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Development and evaluation of a 24-hour method for the detection and quantification of Listeria monocytogenes in meat products

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JOURNAL OF FOOD PROTECTION 2000年第3期63卷 347-353页

作者： Carroll, SA Carr, LE Mallinson, ET Lamichanne, C Rice, BE Rollins, DM Joseph, SW Univ Maryland Dept Mol Genet & Cell Biol College Pk MD 20742 USA Univ Maryland Dept Biol Resources Engn College Pk MD 20742 USA Univ Maryland Dept Vet Med College Pk MD 20742 USA Univ Maryland VPI UMD Reg Coll Vet Med College Pk MD 20742 USA Kirkegaard & Perry Labs Gaithersburg MD USA USN Enter Dis Program Med Res Ctr Bethesda MD 20889 USA

A 24-h filter monitor-based test, Listeria-SELeCT, has been developed to quantify Listeria monocytogenes organisms in meat samples with a sensitivity of less than or equal to 1.0 CFU/g. The technique comprises a filter monitor-based system and a colony lift immunoassay to identify and enumerate the target organism. Meat homogenates were centrifuged and the eluate was filtered to trap and immobilize the microorganisms on the filter. Fraser broth was then added to the filter apparatus to allow the organisms to become established overnight and to inhibit contaminants, after which the filters were transferred onto Modified Oxford medium agar, a selective medium for L. monocytogenes. After 10 to 12 h, a colony lift immunoassay was used to confirm and enumerate suspect colonies on the filter. A correlation study between the Listeria-SELeCT method and the most probable number technique showed the Listeria-SELeCT to be considerably more accurate than the most probable number for quantitatively determining the number of viable organisms in meat samples. Because of ease and speed of testing, the Listeria-SELeCT system also provided major advantages over the most probable number technology.

关键词：细菌学技术离心法/方法集落计数微生物培养基评价研究(主题) 过滤/方法免疫测定/方法单核细胞增生利斯特菌/生长和发育单核细胞增生利斯特菌/分离和提纯肉制品/微生物学敏感性与特异性动物

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Effects of iron and selenium on the production of catalase, superoxide dismutase, and listeriolysin O in Listeria monocytogenes

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JOURNAL OF FOOD PROTECTION 1999年第10期62卷 1206-1209页

作者： Fisher, CW Martin, SE Univ Illinois Dept Food Sci & Human Nutr Anim Sci Lab 486 Urbana IL 61801 USA

Listeria monocytogenes 19112, Scott A, and 10403S were grown in tryptic soy broth (TSB) and TSB supplemented with 25 to 100 mu g/ml of iron (Fe) and 0.5 to 2.5 mu g/ml selenium (Se) to examine the effects on catalase (CA), superoxide dismutase (SOD), and listeriolysin O (LLO) activities. Growth in TSB supplemented with Fe resulted in significant increases in CA, SOD, and LLO activities in all three strains when compared to growth in TSB. The addition of 0.5 mu g/ml Se to TSB resulted in significantly higher CA and LLO activities in L. monocytogenes 19112 but showed no effect on Scott A or 10403S. These results suggest that Fe plays a role in increasing the activities of CA, SOD, and LLO.

关键词：细菌毒素类过氧化氢酶/生物合成热休克蛋白质类/生物合成溶血素蛋白质类铁/药理学单核细胞增生利斯特菌/药物作用单核细胞增生利斯特菌/生长和发育单核细胞增生利斯特菌/代谢硒/药理学超氧化物歧化酶/生物合成

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Behavior of Listeria monocytogenes in pasteurized milk during fermentation with lactic acid bacteria

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JOURNAL OF FOOD PROTECTION 2000年第7期63卷 916-920页

作者： Pitt, WM Harden, TJ Hull, RR Charles Sturt Univ Sch Wine & Food Sci Wagga Wagga NSW 2678 Australia Ron Hull & Associates Mt Waverley Vic 3149 Australia

The behavior of Listeria monocytogenes in pasteurized milk during fermentation with starter and nonstarter lactic acid bacteria was investigated. Pasteurized milk was co-inoculated with approximately 10(4) CFU/ml of L. monocytogenes and 10(6) CFU/ml of Lactococcus lactis, Lactococcus cremoris, Lactobacillus plantarum, Lactobacillus bulgaricus, or Streptococcus thermophilus. Inoculated milks were incubated at 30 degrees C or 37 degrees C for 24 to 72 h. Listeria monocytogenes survived and also grew to some extent during incubation in the presence of all starter cultures;however, inhibition ranged from 83 to 100% based on maximum cell populations. During incubation with L. bulgaricus and L. plantarum, L. monocytogenes was completely inactivated after 20 h and 64 h of incubation at 37 degrees C and 30 degrees C, respectively. The pH of the fermenting milks declined steadily throughout the fermentation periods and was approximately 4.2 at the conclusion of the experimental period regardless both of the starter culture and pathogen combination or the temperature of incubation.

关键词：发酵食品微生物学氢离子浓度乳乳球菌/生长和发育单核细胞增生利斯特菌/生长和发育乳/微生物学链球菌属/生长和发育动物人类

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Application of high hydrostatic pressure to eliminate Listeria monocytogenes from fresh pork sausage

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JOURNAL OF FOOD PROTECTION 1999年第5期62卷 480-483页

作者： Murano, EA Murano, PS Brennan, RE Shenoy, K Moreira, RG Texas A&M Univ Dept Anim Sci College Stn TX 77843 USA Texas A&M Univ Dept Agr Engn College Stn TX 77843 USA

Ground pork patties were inoculated separately with 10(9) CFU/g each of three strains of Listeria monocytogenes obtained from the National Animal Disease Center (NADC). Inoculated patties were packaged under vacuum and treated at 414 megapascals (60,000 lb/in(2)) for up to 60 min by high hydrostatic pressure (HHP). Survivors were determined by surface plating onto modified Oxford agar and trypticase soy agar with yeast extract, as well as by the most probable number method using Listeria enrichment broth. Average D values ranged from 1.89 to 4.17 min, depending on the strain, with the most virulent strain (reported by the NADC) having the highest D value. We tested the usefulness of applying a mild heat treatment at 50 degrees C, simultaneously with HHP, to lower these values. Average D values ranged from 0.37 to 0.63 min, depending on the strain. Thus, a 10-log(10) reduction could be achieved even in the most pressure-resistant strain of L. monocytogenes by a 6-min application of heat and HHP. Shelf life studies were also conducted, with spoilage levels reached after 5 days of storage at 4 degrees C for controls versus 28 days for treated samples. Sensory evaluation of uninoculated grilled patties showed that panelists could not distinguish between those treated by heat and HHP and untreated controls (P < 0.05). Thus, treatment by HHP in combination with mild heating can be used successfully to produce safer, longer-lasting fresh pork without affecting quality.

关键词：集落计数微生物食品处理和加工食品微生物学食品包装热温度流体静力压单核细胞增生利斯特菌/生长和发育单核细胞增生利斯特菌/分离和提纯肉制品/微生物学肉制品/标准猪真空动物

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LISTERIA-MONOCYTOGENES - SYNERGISTIC EFFECTS OF AMPICILLIN AND GENTAMICIN

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AMERICAN JOURNAL OF CLINICAL PATHOLOGY 1979年第6期72卷 974-977页

作者： AZIMI, PH KORANYI, K LINDSEY, KD Division of Infectious Diseases Children’s Hospital Medical Center of Northern California Oakland California

L. monocytogenes infections are most common in newborn infants and persons with impaired defense mechanisms. Although there are reports of successful treatment with ampicillin alone, there is uncertainty as to what regimen constitutes the most effective therapy. The in vitro synergism between ampicillin and gentamicin against L. monocytogenes was studied. Seven L. monocytogenes strains isolated from blood or CSF of infants and 3 control strains obtained from the Center for Disease Control were tested. Minimal inhibitory concentrations of ampicillin and gentamicin were determined in Todd-Hewitt broth with an inoculum of 105 organisms/ml. Killing curves were determined for ampicillin (6 .mu.g/ml), gentamicin (0.5 .mu.g/ml) and the combination of ampicillin (6 .mu.g/ml) plus gentamicin (0.5 .mu.g/ml). Incubation of approximately 107 organisms/ml with these concentrations of ampicillin and gentamicin caused no significant reduction in the viable bacterial population in 24 h. The combination was bactericidal in all 7 strains isolated from patients and 1 control strain. The ultimate test of the superiority of this combination to ampicillin alone probably must come from clinical studies. The synergistic and bactericidal effects of ampicillin with gentamicin may be desirable in treatment of newborns and patients with underlying disease.

关键词：氨苄西林/药理学培养基药物协同作用庆大霉素类/药理学单核细胞增生利斯特菌/药物作用单核细胞增生利斯特菌/生长和发育脑膜炎/血液脑膜炎/脑脊髓液脑膜炎/微生物学儿童人类婴儿新生

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Development and validation of a dynamic growth model for Listeria monocytogenes in fluid whole milk

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JOURNAL OF FOOD PROTECTION 1999年第2期62卷 170-176页

作者： Alavi, SH Puri, VM Knabel, SJ Mohtar, RH Whiting, RC Penn State Univ Dept Agr & Biol Engn University Pk PA 16802 USA Penn State Univ Dept Food Sci University Pk PA 16802 USA Purdue Univ Dept Agr & Biol Engn W Lafayette IN 47906 USA ARS Microbial Food Safety Res Unit USDA ERRC Philadelphia PA 19118 USA

Listeria monocytogenes, a psychrotrophic microorganism, has been the cause of several food-borne illness outbreaks, including those traced back to pasteurized fluid milk and milk products. This microorganism is especially important because it can grow at storage temperatures recommended for milk (less than or equal to 7 degrees C). Growth of L. monocytogenes in fluid milk depends to a large extent on the varying temperatures it is exposed to in the postpasteurization phase, i.e., during in-plant storage, transportation, and storage at retail stores. Growth data for L. monocytogenes in sterilized whale milk were collected at 4, 6, 8, 10, 15, 20, 25, 30, and 35 degrees C, Specific growth rate and maximum population density were calculated at each temperature using these data. The data for growth rates versus temperature were fitted to the Zwietering square root model. This equation was used to develop a dynamic growth model (i.e., the Baranyi dynamic growth model or BDGM) for L. monocytogenes based on a system of equations which had an intrinsic parameter for simulating the lag phase. Results from validation of the BDGM for a rapidly fluctuating temperature profile showed that although the exponential growth phase of the culture under dynamic temperature conditions was modeled accurately, the lag phase duration was overestimated. For an alpha(o) (initial physiological state parameter) value of 0.137, which corresponded to the mean temperature of 15 degrees C, the population densities were underpredicted, although the experimental data fell within the narrow band calculated for extreme values of alpha(o). The maximum relative error between the experimental data and the curve based on an average alpha(o) value was 10.42%, and the root mean square error was 0.28 log CFU/ml.

关键词：集落计数微生物培养基单核细胞增生利斯特菌/生长和发育乳/微生物学模型生物学结果可重复性温度动物

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Growth condition-related response of Listeria monocytogenes 412 to bacteriocin inactivation

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LETTERS IN APPLIED MICROBIOLOGY 2000年第1期31卷 68-72页

作者： Jydegaard, AM Gravesen, A Knochel, S Royal Vet & Agr Univ Dept Dairy & Food Sci DK-1870 Frederiksberg Denmark

Bacteriocin inactivation of Listeria monocytogenes 412 was studied as a function of growth phase. Cells were treated with nisin (300 IU ml(-1)) or pediocin (320 or 2560 AU ml(-1)) for 20 min at 30 degrees C. Inactivation with nisin or the low concentration of pediocin was growth phase dependent, with exponentially growing cells being more susceptible than stationary cells. No effect of growth phase was observed for the high pediocin concentration. Pediocin inactivation (320 AU ml(-1)) of L. monocytogenes 412 exposed to osmotic (6.5% NaCl) or low-temperature (5 degrees C) stress was investigated. Pediocin failed to inactivate osmotically stressed cultures and was unable to inhibit cold-stressed cells to the same degree as unstressed cells.

关键词：细菌素类/药理学冷温度单核细胞增生利斯特菌/药物作用单核细胞增生利斯特菌/生长和发育乳链球菌素/药理学渗透压氯化钠/药理学

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Growth control of Listeria monocytogenes on cold-smoked salmon using a competitive lactic acid bacteria flora

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JOURNAL OF FOOD PROTECTION 1999年第4期62卷 336-342页

作者： Nilsson, L Gram, L Huss, HH Tech Univ Denmark Danish Inst Fisheries Res Dept Seafood Res DK-2800 Lyngby Denmark

A Lactobacillus sake strain LKE5 and four strains of Carnobacterium piscicola were evaluated as biopreservation cultures to control the growth of Listeria monocytogenes on vacuum-packed. cold-smoked salmon stored at 5 degrees C. All five strains were antilisterial as live cultures in an agar diffusion assay. Cell-free supernatants of two strains of C. piscicola and L. sake LKE5 were also antilisterial because of the production of bacteriocins. The presence of high cell numbers of strains of C. piscicola had no influence on the sensory quality of cold-smoked salmon stored at 5 degrees C, but L. sake LKE5 caused strong sulfurous off-flavors and was rejected as a culture for biopreservation of cold-smoked salmon. A bacteriocin-producing strain of C. piscicola (A9b) initially caused a 7-day lag phase of L. monocytogenes, followed by a reduction in numbers of L. monocytogenes from 10(3) CFU/ml to below 10 CFU/ml after 32 days of incubation, coinciding with the detection of antilisterial compounds. The presence of a nonbacteriocin-producing strain of C. piscicola (A10a) prevented the growth of L. monocytogenes during the 32-day incubation. The growth of L monocytogenes was strongly repressed on cold-smoked salmon in the presence of C. piscicola A9b and A10a, respectively. The initial cell numbers of L. monocytogenes that were found on Oxford plates incubated at 25 degrees C reached low maximum cell counts of 10(4) and 2 x 10(3) after 14 and 20 days of storage in mixed culture with C. piscicola A9b and A10a.

关键词：抗生作用共同培养技术冷温度食品处理和加工食品微生物学食品包装食品保存革兰氏阳性菌/生长和发育单核细胞增生利斯特菌/生长和发育鲑/微生物学真空动物

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Inactivation of Escherichia coli O157:H7 and listeria monocytogenes on plastic kitchen cutting boards by electrolyzed oxidizing water

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JOURNAL OF FOOD PROTECTION 1999年第8期62卷 857-860页

作者： Venkitanarayanan, KS Ezeike, GOI Hung, YC Doyle, MP Univ Georgia Ctr Food Safety & Qual Enhancement Coll Agr & Environm Sci Griffin GA 30223 USA Univ Connecticut Dept Anim Sci Storrs CT 06269 USA

One milliliter of culture containing a five-strain mixture of Escherichia coli O157:H7 (similar to 10(10) CFU) was inoculated on a 100-cm(2) area marked on unscarred cutting boards. Following inoculation, the boards were air-dried under a laminar flow hood for 1 h, immersed in 2 liters of electrolyzed oxidizing water or sterile deionized water at 23 degrees C or 35 degrees C for 10 or 20 min;45 degrees C for 5 or 10 min;or 55 degrees C for 5 min. After each temperature-time combination, the surviving population of the pathogen on cutting boards and in soaking water was determined. Soaking of inoculated cutting boards in electrolyzed oxidizing water reduced E. coli O157:H7 populations by greater than or equal to 5.0 log CFU/100 cm(2) on cutting boards. However, immersion of cutting boards in deionized water decreased the pathogen count only by 1.0 to 1.5 log CFU/100 cm(2). Treatment of cutting boards inoculated with Listeria monocytogenes in electrolyzed oxidizing water at selected temperature-time combinations (23 degrees C for 20 min, 35 degrees C for 10 min, and 45 degrees C for 10 min) substantially reduced the populations of L. monocytogenes in comparison to the counts recovered from the boards immersed in deionized water. E coli O157:H7 and L. monocytogenes were not detected in electrolyzed oxidizing water after soaking treatment, whereas the pathogens survived in the deionized water used for soaking the cutting boards. This study revealed that immersion of kitchen cutting boards in electrolyzed oxidizing water could be used as an effective method for inactivating foodborne pathogens on smooth, plastic cutting boards.

关键词：集落计数微生物炊具和餐具消毒/方法电解大肠杆菌O157/生长和发育单核细胞增生利斯特菌/生长和发育氧化还原塑料温度水

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Nisin reduces the thermal resistance of Listeria monocytogenes Scott A in liquid whole egg

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JOURNAL OF FOOD PROTECTION 1999年第9期62卷 999-1003页

作者： Knight, KP Bartlett, FM McKellar, RC Harris, LJ Univ Guelph Dept Food Sci Guelph ON N1G 2W1 Canada Agr & Agri Food Canada Res Branch Food Res Program So Crop Protect & Food Res Ctr Guelph ON N1H 8J7 Canada

D-values (decimal reduction times) and z-values (increase in temperature required for a 1-log change in D-value) for Listeria monocytogenes Scott A were determined in liquid whole egg with nisin (0 or 10 mu g ml(-1)) and NaCl (0 or 10%) by a submerged glass ampoule procedure. Samples were plated onto nonselective agar at appropriate intervals, and D-values were determined using a modified biphasic logistic equation. Addition of NaCl increased D-values at all temperatures tested. The addition of nisin to unsalted liquid whole egg resulted in a rapid 4-log reduction in viable counts within the first hour. Nisin significantly (P less than or equal to 0.05) decreased D-values at lower (<58 degrees C) temperatures in both unsalted and salted liquid whole egg but had little effect on the D-values at current minimum U.S, and Canadian pasteurization temperatures (60 degrees C without NaCl;63 degrees C with NaCl). However, when nisin was added 2 h prior to heat treatment, D-values were significantly (P less than or equal to 0.05) reduced at these temperatures. Inhibitory levels of nisin were detected in the liquid whole egg postpasteurization. Nisin could have a favorable impact on the control of L. monocytogenes in pasteurized liquid egg products.

关键词：抗菌药/药理学鸡培养基蛋类/微生物学食品微生物学食品防腐剂/药理学热温度单核细胞增生利斯特菌/药物作用单核细胞增生利斯特菌/生长和发育乳链球菌素/药理学氯化钠/药理学动物

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