乳酸菌代谢产物对大肠杆菌和金黄色葡萄球菌抑制作用的研究

从燕糖酸奶中分离;“乳酸蔺,研究热、酸、pH值处理等对乳酸菌代谢产物抑制大肠杆菌和金黄色葡萄球菌效果的影响。结果表明：乳酸菌发酵液的最终pH值为3．9;乳酸菌代谢产物具有良好的热稳定性以及较好的抗蛋白酶活性和抗过氧化氧酶活性;pH值处删对乳酸菌代谢产物的抑菌能力具有明显影响,pH值越低乳酸菌代谢产物的抑菌能力越强。     

Antibacterial effects of chitosan solution against Legionella pneumophila, Escherichia coli, and Staphylococcus aureus

Chitosan has been shown to have antibacterial activities on the growth of a wide variety of bacteria. Chitosan solution has been sold commercially for use as an antibacterial agent. Chitosan solution contains not only chitosan but also organic acids as solvents and desalted Japan Sea Proper Water (dJSPW). We aimed to clarify whether chitosan solution has antibacterial activity against bacteria invading bath water, and then to explore the causative factor among these ingredients. The antibacterial activity of full-strength chitosan solution and of 10(2)- and 10(4)-fold chitosan solution diluted with purified water was studied against Legionella pneumophila serogroups 1 (L. pneumophila SG1) and 6 (L. pneumophila SG6), Escherichia coli (E. coli), and Staphylococcus aureus (S. aureus) for 7 days at 37 degrees C. To clarify the causative factor in the antibacterial activity against E. coli, the antibacterial activities of the full-strength and diluted chitosan solutions for 24 h were examined. L. pneumophila SG1 and SG6, and E. coli could not survive in the chitosan solution or in the 10(2)-fold dilute solution for over a day at 37 degrees C. The cells of S. aureus were found to have decreased more than 2.46 log cfu/ml after 1 day of incubation, not only in the chitosan solutions, but also in phosphate buffer solution as a control. No inhibitory effect of dJSPW on the growth of the bacteria was observed. The antibacterial activity of the chitosan solution was lower compared with those of the organic acids solutions, and it increased with decreasing pH value. We observed the antibacterial activity of chitosan solution against L. pneumophila SG1 and SG6, and E. coli, suggesting it may be due to the decreased pH value derived from organic acids rather than from chitosan itself or dJSPW.     

微波加热对三种微生物致死的Weibull模型

探讨不同微波功率加热至不同温度下对沙门氏菌、大肠杆菌和金黄色葡萄球菌等三种对象菌的致死作用,运用Weibull模型描述其致死历程,由Weibull模型计算微波加热使微生物数量减少5-log所需要的时间,并验证其模型的精确度。结果表明,Weibull模型描述沙门氏菌、大肠杆菌和金黄色葡萄球菌的致死历程均有较高的拟合度,通过Weibull模型推算出来的沙门氏菌、大肠杆菌和金黄色葡萄球菌减少5-log的时间与实验结果相近。     

Antimicrobial activity of pediocin-producing Lactococcus lactis on Listeria monocytogenes,Staphylococcus aureus and Escherichia coli O157:H7 in cheese

The antimicrobial activity of two pediocin-producing transformants obtained from wild strains of Lactococcus lactis on the survival of Listeria monocytogenes, Staphylococcus aureus and Escherichia coli O157:H7 during cheese ripening was investigated. Cheeses were manufactured from milk inoculated with the three pathogens, each at approximately 6 log cfu mL⁻¹. Pediococcus acidilactici 347 (Ped⁺), Lc. lactis ESI 153, Lc. lactis ESI 515 (Nis⁺) and their respective pediocin-producing transformants Lc. lactis CL1 (Ped⁺) and Lc. lactis CL2 (Nis⁺, Ped⁺) were added at 1% as adjuncts to the starter culture. After 30 d, L. monocytogenes, S. aureus and E. coli O157:H7 counts were 5.30, 5.16 and 4.14 log cfu g⁻¹ in control cheese made without adjunct culture. On day 30, pediocin-producing derivatives Lc. lactis CL1 and Lc. lactis CL2 lowered L. monocytogenes counts by 2.97 and 1.64 log units, S. aureus by 0.98 and 0.40 log units, and E. coli O157:H7 by 0.84 and 1.69 log units with respect to control cheese. All cheeses made with nisin-producing LAB exhibited bacteriocin activity throughout ripening. Pediocin activity was only detected throughout the whole ripening period in cheese with Lc. lactis CL1. Because of the antimicrobial activity of pediocin PA-1, its production in situ by strains of LAB growing efficiently in milk would extend the application of this bacteriocin in cheese manufacture.     

脱镁叶绿酸a对金黄色葡萄球菌、大肠杆菌的抑制作用

以叶绿素为提取物，进行化学修饰得到光敏活性剂-脱镁叶绿酸α，其对微生物生长影响的研究表明：在光照条件下，脱镁叶绿酸α对金黄色葡萄球菌的生长和大肠杆菌原生质体的再生有明显的抑制作用；在暗培养条件下，脱镁叶绿酸α的抑制作用减弱。     

餐饮具表面的大肠杆菌和金黄色葡萄球菌活性研究

目的研究温度、湿度及餐饮具材质对餐饮具表面大肠杆菌和金黄色葡萄球菌活性的影响。方法分别在同一湿度50%、不同温度(25℃、37℃和60℃)下及同一温度25℃、不同湿度(20%、50%)条件下接种大肠杆菌和金黄色葡萄球菌到陶瓷餐饮具表面,在10、30、60和120 min后检测两种细菌的存活数量;在25℃、湿度50%的条件下分别接种两种细菌到陶瓷、木质、不锈钢和铜合金的餐饮具上,在10、30 min后检测两种细菌的存活数量。结果在同一湿度(50%),25℃时,两种细菌活性均较好;37℃时,存活的大肠杆菌数量比金黄色葡萄球菌低10~2 CFU/m L;60℃时,大肠杆菌10 min后失活,金黄色葡萄球菌60 min后失活。在25℃,湿度20%时,存活的大肠杆菌数量10 min后下降103 CFU/m L,120 min后失活;湿度50%时,存活的大肠杆菌数量120 min后仅下降10~2 CFU/m L。而金黄色葡萄球菌在两种湿度条件下,存活的细菌数量120 min后仅下降10 CFU/m L。在25℃、湿度50%的条件下接种10 min后,铜合金餐饮具上的两种细菌比其他材质的低10~2CFU/m L,30 min后,铜合金餐饮具上的两种细菌均失活。结论大肠杆菌对高温和干燥的耐受性比金黄色葡萄球菌弱。陶瓷、木质和不锈钢餐饮具对大肠杆菌和金黄色葡萄球菌均无抑菌性,而铜合金餐饮具对两种细菌均有抑菌性。     

Aerobic bacterial, coliform, Escherichia coli and Staphylococcus aureus counts of raw and processed milk from selected smallholder dairy farms of Zimbabwe

A cross sectional study was conducted to enumerate total viable bacteria (TBC), coliforms, Escherichia coli and Staphylococcus aureus in raw (n = 120) and processed (n = 20) milk from individual farms from three smallholder dairy schemes of Zimbabwe between October, 2009 and February, 2010. Data on management factors were collected using a structured questionnaire. A standard pour plate technique was used to enumerate total viable bacteria, while for coliforms, E. coli and S. aureus, counts were assessed by the spread plate technique. The association of total viable bacterial counts and management factors was assessed using univariable and a linear regression model. The log₁₀ TBC for raw milk differed significantly (P < 0.05) amongst the schemes with the lowest (5.6 ± 4.7 log₁₀ cfu/ml) and highest (6.7 ± 5.8 log₁₀ cfu/ml) recorded from Marirangwe and Nharira respectively. The mean log₁₀ of TBC of processed milk (6.6 ± 6.0 log₁₀ cfu/ml) were marginally higher than those of raw milk (6.4 ± 5.6 log₁₀ cfu/ml) but not significant (P > 0.05). The coliform, E. coli and S. aureus counts for raw milk significantly differed (P < 0.05) amongst the study areas. The variation in TBC, coliforms, E. coli and S. aureus counts amongst the schemes could be attributed to differences in milking hygiene where farms with more access to training and monitoring of microbiological quality of milk had lower counts. Linear regression analysis revealed dairy scheme, delivery time and season of milking as independently associated with increased TBC of raw milk. The high TBC of raw and processed milk generally indicated low levels of milking hygienic practices, and high level of post-processing contamination, respectively. The high TBC, coliform, E. coli and S. aureus counts of both raw and processed milk may present a public health hazard. Thus, educating the farmers on general hygienic practices, quickening the delivery of milk to collection centres, or availing cooling facilities on-farm will improve the microbiological quality and safety of milk.     

肉桂醛对大肠杆菌和金黄色葡萄球菌的抑菌作用及抑菌机理研究

研究了肉桂醛对大肠杆菌和金黄色葡萄球菌的抑菌作用及其抑菌机理。本文采用滤纸片扩散法测定抑菌圈大小,双倍稀释法测定最低抑菌浓度、最低杀菌浓度,以此评价肉桂醛对大肠杆菌和金黄色葡萄球菌的抑菌性,通过扫描电镜观察、胞膜通透性、胞膜完整性、膜电位实验,阐述肉桂醛抑菌的机理。结果表明:肉桂醛对大肠杆菌和金黄色葡萄球菌的抑菌圈分别为21.75 mm、29.37mm,最低抑菌浓度均为0.25μL/m L,最低杀菌浓度均为0.5μL/m L;肉桂醛破坏了菌体细胞的形态,出现形变;随着肉桂醛浓度的增大,悬液中相对电导率迅速升高,表明肉桂醛影响细菌的膜通透性,而成倍数增长的核酸、蛋白质含量表示胞膜的完整性遭到破坏,肉桂醛降低菌体膜电位,影响其代谢活性,从而抑制细菌生长。肉桂醛主要作用于细胞膜,适宜作为天然防腐剂,抑制食品中腐败菌和致病菌的生长,延长食品货架期。     

Synergetic effects of high-pressure carbon dioxide and nisin on the inactivation of Escherichia coli and Staphylococcus aureus

Synergetic effects of high-pressure carbon dioxide (HPCD) and nisin on Escherichia coli and Staphylococcus aureus were evaluated. Changes in morphology, interior structure, and membrane permeability were analyzed by scanning and transmission electron microscopy, and flow cytometry. Synergetic effects were found, especially in S. aureus. HPCD alone or with nisin led to morphological and intracellular alterations in both bacteria, but nisin alone led to these damages only in S. aureus. A positive correlation between membrane damage and inactivation was found, but ratios of inactivation were higher, probably because of viable but non-culturable state. Mechanisms were proposed for synergism: for E. coli, outer membrane was damaged first by HPCD, and then HPCD and nisin jointly acted on and destroyed the cytoplasmic membrane, leading to further intracellular damage by HPCD; for S. aureus, HPCD and nisin acted on the cytoplasmic membrane together leading to cell death.Industrial RelevanceEscherichia coli and Staphylococcus aureus are two common microorganisms, which exist widely in the environment and easily contaminate food such as vegetables and dairy products, respectively. Considering heat treatment may destroy some heat-sensitive quality of the products, this study evaluated synergetic effects of high-pressure carbon dioxide (HPCD) combined with the bacteriocin nisin. The investigations provided evidence for potentially combined application of HPCD and nisin to help keep food safe in the industry.     

金黄色葡萄球菌在生乳与灭菌乳中生长状况分析

目的 了解并比较金黄色葡萄球菌(S.aureus)在生乳与灭菌乳中的生长状况.方法 采用GB/T4789.37-2008<食品微生物学检验金黄色葡萄球菌检验>,测定不同温度下金黄色葡萄球菌在生乳和灭菌乳中的生长情况,利用MicroFit 1.0软件对所测数据进行分析,利用SPSS统计软件对该菌在生乳与灭菌乳中生长参数进行统计分析.结果 金黄色葡萄球菌在生乳中的最大生长速率明显低于在灭菌乳中的最大生长速率,二者的迟滞期、代时无明显差异.结论 金黄色葡萄球菌在生乳与灭菌乳中的生长情况差异显著.有统计学意义(P<0.05).     

Antibacterial activity of dextran-conjugated lysozyme against Escherichia coli and Staphylococcus aureus in cheese curd

The purposes of this research were to glycosylate lysozyme with dextran under Maillard reaction conditions and assess the antimicrobial characteristics of the lysozyme-dextran conjugate in a culture medium and cheese curd. Solutions containing lysozyme and dextran were incubated at 60 degrees C and at 79% relative humidity. Gel permeation chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis were used to follow the glycosylation process. Under optimum conditions 3.7 mol of dextran were coupled to 1 mol of lysozyme. Lytic activity of the conjugate against the cell wall of Micrococcus luteus was about 62% of that of native lysozyme. Evaluation of the lysozyme-dextran conjugate against test microorganisms (Staphylococcus aureus and Escherichia coli) in culture media indicated a progressive increase in antimicrobial activity, with an increase in enzyme-conjugate concentration. The lysozyme-dextran conjugate was also effective against E. coli in a natural food system, as it reduced the bacterial count by 3 log in cheese curd after 40 days of storage. Unlike E. coli, the antimicrobial action of lysozyme against S. aureus was not improved by conjugation with dextran in both in vitro and in vivo tests. Antimicrobial activity of the lysozyme-dextran conjugate against gram-negative bacteria is probably related to the remaining lytic activity as well as the excellent surfactant properties of the lysozyme-dextran conjugate. These results might increase the applicability of lysozyme as a natural antimicrobial ingredient in different food products.     

大肠埃希菌和金黄色葡萄球菌的最低生长水分活度测定

目的探索大肠埃希菌和金黄色葡萄球菌的最低生长水分活度(water activity,A_w)。方法分别采用定性和定量试验,研究在NaCl、蔗糖、甘油3种水分活度调节剂作用下,水分活度对大肠埃希菌和金黄色葡萄球菌生长规律的影响。结果大肠埃希菌的最低生长水分活度为0.922～0.950,金黄色葡萄球菌的最低生长水分活度为0.864～0.900。根据对生长曲线的分析,随着水分活度下降,大肠埃希菌和金黄色葡萄球菌的总生长量降低,停滞时间延长,比生长速率下降。结论水分活度调节剂会影响细菌的最低生长水分活度,大肠埃希菌对甘油更为耐受,而金黄色葡萄球菌对氯化钠更为耐受。2种菌的比生长速率呈线性下降规律,且在氯化钠和蔗糖的比生长速率下降规律基本一致。     

姜厚朴水提物对大肠杆菌和金黄色葡萄球菌的抑菌机理研究

为了探讨姜厚朴水提物(GMB)对大肠杆菌和金黄色葡萄球菌的抑菌机理,试验对GMB作用下菌体形态结构、膜系统上离子通道的酶活力和能量代谢等方面进行了研究。结果表明,GMB对大肠杆菌和金黄色葡萄球菌的MIC分别为6.25、12.5 mg/m L。大肠杆菌胞外AKP酶和β-半乳糖苷酶吸光度值分别增加1.78和4.24倍,GMB作用4 h后电导率显著上升,膜上Na+K+-ATP酶活性从0.42增加到1.74 mg prot/m L,且为阴性对照的1.7倍;金黄色葡萄球菌体表出现囊泡状、不规则的突起结构,SDH酶活性、总ATP酶活性和胞内蛋白质含量分别降低40%、23.4%和17.9%,且AKP酶活和电导率均有所增加。由此推测出GMB主要是通过破坏大肠杆菌细胞壁、膜结构,增加其渗透性和通透性,造成胞内物质外流和蛋白质合成量下降等现象,进而抑制菌体生长。而GMB抑制金黄色葡萄球菌的作用机制是增加细胞壁的通透性、降低能量代谢相关酶的活性,干扰其正常的代谢活动。     

Antimicrobial Effect of Sour Pomegranate Sauce on Escherichia coli O157 : H7 and Staphylococcus aureus

Pomegranate sauce is one of the most popular pomegranate products produced in Turkey. This study was conducted to determine the minimum inhibitory concentrations (MICs) of both traditional and commercial sour pomegranate sauce samples on Staphylococcus aureus (ATCC 25923) and Escherichia coli O157 : H7 (ATCC 43895). The initial microflora of the pomegranate sauce samples was determined by performing the enumerations of total aerobic mesophilic bacteria, yeast and mold, S. aureus, E. coli, and the determination of Salmonella spp. MIC tests were applied to the neutralized and the original (unneutralized) sour pomegranate sauce samples in order to put forth the inhibition effect depending on low pH value. It was found that inhibitory effect of the traditional and the commercial samples, except one sample, on pathogens was not only due to the acidity of the products. The results of MIC tests indicated that although both traditional and commercial samples showed a considerable inhibitory effect on test microorganisms, the traditional pomegranate sauce samples were more effective than the commercial ones.     

Antibacterial effects of chitosan coating containing Mentha aquatica L. essence against Escherichia coli,Staphylococcus aureus and Listeria monocytogenes in Iranian white cheese

The effect of a chitosan coating and Mentha aquatica L. essence on Iranian white cheese was investigated. Results showed 100% inhibition of Escherichia coli growth using 1.5% essence after 10 days. After 15 days of incubation, the Staphylococcus aureus population was reduced by 44.2%, 70.0%, and 88.5% using 0.5, 1.0 and 1.5% essence, respectively. After 15 days, Listeria monocytogenes growth was inhibited by 63.84%, 70.12%, and 85.9% using 0.5, 1.0, and 1.5% essence, respectively. Inhibition zone diameter studies also confirmed the antibacterial effects of applied coating against all the above‐mentioned bacteria in Iranian white cheese.     

食品中金黄色葡萄球菌的污染状况及耐药性分析

为了解金黄色葡萄球菌对食品的污染情况 ,采集 6类 2 0 4件食品 ,进行金黄色葡萄球菌检测。采用GB 4 789— 1994食品卫生检验方法检测金黄色葡萄球菌 ,用minVIDAS全自动免疫分析仪测定肠毒素 ,用K B法进行药敏试验。在 2 0 4件食品中检出 4 4件金黄色葡萄球菌 ,总检出率2 1 5 6 % ,其中生奶的检出率最高 (39 39% ) ,生肉、水产品次之 (33 33% ) ,熟肉制品、乳制品检出率分别为 6 0 %和 5 0 % ,冰激凌中未检出金黄色葡萄球菌。 4 4株金黄色葡萄球菌有 2 7株产生肠毒素 ,占 6 1 36 %。在药敏试验中 4 4株金黄色葡萄球菌 10 0 %对苯唑西林耐药 ;93 18%对青霉素G耐药 ;86 4 0 %对阿莫西林耐药 ,对丁胺卡那、头孢三嗪、头孢唑啉、万古霉素敏感。金黄色葡萄球菌对奶、肉、水产品的污染比较严重 ,特别是产生肠毒素的菌株存在着引起食物中毒的可能性。     

Survival of Escherichia coli O157:H7, Salmonella enteritidis, Staphylococcus aureus, and Listeria monocytogenes in Kimchi

The survival of gram-positive and gram-negative foodborne pathogens in both commercial and laboratory-prepared kimchi (a traditional fermented food widely consumed in Japan) was investigated. It was found that Escherichia coli O157:H7, Salmonella Enteritidis, Staphylococcus aureus, and Listeria monocytogenes could survive in both commercial and laboratory-prepared kimchi inoculated with these pathogens and incubated at 10 degrees C for 7 days. However, when incubation was prolonged, the S. aureus level decreased rapidly from the initial inoculum level to the minimum detectable level within 12 days, whereas Salmonella Enteritidis and L. monocytogenes took 16 days to reach similar levels in commercial kimchi. On the other hand, E. coli O157:H7 remained at high levels throughout the incubation period. For laboratory-prepared kimchi, the S. aureus level decreased rapidly from the initial inoculum level to the minimum detectable level within 12 days, and L. monocytogenes took 20 days to reach a similar level. E. coli O157:H7 and Salmonella Enteritidis remained at high levels throughout the incubation period. The results of this study suggest that the contamination of kimchi with E. coli O157:H7, Salmonella Enteritidis, S. aureus, or L. monocytogenes at any stage of production or marketing could pose a potential risk.     

Water, sodium chloride and acidified sodium chlorite effects on Escherichia coli O157:H7 and Staphylococcus aureus on beef briskets

Effectiveness of spray application of potable water wash (WW), 25% (w/v) sodium chloride (NaCl), and 0.1% (v/v) acidified sodium chlorite (ASC) was evaluated against Escherichia coli O157:H7 and Staphylococcus aureus inoculated onto beef briskets. The purpose was to identify antimicrobial treatments which may be applied to beef carcasses and more specifically in kosher meat facilities. Treatments were applied for 10-60 s at pressure of 419 kPa. Water wash, NaCl, and ASC significantly reduced E. coli O157:H7 as compared with the control, although, only ASC resulted in improved removal with increased exposure time. Water wash did not significantly reduce S. aureus counts throughout exposure and NaCl was only effective after 60 s of exposure, while ASC reduced counts throughout exposure. E. coli O157:H7 was twice as sensitive to WW and NaCl as S. aureus in terms of percent reduction in cell count.