The antimicrobial activity of microencapsulated thymol and carvacrol

The aim of the present study was to determine the antimicrobial (AM) properties of plastic flexible films with a coating of microcapsules containing carvacrol and thymol as natural AM agents. Microencapsulation of these agents enables their controlled release and leads to the destruction (or growth inhibition) of a broad spectrum of microorganisms such as, Escherichia coli O157:H7, Staphylococcus aureus, Listeria innocua, Saccharomyces cerevisiae and Aspergillus niger. It was found that the studied AM agents are strong inhibitors to the growth of mycelium, but they were not effective against spore germination of mold. Thymol (T) and carvacrol (C) showed a significant AM activity against the studied microorganisms, with minimal inhibitory concentrations (MIC) of 125-250 ppm and 75-375 ppm for thymol and carvacrol respectively. The synergistic effect of combinations of thymol and carvacrol was also studied and it was found that the highest synergism was achieved at a concentration of 50% T and 50% C. The release of the AM agents was carried out at 4 °C during 28 days. The concentration of the microencapsulated AM agents showed a range of zones of inhibition of 4.3-11.3 mm for the microorganisms at 10% of thymol and 10% of carvacrol. At these concentrations the release of the AM agents (within 48 h) was greater than required for the most resistant microorganism (E .coli O157:H7), as reflected by the relatively large zone of inhibition. The results of the present study confirm the suitability of using microencapsulated thymol and carvacrol incorporated in polymer films for AM food packaging.     

Synergistic antimicrobial properties of nanoencapsulated clove oil and thymol against oral bacteria

Food Science and Biotechnology - This study aimed to improve the antimicrobial activity of natural extracts against oral bacteria by synergistic combination and nanoencapsulation. Among five...     

麝香草酚抑菌活性及其影响因素研究

采用滤纸片法和扩散法,研究不同浓度的麝香草酚对食品中常见10种污染菌的体外抑菌作用,并对其抑菌影响因素进行了研究。实验结果表明,麝香草酚对细菌、酵母和霉菌均有一定抑制作用。经测定,麝香草酚对金黄色葡萄球菌、枯草芽孢杆菌、大肠杆菌、变形杆菌、保加利亚乳杆菌、嗜热乳酸链球菌、异常汉逊氏酵母、酿酒酵母、黑曲霉、黄曲霉的最低抑菌浓度分别为10、20、20、40、40、40、80、40、80、160μg/mL。抑菌影响因素研究表明,吐温-80和有机氮（BSA）能明显消弱麝香草酚的抑菌能力;低pH则会明显增强麝香草酚的抑菌作用。      

Microbicidal activity of tripotassium phosphate and fatty acids toward spoilage and pathogenic bacteria associated with poultry

The ability of solutions of tripotassium phosphate (TPP) and fatty acids (lauric and myristic acids) to reduce populations of spoilage and pathogenic microorganisms associated with processed poultry was examined. In vitro studies were conducted with cultures of bacteria (Campylobacter jejuni, Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella Typhimurium, and Staphylococcus aureus) and yeasts (Candida ernobii and Yarrowia lipolytica). Cultures of the bacteria and yeasts were suspended in solutions of TPP or mixtures of TPP with lauric or myristic acid and mixed for 5 min. Viable numbers (log CFU per milliliter) in the suspensions were enumerated on microbiological agar. Results indicated that TPP solutions are highly bactericidal toward gram-negative bacteria and that mixtures of TPP and fatty acids are highly microbicidal toward gram-negative bacteria, gram-positive bacteria, and yeasts. The microbicidal activity of mixtures of TPP and fatty acids toward the native bacterial flora of skin of processed broiler carcasses was also examined. Skin samples were washed in mixtures of TPP and fatty acid, and the populations of total aerobic bacteria, campylobacters, enterococci, E. coli, lactic acid bacteria, pseudomonads, staphylococci, and yeasts in the skin rinsates were enumerated on the appropriate microbiological media. Results indicated that washing the skin in mixtures of TPP and fatty acids produced significant reductions in the number of aerobic bacteria, campylobacters, E. coli, pseudomonads, and yeasts recovered from skin rinsates, but there was no significant reduction in the populations of enterococci, lactic acid bacteria, or staphylococci. These findings indicate that mixtures of TPP and fatty acids possess microbicidal activity against several microorganisms associated with processed poultry and that these solutions could be useful as microbicides to reduce the populations of some bacteria and yeasts associated with some poultry processing operations.     

含氧硫醚类香料对常见致病菌的体外抑菌活性研究

对11种含氧硫醚类香料的抑菌活性进行研究,并探讨其构效关系。以副溶血性弧菌、金黄色葡萄球菌、大肠杆菌和单增李斯特菌为供试致病菌,通过测量抑菌圈直径考察硫醚类香料的抑菌活性,并通过统计分析探讨结构的影响。结果显示在浓度为5 mol/L的条件下,3-（甲硫基）丙醛（MTPD）、2-甲基-3-甲硫基呋喃（MMTF）、糠基异丙基硫醚（FIPS）和甲基糠基二硫醚（MFDS）对四种致病菌均有抑制作用,且抑菌能力为MTPD>MFDS>或≈FIPS>或≈MMTF。对比11种含氧硫醚类香料的抑菌活性,双（2-甲基-3-呋喃基）二硫醚（BMFDS）对金黄色葡萄球菌的抑制作用最强,MTPD次之,而BMFDS对其他三种致病菌无抑制作用。MTPD对副溶血性弧菌、大肠杆菌和单增李斯特菌的抑制作用均最强,且对副溶血性弧菌的作用效果最佳,其最低抑菌浓度为2.44 mmol/L。以上结果说明,醛基的存在对含氧硫醚类香料抑制副溶血性弧菌、金黄色葡萄球菌、大肠杆菌和单增李斯特菌具有重要作用。      

Antibacterial activity of antimicrobial peptide gcDefb1 against foodborne pathogenic bacteria and its application in pork storage

Food Science and Biotechnology - Pork and its products are preferably contaminated by bacteria; thus, it is essential to develop low-cost, high-efficiency and biologically safe preservatives to...     

A study on the antimicrobial activity of thymol intended as a natural preservative

A quantitative investigation on the inhibitory activity of thymol against some microorganisms that could represent a potential spoilage risk both in acid and mild thermally treated foods is presented in this work. In order to assess potential biostatic or biocidal activity of thymol, both the growth kinetics and dose-response profiles were obtained and analyzed. A suitable macrodilution methodology based on a turbidimetric technique was adopted to produce inhibitory data used for characterizing microbial susceptibility against thymol at sub-MIC levels. Microbial growth was monitored through absorbance measurements at 420 nm as a function of contact time with the active compound. Moreover, for each tested microorganism, the noninhibitory concentration (NIC) and the MIC were quantified. Results prove that thymol can exert a significant antimicrobial effect on each phase of the growth cycle. The microbial susceptibility and resistance were found to be nonlinearly dose related. It is worth noting that significant biostatic effects were observed at sub-MIC levels.     

Characterization and antimicrobial activity studies of polypropylene films with carvacrol and thymol for active packaging

Antimicrobial active films based on polypropylene (PP) were prepared by incorporating thymol and carvacrol at three different concentrations: 4, 6 and 8 wt.% of both additives as well as an equimolar mixture of them. A complete thermal, structural, mechanical and functional characterization of all formulations was carried out. SEM micrographs showed certain porosity for films with high additives concentrations. A decrease in elastic modulus was obtained for the active formulations compared with neat PP. The presence of additives did not affect the thermal stability of PP samples, but decreased PP crystallinity and oxygen barrier properties. The presence of thymol and carvacrol also increased stabilization against thermo-oxidative degradation, with higher oxidation induction parameters. Finally, thymol showed higher inhibition against bacterial strain present in food compared with carvacrol, leading to higher antimicrobial activity. The obtained results proved the permanence of certain amounts of the studied additives in the polymer matrix after processing making them able to be used as active additives in PP formulations.     

抗菌肽brevilaterin与食品防腐剂联用对食源性致病菌的抑制

侧孢短芽孢杆菌抗菌肽brevilaterin对细菌具有广谱抑菌活力,但是对革兰氏阴性菌的最小抑菌浓度显著高于革兰氏阳性菌,只有增大用量才能发挥广谱抑菌活性。该研究以食源性致病菌金黄色葡萄球菌、单核细胞增生李斯特菌、大肠杆菌、鼠伤寒沙门氏菌为指示菌,首先测定了食品中常用抑菌剂的最小抑菌浓度,然后分别考察了抗菌肽brevilaterin与各添加剂的联合抑菌效应,筛选了与brevilaterin具有协同作用的添加剂,进一步通过复配形成brevilaterin广谱高效抑菌配方。结果显示,天然防腐剂的抑菌效果优于化学防腐剂,且天然防腐剂对革兰氏阳性菌的抑菌效果普遍优于革兰氏阴性菌; brevilaterin分别与ε-聚赖氨酸、nisin联用对革兰氏阳性致病菌具有协同抑菌效应,与EDTA-Na_2、柠檬酸、Na_3PO_4联用对革兰氏阴性菌具有协同抑菌效应;选取brevilaterin、nisin和柠檬酸进行复配,时间杀菌曲线结果表明该组合能够发挥协同广谱抑菌效应,brevilaterin添加量降低为原用量的1/8。说明协同抑菌物质复配可有效降低brevilaterin使用剂量,且对食源性致病菌具有广谱抑菌活性。     

Mastitis: I. In vitro antimicrobial activity of alkyl amines against mastitic bacteria.

The activities of branched and straight chain amines (10 to 18 carbons chain length) were compared in inhibiting the growth of five microorganisms that cause about 95% of bovine mastitis. Three gram-positive (Streptococcus agalactiae, Streptococcus uberis, Staphylococcus aureus) and two gram-negative (Escherichia coli, Klebsiella pneumoniae) bacteria were used in a trypticase soy broth tube culture growth assay. Sixty-two compounds were screened at concentrations of 200, 100, 50, 25, 10, 5, and 1 ppm in broth culture to determine the effective minimum inhibitory concentration. Alkyl secondary N-substituted monoethyl [CH3(CH2)nNHCH2CH3] and tertiary N,N-substituted dimethyl [CH3(CH2) nN(CH3)2] amines with chain lengths of 11 to 14 carbon atoms were active against both gram-positive and gram-negative organisms. Antimicrobial activity against gram-positive organisms increased with increasing chain length and carbon-14 to 18 amines were active at 1 to 5 ppm. The carbon-11 to 13 alkyl amines were most active against gram-positive organisms; longer chain amines (more than 14 carbons) were inactive. Branching of the alkyl chain caused a loss of activity against gram-negative but not against gram-positive bacteria. Antimicrobial testing of monoamines, polyamines, and the influence of order substituents were investigated to correlate structure-acitivity relationships.     

产抗菌肽乳源乳酸菌的筛选及定向培养

为了获得乳酸菌高效表达抗菌肽的代谢调控方法,对德氏乳杆菌保加利亚亚种等7种乳酸菌进行了产抗菌肽能力的筛选和定向培养。筛选出具有较高抑菌活性的菌株嗜酸乳杆菌和干酪乳杆菌,它们产生的抑菌物质经排除酸、过氧化氢后,仍具有抑菌活性,然而经蛋白酶处理后其抑菌活性明显下降。结果表明,两种菌发酵上清液对金黄色葡萄球菌和大肠杆菌均有抑制作用。经一系列定向培养嗜酸乳杆菌抑菌直径达到(23.53±0.06)mm,与未经定向培养的抑菌直径(11.63±0.15)mm相比抑菌活性提高了102%;经定向培养的干酪乳杆菌抑菌直径达到(21.27±0.25)mm,与未经定向培养的抑菌直径(12.50±0.10)mm相比抑菌活性提高了70.2%。     

Short communication: Interaction of the isomers carvacrol and thymol with the antibiotics doxycycline and tilmicosin: In vitro effects against pathogenic bacteria commonly found in the respiratory tract of calves

Bovine respiratory disease is the major problem faced by cattle, specially calves, leading to reduced animal performance and increased mortality, consequently causing important economic losses. Hence, calves must be submitted to antibiotic therapy to counteract this infection usually initiated by the combination of environmental stress factors and viral infection, altering the animal's defense mechanism, and thus allowing lung colonization by the opportunistic bacteria Mannheimia haemolytica and Pasteurella multocida. Essential oils appear to be candidates to replace antibiotics or to act as antibiotic adjuvants due to their antimicrobial properties. In the present study, we aimed to evaluate the 4 essential oil components carvacrol, thymol, trans-anethole, and 1,8 cineole as antibacterial agents or as adjuvants for the antibiotics doxycycline and tilmicosin against M. haemolytica and P. multocida. Bacteria were cultured according to standard protocols, followed by the determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration. A checkerboard assay was applied to detect possible interactions between components, between antibiotics, and between components and antibiotics. Doxycycline at 0.25 and 0.125 μg/mL inhibited the growth of P. multocida and M. haemolytica, respectively, whereas tilmicosin MIC values were 1.0 and 4.0 μg/mL for P. multocida and M. haemolytica, respectively. Carvacrol MIC values were 2.5 and 1.25 mM for P. multocida and M. haemolytica, respectively, whereas thymol MIC values were 1.25 and 0.625 mM for P. multocida and M. haemolytica, respectively. Trans-anethole and 1,8 cineole did not present any antibacterial effect even at 40 mM against the investigated pathogens. All minimum bactericidal concentration values were the same as MIC, except when thymol was tested against M. haemolytica, being twice the MIC data (i.e., 1.25 mM thymol). Based on fractional inhibitory concentration checkerboard assay, no interaction was observed between doxycycline and tilmicosin. Carvacrol and thymol presented an additive effect when one of them was combined with tilmicosin. Additive effect was also observed when doxycycline was combined with thymol. Synergism was observed when carvacrol was combined with doxycycline or with thymol. Although the antibacterial effects of the tested essential oil components were observed at high concentrations for in vitro conditions, the additive and synergic effects of carvacrol and thymol with antibiotics suggest the option to apply them as antibiotic adjuvants.     

蒜渣多糖体外抑菌效果的研究

采用分光光度法测定蒜渣水提多糖和碱提多糖在体外对大肠杆菌,沙门氏菌,金黄色葡萄球菌的作用。结果表明:10、1、0.1、0.01、0.001 mg/mL的多糖液对大肠杆菌,沙门氏菌,金黄色葡萄球菌的生长均有一定的抑制作用,并且随着多糖浓度的增加,多糖抑菌效果越明显。     

Comparative antimicrobial activity of enterocin L50, pediocin PA-1, nisin A and lactocin S against spoilage and foodborne pathogenic bacteria

The present work compares, under the same stated experimental conditions, the antimicrobial activity of crude and purified enterocin L50, pediocin PA-1, nisin A and lactocin S, produced by lactic acid bacteria (LAB) isolated from Spanish dry-fermented sausages. The bacteriocins were purified to homogeneity by ammonium sulphate precipitation, gel filtration (for lactocin S), and cation-exchange, hydrophobic-interaction, and reverse-phase-chromatography; high yields of pure bacteriocins were obtained. Minimal inhibitory concentration (MIC) of pure enterocin L50, pediocin PA-1, nisin A and lactocin S was determined against a broad spectrum of Gram-positive bacteria, including spoilage and foodborne pathogenic bacteria. The purified bacteriocins showed a broad antimicrobial spectrum similar to that exerted by crude bacteriocins. Enterocin L50 and pediocin PA-1 were very active againstListeria monocytogenes, which was quite resistant to nisin A and lactocin S. Enterocin L50 also displayed antimicrobial activity againstStaphylococcus aureus,Clostridium perfringensandClostridium botulinum. However, these pathogens were weakly inhibited, or not at all, by the other pure bacteriocins.     

姜油对番茄致病菌的抑制效果及抑菌机制初探

目的研究姜油对番茄致病菌的抑制效果及抑菌机制。方法通过体外抑菌试验检测姜油对番茄早疫病菌、番茄灰霉病菌、番茄疮痂病菌3种番茄致病菌的抗菌性及其抗菌强度,通过体内试验验证姜油对番茄致病菌的抑制效果;并通过测定菌体湿重、细胞膜通透性初步探讨姜油抑菌机制。结果姜油对3种番茄致病菌均有一定的抑制作用;体内试验研究发现采用熏蒸方式处理的番茄其腐烂率低于直接接触的方式;姜油能抑制3种番茄致病菌菌体湿重的增加,增大菌体培养液电导率。结论姜油可能通过抑制菌丝体正常的生长和繁殖和破坏菌体细胞膜来达到抑菌效果。     

糙米的体外肠道益生菌调节及抗氧化活性

以糙米为研究对象,围绕其体外消化物的肠道益生菌调节功效和抗氧化活性开展研究。研究结果表明:相对精白米,糙米体外消化物中膳食纤维含量高(约11%),体外模拟肠道菌群培养实验中能更好促进益生菌——双歧杆菌(9.69个对数)和乳酸杆菌(7.30个对数)增殖,总短链脂肪酸含量提高约12%。铁离子还原/抗氧化能力(ferric-reducing antioxidant power,FRAP)和氧自由基清除能力(oxygen radical absorbance capacity,ORAC)实验结果表明,糙米体外消化物具有较好抗氧化活性,活性大小与所含酚类物质含量趋势较为一致。糙米消化物具有良好的维护肠道微生态和健康的功效。     

5味收涩药对奶牛乳腺炎病原菌体外抗菌活性的比较

采用琼脂平板二倍稀释法测定了诃子等5味收涩药对15个种属33种120株奶牛乳腺炎病原菌的最低抑菌浓度,统计分析了它们对葡萄球菌、链球菌、大肠埃希菌、阴沟肠杆菌和单胞菌等共11个种属的MIC50和MIC90,并采用SPSS17.0软件中单因素方差分析法比较分析了5味收涩药分别对葡萄球菌、鲁氏不动杆菌和芽孢杆菌等11个种属菌株押菌活性的强弱.结果表明,5味收涩药对受试菌均有较强的抗菌活性,总体以诃子的抗菌活性最强,其次为乌梅和石榴皮,再次为五味子,活性最差为山茱萸;且5味收涩药对革兰氏阳性菌的抗菌活性较对革兰氏阴性菌的活性强.     

Antimicrobial activity of cetylpyridinium chloride washes against pathogenic bacteria on beef surfaces

Cetylpyridinium chloride (CPC), a water-soluble, neutral pH, colorless compound, is widely used in oral hygiene products to inhibit bacteria responsible for plaque. Previously, researchers have demonstrated that CPC not only reduces Salmonella typhimurium on poultry but also prevents cross-contamination. To determine the effectiveness of CPC against pathogens associated with lean and adipose beef surfaces, several spray-washing experiments (862 kPa, 15 s, 35 degrees C) with 1% (wt/vol) CPC were conducted. On lean beef surfaces, CPC immediately reduced 5 to 6 log10 CFU/cm2 of Escherichia coli O157:H7 and Salmonella typhimurium to virtually undetectable levels (0 log10 CFU/cm2), as well as after 35 days of refrigerated (4 degrees C), vacuum-packaged storage. On adipose beef surfaces, 5 log10 CFU/cm2 Salmonella typhimurium and E. coli O157:H7 were reduced immediately (>2.5 log10 CFU/cm2) with 1% CPC; by day 35 the reduction was <1.3 log10 CFU/cm2. Further plate overlay analyses indicated that the effectiveness of CPC against pathogens on adipose surfaces was not hampered by the presence of meat components or fatty acids. Additional chemical and microbiological analyses of 1% CPC-treated beef surfaces subjected to a secondary water wash (following contact times of 0, 5, 10, 15, or 30 min) or grinding did reduce pathogenic bacteria and CPC levels. However, residual CPC levels following any of the treatments were considered excessive for human consumption. Despite the residual levels, this study is the first to demonstrate the effect of CPC on pathogenic bacteria associated with beef surfaces immediately after treatment and also after long-term, refrigerated, vacuum-packaged storage.     

乳酸对三种食源性致病菌的抑菌及杀菌作用

选用金黄色葡萄球菌、蜡样芽孢杆菌、埃希氏大肠杆菌3株常见的食源性致病菌,用于测定乳酸的抑菌效果、最小抑菌浓度(MIC)及最小杀菌浓度(MBC),并研究乳酸对3株致病菌细胞对数期代时的影响,同时研究不同浓度乳酸对大肠杆菌膜电位的影响.试验结果表明:乳酸对3株食源性致病菌均有不同程度的抑制作用,并得出最小抑菌浓度(MIC)及最小杀菌浓度(MBC),分别是金黄色葡萄球菌MIC 1.8 mg/mL,MBC3.6 mg/mL;蜡样芽孢杆菌MIC 3.6 mg/mL,MBC 7.2 mg/mL;大肠杆菌MIC 0.9 mg/mL,MBC 1.8 mg/mL;乳酸在最小抑菌浓度下显著(p≤0.05)延了3株食源性致病菌对数生长期的代时.大肠杆菌对乳酸的敏感性较强,代时增加128%.采用流式细胞仪测定大肠杆菌的膜电位.发现乳酸对大肠杆菌细胞膜电位有一定的影响,随着乳酸浓度的增加,细胞膜电位逐渐增加,导致细胞的超极化程度越来越严重直至细胞死亡.     

State of the art: Lateral flow assays toward the point-of-care foodborne pathogenic bacteria detection in food samples

Diverse chemicals and some physical phenomena recently introduced in nanotechnology have enabled scientists to develop useful devices in the field of food sciences. Concerning such developments, detecting foodborne pathogenic bacteria is now an important issue. These kinds of bacteria species have demonstrated severe health effects after consuming foods and high mortality related to acute cases. The most leading path of intoxication and infection has been through food matrices. Hence, quick recognition of foodborne bacteria agents at low concentrations has been required in current diagnostics. Lateral flow assays (LFAs) are one of the urgent and prevalently applied quick recognition methods that have been settled for recognizing diverse types of analytes. Thus, the present review has stressed on latest developments in LFAs-based platforms to detect various foodborne pathogenic bacteria such as Salmonella, Listeria, Escherichia coli, Brucella, Shigella, Staphylococcus aureus, Clostridium botulinum, and Vibrio cholera. Proper prominence has been given on exactly how the labels, detection elements, or procedures have affected recent developments in the evaluation of diverse bacteria using LFAs. Additionally, the modifications in assays specificity and sensitivity consistent with applied food processing techniques have been discussed. Finally, a conclusion has been drawn for highlighting the main challenges confronted through this method and offered a view and insight of thoughts for its further development in the future.