Inactivation of Staphylococcus aureus by the synergistic action of charged and reactive plasma particles

In this paper, a low-pressure capacitively coupled plasma discharge sustained in an argonoxygen mixture was studied in order to evaluate its properties in terms of inactivation of Staphylococcus aureus. The plasma parameters as electron temperature and plasma density were measured by the Langmuir probe (N_e ≈ 10¹⁵ m⁻³, T_e ≈ 1.5 eV), while the neutral atom density was in the range of 10²¹ m⁻³. In the plasma phase, oxygen radicals were taken as reference of the reactive species with antimicrobial activity, and oxygen spectral lines, over a range of plasma process parameters, were investigated by the optical emission spectroscopy. Optimal plasma conditions were found, and a count reduction of 4 log in a few minutes of the bacterium proves the potentiality of an industrial grade plasma reactor as a sterilization agent.     

The Antimicrobial Peptide Temporin G: Anti-Biofilm,Anti-Persister Activities,and Potentiator Effect of Tobramycin Efficacy Against Staphylococcus aureus

Bacterial biofilms are a serious threat for human health, and the Gram-positive bacterium Staphylococcus aureus is one of the microorganisms that can easily switch from a planktonic to a sessile lifestyle, providing protection from a large variety of adverse environmental conditions. Dormant non-dividing cells with low metabolic activity, named persisters, are tolerant to antibiotic treatment and are the principal cause of recalcitrant and resistant infections, including skin infections. Antimicrobial peptides (AMPs) hold promise as new anti-infective agents to treat such infections. Here for the first time, we investigated the activity of the frog-skin AMP temporin G (TG) against preformed S. aureus biofilm including persisters, as well as its efficacy in combination with tobramycin, in inhibiting S. aureus growth. TG was found to provoke ~50 to 100% reduction of biofilm viability in the concentration range from 12.5 to 100 µM vs ATCC and clinical isolates and to be active against persister cells (about 70–80% killing at 50–100 µM). Notably, sub-inhibitory concentrations of TG in combination with tobramycin were able to significantly reduce S. aureus growth, potentiating the antibiotic power. No critical cytotoxicity was detected when TG was tested in vitro up to 100 µM against human keratinocytes, confirming its safety profile for the development of a new potential anti-infective drug, especially for treatment of bacterial skin infections.     

食源性微生物MRSA及其检测方法在食品安全中的研究进展

食品安全在世界卫生组织的定义是指所有食品中有毒、有害物质对人体健康影响的公共卫生问题。2008年"三聚氰胺"事件后,在近几年的全国两会上,食品安全问题连续成为焦点话题;而同期全国人大常委会通过的《食品安全法》,更显示了食品安全的严重与令人担忧,其监测与控制显得迫在眉睫。作为典型的食源性微生物,金葡菌尤其是耐甲氧西林金黄色葡萄球菌(Methicillin-resistant Staphylococcus aureus,MRSA)其新型的耐药特点显示了细菌耐药性的发展和进化可能是由于大量抗生素在畜牧业中的滥用而造成的。由于抗菌药物的研制周期跟不上耐药性出现的速度,使得细菌治疗面临越来越严峻的考验,甚至出现无药可用的情况,严重威胁人类健康。本文结合食品安全抗生素滥用问题与最近出现的超级细菌耐药问题,根据在相关领域多年的研究数据,对常见的食源性微生物MRSA及其检测方法在食品安全中的研究进展进行综述。     

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.     

合肥市即食肉类食品中金黄色葡萄球菌污染情况及耐药和基因型分布

目的调查合肥市即食肉类食品中金黄色葡萄球菌的污染情况,并对分离株进行耐药性分析及多位点序列分型研究。方法 2017年10月—2018年10月自合肥市区范围内的超市和开放型菜市场共采集744份即食型肉类食品样品。根据GB 4789.10—2016《食品安全国家标准食品微生物学检验金黄色葡萄球菌检验》中的方法对样品进行金黄色葡萄球菌定性和定量分析,采用K-B纸片扩散法检测分离株的耐药性,采用多位点序列分型法对分离株进行ST分型,使用MEGA 7.0绘制聚类树状图。结果样品中金黄色葡萄球菌检出率为4.2%(31/744),其中卤肉制品检出率最高为8.1%(15/185),其次为烤肉制品(6.3%,11/174),定量分析显示超过90%的样品金黄色葡萄球菌污染水平在0.3～10 MPN/g范围内。耐药性分析结果显示80.6%(25/31)的菌株对青霉素G耐药,40%以上的菌株对链霉素、红霉素和卡那霉素耐药;多重耐药菌株占比为61.3%(19/31)。分型分析共获得8个ST型,分别为ST6、ST7、ST15、ST59、ST72、ST188、ST398和ST2196型,其中以ST188和ST72型为主。结论合肥市卤肉和烤肉制品中存在金黄色葡萄球菌污染,且多重耐药菌株比例较高,对消费者的健康有潜在威胁,有必要持续监测污染率、菌株耐药和基因型流行趋势,完善合肥市食源性金黄色葡萄球菌感染的风险评估。     

Growth, survival and inactivation of Pseudomonas aeruginosa and Staphylococcus aureus strains of various origin in the presence of ethanol

The influence of ethanol on the behaviour of Pseudomonas aeruginosa and Staphylococcus aureus strains was evaluated throughout this study. Strains of different origin were used: collection, clinical and industrial strains were selected. Concentrations of ethanol from 0 to 20% (v/v) were evaluated by automated optical density measurements and by enumeration. When growth conditions were observed, predictive microbiology models were used to assess quantitatively for the ethanol effect. Primary modelling of kinetics was performed to determine growth rate values; secondary modelling was performed on these growth rates as influenced by ethanol, and minimum inhibitory concentrations of ethanol were determined for each strain. Staphylococcus aureus strains were more resistant to ethanol than P. aeruginosa strains, in growth conditions as well as in inactivation conditions. Furthermore, clinical S. aureus strains were more resistant than the collection strain. The method was promising for management of microbiological safety in cosmetics.     

紫甘薯花色苷色素抑制金黄色葡萄球菌作用初探

本实验研究紫甘薯花色苷色素对金黄色葡萄球菌的抑制作用.结果表明,紫甘薯花色苷色素对金黄色葡萄球菌抑制的最低浓度为200μg/ml.金黄色葡萄球菌生长曲线和透射电镜观察表明,紫甘薯花色苷的抑菌作用可能是通过增强细胞膜的通透性,使细胞异常生长,抑制对数生长期的细胞分裂,使细胞质稀薄、解体,导致细胞死亡.SDS-PAGE分析表明,紫甘薯花色苷对大肠杆菌和金黄色葡萄球菌蛋白表达影响不明显,未见特征性条带的消失,仅对部分蛋白质合成量有影响.     

猪源金黄色葡萄球菌vwb基因分布及对不同动物体外凝血致病作用的研究

为调查猪源金黄色葡萄球菌(Staphylococcus aurues,S. aureus)对不同动物宿主具有凝血致病作用及是否携带S. aureus凝固酶基因vwb~C、vwb~Sbo4、vwb~Sov2和vwb~Seq1,本文以厦门地区生猪养殖场、屠宰场和终端市场分离的130株S. aureus为研究对象,通过血浆凝固酶实验研究菌株对兔血浆、牛血浆和羊血浆的凝血致病性,采用PCR方法对实验菌株进行vwb~C、vwb~(Sbo4)、vwb~(Sov2)和vwb~(Seq1)基因的扩增。结果表明,兔血浆、牛血浆和羊血浆的阳性凝血率分别为100.00%、28.46%、28.46%。S.aureus凝固酶vwb~C,vwb~(Sbo4)和vwb~(Sov2)基因的检出率分别为100.00%(130/130),26.92%(35/130)和26.93%(38/130),vwb~(Seq1)基因未检出;来自生猪养殖场S.aureus中vwb~(Sbo4)和vwb~(Sov2)基因的检出率以及对牛血浆和羊血浆的阳性凝血率明显高于另外两种来源S. aureus,有显著性差异(p0.05)。研究结果说明猪源S. aureus对不同动物宿主具有凝血致病作用,为猪源S. aureus对不同动物宿主的凝血致病作用和适应性提供研究基础。     

Synthesis of Silver Nanoparticles and Exhaustion on Cotton Fabric Simultaneously Using Laser Ablation Method

ABSTRACT

In this experimental research, the silver nanoparticles were synthesized on cotton fabric using laser ablation method in the same bath. Also the effects of the size of silver nanoparticles (NPs) on the structural and antibacterial properties of silver NP-coated cotton fabric have been investigated experimentally. A pulsed laser beam was used for synthesis of Ag NPs on cotton fabric. Pulses of a Q-switched Nd:YAG laser of 1064 nm wavelengths at 7 ns pulse width and different fluencies was employed to irradiate the Ag target in deionized water in the presence of cotton fabric. Four samples were prepared using different laser fluencies. The amount, size, morphology, and structure of produced NPs were studied using their spectrum in the range of UV to IR, and scanning electron microscopy methods. Fabrics were polluted by gram-positive Staphylococcus aureus bacteria. The colony counting method was used to investigate the antibacterial activity of prepared cotton samples. Results show that laser ablation for synthesis of Ag nanoparticles on cotton fabric is an inexpensive fast method for producing antibacterial fabrics.