Efficacy of two hydrogen peroxide teat disinfectants against Staphylococcus aureus and Streptococcus agalactiae

An experimental teat dip containing 0.5% hydrogen peroxide as the active ingredient was compared with a teat disinfectant also containing 0.5% hydrogen peroxide that is commercially available throughout North America. The study was conducted under conditions of experimental challenge with a positive control following the guidelines recommended by the National Mastitis Council. The efficacy of the test product and the positive control product were compared in 45 cows, with 89 total teats receiving each product after milking during a 10-wk study period. There was no significant difference between the experimental hydrogen peroxide product and the positive control in new intramammary infections caused by Staphylococcus aureus (27.0 and 18.0% in the treatment groups, respectively). Additionally, there was no significant difference between the experimental product (6.7%) and the positive control groups (4.5%) in new intramammary infections caused by Streptococcus agalactiae. Traditional analysis of teat skin condition changes supported improved teat skin condition with the test disinfectant. After accounting for the correlation of teats within cow, significant differences were also observed between the treatment groups for teat skin condition. The experimental hydrogen peroxide-based teat disinfectant provided efficacy similar to that of the positive control teat disinfectant, with significant improvement in teat skin condition and no adverse effects on teat end condition.     

Alliinase-independent Inhibition of Staphylococcus aureus B33 by Heated Garlic

ABSTRACT: Heated (121 °C) garlic extract in which alliinase was inactivated before crushing exhibited complete bacteriostatic activity at 15% against Staphylococcus aureus. Garlic heated for 45 min showed the highest antibacterial activity and the relative peak areas of 4-heptenal, methyl allyl disulfide, diallyl disulfide, 2-vinyl-4H-1,3-dithiin, and diallyl trisulfide (DATS) were highest at 45 min of heating. Other than 4-heptenal, all these compounds are known to possess different degrees of antibacterial activity. DATS was thought to be the primary antibacterial compound in heated garlic extract. It was tentatively concluded that antibacterial compounds were formed from alliin unreacted by alliinase by marked heating. Diallyl compounds with more than three sulfur atoms and the oxidized form of allicin were not detected.     

丁香精油对金黄色葡萄球菌生物膜的抑制作用研究

金黄色葡萄球菌能在物体表面形成耐药性强的生物膜,给食品等领域带来严重的安全隐患。本实验研究的丁香精油对浮游细菌有较好的杀菌性能,但是对生物膜的抑制作用研究甚少。本实验着重研究了丁香精油对金黄色葡萄球菌生物膜的抑制作用。从实验结果表明,丁香精油对金黄色葡萄球菌生物膜有较好的抑制和清除作用。从实验结果可知,0.1%丁香精油对生物膜的抑制率达到99.73%,清除率达到99.93%。本实验通过激光共聚焦显微镜、环境扫描电子显微镜直接观察了丁香精油对生物膜的清除情况。从结果图可以直观地看出,0.1%的丁香精油对生物膜有较好的清除作用。     

Inhibition of Salmonella enteritidis and Staphylococcus aureus in nutrient broth by mint essential oil

The effect of different concentrations (0–1.2% v/v) of mint (Mentha piperita) essential oil on the growth/survival of Salmonella enteritidis and Staphylococcus aureus was studied in nutrient broth, using the viable count method and conductance measurements. In particular the addition of mint essential oil reduced the total viable counts of St. aureus about 6–7 logs while this of S. enteritidis only ca. 3 logs. The detection time measurements showed also that the inhibitory effect of mint essential oil was affected by the incubation temperature as well as by the concentration of essential oil added in the growth medium. At low concentration of essential oil (<0.1%), the addition of glucose in the growth medium prevented the formation of staphylococcal enterotoxin B, while the reduction of viable cells was only 2 logs. This glucose effect was not evident in Salmonella enteritidis samples. The percentage of glucose utilization in the growth medium of both pathogens, was reduced drastically with the addition of essential oil and as a consequence the assimilation or formation of different compounds, such as lactate, formate and acetate in the growth medium was also affected.     

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。     

安石榴苷对金黄色葡萄球菌毒力因子表达的抑制作用

分别采用溶血试验法、凝固酶效价法和酶联免疫反应法检测了安石榴苷处理后金黄色葡萄球菌溶血素、血浆凝固酶和总肠毒素的表达变化,并通过反转录实时荧光定量PCR技术检测毒力相关基因的表达情况。结果表明,安石榴苷能显著减少α-溶血素的产生,但对溶血素的抑制作用未呈现浓度依赖性;在高于1/4 MIC浓度下安石榴苷能降低血浆凝固酶的表达;在高于1/2 MIC浓度下,安石榴苷显著降低总肠毒素的产生;安石榴苷对肠毒素基因sea、溶血素基因hla和调节基因agrA的转录产生显著抑制作用,在1/8 MIC浓度下3个基因的相对表达量分别为对照组的3%,5%,5%。     

Bacteriophage performance against Staphylococcus aureus in milk is improved by high hydrostatic pressure treatments

The combined effect of bacteriophages, vB_SauS-phi-IPLA35 (phiIPLA35) and vB_SauS-phi-IPLA88 (phiIPLA88), and high hydrostatic pressure (HHP) on Staphylococcus aureus Sa9 was evaluated in pasteurized whole milk under a simulated cold chain break, which was simulated by incubation of milk at 25°C for 48 h. Four-hundred MPa was found to be the most suitable pressure to be used in combination with these phages. Two different levels of staphylococcal initial contamination (1×10(4) and 1×10(6) CFU/mL) were tested. A synergistic effect between HHP and phages was observed in both cases. Compared to each single treatment, the combined treatment was able to reduce the initial S. aureus contamination below the detection limit (<10 CFU/mL). Bacteriophage performance in pressurize milk against S. aureus enabled milder hydrostatic pressure treatments, therefore phages can be regarded as a valuable hurdle on minimally processed food.     

Inactivation of Staphylococcus aureus by pulsed UV-light sterilization

Pulsed UV light is a novel technology to inactivate pathogenic and spoilage microorganisms in a short time. The efficacy of pulsed UV light (5.6 J/cm2 per pulse) for the inactivation of Staphylococcus aureus as suspended or agar seeded cells was investigated. A 12-, 24-, or 48-ml cell suspension in buffer was treated under pulsed UV light for up to 30 s, and 0.1 ml of sample was surface plated on Baird-Parker agar and incubated at 37 degrees C for 24 h to determine log reductions. Also, 0.1 ml of cell suspension in peptone water was surface plated on Baird-Parker agar plates, and the plates were treated under pulsed UV light for up to 30 s. The treated and untreated plates were incubated in the conditions described above. A 7- to 8-log CFU/ml reduction was observed for suspended and agar-seeded cells treated for 5 s or longer. In the case of suspended cells, the sample depth, time, treatment, and interaction were significant (P < 0.05). In the case of agar-seeded cells, the treatment time was significant (P < 0.05). Our results clearly indicate that pulsed UV technology has potential for the inactivation of pathogenic microorganisms.     

碳纳米生物传感检测金黄色葡萄球菌

目的建立一种基于碳纳米材料的适配体传感器快速检测金黄色葡萄球菌的方法。方法利用核酸适配体与其靶标之间的特异性结合能力以及碳纳米管的荧光猝灭特性,构建一种新型快速的金黄色葡萄球菌检测方法。结果该方法特异性良好,与非目标菌株无交叉反应。同时,该方法对金黄色葡萄球菌的检出限为10~5 CFU/mL,线性范围为10~5～10~9 CFU/mL,而且在此浓度范围之间呈现良好的线性关系,线性方程为Y=53.22X-39.99,线性相关系数r~2=0.992。结论该方法具有检测速度快、操作简便、检测成本低等特点,为金黄色葡萄球菌的快速检测提供了一种有效手段。     

应用基因芯片技术鉴定食源性金黄色葡萄球菌的研究

目的:建立快速鉴定食源性金黄色葡萄球菌的基因芯片技术。方法:采用PCR方法扩增金黄色葡萄球菌16SrRNA基因的DNA片段,序列进行BLAST比较并通过软件设计其特异性探针,采用基因芯片杂交技术鉴定食源性金黄色葡萄球菌样品。结果:对所有样品进行基因芯片杂交技术处理并扫描观察,金黄色葡萄球菌的杂交结果呈阳性,其检测结果与传统方法鉴定结果一致。结论:应用基因芯片鉴定技术可快速、准确地鉴定食源性金黄色葡萄球菌,值得推广应用。     

Inhibition of Staphylococcus aureus and spheroplasts of Gram-negative bacteria by an antagonistic compound produced by a strain of Lactobacillus plantarum

A strain of Lactobacillus plantarum was examined for production of an extracellular antagonistic compound. Cellfree preparations, dialyzed to remove organic acids, were used in inhibition studies which revealed that Gram-positive bacteria were sensitive. Among these, Staphylococcus aureus was chosen for further characterization of the agent. The antagonistic compound was susceptible to breakdown by proteolytic enzymes and its effect was completely lost after heat treatment at 121°C for 15 min. Ultrafiltration studies indicated that the agent had a molecular weight of over 100, 000, suggesting a complex protein-containing aggregate. The antagonistic effect was found to be highest at low pH values and S. aureus was shown to be able to adapt to the agent. Most Gram-negative bacteria were resistant to the compound. However, after their transformation to spheroplasts, which removed most of the cell envelopes, these bacteria were sensitized. The conclusion is that the antagonistic mechanism probably includes agent influence on the cell surface.     

酸性氧化电解水对金黄色葡萄球菌生物被膜清除效果的研究

研究酸性氧化电解水对金黄色葡萄球菌生物被膜的清除效果。通过观察放大5 000倍的金黄色葡萄球菌生物被膜的扫描电镜照片发现,经酸性氧化电解水处理后,细菌外部基质基本被破坏,细胞破裂严重,生物被膜态细菌量下降,清除效果明显。增加保存酸性氧化电解水的时间、提高保存温度以及存在有机干扰物时均会显著降低清除效果;闭口储存的电解水清除生物被膜的能力高于敞口保存。有效氯、pH值和氧化还原电位对清除效果具有协同作用:有效氯含量较低时,电解水清除能力影响明显,有效氯含量较高时,清除效果无明显影响;低pH值条件下,清除效果较好;氧化还原电位与清除效果有明显正相关关系。     

Inhibition of Staphylococcus aureus Growth in Laboratory Media of Water Activity Adjusted with Polyethylene Glycols

Present work studied the growth behavior at 30°C of Staphylococcus aureus strains ATCC 6538 P, C-243 and S-6 in laboratory media with water activity (a_w) adjusted by addition of polyethylene glycol 200 (PEG-200) or polyethylene glycol-400 (PEG-400). No growth of strains ATCC 6538 P and S-6 was observed in any of the polyethylene glycols (PEG-200 or PEG-400) at or below a_w about 0.93. Strain C-243, however, showed slow growth in PEG-400 at a_w= 0.93 although was inhibited at a_w= 0.92; in the case of PEG-200 growth inhibition of this strain was observed at a_w= 0.93. All strains showed good growth (either in PEG-200 or PEG-400) at a_w= 0.96. The results confirm that PEG-200 and PEG-400 have a bactericidal effect on S. aureus cells that cannot be solely explained in terms of lowering of a_w.     

PCR技术检测金黄色葡萄球菌进展

金黄色葡萄球菌(Staphylococcusaureus,S.aureus)是引起食物中毒的主要致病菌之一,其传统方法包括选择性培养、生化鉴定等步骤,耗时长、灵敏性差,很难满足食品安全快速检测要求。PCR技术是近年来广泛应用于食品中致病微生物快速检测的现代方法之一,其目的基因多种多样,主要包括耐药性相关基因、毒素基因、酶基因及多种特异性鉴别基因。本文综述了PCR技术应用于金黄色葡萄球菌检测的各种目的基因,并简要介绍了多重PCR及实时定量PCR等新技术的应用。     

香菇多糖的过氧化氢脱色工艺研究

为了脱除香菇多糖液中的色素,以过氧化氢(H2O2)为脱色剂,选择脱色时间、脱色温度、pH和过氧化氢的质量百分比浓度等因素为实验因素,进行单因素实验,以此为基础进行4因素3水平的正交实验。结果表明,在脱色时间3h、温度55℃、pH7和过氧化氢的质量分数为7%的脱色条件下,可以有效地去除香菇多糖液中的色素。过氧化氢脱色时间短,香菇多糖保留率高,脱色效果优于树脂。     

Degradation of various fruit juice anthocyanins by hydrogen peroxide

Degradation kinetics of anthocyanins was studied in sour cherry nectar, pomegranate and strawberry juices at high hydrogen peroxide (H₂O₂) concentrations (9.31–27.92 mmol l⁻¹) at 10–30 °C and in only sour cherry nectar at low H₂O₂ concentrations (0.23–2.33 mmol l⁻¹) at 20 °C. Degradation of anthocyanins followed the first-order reaction kinetics. Sour cherry anthocyanins were the most resistant to H₂O₂, followed by pomegranate and strawberry anthocyanins. Degradation of anthocyanins was also studied in sour cherry nectar and pomegranate juice in the presence of ascorbic acid at 60 and 80 mg l⁻¹ concentrations at 20 °C. At 80 mg level, ascorbic acid significantly accelerated the degradation of anthocyanins in sour cherry nectar at 4.65, 6.98 and 9.31 mmol l⁻¹ H₂O₂ concentrations. In contrast, ascorbic acid at both 60 and 80 mg levels protected the anthocyanins from degradation by H₂O₂ in pomegranate juice.