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Changes in viability and macromolecular content of long-term batch cultures of Salmonella typhimurium measured by flow cytometry

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JOURNAL OF APPLIED MICROBIOLOGY 2000年第1期89卷 90-99页

作者： Turner, K Porter, J Pickup, R Edwards, C Univ Liverpool Sch Biol Sci Liverpool L69 7ZB Merseyside England Inst Freshwater Ecol Windermere England

Exposure of many Gram-negative bacteria to prolonged starvation induces alternative programmes of gene expression, along with a transition into a dormant condition sometimes referred to as a viable non-culturable (VBNC) slate. Knowledge of how pathogenic species respond to nutrient limitation is therefore important for their detection and dissemination. This study used flow cytometry, coupled with fluorescent dyes for viability and macromolecular content, to study the responses of the pathogen Salmonella typhimurium to prolonged batch culture. Statistical analysis of the flow cytometric data, together with total and culturable cell counts, failed to demonstrate a VBNC state in this pathogen, contrary to reports from other workers. Analysis of rRNA and protein content identified a small proportion of cells in 110 day-old cultures that represented an active sub-population. This observation may provide an explanation for the long-term survival properties of this organism during prolonged exposure to nutrient limitation, as well as the high degree of heterogeneity observed in labelled cells.

关键词：细菌蛋白质类/代谢集落计数微生物培养基流式细胞术荧光染料模型生物学模型统计学普罗匹定 RNA 细菌/代谢 RNA 核糖体/代谢鼠伤寒沙门菌/生长和发育鼠伤寒沙门菌/代谢鼠伤寒沙门菌/生理学

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Modulation of Salmonella infection by the lectins of Canavalia ensiformis (Con A) and Galanthus nivalis (GNA) in a rat model in vivo

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JOURNAL OF APPLIED MICROBIOLOGY 2000年第4期88卷 720-727页

作者： Naughton, PJ Grant, G Bardocz, S Pusztai, A Rowett Res Inst Aberdeen Scotland

The plant lectins, Concanavalin A (Con A) and Galanthus nivalis agglutinin (GNA) have been prefed to rats for 3 d pre- and 6 d postinfection with Salmonella typhimurium S986 or Salm. enteritidis 857. Con A significantly increased numbers of Salm. typhimurium S986 in the large intestine and in faeces, and severely impaired growth of the rats, more severely than is the case of infection with Salmonella typhimurium alone. Con A had much less effect on rats infected with Salm. enteritidis 857 only showing a significant increase in numbers in the colon, accompanied by intermittent increases of Salmonella in the faeces during the study. GNA significantly reduced pathogen numbers in the lower part of the small bowel and the large intestine of rats infected with Salm. typhimurium S986 and significantly improved rat growth. GNA had little effect on infection by Salm. enteritidis 857 with slight decreases in Salmonella numbers in the small intestine and large intestine and transient increases in the faeces.

关键词：伴刀豆球蛋白A/投药和剂量伴刀豆球蛋白A/代谢粪便/微生物学雪花莲属外源凝集素类/投药和剂量外源凝集素类/代谢甘露糖结合凝集素类植物凝集素类沙门菌感染动物/微生物学肠炎沙门菌/生长和发育肠炎沙门菌/代谢肠炎沙门菌/生理学鼠伤寒沙门菌/生长和发育鼠伤寒沙门菌/代谢鼠伤寒沙门菌/生理学体重增长动物人类男(雄)性大鼠

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Comparison of methods for the recovery and detection of low levels of injured Salmonella in ice cream and milk powder

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LETTERS IN APPLIED MICROBIOLOGY 2000年第4期30卷 320-324页

作者： Baylis, CL MacPhee, S Betts, RP Campden & Chorleywood Food Res Assoc Chipping Campden GL55 6LD Glos England

This study compared the ability of four rapid methods and a standard cultural method to detect low levels of heat-injured cells of Salmonella typhimurium in ice cream and skimmed milk powder. The detection of Salmonella in samples contaminated with low levels (< 10 cfu 25 g(-1)) was significantly greater with the novel broth method than with the other methods (P less than or equal to 0.01). At contamination levels > 10 cfu 25 g(-1), there was no significant difference between the methods except for the novel broth method and a dipstick-based immunoassay (P less than or equal to 0.05). The novel broth method, S.P.R.I.N.T. Salmonella, which incorporates a specifically formulated peptone and Oxyrase(R) combination followed by the timed release of selective agents into the recovery medium, was shown to improve the rate of detection of low numbers of injured cells of Salmonella after 24 h enrichment.

关键词：细菌学技术集落计数微生物培养基乳制品/微生物学酶联免疫吸附测定乳/微生物学聚合酶链反应鼠伤寒沙门菌/生长和发育鼠伤寒沙门菌/分离和提纯动物

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Inhibition of Salmonella on poultry skin using protein- and polysaccharide-based films containing a nisin formulation

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JOURNAL OF FOOD PROTECTION 2000年第9期63卷 1268-1272页

作者： Natrajan, N Sheldon, BW N Carolina State Univ Dept Food Sci Raleigh NC 27695 USA

The objective of this study was to examine the use of protein- and polysaccharide-based films containing bacteriocin formulations for inhibiting salmonellae on fresh broiler skin. The lethality of the films containing a nisin-based formulation was determined against Salmonella Typhimurium-contaminated broiler drumstick skin samples coated with the film. In the first study, varying concentrations of nisin (0, 100, 300, and 500 mu g/ml) plus 3% citric acid, 5.0 mM EDTA, and 0.5% Tween 80 were incorporated into 0.5% calcium alginate films at a 20% level (wt/wt) and then applied to Salmonella Typhimurium(NAr)- contaminated skin samples (log(10) 5.0) at a 1:2 weight ratio (film:skin). Salmonella Typhimurium(NAr) skin population reductions ranged from 1.98 to 3.01 log cycles after a 72-h exposure at 4 degrees C. In comparison to the 0- and 100-mu g/ml nisin concentrations, significantly greater population reductions were achieved at nisin concentrations of 300 and 500 mu g/ml. In related studies, the 500-mu g/ml nisin formulation was incorporated into 0.75 and 1.25% agar gels and applied to contaminated broiler drumstick skin samples (log(10) 7.0). Salmonella Typhimurium(NAr) skin population reductions following a 96-h exposure at 4 degrees C were 1.8(1.25% agar gel) and 4.6-log cycles (0.75% agar gel). These results demonstrated that the inclusion of nisin-based treatments into either calcium alginate or agar gels that were subsequently applied to contaminated broiler drumstick skin yielded significant Salmonella Typhimurium(NAr) population reductions ranging between 1.8 to 4.6 log cycles after 72 to 96 h of exposure at 4 degrees C. The level of kill was affected by film type and gel concentration (i.e., gel network formation), exposure time, and nisin concentration.

关键词：琼脂藻酸盐抗菌药/药理学鸡/微生物学集落计数微生物/方法食品微生物学食品包装/标准葡糖醛酸己糖醛酸类乳链球菌素/药理学鼠伤寒沙门菌/药物作用鼠伤寒沙门菌/生长和发育鼠伤寒沙门菌/分离和提纯皮肤/微生物学时间因素动物

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Bactericidal effect of sodium chlorate on Escherichia coli O157:H7 and Salmonella typhimurium DT104 in rumen contents in vitro

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JOURNAL OF FOOD PROTECTION 2000年第8期63卷 1038-1042页

作者： Anderson, RC Buckley, SA Kubena, LF Stanker, LH Harvey, RB Nisbet, DJ USDA Agr Res Serv So Plains Agr Res Ctr Food & Feed Res Unit College Stn TX 77845 USA

Escherichia coli O157:H7 and Salmonella Typhimurium DT104 are important foodborne pathogens affecting the beef and dairy industries and strategies are sought to rid these organisms from cattle at slaughter Both pathogens possess respiratory nitrate reductase that also reduces chlorate to the lethal chlorite ion. Because most anaerobes lack respiratory nitrate reductase, we hypothesized that chlorate may selectively kill E. coli O157:1-17 and Salmonella Typhimurium DT104 but not potentially beneficial anaerobes. In support of this hypothesis, we found that concentrations of E. coli O157:H7 and Salmonella Typhimurium DT104 were reduced from approximately 1,000,000 colony forming units (CFU) to below our level of detection (less than or equal to 10 CFU) following in vitro incubation (24 h) in buffered ruminal contents (pH 6.8) containing 5 mM added chlorate. In contrast, chlorate had little effect on the most probable number (mean +/- SD) of total culturable anaerobes (ranging from 9.9 +/- 0.72 to 10.7 +/- 0.01 log(10) cells/ml). Thus, chlorate was bactericidal to E, coli O157:1-17 and Salmonella Typhimurium DT104 but not to potentially beneficial bacteria. The bactericidal effect of chlorate was concentration dependent (less at 1.25 mM) and markedly affected by pH (more bactericidal at pH 6.8 than pH 5.6).

关键词：氯酸盐类/药理学剂量效应关系药物大肠杆菌O157/药物作用大肠杆菌O157/生长和发育氢离子浓度硝酸还原酶硝酸盐还原酶类/代谢瘤胃/微生物学鼠伤寒沙门菌/药物作用鼠伤寒沙门菌/生长和发育动物牛

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Rapid detection of Salmonella typhimurium in chicken carcass wash water using an immunoelectrochemical method

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JOURNAL OF FOOD PROTECTION 2000年第8期63卷 1043-1048页

作者： Che, YH Li, YB Slavik, M Paul, D Univ Arkansas Dept Biol & Agr Engn Fayetteville AR 72701 USA Univ Arkansas Dept Poultry Sci Fayetteville AR 72701 USA Univ Arkansas Dept Chem & Biochem Fayetteville AR 72701 USA

An immunoelectrochemical method coupled with immunomagnetic separation was developed for rapid detection of Salmonella Typhimurium in chicken carcass wash water. Samples of chicken carcass wash water were inoculated with Salmonella Typhimurium at different cell numbers. Possible nonspecified inhibitors in the wash water were minimized by filtration and centrifugation. An approximately 9.4% toss of Salmonella cells was found after filtration (P < 0.01). The samples were mixed with anti-Salmonella-coated magnetic beads (ASCMB) and alkaline phosphatase-labeled anti-Salmonella (APLAS) to form ASCMB-Salmonella-APLAS conjugates. The conjugates were separated from the solution using a magnetic separator and then incubated with phenylphosphate substrate to produce phenol. The number of Salmonella was determined by measuring the phenol concentration using an amperometric tyrosinase carbon paste electrode in a flow injection analysis system. Under optimized parameters (1 mM MgCl2, 0.2 mu g/ml APLAS, and 1 mM phenylphosphate in pH 7.0 Tris buffer solution), Salmonella Typhimurium in chicken carcass wash water could be identified and enumerated within 2.5 h with a detection limit of 5 x 10(3) CFU/ml. A linear relationship on a log-log scale was found between Salmonella cell number and the peak current ratio for Salmonella concentrations ranging from 10(3) to 10(7) CFU/ml (R-2 = 0.963). The peak currents of multibacteria samples, containing Salmonella Typhimurium, Listeria monocytogenes, and Campylobacter jejuni, were not significantly different from Salmonella-only samples (P > 0.01).

关键词：生物传感技术鸡电化学/方法免疫酶技术/方法免疫磁化分离/方法线性模型鼠伤寒沙门菌/生长和发育鼠伤寒沙门菌/分离和提纯敏感性与特异性水微生物学动物

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Efficacy of nisin-coated polymer films to inactivate Salmonella Typhimurium on fresh broiler skin

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JOURNAL OF FOOD PROTECTION 2000年第9期63卷 1189-1196页

作者： Natrajan, N Sheldon, BW N Carolina State Univ Dept Food Sci Raleigh NC 27695 USA

Nisin is an antimicrobial peptide produced by the food-grade microorganism Lactococcus lactis subsp. lactis. This peptide inhibits many gram-positive bacteria, and when combined with chelating agents it inhibits gram-negative bacteria such as Salmonella sp. The efficacy of packaging films treated with nisin-containing formulations to reduce Salmonella contamination of fresh broiler drumstick skin and increase the refrigerated shelf life was investigated. Three films (5.1 cm(2)) of varying hydrophobicities (polyvinyl chloride [PVC], Linear low density polyethylene, nylon) were coated with one of three liquid formulations (pH 3.5 to 3.8) composed of 100 mu g/ml nisin and varying concentrations of citric acid, EDTA, and Tween 80. The treated films were applied either wet or dry to 5.1-cm(2) broiler drumstick skin samples inoculated with a nalidixic acid-resistant (NAr) strain of Salmonella Typhimurium. After incubation at 4 degrees C for 24 h the populations of surviving Salmonella Typhimurium(NAr) organisms were recovered from the skin and film samples using a rinse procedure and enumerated on brain heart infusion agar containing 800 ppm NA. Log reductions (untreated versus treated skin) in Salmonella Typhimurium(NAr) populations ranged from 0.4 to 2.1. Treatment formulation compositions and wet versus dry treatment application also influenced the extent of kill. The shelf life of refrigerated broiler drumsticks was extended by 0.6 to 2.2 days following a 3-min immersion in a nisin-containing treatment solution and subsequent storage in a foam tray pack containing a nisin-treated PVC overwrap and a nisin-treated absorbent tray pad. These findings demonstrated that Salmonella Typhimurium and spoilage microorganism populations on the surface of fresh broiler skin and drumsticks can be significantly reduced using immersion treatments, absorbent tray pads, and packaging films treated with nisin-containing formulations.

关键词：抗菌药/药理学鸡/微生物学集落计数微生物食品污染/预防和控制食品微生物学食品包装乳链球菌素/药理学聚合物/药理学家禽产品/微生物学家禽产品/标准鼠伤寒沙门菌/药物作用鼠伤寒沙门菌/生长和发育皮肤/微生物学时间因素水动物

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Interventions for the reduction of Salmonella Typhimurium DT 104 and non-O157:H7 enterohemorrhagic Escherichia coli on beef surfaces

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JOURNAL OF FOOD PROTECTION 2000年第10期63卷 1326-1332页

作者： Cutter, CN Rivera-Betancourt, M ARS USDA Roman L Hruska US Meat Anim Res Ctr Clay Ctr NE 68933 USA

A study was conducted to determine if slaughter interventions currently used by the meat industry are effective against Salmonella Typhimurium definitive type 104 (DT 104) and two non-O157:H7 enterohemorrhagic Escherichia coli (EHEC). Three separate experiments were conducted by inoculating prerigor beef surfaces with a bovine fecal slurry containing Salmonella Typhimurium and Salmonella Typhimurium DT 104 (experiment I), E. coli O157:H7 and E. coli O111:H8 (experiment 2), or E. coli O157:H7 and E. coli O26:H11 (experiment 3) and spray washing with water, hot water (72 degrees C), 2% acetic acid, 2% lactic acid, or 10% trisodium phosphate (15 s, 125 +/- 5 psi, 35 +/- 2 degrees C). Remaining bacterial populations were determined immediately after treatments (day 0), after 2 days of aerobic storage at 4 degrees C, and after 7, 21, and 35 days of vacuum-packaged storage at 4 degrees C. In addition to enumeration, confirmation of pathogen serotypes was performed for all treatments on all days. Of the interventions investigated, spray treatments with trisodium phosphate were the most effective, resulting in pathogen reductions of >3 log(10) CFU/cm(2), followed by 2% lactic acid and 2% acetic acid (>2 log(10) CFU/cm(2)). Results also indicated that interventions used to reduce Salmonella Typhimurium on beef surfaces were equally effective against Salmonella Typhimurium DT 104 immediately after treatment and again after long-term, refrigerated, vacuum-packaged storage. Similarly, E. coli O111:H8 and E. coli O26:H11 associated with beef surfaces were reduced by the interventions to approximately the same extent as E. coli O157:H7 immediately after treatment and again after long-term, refrigerated, vacuum-packaged storage. It was also demonstrated that phenotypic characterization may not be sufficient to identify EHECs and that the organisms should be further confirmed with antibody- or genetic-based techniques. Based on these findings, interventions used by the meat industr

关键词：醋酸/药理学集落计数微生物大肠杆菌/分类大肠杆菌/药物作用大肠杆菌/生长和发育食品处理和加工/方法食品微生物学乳酸/药理学肉/微生物学磷酸盐类/药理学鼠伤寒沙门菌/分类鼠伤寒沙门菌/药物作用鼠伤寒沙门菌/生长和发育血清分型动物牛

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Response surface models for effects of temperature, pH, and previous growth pH on growth kinetics of Salmonella typhimurium in brain heart infusion broth

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JOURNAL OF FOOD PROTECTION 1999年第2期62卷 106-111页

作者： Oscar, TP Univ Maryland Eastern Shore Eastern Reg Res Ctr Microbial Food Safety Res Unit USDAARS Princess Anne MD 21853 USA

Response surface models were developed for effects of temperature (15 to 40 degrees C), pH (5.2 to 7.4), and previous growth pH (5.7 to 8.6) on lag time (lambda) and specific growth rate (mu) of Salmonella Typhimurium in brain heart infusion broth (BHIB). Seventy-five growth curves for model development and 30 growth curves for model validation were fit to a two-phase linear growth model to obtain direct estimates of lambda and mu of Salmonella Typhimurium in BPIIB. Response surface models for natural logarithm transformations of lambda and mu as a function of temperature, pH, and previous growth pH were obtained by regression analysis. Previous growth pH did not alter (P > 0.05) or interact with temperature or pH to alter subsequent growth kinetics of Salmonella Typhimurium. However, lambda and mu of Salmonella Typhimurium in BHIB were affected (P < 0.05) by linear and quadratic effects of temperature and pH. The models were validated against data not used in their development. Mean absolute relative error of predictions (model accuracy) was 7.8% for lambda and 6.6% for mu. Median relative error of predictions (model bias) was -1.8% for lambda and -2.8% for mu. Results of the current study indicated that the models developed accurately predicted growth kinetics of Salmonella Typhimurium in BHIB within the matrix of factors modeled and that the range of previous growth pH (5.7 to 8.6) investigated did not alter the subsequent growth kinetics of Salmonella Typhimurium in BHIB.

关键词：集落计数微生物培养基氢离子浓度动力学模型生物学鼠伤寒沙门菌/生长和发育温度

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Response surface models for effects of temperature and previous temperature on lag time and specific growth rate of Salmonella typhimurium on cooked ground chicken breast

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JOURNAL OF FOOD PROTECTION 1999年第10期62卷 1111-1114页

作者： Oscar, TP Univ Maryland Eastern Shore Eastern Reg Res Ctr Agr Res Serv USDA Princess Anne MD 21853 USA

Response surface models were developed for effects of temperature (16 to 34 degrees C) and previous temperature (pretemperature;16 to 34 degrees C) on lag time (lambda) and specific growth rate (mu) of Salmonella Typhimurium on cooked ground chicken breast. The primary objective was to determine whether pretemperature is a major factor affecting growth of Salmonella Typhimurium. Growth curves for model development (n = 32) and model testing (n = 18) were fit to a two-phase linear equation that directly estimated lambda and mu. Response surface models for ln lambda and ln mu as a function of temperature and pretemperature were obtained by regression analysis. Lag time and mu of Salmonella Typhimurium were affected by temperature but not pretemperature, Models were tested against data not used in their development. Prediction error (model accuracy) was 13.4% for lambda and 11.3% for mu, whereas the median relative error of predictions (model bias) was -3.0% for lambda and 6.8% for mu. Results indicated that the models provide reliable predictions of lambda and mu of Salmonella Typhimurium on cooked ground chicken breast within the matrix of conditions modeled. In addition, pretemperature (16 to 34 degrees C) is not a major factor affecting growth of Salmonella Typhimurium.

关键词：鸡食品微生物学热温度肉/微生物学鼠伤寒沙门菌/生长和发育鼠伤寒沙门菌/分离和提纯时间因素动物

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