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Physical and metabolic causes of sub-lethal damage in Listeria monocytogenes after long-term chilled storage at 4°C

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JOURNAL OF APPLIED MICROBIOLOGY 1999年第6期87卷 915-922页

作者： Dykes, GA MIRINZ Food Technol & Res Ltd Hamilton New Zealand

Cells of Listeria monocytogenes display sub-lethal injury when subjected to long-term chill-storage in a nutrient-poor environment. The physical and metabolic causes or sub-lethal injury to two meat (L61 and L62) and two clinical (L98 and L99) L. monocytogenes strains chill-stored (4 degrees C) for 4 weeks in phosphate-buffered saline at pH 7.0 and pH 5.5, and pH 5.5 in the presence of 0.3% potassium sorbate, were characterized. Causes of sub-lethal injury were determined by examining changes in the cell structure, leakage of nucleic acids and proteins from the cells, and cell recovery from injury in the presence of the metabolic inhibitors rifampicin, D-cycloserine, carbonyl cyanide m-chlorophenylhydrazone and chloramphenicol. Visible shrinkage of the cytoplasm and slight cell wall damage were apparent over the 4 week storage period by electron microscopy for all four strains and three storage conditions. By contrast, over the same storage period, only three of the strains (L62, L98 and L99) displayed slight leakage of cellular content in all three storage media, while one strain (L61) displayed greater leakage. The three strains also displayed similar storage media-dependent metabolic damage. For these strains, phosphate-buffered saline pH 5.5 caused the least damage and potassium sorbate, the most. Recovery experiments also indicated that at pH 5.5, the energy transduction system of these three strains remained undamaged, and that injury to the cell transcription machinery was greatest at pH 7.0. The fourth strain, L61, displayed less damage than the others but this was attributed to the death of the injured cell sub-population in this strain. In this study, damage to sub-lethally injured chill-stored L. monocytogenes was different from that caused by other agents, such as heat. Therefore, cells injured by chill-storage under starvation conditions may require novel protocols to assure their effective recovery.

关键词：缓冲剂培养基酶抑制剂/药理学食品微生物学氢离子浓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/生长和发育单核细胞增生利斯特菌/分离和提纯单核细胞增生利斯特菌/超微结构肉/微生物学致冷

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Combined action of S-carvone and mild heat treatment on Listeria monocytogenes Scott A

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JOURNAL OF APPLIED MICROBIOLOGY 2000年第2期89卷 296-301页

作者： Karatzas, AK Bennik, MHJ Smid, EJ Kets, EPW DLO ATO Agrotechnol Res Inst NL-6700 AA Wageningen Netherlands Wageningen Ctr Food Sci Wageningen Netherlands

The combined action of the plant-derived volatile, S-carvone, and mild heat treatment on the food-borne pathogen, Listeria monocytogenes, was evaluated. The viability of exponential phase cultures grown at 8 degrees C could be reduced by 1.3 log units after exposure to S-carvone (5 mmol l(-1)) for 30 min at 45 degrees C, while individual treatment with S-carvone or exposure to 45 degrees C for 30 min did not result in a loss in viability. Other plant-derived volatiles, namely carvacrol, cinnamaldehyde, thymol and decanal, were also found to reduce the viability of L. monocytogenes in combination with the same mild heat treatment at concentrations of 1.75 mmol l(-1), 2.5 mmol l(-1), 1.5 mmol l(-1) and 2 mmol l(-1), respectively. These findings show that essential oil compounds can play an important role in minimally processed foods, and can be used in the concept of Hurdle Technology to reduce the intensity of heat treatment or other individual hurdles.

关键词：集落计数微生物食品保存/方法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/生长和发育微生物敏感性试验单萜类油类挥发/药理学植物油类/药理学萜类/药理学

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Growth of Listeria monocytogenes and Yersinia enterocolitica colonies under modified atmospheres at 4 and 8 °C using a model food system

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JOURNAL OF APPLIED MICROBIOLOGY 2000年第1期88卷 38-43页

作者： Harrison, WA Peters, AC Fielding, LM Univ Wales Inst Sch Appl Sci Food Safety Res Grp Cardiff CF23 9XR S Glam Wales

The growth of Listeria monocytogenes and Yersinia enterocolitica colonies was studied on solid media at 4 and 8 degrees C under modified atmospheres (MAs) of 5% O-2 : 10% CO2 : 85% N-2 (MA(1)), 30% CO2 : 70% N-2 (MA(2)) and air (control). Colony radius, determined using computer image analysis, allowed specific growth rates (mu) and the time taken to detect bacterial colonies to be estimated, after colonies became visible. At 4 degrees C both MAs decreased the growth rates of L. monocytogenes by 1.5- and 3.0-fold under MA(1) (mu = 0.02 h(-1)) and MA(2) (mu = 0.01 h(-1)), respectively, as compared with the control (mu = 0.03 h(-1)). The time to detection of bacterial colonies was increased from 15 d (control) to 24 (MA(1)) and 29 d (MA(2)). At 8 degrees C MA(2) decreased the growth rate by 1.5-fold (mu = 0.04 h(-1)) as compared with the control (mu = 0.06 h(-1)) and detection of colonies increased from 7 (control) to 9 d (MA(2)). At 4 degrees C both MAs decreased the growth rates of Y. enterocolitica by 1.5- and 2.5-fold under MA(1) (mu = 0.03 h(-1)) and MA(2) (mu = 0.02 h(-1)), respectively, as compared with the control (mu = 0.05 h(-1)). At 8 degrees C identical growth rates were obtained under MA(1) and the control (mu = 0.07 h(-1)) whilst a decrease in the growth rate was obtained under MA(2) (mu = 0.04 h(-1)). The detection of colonies varied from 6 (8 degrees C, aerobic) to 19 d (4 degrees C, MA(2)). Refrigerated modified atmosphere packaged foods should be maintained at 4 degrees C and below to ensure product safety.

关键词：二氧化碳/药理学冷温度集落计数微生物食品微生物学单核细胞增生利斯特菌/生长和发育氮/药理学氧/药理学致冷回归分析小肠结肠炎耶尔森菌/生长和发育

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Purification and some characteristics of enterocin ON-157, a bacteriocin produced by Enterococcus faecium NIAI 157

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JOURNAL OF APPLIED MICROBIOLOGY 2000年第1期88卷 81-89页

作者： Ohmomo, S Murata, S Katayama, N Nitisinprasart, S Kobayashi, M Nakajima, T Yajima, M Nakanishi, K Minist Agr Forestry & Fisheries Natl Inst Anim Ind Tsukuba Ibaraki 3050901 Japan Shizuoka Prefecture Toubu Livestock Hlth & Hyg Of Shizuoka Japan Tokyo Univ Agr Tokyo Japan Kasetsart Univ Fac Agroind Bangkok Thailand Asahi Chem Ind Co Ltd Chuo Ku Tokyo Japan

Bacteriocin-like activity (BLA) was screened in 690 strains of lactic acid bacteria isolated from plant materials such as silages and fermented vegetables. Among them, a strain identified as Enterococcus faecium NIAI 157 showed a clear BLA against the indicator strain, Ent. faecium IFO 13712. The proteinaceous nature and antimicrobial activity against closely related species strongly indicated that this BLA was a bacteriocin and was designated enterocin ON-157. The bacteriocin activity of this strain was extracellularly produced in the logarithmic growth phase in MRS broth and purified by ultrafiltration, ammonium sulphate precipitation and cation-exchange chromatography. Purified enterocin ON-157 had a molecular weight of approximately 2500 Da in SDS-PAGE analysis and was easily inhibited by treatment with alpha-amylase and proteolytic enzymes. Enterocin ON-157 had a bactericidal mode of action and inhibited the growth of the enterococci, Lactobacillus sake and Listeria monocytogenes. Enterococcus faecium NIAI 157 harboured two plasmids, 49.0 kb and 43.7 kb, and a variant missing a larger plasmid by curing with novobiocin lost the bactriocin activity.

关键词：抗菌药/药理学细菌素类/分离和提纯细菌素类/药理学电泳琼脂凝胶电泳聚丙烯酰氨凝胶屎肠球菌/化学屎肠球菌/药物作用屎肠球菌/代谢乳杆菌属/药物作用乳杆菌属/生长和发育单核细胞增生利斯特菌/药物作用单核细胞增生利斯特菌/生长和发育微生物敏感性试验乳链球菌素/药理学质粒

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Limitation of adhesion and growth of Listeria monocytogenes on stainless steel surfaces by Staphylococcus sciuri biofilms

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JOURNAL OF APPLIED MICROBIOLOGY 2000年第4期88卷 594-605页

作者： Leriche, V Carpentier, B AFSSA Lerpac F-94709 Maisons Alfort France SODIAAL Union Paris France

The adhesion and subsequent development of Listeria monocytogenes on stainless steel was studied in the absence and in the presence of a Staphylococcus sciuri biofilm. In the three growth media studied, the percentage of adherent cells was reduced to nearly the same extent by the presence of 1-day biofilms of Staph. sciuri for the two strains of L. monocytogenes studied. One-day biofilms of Staph. sciuri exhibited the same exopolysaccharide content per square centimetre, although they colonized from 3.5 to 35% of the stainless steel depending on the growth media. This suggests that extracellular substances rather than cell-to-cell interactions were involved in the decreased adhesion. After 3 days of culture, Staphylococcus biofilms prevented the adherent L. monocytogenes population from increasing within the biofilm, leading to an average logarithmic cfu difference of 0.9-2.7 between the pure and mixed culture. A competition for nutrients by Staph. sciuri was observed in one of the three media. A role for extracellular polysaccharides produced by the Staphylococcus biofilm in preventing the adhesion of L. monocytogenes and in modifying the balance existing between its planktonic and biofilm phase is hypothesized. A higher proportion of L. monocytogenes cells was observed in the planktonic phase in mixed cultures, suggesting that the extracellular substances produced by Staph sciuri biofilms and involved in the decreased adhesion of L. monocytogenes could modify the balance existing between planktonic and biofilm populations. In addition, co-cultures of L. monocytogenes and Staph. sciuri in broth showed competition for nutrients for Staph. sciuri in one of the three media.

关键词：细菌黏附/生理学细菌蛋白质类/代谢生物膜/生长和发育共同培养技术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/生理学聚合物多糖类细菌/代谢不锈钢葡萄球菌属/代谢

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The effect of culture growth phase on induction of the heat shock response in Yersinia enterocolitica and Listeria monocytogenes

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JOURNAL OF APPLIED MICROBIOLOGY 2000年第2期89卷 198-206页

作者： McMahon, CMM Byrne, CM Sheridan, JJ McDowell, DA Blair, IS Hegarty, T TEAGASC Natl Food Ctr Dublin 15 Ireland Univ Ulster Food Studies Res Unit Newtownabbey Co Antrim North Ireland TEAGASC Dept Stat Dublin 15 Ireland

The effect of culture growth phase on induction of the heat shock response in Yersinia enterocolitica and Listeria monocytogenes, was examined. Exponential or stationary preconditioned cultures were heat shocked and survivor numbers estimated using selective and overlay/resuscitation recovery techniques. The results indicate that prior heat shock induced increased heat resistance in both micro-organisms to higher heat treatments. Heat-shocked cells of each micro-organism were able to survive much longer than non-heat-shocked cells when heated at 55 degrees C. The size of the change in heat resistance between heat-shocked and non-heat-shocked cells was greatest for exponential cultures (X:X). Results indicate that the overall relative thermal resistance of each pathogen was dependent on cell growth phase. Stationary cultures (S:S) were significantly (P < 0.01) more thermotolerant than exponential cultures (X:X) under identical processing conditions. Under most conditions, the use of an overlay/resuscitation recovery medium resulted in higher D-values (P < 0.05) compared with a selective recovery medium.

关键词：集落计数微生物培养基热休克反应热温度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/生理学小肠结肠炎耶尔森菌/生长和发育小肠结肠炎耶尔森菌/生理学

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The growth and resistance to sodium hypochlorite of Listeria monocytogenes in a steady-state multispecies biofilm

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JOURNAL OF APPLIED MICROBIOLOGY 2000年第3期88卷 512-520页

作者： Norwood, DE Gilmour, A Queens Univ Belfast Dept Food Sci Food Microbiol Belfast BT9 5PX Antrim North Ireland Dept Agr No Ireland Belfast BT9 5PX Antrim North Ireland

A constant-depth film fermenter (CDFF) was used to culture a steady-state multispecies biofilm consisting of one strain each of Listeria monocytogenes, Pseudomonas fragi and Staphylococcus xylosus. These bacteria were initially grown together in a conventional chemostat to achieve a steady state before being inoculated into the CDFF over an 18-h period. A dilute tryptone soya broth (TSB) medium was supplied to the CDFF and the biofilm allowed to develop over a 28-d period. This mature biofilm was then subjected to increasing levels of sodium hypochlorite solution to measure any antimicrobial effect. The three organisms were seen to reach a steady state after 6 d in the chemostat before being transferred to the CDFF where the mature multispecies biofilm reached steady state at 17 d. Listeria monocytogenes in both planktonic and biofilm growth stabilized at 1.8 and 1.5%, respectively, of the total plate counts, while Ps. fragi and Staph. xylosus were the predominant organisms in the biofilm at 59% and 39.5%, respectively, of the total microbial population. Steady-state biofilms in the CDFF were exposed to increasing strengths of sodium hypochlorite;200, 500 and 1000 p.p.m. free chlorine, but a substantial two-log cycle drop in bacterial numbers was only achieved at 1000 p.p.m. free chlorine. In planktonic culture all three organisms were completely eliminated when exposed to 10 p.p.m. free chlorine for a 30-s period.

关键词：生物膜/药物作用生物膜/生长和发育生物反应器集落计数微生物抗药性微生物单核细胞增生利斯特菌/药物作用单核细胞增生利斯特菌/生长和发育假单胞菌属/药物作用假单胞菌属/生长和发育次氯酸钠/药理学葡萄球菌属/药物作用葡萄球菌属/生长和发育

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Physicochemical surface properties of five Listeria monocytogenes strains from a pork-processing environment in relation to serotypes, genotypes and growth temperature

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JOURNAL OF APPLIED MICROBIOLOGY 2000年第6期88卷 992-1000页

作者： Giovannacci, I Ermel, G Salvat, G Vendeuvre, JL Bellon-Fontaine, MN CTSCCV F-94700 Maisons Alfort France Agence Francaise Secur Sanit Aliments Unite Rech Hyg & Qual Prod Avicoles & Porcins Ploufragan France INRA Unite Rech Bioadhes & Hyg Mat Massy France

Physicochemical surface properties, related to electrostatic, van der Waals and Lewis acid-base interactions, of five Listeria monocytogenes strains isolated from pork-processing environments were determined after two subcultures at 37 degrees C and a final culture at three temperatures: 37, 10 and 4 degrees C. Three strains (Lm1, Lm114 and Lm191) were genetically related while two were unrelated (Lm25 and Lm74) according to ApaI-macrorestriction and pulsed-field gel electrophoresis (PFGE) typing. Listeria monocytogenes cell surfaces were generally negatively charged regardless of pH and tended to be hydrophilic due to a basic character. However, variable physicochemical surface properties of the five Listeria monocytogenes isolates were observed after growth at 37 degrees C. After growth at 10 degrees C, the three genetically related isolates exhibited similar surface properties and were slightly more hydrophilic and basic than the others. After growth at 4 degrees C, the five isolates displayed the same weak affinity for all kinds of solvents and low electrophoretic mobility values. A sharp decrease of temperature and subsequent growth of various Listeria monocytogenes strains resulted in loss of the physicochemical surface property variability, which may suggest the role of common chill adaptation mechanisms affecting surface properties.

关键词：屠宰场细菌黏附细菌分型技术细胞壁/化学聚类分析电泳凝胶脉冲场食品微生物学氢离子浓度酰亚胺酯类/分析单核细胞增生利斯特菌/化学单核细胞增生利斯特菌/遗传学单核细胞增生利斯特菌/生长和发育肉/微生物学溶剂静电学表面特性猪温度动物

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Solubility and antimicrobial efficacy of protamine on Listeria monocytogenes and Escherichia coli as influenced by pH

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JOURNAL OF APPLIED MICROBIOLOGY 2000年第6期88卷 1049-1055页

作者： Hansen, LT Gill, TA Dalhousie Univ DalTech Dept Food Sci & Technol Halifax NS B3J 2X4 Canada

The antimicrobial efficacy of protamine on Listeria monocytogenes and Escherichia coli was evaluated at concentrations from 50 to 10 000 mu g ml(-1) and pH levels from 5.5 to 8.0. The minimum inhibitory concentrations decreased with increasing pH. Protamine inhibited E. coli at all pH values while L. monocytogenes was inhibited at pH 6.5 and above. The antimicrobial efficacy of protamine decreased in the presence of negatively charged gelatine B but remained almost unchanged with addition of the positively charged gelatine A. Binding studies showed that the amount of protamine adsorbed to culture media components in tryptic soy broth and bacterial cells increased with increasing pH values. The increased efficacy of protamine at alkaline pH may be explained on the basis of an increase in electrostatic affinity for the cell surface of target cells. E. coli produced a protamine-degrading enzyme, however, was still susceptible to protamine.

关键词：抗菌药/药理学培养基剂量效应关系药物大肠杆菌/药物作用大肠杆菌/生长和发育大肠杆菌/代谢氢离子浓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/生长和发育单核细胞增生利斯特菌/代谢微生物敏感性试验鱼精蛋白类/药理学蛋白质结合

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The growth of Listeria monocytogenes in cheese packed under a modified atmosphere

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JOURNAL OF APPLIED MICROBIOLOGY 2000年第1期88卷 52-57页

作者： Whitley, E Muir, D Waites, WM Brackenhurst Coll Newark NG25 0QF Notts England Univ Nottingham Loughborough Leics England Hannah Res Inst Ayr KA6 5HL Scotland

The effect of Modified Atmosphere Packaging (MAP) on the growth of Listeria monocytogenes in mould ripened cheeses was studied at refrigeration temperatures (2-8.3 degrees C) over a storage period of 6 weeks. Control experiments in cling film with no atmospheric modification produced a lag time before growth of up to 1 week and rapid subsequent growth. MAP with a CO2 concentration of less than 20% allowed growth to occur but when O-2 was incorporated;the lag time was reduced from 3 to 2 weeks and subsequent growth was also faster, producing an increase in cell numbers of 1.4 log cycles over the incubation period. N-2-MAP in the absence of O-2 increased the lag time to 3 weeks and slowed growth, while the inclusion of CO2 extended the lag to 3 weeks and slowed subsequent growth even more. In MAP with 80:10:10 (v/v/v) N-2:CO2:O-2, there was a lag period of 2-3 weeks before growth of L. monocytogenes occurred, while the total viable aerobic count (TVAC) decreased by 2-3 log cycles and the total Lactobacillus count showed little change. It was concluded that MAP was not suitable for preventing the growth of L. monocytogenes in such cheeses.

关键词：二氧化碳/药理学干酪/微生物学冷温度食品包装氢离子浓度单核细胞增生利斯特菌/生长和发育氮/药理学氧/药理学

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