last updated 9/21/2011)



Two tables are included within this file:

1) a table detailing studies where insects captured under natural conditions were assayed for the presence of pathogens; and

2) a table detailing studies where insects were experimentally exposed to enteric pathogens and examination of the fate of those pathogens
Reviews


  • Graczyk T,K., R. Knight, and L. Tamang. 2005. Mechanical transmission of human protozoan parasites by insects. Clin. Microbiol. Rev. 18:128-132.

  • Wales, A.D., J.J. Carrique-Mas, M. Rankin, B. Bell, B.B. Thind, and R.H. Davies. 2010. Review of the carriage of zoonotic bacteria by arthropods, with special reference to Salmonella in mites, flies and litter beetles. Zoonoses and Public Health 57:299-314.


Natural contamination

Alam, M.J. and L. Zurek. 2004. Association of Escherichia coli O157:H7 with houseflies on a cattle farm. Appl. Environ. Microbiol. 70:7578-7580.

House flies (Musca domestica L.) were collected from two sites on a cattle farm over a 4-month period. The prevalence of E. coli O157:H7 was 2.9 and 1.4% in house flies collected from feed bunks and a cattle feed storage shed, respectively. E. coli O157:H7 counts ranged from 3.0 x 101 to 1.5 x 105 CFU among the positive house flies. Large populations of house flies on cattle farms may play a role in the dissemination of E. coli O157:H7 among animals and to the surrounding environment. The dispersal range of house flies is usually 0.5 to 2 miles, although distances as great as 10 to 20 miles have been reported.



Caldwell, K.N., B.B. Adler, G.L. Anderson, P.L. Williams, and L.R. Beuchat. 2003. Ingestion of Salmonella enterica serotype Poona by a free-living nematode, Caenorhabditis elegans, and protection against inactivation by produce sanitizers. Appl. Environ. Microbiol. 69:4103-4110.

Protection of C. elegans-ingested Salmonella enterica serotype Poona occurred when sanitizers (20 ppm chlorine, 850 or 1200 ppm Sanova, 20 or 40 ppm Tsunami 200, or 2% acetic acid) were applied to lettuce.



Graczyk, T.K., R. Fayer, R. Knight, B. Mhangami-Ruwende, J.M. Trout, A.J. Da Silva, and N.J. Pieniazek. 2000. Mechanical transport and transmission of Cryptosporidium parvum oocysts by wild filth flies. Am. J. Trop. Med. Hyg. 63:178-183.

Wild filth flies were collected from traps left for 7-10 days in a barn with or without a calf shedding Cryptosporidium parvum Genotype 2. The oocysts of C. parvum transported on the flies’ exoskeletons and eluted from their droplets left on visited surfaces and were infectious for mice. The mean number of oocysts carried by a fly varied from 4 to 131 and the total oocyst number per collection varied from 56 to approximately 4.56 x 103. Molecular data showed that the oocysts shed by infected calves were carried by flies for at least 3 weeks.



Holt, P.S., C.J. Geden, R.W. Moore, and R.K. Gast. 2007. Isolation of Salmonella enterica serovar Enteritidis from houseflies (Musca domestica) found in rooms containing Salmonella serovar Enteritidis-challenged hens. Appl. Environ. Microbiol. 73:6030-6035.

48 h after houseflies released into rooms containing Salmonella-contaminated hens, 40 to 50% of flies were contaminated. At 4, 7 and 15 days postexposure, the % of flies positive for Salmonella were 50%, 70%, and 30%, respectively. An aqueous rinse failed to recover surface contamination, however, 0.5% detergent incorporated into the rinse, led to high recoveries of bacteria. Salmonella serovar Enteritidis was isolated routinely from the fly gut, on rare occasions from the crop, and never from the salivary gland. Force feeding hens contaminated flies resulted in gut colonization of a third of the birds; however, release of contaminated flies into a room of uncontaminated chickens failed to result in colonization of any of the subject birds.



Kopanic, R.J., Jr., B.W. Sheldon, and C.G. Wright. 1994. Cockroaches as vectors of Salmonella: Laboratory and field trials. J. Food Prot. 57:125-132.

American cockroaches sampled at a commercial poultry feed mill and hatchery.

11.1% of 45 feed mill and 17.8% of 45 hatchery cockroach samples were positive for S. Typhimurium.


Lacharme-Lora, L., S.E. Perkins, T.J. Humphrey, P.J. Hudson, and V. Salisbury. 2009. Use of bioluminescent bacterial biosensors to investigate the role of free-living helminthes as reservoirs and vectors of Salmonella. Environ. Microbiol. Rept. 1:198-207.

Inside helminthes, Salmonella exhibited enhanced survival when exposed to UV irradiation.



Olsen, A.R.and T.S. Hammack. 2000. Isolation of Salmonella spp. from the housefly Musca domestica L., and the dump fly, Hydrotaea aenescens (Wiedemann) (Diptera: Muscidae) at caged-layer houses. J. Food Prot. 63:958-960.

18.2% of 22 samples positive for Salmonella.

75% of positive samples were from housefly pooled samples and the remainder from the dump fly pooled samples


Skov, M.N., A.G. Spencer, B. Hald, L. Petersen, B. Nauerby, B. Carstensen, and M. Madsen. 2004. The role of litter beetles as potential reservoir for Salmonella enterica and thermophilic Campylobacter spp. between broiler flocks. Avian Dis. 48:9-18.

Beetles in broiler houses infrequently are positive for Salmonella. However, transmission of S. Indiana between two consecutive broiler flocks can coincide with the presence of Salmonella-contaminated beetles in the empty period, indicating that the beetles were the reservoir of S. Indiana between the two flocks. Concerning Campylobacter, the results suggest that beetles do not play a significant role as a reservoir of Campylobacter from one rotation to the next.



Skov, M.N., J.J. Madsen, C. Rahbek, J. Lodal, J.B. Jespersen, J.C. Jørgensen, H.H. Dietz, M. Chriél, and D.L. Baggesen. 2008. Transmission of Salmonella between wildlife and meat-production animals in Denmark. J. Appl. Microbiol. 105:1558-1568.

22.6% of 31 pooled insect samples were positive for Salmonella.



Sproston, E.L., M. Macrae, I.D. Ogden, M.J. Wilson, and N.J.C. Strachan. 2006. Slugs: Potential novel vectors of Escherichia coli O157. Appl. Environ. Microbiol. 72:144-149.

0.21% of 33 pooled field slug samples collected from an Aberdeenshire sheep farm were positive



Williams, A.P., P. Roberts, L.M. Avery, K. Killham, and D.L. Jones. 2006. Earthworms as vectors of Escherichia coli O157:H7 in soil and vermicomposts. FEMS Microbiol. Ecol. 58:54-64.

Anecic earthworms such as Lumbricus terrestris maintain deep vertical burrows whereas epigeic species such as Dendrobaena veneta inhabit surface organic layers. In this study, E. coli O157:H7 movement by L. terrestris was limited to a vertical plane, whereas movement by D. veneta was observed in the horizontal plane. Bacterial movement may be attributed to both worm excretion and to carriage on worm exterior; although the relative proportions attributable to each were not determined. The gut transit time in most earthworms is approximately 1-5 h and may prove sufficient to allow partial bacterial growth or for the resuscitation of VBNC bacteria. Thus, this study also suggested that earthworm digestion and presence may lead to temporarily higher numbers of E. coli O157:H7 in some substrates, especially soil. Despite this initial proliferation, long-term persistence of E. coli O157:H7 in soil and compost was unaffected by the presence of earthworms.





Experimental contamination

Reference

Expt. Details

Results

Ahmad, A., T.G. Nagaraja, and L. Zurek. 2007. Transmission of Escherichia coli O157:H7 to cattle by house flies. Prev. Vet. Med. 80:74-81.


Eight calves were individually exposed to house flies that were orally inoculated with a mixture of 4 strains of E. coli O157:H7 for 48 h.

On day 1 after the exposure, fecal samples of all 8 calves and drinking water samples of 5 of 8 calves exposed to inoculated flies tested positive for E. coli O157:H7. The concentration in feces ranged over time from detectable only by enrichment (<102) to up to 1.1 x 106 CFU/g. Feces of all calves remained positive for E. coli O157:H7 up to 11 days after the exposure and 62% were positive until the end of the experiment.

Amaravadi, L., M.S. Bisesi, and R.F. Bozarth. 1990. Vermial virucidal activity: Implications for management of pathogenic biological wastes on land. Biological Wastes 34:349-358.

5 to 6 earthworms added to a dish which contained cellulose saturated with a virus-buffer suspension at pH 7.0 containing virus (0.025 to 0.5 mg). Excreted castings were analyzed for structurally intact virus protein using enzyme-linked immunosorbent assay (ELISA) and virus infectivity by local lesion assays.

Reductions in the infectivity of both cowpea mosaic virus and tobacco mosaic (model agents) occurred when the earthworm (Eisenia fetida) were fed virus suggesting that earthworms may possess a virucidal enzyme system and, accordingly, may contribute to the inactivation of pathogenic viruses potentially associated with land application of sewage sludges and livestock manures.

Anderson, G.L., K.N. Caldwell, L.R. Beuchat, and P.L. Williams. 2003. Interaction of a free-living soil nematode, Caenorhabditis elegans, with surrogates of foodborne pathogenic bacteria. J. Food Prot. 66:1543-1549.

3-day-old adult worms placed on an agar medium having discrete areas containing cultures of E. coli, an avirulent strain of Salmonella Typhimurium, Listeria welshimeri, and Bacillus cereus.

Over 90% of worms entered colonies within 16 min after inoculation. Worms survived and reproduced with the use of nutrients derived from all test bacteria. Development was slightly slower for worms fed gram-positive bacteria than for worms fed gram-negative bacteria. Worms that fed for 24 h on bacterial lawns formed on tryptic soy agar dispersed bacteria over a 3-h period when they were transferred to a bacteria-free agar surface.

Anderson, G.L., S.J. Kenney, P.D. Millner, L.R. Beuchat, and P.L. Williams. 2006. Shedding of foodborne pathogens by Caenorhabditis elegans in compost-amended and unamended soil. Food Microbiol. 23:146-153.

Worms were fed on E. coli O157:H7 and then inoculated into soil and soil amended with turkey manure compost

E. coli O157:H7 was detected at 4 and 6 days post inoculation in compost-amended and unamended soil. Populations of C. elegans persisted in compost-amended soil for at least 7 days, but declined in unamended soil. Populations of E. coli O157:H7 in soil amended with turkey manure compost were significantly higher than those in unamended soil.

Caldwell, K.N., G.L. Anderson, P.L. Williams, and L.R. Beuchat. 2003. Attraction of a free-living nematode, Caenorhabditis elegans, to foodborne pathogenic bacteria and its potential as a vector of Salmonella Poona for preharvest contamination of cantaloupe. J. Food Prot. 66:1964-1971.

20 to 30 adult worms were placed on the surface of K agar midway between a 24-h bacterial colony (7 strains of E. coli O157:H7; 8 serotypes of Salmonella, 6 strains of L. monocytogenes), uninoculated tryptic soy broth, or cantaloupe juice. Numbers of worms migrating to the respective areas were counted.
Adult worms that had been immersed in a suspension of Salmonella Poona were deposited 1 or 3 cm below the surface of soil on which a piece of cantaloupe rind was placed.

The nematode was attracted to colonies of all test pathogens and survived and reproduced within colonies for up to 7 days. C. elegans was not attracted to cantaloupe juice.
The presence of Salmonella Poona was evident more quickly on rinds positioned on soil beneath which C. elegans inoculated with Salmonella Poona was initially deposited than on rinds deposited on soil beneath which Salmonella Poona alone was deposited.

De Jesús, A.J., A.R. Olsen, J.R. Bryce, and R.C. Whiting. 2004. Quantitative contamination and transfer of Escherichia coli from foods by houseflies, Musca domestica L. (Diptera: Muscidae). Int. J. Food Microbiol. 93:259-262.

40-60 houseflies were transferred to a sterile cage containing E. coli-contaminated potato salad or sugar-milk solution (8 log CFU/g) or surface-contaminated steak. After 30 min, E. coli on the flies were enumerated.
Contaminated flies were transferred to a sterile jar and transfer to the surfaces of that jar was determined.

43%, 53%, and 62% of the flies had detectable E. coli (> 1.7 log CFU/fly) with geometric mean carriage of 2.9, 3.8 and 2.2 log CFU/fly following exposure to contaminated sugar/milk, steak, and potato salad, respectively.
Contaminated flies can cross contaminate other surfaces with approximately 0.001% of the original numbers in the contaminated source.

Fayer, R., J.M. Trout, E. Walsh, and R. Cole. 2000. Rotifers ingest oocysts of Cryptosporidium parvum. J. Eukaryot. Microbiol. 47:161-163.

10-20 rotifers were placed into 11-mm diameter wells containing 2 x 104 oocysts.

Rotifers of all six genera (Philodina, Monostyla, Epiphanes, Euchlanis, Brachionus, and Asplanchna) were observed ingesting oocysts. Euchlanis and Epiphanes were observed excreting boluses containing up to 8 oocysts; however, it was not determined whether rotifers digested or otherwise rendered oocysts nonviable.

Gibbs, D.S., G.L. Anderson, L.R. Beuchat, L.K. Carta, and P.L. Williams. 2005. Potential role of Diploscapter sp. strain LKC25, a bacterivorous nematode from soil, as a vector of food-borne pathogenic bacteria to preharvest fruits and vegetables. Appl. Environ. Microbiol. 71:2433-2437.

A suspension of Diploscapter sp. strain LKC25, containing 25 to 50 worms, was placed on the surface of a tryptic soy agar plate such that it was equidistant from sites which had been inoculated with one of 4 bacteria: E. coli O157:H7, S. enterica, L. monocytogenes, or E. coli. The plate was incubated at 21°C for up to 24 h and location of the worms on the surface monitored by a computer-captured image technique.

85% of the worms had migrated to bacterial colonies of E. coli O157:H7, Salmonella enterica serotype Poona, and Listeria monocytogenes that were initially placed 0.5 to 1 cm and within 24 h, more than 90% of the worms were embedded in colonies. When these exposed worms were added to soil or a mixture of soil and composted turkey manure, the worms were capable of shedding the pathogenic bacteria into the soil.

Gourabathini, P., M.T. Brandl, K.S. Redding, J.H. Gunderson, and S.G. Berk. 2008. Interactions between food-borne pathogens and protozoa isolated from lettuce and spinach. Appl. Environ. Microbiol. 74:2518-2525.

Initial # of protozoan cells/ml ranged from 2.0 to 4.3 x 103 cells/ml and were suspended in Tris-buffered saline solution along with the pathogen that had been grown for 24-h and centrifuged.

Distribution of types of protozoa among produce samples was heterogeneous containing flagellates, amoebae, and ciliates. Vesicles were produced by Glaucoma sp. with Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes, although L. monocytogenes resulted in the smallest number per ciliate. Vesicle production was observed also during grazing of Tetrahymena on E. coli O157:H7 and S. enterica but not during grazing on L. monocytogenes, in vitro and on leaves. Such vesicles would only be produced when the surface of produce is wet in order to enable Tetrahymena to graze by filter feeding on bacteria that are free in the water film on the plant surface. These conditions may be met in the preharvest environment during dew, rain, or overhead irrigation. 4 h after addition of spinach extract, the bacteria multiplied and escaped the vesicles. In contrast, Colpoda steinii and the amoeba did not produce vesicles from any of the enteric pathogens, nor were pathogens trapped within their cysts.

Huamanchay, O., L. Genzlinger, M. Iglesias, and Y.R. Ortega. 2004. Ingestion of Cryptosporidium oocysts by Caenorhabditis elegans. J. Parasitol. 90:1176-1178.

Between 100 and 200 adult nematodes were placed on K-agar plates with 2 x 106 fluorescein isothiocyanate-tagged C. parvum oocysts. After specific incubation times, worms were washed and observed by UV and differential interference contrast (DIC) microscopy.

70 to 85% of worms ingested between 0 and 500 oocysts after 1 and 2 h incubation with oocysts. Most of the nematodes ingested between 101 and 200 oocysts after 2 h. Intact oocysts and empty shells were excreted by nematodes. Adult C. elegans containing C. parvum kept in water were infective for mice. Cyclospora oocysts were not ingested by C. elegans.

Janisiewicz, W.J., W.S. Conway, M.W. Brown, G.M. Sapers, P. Fratamico, and R.L. Buchanan. 1999. Fate of Escherichia coli O157:H7 on fresh-cut apple tissue and its potential for transmission by fruit flies. Appl. Environ. Microbiol. 65:1-5.

Ten fruit flies were put in a chamber and allowed to feed on a filter paper soaked in a suspension of E. coli ATCCF-11775 at 8 x 108 CFU/ml in 20% apple juice. Fruit flies were sampled after 2, 6, 24 and 48 h.

Fruit flies were easily contaminated externally and internally with E. coli after contact with the bacterium source. The flies transmitted this bacterium to uncontaminated apple wounds.

Kenney, S.J., G.L. Anderson, P.L. Williams, P.D. Millner, and L.R. Beuchat. 2005. Persistence of Escherichia coli O157:H7, Salmonella Newport, and Salmonella Poona in the gut of a free-living nematode, Caenorhabditis elegans, and transmission to progeny and uninfected nematodes. Int. J. Food Microbiol. 101:227-236.

Worms were fed for 3 h at 20°C on a lawn of E. coli O157:H7, S. Newport, or S. Poona. Worms were incubated at 4, 20 or 37°C for up to 5 days. At temperatures of 4 or 20°C, incubation conditions also varied relative humidity (33%, 75%, or 98%).

Initial populations within worms (2.8 to 3.2 log CFU/worm) significantly increased by up to 2.93 log CFU/worm within 1 day at 20°C on K agar and remained constant for an additional 4 days. When worms were placed on Bacto agar, populations of ingested pathogens remained constant at 4°C, decreased significantly at 20°C, and increased significantly at 37°C within 3 days. Fewer cells of the pathogens survived incubation at 33% relative humidity compared to higher relative humidities. S. Newport was isolated from C. elegans two generations removed from exposure to the pathogen.

Kenney, S.J., G.L. Anderson, P.L. Williams, P.D. Millner, and L.R. Beuchat. 2006. Migration of Caenorhabditis elegans to manure and manure compost and potential for transport of Salmonella newport to fruits and vegetables. Int. J. Food Microbiol. 106:61-68.

Bovine manure and bovine manure compost inoculated with S. Newport (8.6 log CFU/g) were separately placed in the bottom of a glass jar and covered with a layer of soil (5 cm) inoculated (50 worms/g) or not inoculated with C. elegans. A piece of lettuce, strawberry, or carrot was placed on top of the soil before jars were sealed and held at 20°C for up to 10 days.

The pathogen was detected on lettuce, strawberry, and carrot within 1, 7 and 1 day, respectively, when initially present in bovine manure compost (detection by enrichment only, no attempts at enumeration)

Kopanic, R.J., Jr., B.W. Sheldon, and C.G. Wright. 1994. Cockroaches as vectors of Salmonella: Laboratory and field trials. J. Food Prot. 57:125-132.

2 ml of a S. typhimurium culture (~ 7-8 log CFU/ml) was inoculated onto five food pellets and then 20 cockroaches placed with these pellets in an environmental chamber. After 24, 48, 72, and 96 h, cockroaches were individually sampled.

American and Oriental cockroaches were contaminated twice as often as German cockroaches. Cross-contamination between infected and non-infected cockroaches was most frequent within 24 h of contamination event.

Mumcuoglu, K.Y., J. Miller, M. Mumcuoglu, M. Friger, and M. Tarshis. 2001. Destruction of bacteria in the digestive tract of the maggot of Lucilia sericata (Diptera: Calliphoridae). J. Med. Entomol. 38:161-166.

15-25 sterile maggots were transferred to a piece of gauze and fed for 2-15 h on 5 ml of brain heart broth containing 108 – 1010 gfp-labeled E. coli/ml. The maggots were viewed with a laser scanning confocal microscope.

Preliminary studies using a vital dye showed that food ingested by the maggots passed through their intestine within 1-1.5 h. It was shown that 66.7% of the crops, 52.8% of the midgets, 55.6% of the anterior hindguts, and 17.8% of posterior hindguts harbored living bacteria. With passage through the digestive tract, the majority of bacteria are killed; however, small numbers of bacteria may remain in the feces.

Petridis, M., M. Bagdasarian, M.K. Waldor, and E. Walker. 2006. Horizontal transfer of Shiga toxin and antibiotic resistance genes among Escherichia coli strains in house fly (Diptera: Muscidae) gut. J. Med. Entomol. 43:288-295.

House flies were immobilized and force fed suspensions of defined, donor strains of E. coli containing chloramphenicol resistance genes on a plasmid, or lysogenic bacteriophage-born Shiga toxin gene stx1. Recipient strains were E. coli lacking these mobile elements and genes but having rifampicin as a selectable marker.

Findings show that genes encoding antibiotic resistance or toxins will transfer horizontally among bacteria in the house fly gut via plasmid transfer or phage transduction.

Sasaki, T., M. Kobayashi, and N. Agui. 2000. Epidemiological potential of excretion and regurgitation by Musca domestica (Diptera: Muscidae) in the dissemination of Escherichia coli O157:H7 to food. J. Med. Entomol. 37:945-949.

House flies (adult, 6-8 old) fed on tryptic soy broth containing ~ 109 CFU/ml E. coli O157:H7 for 30 min.

The number of E. coli O157:H7 in an excreted droplet was ~ 104 1 h after bacterial feeding, > 1.8 x 105 3 h after feeding, and then drastically decreased after 24 h. E. coli O157:H7 persisted in the crop of house flies for at least 4 days.

Sela, S., D. Nestel, R. Pinto, E. Nemny-Lavy, and M. Bar-Joseph. 2005. Mediterranean fruit fly as a potential vector of bacterial pathogens. Appl. Environ. Microbiol. 71:4052-4056.

Adult flies (ca. 2 d old) were exposed to a 20% sucrose solution containing 6-9 log CFU/ml of E. coli.

Flies exposed to fecal material enriched with GFP-tagged E. coli were contaminated and were capable of transmitting E. coli to intact apples in a cage model system. Flies inoculated with E. coli harbored the bacteria for up to 7 days following contamination. Microscopic analysis suggested that the main organ involved in bacterial uptake is the fly's mouthparts.

Sproston, E.L., M. Macrae, I.D. Ogden, M.J. Wilson, and N.J.C. Strachan. 2006. Slugs: Potential novel vectors of Escherichia coli O157. Appl. Environ. Microbiol. 72:144-149.

Slugs were inoculated by placement in a petri dish with 5 ml of a nalidixic acid-resistant E. coli suspension (5.8-6.0 x 109 CFU/ml) and survival on slug surface and feces was measured.

Viable E. coli was detected on the slug surface for up to 14 days. Slugs that had been fed E. coli shed viable bacteria in their feces with numbers showing a short but statistically significant linear log decline. Further, it was found that E. coli persisted for up to 3 weeks in excreted slug feces.

Strother, K.O., C.Dayton Steelman, and E.E. Gbur. 2005. Reservoir competence of lesser mealworm (Coleoptera: Tenebrionidae) for Campylobacter jejuni (Campylobacterales: Campylobacteraeae). J. Med. Entomol. 42:42-47

Adult and larval beetles were swabbed with C. jejuni (9 log CFU/ml) and survival determined for up to 72 h.

Adult and larval beetles drank from a solution containing C. jejuni (9 log CFU/ml) and duration of internal carriage and fecal shedding determined for up to 144 h.

3-d-old chickens fed either 1 or 10 infected beetles and cloacal swabs tested periodically for Campylobacter.


C. jejuni was detected on the exterior of larval beetles for up to 12 h.

C. jejuni was detected in the interior of larvae for 72 h and from the feces of larvae for 12 h after exposure.

90% of the birds that consumed a single adult or larval beetle became Campylobacter-positive, whereas 100% of the birds that consumed 10 adults or larvae became positive.



Templeton, J.M., A.J. De Jong, P.J. Blackall, and J.K. Miflin. 2006. Survival of Campylobacter spp. in darkling beetles (Alphitobius diaperinus) and their larvae in Australia. Appl. Environ. Microbiol. 72:7909-7911.

Beetles were either sprayed with a Campylobacter culture (2.6 x 108 CFU/ml) or allowed to feed for 24 h on an apple (soaked in the Campylobacter culture for 20 min). Beetles were tested every 24 h for Campylobacter by direct culture and enrichment.

45% of 20 of spray-inoculated beetles were still positive after 72 h but only 5.6% of 18 beetles were positive after 96 h.

14% of 20 feed-inoculated beetles were positive after 48 h but were all negative at later time points.





Compiled by Marilyn Erickson, Center for Food Safety, University of Georgia Page

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