山葵杀菌作用的研究

报道了山葵提取物对细菌的致死作用 ,特别是山葵对病原菌有明显的杀灭作用。在山葵提取物浓度为 0.5 %～ 0.8%,作用时间为 90～ 1 2 0min的条件下 ,对几种病原菌的杀菌率为 80 %～ 97%。这对杀灭有害病原菌找到了一条新途径 ,对防止病原菌的传播搞好环境卫生、保证人类健康有积极意义。     

消毒剂过氧化氢脲性能的实验研究

过氧化氢脲为过氧化氢类消毒剂,实验表明,其5%水溶液25℃时有良好的的杀菌作用。杀灭细菌营养繁殖体需2min,作用15min可将细菌芽孢全部杀灭。作用30min可将HbBsAg完全灭活。提高浓度、温度,延长作用时间或降低pH值,可加强其杀菌作用。     

三种芦荟汁的抑菌活性及其影响因素研究

目的：探索美国库拉索芦荟、日本木立芦荟和中华芦荟汁液的抑菌作用。方法：测定三种芦荟叶片提取物对一系列供试细菌和真菌的最低抑菌浓度（MIC）、最低杀菌浓度（MBC）,对比121℃热处理30min前后提取物对金黄色葡萄球菌的抑菌作用。结果：三种芦荟提取物对供试细菌的金黄色葡萄球菌最低抑菌浓度均为0.4%;对供试菌真菌的黑曲霉都有不同程度的抑制作用,其最低抑菌浓度为0.2%。热处理后抑菌效应没有明显的下降。结论：芦荟叶提取物的抑菌作用随浓度的增加和抑菌时间的延长而增强,热处理不会影响其抑菌效果。     

金钱草提取物抑制NDMA形成的研究

目的:研究金钱草提取后得到的活性物质,在模拟人体胃液条件下,对N-亚硝基二甲胺(NDMA)形成的抑制作用。方法:在37℃、pH 3.4条件下观察金钱草的活性提取物对NDMA形成的抑制效果。采用气相色谱质谱联用仪测定了不同浓度下金钱草提取物对NDMA形成的抑制率,利用分光光度法测定了金钱草提取物随时间变化对亚硝酸根离子的清除率。结果:金钱草提取物在浓度为0.1 mg/mL时对NDMA的抑制率就达到了63.5%,且随着浓度增加抑制效果也在加强,当浓度为1 mg/mL时抑制率高达91.3%。金钱草提取物对亚硝酸根离子的清除率随着时间延长不断增加,到30 min时清除率达到最大,最大清除率是30.5%。结论:金钱草提取物对阻断NDMA的形成具有显著效果,对亚硝酸根离子也具有一定的清除作用。     

二氧化氯杀灭除盐水系统中有害菌的研究

本文报道了杀菌剂二氧化氯对热电厂除盐水系统中有害菌的杀灭作用,并与氯的杀菌率作了比较。利用二氧化氯进行杀菌时,对粘液异养菌使用2ppm;铁细菌、硫酸盐还原菌使用1ppm;真菌使用2ppm,杀菌率达90—99％;而使用氯达到同样杀菌率需4—5 ppm。杀灭天然菌膜中细菌、真苗则需比人工混合菌提高三分之一以上的投药量。在5—60 min的接触时间内杀菌率提高5％,低剂量下随环境pH值(6一11)和温度(10—50℃)的上升,杀菌率有所提高。除50ppm以上的蛋白胨外,所试的糖、酸、氨均不影响二氧化氯的杀菌活性,但明显降低氯的杀菌作用。二氧化氯杀菌中出现失话余量,它同初始投量相比,杀菌率最高可差20—30％。     

烟草在PVYN病毒与烟蚜作用下对高CO2浓度的响应

以CO2浓度为主处理因子,研究了加倍CO2浓度和对照大气CO2浓度条件下,烟蚜、马铃薯Y病毒N株(PVYN)以及二者共同作用下烟草各指标的响应。结果表明,在当前CO2浓度条件下,PVYN、烟蚜及两者联合作用对烟草生物量影响不显著;而在未来高CO2浓度条件下,PVYN、烟蚜及两者联合作用对烟草生物量影响很大。CO2浓度升高后,PVYN和蚜虫二者联合作用显著降低烟草产量,危害加重,高CO2的"肥料"作用被极大地削弱。在有烟蚜、PVYN以及两者共同作用时烟草的化学物质及主要的次生代谢物烟碱的含量对CO2浓度升高的响应也发生一定的变化,表现在:高CO2浓度条件下,蚜虫、蚜虫与PVYN共同作用显著增加了烟草的含氮量;显著减少了烟叶含糖量;PVYN及其与蚜虫共同作用显著升高叶片可溶性蛋白含量;当高CO2浓度下,各处理的烟草烟碱含量均显著下降,而且PVYN感染的烟叶烟碱含量无论在哪一种CO2浓度条件下,都比无毒无虫的对照烟叶烟碱含量升高。结果显示,烟蚜和马铃薯Y病毒N株(PVYN)对烟草的产量、营养物质及防御物质都有影响;CO2浓度升高对烟草的生长有促进作用,增加了烟草的产量,但蚜虫的危害和PVYN感染使烟草产量下降,在高CO2浓度条件下,烟蚜和PVYN共同作用相对于目前CO2浓度对烟草产量的危害加重。     

垂序商陆叶片总皂苷的提取及杀虫活性研究

对纤维素酶-微波协同提取垂序商陆(Phytolacca americana Linn.)叶片总皂苷过程中纤维素酶用量、纤维素酶作用时间、微波提取时间和微波功率进行单因子实验和L9(34)正交实验,测定了4月至10月叶片总皂苷含量及总皂苷提取物对小菜蛾[Plutella xylostella(Linn.)]的灭杀活性。结果表明:纤维素酶用量、纤维素酶作用时间、微波提取时间和微波功率均对垂序商陆叶片总皂苷得率有明显影响。垂序商陆叶片总皂苷的最佳提取条件为纤维素酶用量0.08 g·g~(-1)、纤维素酶作用时间100 min、微波提取时间35 s和微波功率400 W;该条件下叶片总皂苷得率为2.53%。随着时间的推移,垂序商陆叶片总皂苷含量呈"升高—稳定—降低"的趋势,总皂苷含量在8月最高,9月之后急剧下降。在同一处理时间,小菜蛾的校正死亡率随着总皂苷提取物质量浓度的提高逐渐升高;同一质量浓度总皂苷提取物条件下,小菜蛾的校正死亡率随着处理时间的延长也逐渐升高。质量浓度5.0 mg·m L-1总皂苷提取物处理96 h时小菜蛾的校正死亡率达73.3%。9月总皂苷提取物对小菜蛾的灭杀效果优于5月和7月。本研究初步建立垂序商陆叶片总皂苷的纤维素酶-微波协同提取条件,明确其叶片总皂苷提取物对小菜蛾具有一定的灭杀活性,为利用垂序商陆叶片开发生物农药提供参考。     

常压低温等离子体对羊肚菌培养基质的杀菌效果及工艺优化

以羊肚菌培养基质为试验对象,采用常压低温等离子体技术对其进行杀菌处理,分别研究了等离子体处理过程中电压、频率、时间和次数4种单因素变量对菌落数和水分的影响,并通过正交实验优化了处理工艺条件。结果表明,细菌和真菌的杀菌率随常压等离子体处理电压、处理时间和处理次数的增大而增加,水分损失也随之增加,而随着频率的增大,杀菌率呈现先增大后减小的“火山型”趋势。不同处理条件下的杀菌效果普遍存在显著性差异(P<0.05)。正交实验表明4种影响因素大小为：频率>电压>时间>次数,最佳杀菌工艺条件为：电压30kV,频率9.6kHz,时间45 min,次数1次,此条件下细菌和真菌杀菌率分别为96.87%和93.77%,且水分损失较少。     

臭氧对无土栽培营养液的消毒作用研究

采用稀释平板法和MPN法,测定了臭氧对无土栽培营养液的消毒杀菌作用。结果表明,随着臭氧浓度(时间)的增加,对微生物杀灭率明显上升;连续处理20min,可杀灭90%以上的细菌、真菌和藻类;臭氧间歇曝气消毒营养液,有效控制微生物的滋生,对莴苣根系无不良影响,增加产量36.8%。     

微波法制备壳聚糖研究

采用微波炉加热,在敞口容器中,进行甲壳素脱乙酰反应,制备壳聚糖。考察了碱溶液浓度和微波加热时间对壳聚糖脱乙酰度的影响。固定微波加热时间30min,随NaOH溶液浓度增加,脱乙酰度先增加,后减小;NaOH溶液浓度为45％时,壳聚糖的脱乙酰度最高。固定NaOH溶液浓度为45％,随着微波加热时间延长,壳聚糖的脱乙酰度增加。微波加热的最佳时间为30min。加热时间继续延长,壳聚糖变黑。碱溶液浓度和微波加热时间对壳聚糖的粘均分子量影响都不大。本文试图从微波场的能量分布和微波加热机理方面解释实验结果。     

New water disinfection system using UVA light-emitting diodes

AIM: To evaluate the ability of high-energy ultraviolet A (UVA) light-emitting diode (LED) to inactivate bacteria in water and investigate the inactivating mechanism of UVA irradiation. METHODS AND RESULTS: We developed a new disinfection device equipped with high-energy UVA-LED. Inactivation of bacteria was determined by colony-forming assay. Vibrio parahaemolyticus, enteropathogenic Escherichia coli, Staphylococcus aureus and Escherichia coli DH5alpha were reduced by greater than 5-log(10) stages within 75 min at 315 J cm(-2) of UVA. Salmonella enteritidis was reduced greater than 4-log(10) stages within 160 min at 672 J cm(-2) of UVA. The formation of 8-hydroxy-2'-deoxyguanosine in UVA-LED irradiated bacteria was 2.6-fold higher than that of UVC-irradiated bacteria at the same inactivation level. Addition of mannitol, a scavenger of hydroxyl radicals (OH(*)), or catalase, an enzyme scavenging hydrogen peroxide (H(2)O(2)) to bacterial suspensions significantly suppressed disinfection effect of UVA-LED. CONCLUSION: This disinfection system has enough ability to inactivate bacteria and OH(*) and H(2)O(2) participates in the disinfection mechanism of UVA irradiation. SIGNIFICANCE AND IMPACT OF THE STUDY: We newly developed UVA irradiation system and found that UVA alone was able to disinfect the water efficiently. This will become a useful disinfection system.     

Successful disinfection of trumpet mouthpieces using domestic steam disinfection

There have been numerous reports in the literature describing the diversity of microbial flora isolated from woodwind and brass instruments, with potential infection risks for players, especially when such instruments are shared. Steam disinfection has become established as a trusted method of decontamination; however, there have been no reports on the employment of this technology to disinfect parts of musical instruments, hence it was the aim of this study to examine the fate of bacterial and yeast pathogens on artificially contaminated trumpet mouthpieces and to evaluate whether such disinfection is an effective method of disinfection for such instrument parts. Trumpet mouthpieces were artificially contaminated with 18 microbial strains (17 bacteria from four genera (Enterococcus, Escherichia, Staphylococcus and Streptococcus) and one yeast (Candida)), each at an inoculum density of approximately 1·5 × 10⁷ colony forming units and subjected to a disinfection cycle. The experiment was repeated including 50% (v/v) sterile sputum as soil. No bacteria or yeast organisms were recovered post disinfection, including following recovery and with nonselective cultural enrichment techniques.     

Disinfection of contaminated water by using solar irradiation

Contaminated water causes an estimated 6 to 60 billion cases of gastrointestinal illness annually. The majority of these cases occur in rural areas of developing nations where the water supply remains polluted and adequate sanitation is unavailable. A portable, low-cost, and low-maintenance solar unit to disinfect unpotable water has been designed and tested. The solar disinfection unit was tested with both river water and partially processed water from two wastewater treatment plants. In less than 30 min in midday sunlight, the unit eradicated more than 4 log10 U (99.99%) of bacteria contained in highly contaminated water samples. The solar disinfection unit has been field tested by Centro Panamericano de Ingenieria Sanitaria y Ciencias del Ambiente in Lima, Peru. At moderate light intensity, the solar disinfection unit was capable of reducing the bacterial load in a controlled contaminated water sample by 4 log10 U and disinfected approximately 1 liter of water in 30 min.     

Transport limitation of chlorine disinfection of Pseudomonas aeruginosa entrapped in alginate beads

An artificial biofilm system consisting of Pseudomonas aeruginosa entrapped in alginate and agarose beads was used to demonstrate transport limitation of the rate of disinfection of entrapped bacteria by chlorine. Alginate gel beads with or without entrapped bacteria consumed chlorine. The specific rate of chlorine consumption increased with increasing cell loading in the gel beads and decreased with increasing bead radius. The value of an observable modulus comparing the rates of reaction and diffusion ranged from less than 0.1 to 8 depending on the bead radius and cell density. The observable modulus was largest for large (3-mm-diameter) beads with high cell loading (1.8 x 10(9) cfu/cm(3)) and smallest for small beads (0.5 mm diameter) with no cells added. A chlorine microelectrode was used to measure chlorine concentration profiles in agarose beads (3.0 mm diameter). Chlorine fully penetrated cell-free agarose beads rapidly; the concentration of chlorine at the bead center reached 50% of the bulk concentration within approximately 10 min after immersion in chlorine solution. When alginate and bacteria were incorporated into an agarose bead, pronounced chlorine concentration gradients persisted within the gel bead. Chlorine did gradually penetrate the bead, but at a greatly retarded rate; the time to reach 50% of the bulk concentration at the bead center was approximately 46 h. The overall rate of disinfection of entrapped bacteria was strongly dependent on cell density and bead radius. Small beads with low initial cell loading (0.5 mm diameter, 1.1 x 10(7) cfu/cm(3)) experienced rapid killing; viable cells could not be detected (<1.6 x 10(5) cfu/cm(3)) after 15 min of treatment in 2.5 mg/L chlorine. In contrast, the number of viable cells in larger beads with a higher initial cell density (3.0 mm diameter, 2.2 x 10(9) cfu/cm(3)) decreased only about 20% after 6 h of treatment in the same solution. Spatially nonuniform killing of bacteria within the beads was demonstrated by measuring the transient release of viable cells during dissolution of the beads. Bacteria were killed preferentially near the bead surface. Experimental results were consistent with transport limitation of the penetration of chlorine into the artificial biofilm arising from a reaction-diffusion interaction. The methods reported here provide tools for diagnosing the mechanism of biofilm resistance to reactive antimicrobial agents in such applications as the treatment of drinking and cooling waters. (c) 1996 John Wiley & Sons, Inc.     

Adding denture cleanser to microwave disinfection regimen to reduce the irradiation time and the exposure of dentures to high temperatures

Background: The microwave energy is an efficient disinfection method; however, it can generate high temperatures that can result in distortion of the dentures. objectives: To evaluate whether the addition of an enzymatic cleanser to microwave disinfection regimen would disinfect dentures with shorter irradiation time. Materials and methods: Seven resin discs colonized with Candida albicans biofilm were placed on the palatal surface of sterile dentures to be randomly assigned to the following treatments: immersion in distilled water for 3 min with 0 (DW), 1 (DW + M1), 2 (DW + M2), or 3 min (DW + M3) of microwave irradiation; or immersion in denture cleanser for 3 min with 0 (DC), 1 (DC + M1), 2 (DC + M2) or 3 min (DC + M3) of irradiation. After the treatments, the viable cells were counted by a blinded examiner. The temperature was measured immediately after irradiation. The data were analyzed by ANOVA and Tukey post hoc tests (α = 0.05). Results: No viable cells were found after DC + M2, DC + M3, and DW + M3 treatments, of which DC + M2 achieved the lowest temperature. No significant difference was found between the effectiveness of DW, DW + M1 and DC treatments (p > 0.05). Conclusion: Within the limits of this study, the association of a denture cleanser and microwave energy is efficient to disinfect dentures in lower irradiation time and temperature.     

Disinfection of Contaminated Water by Using Solar Irradiation

Contaminated water causes an estimated 6 to 60 billion cases of gastrointestinal illness annually. The majority of these cases occur in rural areas of developing nations where the water supply remains polluted and adequate sanitation is unavailable. A portable, low-cost, and low-maintenance solar unit to disinfect unpotable water has been designed and tested. The solar disinfection unit was tested with both river water and partially processed water from two wastewater treatment plants. In less than 30 min in midday sunlight, the unit eradicated more than 4 log₁₀ U (99.99%) of bacteria contained in highly contaminated water samples. The solar disinfection unit has been field tested by Centro Panamericano de Ingenieria Sanitaria y Ciencias del Ambiente in Lima, Peru. At moderate light intensity, the solar disinfection unit was capable of reducing the bacterial load in a controlled contaminated water sample by 4 log₁₀ U and disinfected approximately 1 liter of water in 30 min.     

Decontamination efficacy against Mycoplasma

Aims: Mycoplasma is minute bacteria that can be found ubiquitously in the environment and also in human, animal and plant tissues. In addition to their public health importance as aetiological agents of infections and possible association with certain cancers, mycoplasma is a major contamination concern in biotechnology. These bacterial cells are very small, can form biofilms and survive for extended periods of time when dried onto surfaces. Despite these concerns, there is little information concerning their resistance to currently used disinfection methods. The objective of this study was to evaluate commonly used biocidal treatments against three representative mycoplasma species. Methods and Results: Mycoplasma was dried onto stainless steel coupons and exposed to decontamination products. All strains survived drying and any significant viability loss because of the test method (including neutralization), as demonstrated by a ≤0·5 log₁₀ for each tested species. The quaternary ammonium compound (QAC) tested presented poor efficacy, whereas 70% ethanol was fully efficient with complete inactivation after 5‐min exposure. Alkaline cleaner formulations presented increasing efficacy when tested at 0·2, 0·4 and 0·8% concentrations, with complete kill observed at 0·8% of two products tested. Decontamination with vaporized (gaseous) hydrogen peroxide (VHP) was very efficient at concentrations used for room and small enclosures decontamination (180–1200 ppm with various time exposures), as well as for device sterilization applications. Conclusions: Ethanol and alkaline detergent formulations were particularly efficient against mycoplasma, but a QAC formulation was not. VHP in room disinfection and device sterilization applications was effective against all mycoplasma species tested. Significance and Impact of the Study: Mycoplasma can provide resistance to environmental factors (such as drying) and disinfectants. Further studies are required to confirm the effectiveness of other disinfectants and the mechanisms of mycoplasma resistance.     

Decontamination of dental unit water systems with hydrogen peroxide

AIMS: Transmission of microbial pathogens to patients from water in dental units is a concern. To reduce this risk, the decontaminating efficiency of hydrogen peroxide was evaluated. METHODS AND RESULTS: Three percent hydrogen peroxide diluted 1 : 4 in distilled water (contact time 15 min) was used daily to disinfect the waterlines of a pilot unit previously contaminated with Pseudomonas aeruginosa or Staphylococcus aureus. The behaviour of the test bacteria was seen to differ over time. Staph. aureus numbers slowly decreased until only low numbers were recovered, after which the levels remained stable. Ps. aeruginosa abatement was more rapid and the density of the bacteria reached a peak when the circuit was empty. CONCLUSIONS: Staph. aureus and Ps. aeruginosa treated with hydrogen peroxide fell from 6 to 4 log. SIGNIFICANCE AND IMPACT OF THE STUDY: Treatment of dental unit waterlines with hydrogen peroxide was seen to be able to keep the number of the bacteria under control, as long as the treatment was repeated daily.     

Disinfection and hygiene in the veterinary field and disinfection of animal houses and transport vehicles

Disinfection in animal houses means always a combination between cleaning and disinfection because the high amount of organic material present in such an environment will neutralize rapidly each disinfectant brought to the surface if no cleaning step had been done before. Depending on the kind of material, cleaning gives a 3 log reduction of total bacterial count on the surface and disinfection another 3 log reduction. This means that under practical conditions generally 10³ cfu of bacteria remain per cm² of surface, mostly sporeformers. The choice of disinfectant depends on the purpose of disinfection. In the case of notifiable diseases, it must be active against a defined pathogen. In the case of prophylactic disinfection, it must be active against a broad spectrum of microorganisms.Only disinfectants which are tested for their activity on surfaces which are representative for animal houses e.g. wood should be used, otherwise the failure under practical conditions can be predicted and work, as well as money, will be wasted. The optimal temperature for the liquids used in cleaning and disinfection is 40°C and the optimal temperature of surfaces is 20°C. Colder surfaces require higher concentrations of active substances in the solution, below 10°C the effect of practical disinfection is incomplete. Low air humidity and high air velocity have a negative influence on the action of most disinfectants on surfaces. The amount of disinfectant necessary to disinfect a surface in an animal house is at least 0.4 l/m². Transport vehicles are very difficult to disinfect, especially in winter-time. They should be cleaned with hot water, the remaining liquid should be removed by a suitable vacuum cleaner and the concentration of the disinfectant should be elevated at least for the factor 3. Mechanic action will improve the disinfecting effect in vehicles as well as preliminary disinfection prior cleaning.     

Assessment of performance of UV sterilizer for room air bacteria

Paper presents a technique for performance of UV sterilizer for room air bacteria. Patterns of decay of room air bacteria concentration during sterilization and build-up there after as a function of time is studied. Decay process seems to follow exponential pattern. Half-lives during decay are estimated. For single sterilizer unit with a dose of 16 W the decay half-life is around 8.6 min. For the dose of 32 W (2 sterilizers), half-life is estimated to be 6.18 min. The removal rates of room air bacteria due to sterilizer are compared with the natural decay of aerosols at steady state. The importance of decay half-life in the assessment has been stated. The bacteria concentration buildup process after putting off the sterilizers seems to be sigmoidal in nature. The buildup half-life is estimated to be around 53 min for present experimental conditions.