Comparison of Four Procedures to Detect Listeria spp. in Foods

Heisick, Judy E.; Harrell, Fannie; Peterson, Eugene H.; McLaughlin, S.H.; Wagner, Dean E.; Wesley, Irene V.; Bryner, John H.

doi:10.4315/0362-028x-52.3.154

Cited by 34 publications

(12 citation statements)

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“…Published studies have examined the incidence and fate of L. monocytogenes in fresh vegetables (Beuchat, 1996;Petran et al, 1988). In two surveys of fresh market produce, L. monocytogenes was detected on 27.1% (Heisick et al, 1989a) and 25.8% (Heisick et al, 1989b) of potato samples tested. The organism has been isolated from the feces of animals (Weis and Seeliger, 1975) which may be a potential source of fresh produce contamination (Schlech et al, 1983).…”

Section: Introductionmentioning

confidence: 99%

Control of Listeria monocytogenes in Vacuum‐Packaged Pre‐Peeled Potatoes

Juneja¹,

Martin²,

Sapers³

1998

Journal of Food Science

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Growth of Listeria monocytogenes on the surface of fresh peeled potatoes, treated with sulfite or a commercial browning inhibitor (CBI), packaged under vacuum and stored at 4, 15 and 28°C was determined. At 4°C, L. monocytogenes did not grow in all treated potatoes even after 21 days. At 15°C, L. monocytogenes grew to 7 log 10 CFU/g within 12 days in the potatoes treated with sulfite or CBI. At 28°C, L. monocytogenes population was greater than 3 log 10 CFU/g by 24 h in all samples regardless of treatment. Sulfites or a CBI appeared to provide a measure of safety in pre-peeled potatoes packaged under vacuum when kept at proper refrigeration temperatures.Key Words: Listeria monocytogenes, browning inhibitor, potatoes for inoculum preparation prior to all experiments. Preparation of inoculumInoculated BHI was incubated at 37°C for 18h. The cells were harvested by centrifugation at room temperature for 10 min at 7,700 ∞ g, the cell pellet washed twice, resuspended and diluted in sterile 0.1% peptone water (w/v) (Difco). Sample preparation and inoculationFresh, raw Russet potatoes ( 80-110g each) were obtained from a commercial potato distributor. Potatoes were abrasionpeeled for 2 min with a Vegetable Peeler (Model A1-15, Toledo Scale Co., Toledo, OH) and held under water up to 30 min prior to treatment. Potatoes received one of 4 different treatments: (1) immersion in 1.2% (w/ v) sodium bisulfite for 2 min, (2) immersion in a 2% (w/v) solution of a commercial browning inhibitor (CBI) consisting of citric acid, ascorbic acid, sodium acid pyrophosphate and L-cysteine HCl for 5 min, (3) immersion in a 2% solution of the CBI for 5 min, followed by a brief rinse with tap water (30 mL rinse/kg potatoes), or (4) untreated control. Residual sulfite levels were determined in uninoculated control samples by the Optimized Monier-Williams Method (Hillary et al., 1989).Duplicate sets of two potatoes ( 100g each) were weighed into filter stomacher bags (SFB-0410; Spiral Biotech., Bethesda, MD) and inoculated with 1 mL of an appropriate dilution of L. monocytogenes cell suspension to yield a final concentration of 1-2 log 10 CFU/g. Thereafter, the bags were manually massaged to ensure even distribution of organisms on the surface of the potatoes. The bags were placed in 17.8 ∞ 20.3 cm barrier bags (Koch Model 01 46 09, Kansas City, MO). The oxygen transmission rate (by manufacturer) of the nylon/polyethylene film was 54.2 cc/m 2 in 24h measured at 24°C and 75% relative humidity. The bags were evacuated to a negative pressure of 1000 millibars and heat sealed using a Multivac Model A300/ 16 gas packaging machine (Germany). Two replications were performed for each treatment. For each replicate experiment, two bags of each treatment were prepared for each sampling time and temperature. Controls consisted of inoculated, untreated potatoes stored under vacuum.

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Section: Introductionmentioning

confidence: 99%

Control of Listeria monocytogenes in Vacuum‐Packaged Pre‐Peeled Potatoes

Juneja¹,

Martin²,

Sapers³

1998

Journal of Food Science

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“…Others have isolated it from corn and grain plants, lettuce, parsley, and watercress (46, 58). Many studies have indicated that L. monocytogenes can grow or survive on fresh or processed produce, including asparagus, broccoli, cauliflower, and leafy vegetables, and it has been isolated from many prepared salads (9,16,22,28,35). The only types of produce that seem to inhibit growth or kill L. monocytogenes are tomatoes and carrots (11,42).…”

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confidence: 99%

Attachment of Listeria monocytogenes to Radish Tissue Is Dependent upon Temperature and Flagellar Motility

Gorski

Palumbo

Mandrell

2003

Appl Environ Microbiol

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Outbreaks of listeriosis and febrile gastroenteritis have been linked to produce contamination by Listeria monocytogenes. In order to begin to understand the physiology of the organism in a produce habitat, the ability of L. monocytogenes to attach to freshly cut radish tissue was examined. All strains tested had the capacity to attach sufficiently well such that they could not be removed during washing of the radish slices. A screen was developed to identify Tn917-LTV3 mutants that were defective in attachment to radish tissue, and three were characterized. Two of the three mutations were in genes with unknown functions. Both of the unknown genes mapped to a region predicted to contain genes necessary for flagellar export; however, only one of the two insertions caused a motility defect. The third insertion was found to be in an operon encoding a phosphoenolpyruvate-sugar phosphotransferase system. All three mutants were defective in attachment when tested at 30°C; the motility mutant had the most severe phenotype. However, not all of the mutants were defective when tested at other temperatures. These results indicate that L. monocytogenes may use different attachment factors at different temperatures and that temperature should be considered an important variable in studies of the molecular mechanisms of Listeria fitness in complex environments.Listeria monocytogenes is a gram-positive pathogen that causes a multitude of symptoms, including septicemia, abortion, liver failure, and meningitis (50). When L. monocytogenes is not living as an intracellular invader, it can be isolated from the feces of animals as well as humans and from the soil, where it can survive as a saprophyte for 10 to 12 years. From these locations, it can contaminate the food supply in many ways. It can survive in sewage and enter the soil, where it may become associated with plants and/or farm animals before entering food-processing plants, grocery stores, and home refrigerators (2, 10). In all of these niches, L. monocytogenes can survive and even thrive, leading to contamination of foods and ingestion of the pathogen. L. monocytogenes is quite hardy under a variety of environmental stresses. It has been reported that it can grow at temperatures of between Ϫ0.4 and 50°C and withstand extremes of osmotic pressure, as evidenced by growth in 10% NaCl, and it displays a pH range of 4.3 to 9 (18, 21).While food contamination with L. monocytogenes is most often associated with smoked meats and dairy products, fresh produce has also been implicated in outbreaks and sporadic cases of listeriosis. Specific produce-related outbreaks of listeriosis and febrile gastroenteritis caused by L. monocytogenes have been associated with contaminated cabbage, corn, and lettuce and/or celery (8,30,51). In addition, this organism has caused the recall of vegetables, including red peppers, sprouts, and lettuce, and potato salad (4-7, 13). L. monocytogenes has been isolated from radishes, potatoes, cucumbers, and cabbage in surveys of produce from U.S. grocery s...

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“…Some of these tests have been applied to pathogens of a bovine origin, such as the Minitek GramPositive Set for Streptococcus (29), but with no success because of a lack of information on veterinary pathogens in the database. Enzyme-linked immunosorbent assay methods exist for S. aureus detection in cases of BM (10), but the antibody titer does not correlate with the amount of infecting bacteria (10,15). Other enzyme-linked immunosorbent assays were developed to screen milk for contamination with Listeria organisms (1,9).…”

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Development of a Rapid and Sensitive Test for Identification of Major Pathogens in Bovine Mastitis by PCR

et al. 2001

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Bovine mastitis is the most important source of loss for the dairy industry. A rapid and specific test for the detection of the main pathogens of bovine mastitis is not actually available. Molecular probes reacting in PCR with bacterial DNA from bovine milk, providing direct and rapid detection of Escherichia coli, Staphylococcus aureus, Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus parauberis, and Streptococcus uberis, have been developed. Two sets of specific primers were designed for each of these microorganisms and appeared to discriminate close phylogenic bacterial species (e.g., S. agalactiae and S. dysgalactiae). In addition, two sets of universal primers were designed to react as positive controls with all major pathogens of bovine mastitis. The sensitivities of the test using S. aureus DNA extracted from milk with and without a pre-PCR enzymatic lysis step of bacterial cells were compared. The detection limit of the assay was 3.125 ؋ 10 2 CFU/ml of milk when S. aureus DNA was extracted with the pre-PCR enzymatic step compared to 5 ؋ 10 3 CFU/ml of milk in the absence of the pre-PCR enzymatic step. This latter threshold of sensitivity is still compatible with its use as an efficient tool of diagnosis in bovine mastitis, allowing the elimination of expensive reagents. The two PCR tests avoid cumbersome and lengthy cultivation steps, can be performed within hours, and are sensitive, specific, and reliable for the direct detection in milk of the six most prevalent bacteria causing bovine mastitis.Bovine mastitis (BM) is an inflammation of the mammary gland, usually due to a microbial infection (28), which causes North American dairy producers to lose billions of dollars every year. These losses are primarily due to lower milk yields, reduced milk quality, and higher production costs. BM often becomes chronic, and it is important to identify quickly the new clinical cases in order to control infection in the herd. The bacteria responsible for BM can be classified as environmental (Escherichia coli, Streptococcus dysgalactiae, Streptococcus parauberis, and Streptococcus uberis) or contagious (Staphylococcus aureus and Streptococcus agalactiae) depending of their primary reservoir (environment versus infected mammary gland quarter) (11,25).The suitability of a detection method for routine diagnosis depends on several factors, such as specificity, sensitivity, expense, amount of time, and applicability to large numbers of milk samples. The most common but unspecific method (2) to identify potential chronic infections is a somatic cell count: the California Mastitis Test in field conditions and the automated method in the diagnosis laboratory. Currently, the method of identification of the mammary gland pathogens is by in vitro culture, which provides the "gold standard"; however, this technique is labor-intensive and time-consuming. Two other problems can be encountered when these methods of identification are used: first, 2 to 3 days are required to grow, isolate, and identify the pathoge...

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Comparison of Four Procedures to Detect Listeria spp. in Foods

Cited by 34 publications

References 0 publications

Control of Listeria monocytogenes in Vacuum‐Packaged Pre‐Peeled Potatoes

Control of Listeria monocytogenes in Vacuum‐Packaged Pre‐Peeled Potatoes

Attachment of Listeria monocytogenes to Radish Tissue Is Dependent upon Temperature and Flagellar Motility

Development of a Rapid and Sensitive Test for Identification of Major Pathogens in Bovine Mastitis by PCR

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