Effect of abiotic factors on the antibacterial activity of chitosan against waterborne pathogens

To assess the adaptability of chitosan (from agricultural waste) as a natural disinfectant, its antibacterial activity against bacteria associated with waterborne diseases was investigated by varying such abiotic conditions, as pH and ionic strength and by adding different amounts of acid solvent, metal ions, and EDTA. Two major waterborne pathogens, Escherichia coli and Staphylococcus aureus, were examined. Results showed that organic acids with low carbon number were better solvents for chitosan than were inorganic acids. The effect of pH below 6 on the antibacterial activity of chitosan was significant. The antibacterial activity of chitosan increased with ionic strength but decreased with the addition of metal ions. The addition of Zn(2+) ions inhibited the antibacterial activity of chitosan the most, while the addition of Mg(2+) ions inhibited the antibacterial activity of chitosan the least. This was due to the chelating capacity of chitosan toward metal ions. The antibacterial activity of chitosan against E. coli was enhanced by EDTA. However, the antibacterial activity of chitosan against S. aureus was partially suppressed by EDTA. The antibacterial activity of chitosan was also dependent on its charges and solubility. The antibacterial mechanism of chitosan has currently been hypothesized as being related to surface interference. The results show that the chitosan is a potential bactericide under various environmental conditions.     

Antibacterial components of honey

The antibacterial activity of honey has been known since the 19th century. Recently, the potent activity of honey against antibiotic-resistant bacteria has further increased the interest for application of honey, but incomplete knowledge of the antibacterial activity is a major obstacle for clinical applicability. The high sugar concentration, hydrogen peroxide, and the low pH are well-known antibacterial factors in honey and more recently, methylglyoxal and the antimicrobial peptide bee defensin-1 were identified as important antibacterial compounds in honey. The antibacterial activity of honey is highly complex due to the involvement of multiple compounds and due to the large variation in the concentrations of these compounds among honeys. The current review will elaborate on the antibacterial compounds in honey. We discuss the activity of the individual compounds, their contribution to the complex antibacterial activity of honey, a novel approach to identify additional honey antibacterial compounds, and the implications of the novel developments for standardization of honey for medical applications.     

Distribution and significance of heterotrophic marine bacteria with antibacterial activity.

Bacteria with antibacterial activity were isolated from seawater, sediments, phytoplankton, and zooplankton of Suruga, Sagami, and Tokyo Bays and from soft corals and sponges collected from the Taiwan coast. Of the 726 strains isolated, 37 showed antibacterial activity against either Vibrio parahaemolyticus (ATCC 17802) or Staphylococcus aureus (P209). Sediment harbored the lowest number of these forms of bacteria, and those from Tokyo Bay did not show any activity. Attached isolates showed greater activity compared with free-living forms. Relatively high numbers of strains with antibacterial activity were associated with phytoplankton. Among the zooplankton isolates, cladocerans harbored the maximum number of antibacterial strains. Isolates were more inhibitory to gram-positive test cultures. Autoinhibition was observed only among 8% of the isolates. Marine nonproducers were more susceptible. Pseudomonas/Alteromonas species made up 81.0% of isolates, of which 30% were pigmented strains. The absence or reduction in number of bacteria with antibacterial activity in Tokyo Bay is attributed to its eutrophic nature, which may tend to moderate the production of antibacterial compounds.     

Distribution and significance of heterotrophic marine bacteria with antibacterial activity

Bacteria with antibacterial activity were isolated from seawater, sediments, phytoplankton, and zooplankton of Suruga, Sagami, and Tokyo Bays and from soft corals and sponges collected from the Taiwan coast. Of the 726 strains isolated, 37 showed antibacterial activity against either Vibrio parahaemolyticus (ATCC 17802) or Staphylococcus aureus (P209). Sediment harbored the lowest number of these forms of bacteria, and those from Tokyo Bay did not show any activity. Attached isolates showed greater activity compared with free-living forms. Relatively high numbers of strains with antibacterial activity were associated with phytoplankton. Among the zooplankton isolates, cladocerans harbored the maximum number of antibacterial strains. Isolates were more inhibitory to gram-positive test cultures. Autoinhibition was observed only among 8% of the isolates. Marine nonproducers were more susceptible. Pseudomonas/Alteromonas species made up 81.0% of isolates, of which 30% were pigmented strains. The absence or reduction in number of bacteria with antibacterial activity in Tokyo Bay is attributed to its eutrophic nature, which may tend to moderate the production of antibacterial compounds.     

家蝇抗菌肽的抑菌动力学研究及其机理初探

利用鼠伤寒沙门氏菌针刺诱导家蝇幼虫表达抗菌肽,对抗菌肽的抑菌动力学进行研究,并通过抗菌肽样品对不同细菌动力学特性的研究出发对抗菌肽抑菌作用机制进行探讨。研究发现抗菌肽样品的活性与作用时间有关,24h内出现一到两个活性峰,同一抗菌肽样品对不同细菌的抑菌动力学有差异,抗菌肽的抑菌动力学机制应该与它的的抑菌作用机制有关。通过电镜观测、细胞磷代谢、紫外吸收物测定以及抗菌肽与细菌DNA相互作用结果可知,微生物诱导家蝇表达的抗菌肽样品不仅能够造成细菌细胞的快速坍塌破裂而且能够破坏细胞核心,与DNA结合作用。抗菌肽抑菌动力学的解释：微生物诱导产物中含有两类抗菌肽,一类抗菌肽能造成细胞膜的快速坍塌破裂形成第一个活性峰;另一类抗菌肽可进入细胞,破坏细胞核心,造成紫外吸收物大量外泄形成第二个活性峰。     

人工栽培猴头菌多糖提取工艺及抑菌作用研究

研究人工栽培猴头菌多糖最佳提取工艺和抑菌作用。采用正交试验法研究人工栽培猴头菌多糖的提取工艺,经透析、除蛋白、真空干燥后,采用DEAE-52阴离子交换纤维素进行分离纯化,Nacl分段梯度洗脱得到纯化的人工栽培猴头菌多糖0.2M组分,采用滤纸片扩散法研究人工栽培猴头菌多糖的抑菌作用、pH值对抑菌作用的影响和最小抑菌浓度(MIC)。结果表明:人工栽培猴头菌多糖的最佳提取工艺为浸提温度60℃、提取时间4 h、料液比1∶25,人工栽培猴头菌多糖对大肠杆菌有一定的抑制作用,对金黄色葡萄球菌、枯草芽孢杆菌、沙门氏菌几乎没有抑菌作用。     

The major bactericidal activity of human seminal plasma is zinc-dependent and derived from fragmentation of the semenogelins

One of the major roles of seminal plasma is to provide antimicrobial protection for the spermatozoa in the female reproductive tract. We found that the bactericidal activity of seminal plasma was highest after resolution of the seminal clot and that this antibacterial activity subsequently became greatly diminished. The antibacterial activity was derived from peptides generated by fragmentation of the semenogelins while the semenogelin holoproteins displayed no antibacterial activity. After ejaculation the semenogelin-derived peptides were fragmented to smaller and smaller fragments over time and thereby lost antibacterial activity. This paralleled the loss of antibacterial activity of whole seminal plasma both in vitro and after sexual intercourse. Moreover, the antibacterial activity of the semenogelin-derived peptides generated in seminal plasma was strictly zinc-dependent both at neutral and low pH. These data provide novel roles for the resolution of seminal clots and for the high zinc concentration in human seminal plasma.     

In vitro antibacterial activity of Chilean red wines against Helicobacter pylori

The antibacterial activity of sixteen Chilean red wines (Cabernet Sauvignon, Cabernet Merlot, Cabernet Organic and Pinot Noir), and the active extracts of two randomly selected wines were assayed for their antibacterial activity on six strains of Helicobacter pylori isolated from gastric biopsies. The active fraction of the wines was obtained by dichloromethane extraction, and the antibacterial activity of the wines and extracts was evaluated by an agar diffusion method. All the red wines studied showed some antibacterial activity on the six strains of H. pylori, although the strains were heterogeneous in their susceptibility to each particular wine. The active fraction of the two wines selected also showed good activity against the strains tested. The main active compound was identified as resveratrol. The results presented indicate that Chilean red wines have antibacterial activity against H. pylori, which depends mainly on the presence of resveratrol.     

Effect of temperature on antibacterial activity of lidocaine to Staphylococcus aureus and Pseudomonas aeruginosa

The effect of temperature on the antibacterial activity of lidocaine to Staphylococcus aureus and Pseudomonas aeruginosa was investigated in vitro. At 10 C at which S. aureus organisms do not grow and might be metabolically inactive, the antibacterial activity of lidocaine to S. aureus was not observed in a concentration of 1%, which was quite antibacterial to S. aureus at 37 C. On the other hand, at 40 C a conspicuously increased antibacterial activity to S. aureus of lidocaine was observed in a concentration of 0.25% which was not antibacterial to S. aureus organisms at 37 C. Similar results were obtained when P. aeruginosa organisms were examined in place of S. aureus, although P. aeruginosa was found to be less susceptible to lidocaine than S. aureus. The clinical significance of the thermal effect on the antibacterial activity of lidocaine was discussed in brief.     

Effect of hydrogen peroxide on antibacterial activities of Canadian honeys

Honey is recognized as an efficacious topical antimicrobial agent in the treatment of burns and wounds. The antimicrobial activity in some honeys depends on the endogenous hydrogen peroxide content. This study was aimed to determine whether honey's hydrogen peroxide level could serve as a honey-specific, activity-associated biomarker that would allow predicting and assessing the therapeutic effects of honey. Using a broth microdilution assay, I analyzed antibacterial activities of 42 Canadian honeys against two bacterial strains: Escherichia coli (ATCC 14948) and Bacillus subtilis (ATCC 6633). The MIC90 and MIC50 were established from the dose-response relationship between antibacterial activities and honey concentrations. The impact of H2O2 on antibacterial activity was determined (i) by measuring the levels of H2O2 before and after its removal by catalase and (ii) by correlating the results with levels of antibacterial activities. Canadian honeys demonstrated moderate to high antibacterial activity against both bacterial species. Both MIC90 and MIC50 revealed that the honeys exhibited a selective growth inhibitory activity against E. coli, and this activity was strongly influenced by endogenous H2O2 concentrations. Bacillus subtilis activity was marginally significantly correlated with H2O2 content. The removal of H2O2 by catalase reduced the honeys' antibacterial activity, but the enzyme was unable to completely decompose endogenous H2O2. The 25%-30% H2O2 "leftover" was significantly correlated with the honeys' residual antibacterial activity against E. coli. These data indicate that all Canadian honeys exhibited antibacterial activity, with higher selectivity against E. coli than B. subtilis, and that these antibacterial activities were correlated with hydrogen peroxide production in honeys. Hydrogen peroxide levels in honey, therefore, is a strong predictor of the honey's antibacterial activity.     

肠球菌E4及其抑菌产物特性的研究

目的获得抑制微生物生长的菌株。方法根据形态学和生理生化学特性进行菌种鉴定;采用牛津杯法测定抑菌谱和抑菌物质的理化特性。结果排除了过氧化氢和有机酸的作用,该菌发酵上清液对苏云金杆菌、枯草杆菌、大肠埃希菌、鸡白痢沙门菌等有抑制作用。根据菌株的生理生化特征,该菌株初步定为肠球菌属,定名为E4（Enterococcus sp．）。所产抑菌物质具有较好的热稳定性,在酸性条件下稳定且活性高。结论分离筛选了1株可产抑菌物质的肠球菌,其产生的抑菌物质具有良好的生物化学特性和广谱的抑菌能力。     

Antibacterial activity of bactenecin 5 fragments and their interaction with phospholipid membranes.

Bactenecin 5 (Bac 5) is an antibacterial 43mer peptide isolated from bovine neutrophils. It consists of an Arg-rich N-terminal region and successive repeats of Arg-Pro-Pro-Ile (or Phe). We synthesized Bac 5(1-23) and several related peptides to clarify the roles these regions play in antibacterial activity. An assay of antibacterial activity revealed that such activity requires the presence of Arg residues at or near the N-terminus, as well as a chain length exceeding 15 residues. None of the peptides exhibited haemolytic activity. Polyproline II-like CD curves were observed for most of the peptides. Measurements of the membrane perturbation and fusion indicated that the perturbation and fusogenic activities of the peptides were, generally, parallel to their antibacterial activities. Amino acid substitution in the repeating region had some effect on antibacterial activity.     

海绵共栖细菌NJ6-3-1基于群体感应调控的抗菌活性

[目的]选择一株海绵共栖细菌Pseudoalteromonas sp.NJ6-3-1,研究其抗菌物质的代谢是否受到群体感应的调控.[方法]我们研究了在不同生长条件细菌NJ6-3-1代谢物的抗菌活性与细胞密度的关系;通过模拟自然的竞争环境,研究了低密度条件下的细菌NJ6-3-1与外源细菌Staphylococcus aureus共培养时的抗菌活性情况.[结果]实验发现细菌NJ6-3-1代谢抗菌物质的行为与细胞密度密切相关,只有当细胞密度达到一定的阈值OD630=0.4时,NJ6-3-1才能代谢抗菌物质;同时发现外源病原菌S.aureus代谢产物中存在某种信号分子,能诱导NJ6-3-1在不产生抗菌物质的生长条件下代谢抗菌物质.[结论]以上结果初步说明NJ6-3-1的抗菌活性受到种内和种间群体感应系统的调控.     

家蝇幼虫分泌物抗菌肽的生化特性初步研究

研究了不同温度、蛋白酶及反复冻溶对家蝇 Musca domestica 幼虫活体浸泡法获得的分泌物抗菌肽抗菌活性的影响;并检测其凝血效应;试管稀释法测定其最低抑菌浓度（MIC）、最低杀菌浓度（MBC）;SDS-PAGE分析其分子量范围。结果表明,该抗菌肽具有较强的热稳定性、酶稳定性及较强抗菌活性的特性,无凝血作用。对大肠埃希菌的最低抑菌浓度为37 μg/mL、最低杀菌浓度为75 μg/mL;分子量约10 kD。     

Design,synthesis, and antibacterial activity of 2,5-dihydropyrrole formyl hydroxyamino derivatives as novel peptide deformylase inhibitors

The synthesis and antibacterial activity of 2,5-dihydropyrrole formyl hydroxyamino derivatives are reported. The antibacterial activities of these derivatives were evaluated, and some of these derivatives showed better in vitro antibacterial activity than existing drugs, including penicillin, ciprofloxacin, vancomycin, and linezolid.     

杨梅果实不同溶剂提取物抑菌特性的研究

目的探讨4种溶剂杨梅果实提取物对14种致病菌的抑菌作用,并对其中活性成分的含量进行测定和比较。方法利用常压浸提法制备杨梅果实的水、乙醇、乙酸乙酯和丙酮提取物;采用管碟法、琼脂平板稀释法测定各种杨梅提取物的抑菌活性,采用常规含量测定方法对各提取物中的主要成分及含量进行研究。结果4种杨梅果实提取物对革兰阴性和阳性菌均表现出了较强的抑菌活性,其中水提取物的抑菌活性最强。含量测定结果表明4种提取物的主要成分中总酚、黄酮含量以及总酸度相差较大,单宁含量差异较小。结论推测提取物中的主要抑菌成分为单宁类物质并确定杨梅果实的最佳提取溶剂为水。     

Synthesis and antibacterial activity of littorachalcone and related diphenyl ethers

Littorachalcone (1) and diacid 10 were synthesized by direct routes. The antibacterial activity of 1, 10 and synthetic precursors were evaluated. Dialdehyde 3a showed potent antibacterial activity.     

Designing Chimeric Peptides: A Powerful Tool for Enhancing Antibacterial Activity

Chimeric peptides containing short sequences derived from bovine Lactoferricin (LfcinB) and Buforin II (BFII) were synthetized using solid-phase peptide synthesis (SPPS) and characterized via reversed-phase liquid chromatography and mass spectrometry. The chimeras were obtained with high purity, demonstrating their synthetic viability. The chimeras’ antibacterial activity against Gram-positive and Gram-negative strains was evaluated. Our results showed that all the chimeras exhibited greater antibacterial activity against the evaluated strains than the individual sequences, suggesting that chemical binding of short sequences derived from AMPs significantly increased the antibacterial activity. For each strain, the chimera with the best antibacterial activity exerted a bacteriostatic and/or bactericidal effect, which was dependent on the concentration. It was found that: (i) the antibacterial activity of a chimera is mainly influenced by the linked sequences, the palindromic motif RLLRRLLR being the most relevant one; (ii) the inclusion of a spacer between the short sequences did not significantly affect the chimera's synthesis process; however, it enhanced its antibacterial activity against Gram-negative and Gram-positive strains; on the other hand, (iii) the replacement of Arg with Lys in the LfcinB or BFII sequences improved the chimeras’ synthesis process without significantly affecting their antibacterial activity. These results illustrate the great importance of the synthesis of chimeric peptides for the generation of promising antibacterial peptides.     

Antibacterial activity of peptides derived from the C-terminal region of a hemolytic lectin, CEL-III, from the marine invertebrate Cucumaria echinata

Several synthetic peptides derived from the C-terminal domain sequence of a hemolytic lectin, CEL-III, were examined as to their action on bacteria and artificial lipid membranes. Peptide P332 (KGVIFAKASVSVKVTASLSK-NH(2)), corresponding to the sequence from residue 332, exhibited strong antibacterial activity toward Gram-positive bacteria. Replacement of each Lys in P332 by Ala markedly decreased the activity. However, when all Lys were replaced by Arg, the antibacterial activity increased, indicating the importance of positively charged residues at these positions. Replacement of Val by Leu also led to higher antibacterial activity, especially toward Gram-negative bacteria. The antibacterial activity of these peptides was correlated with their membrane-permeabilizing activity toward the bacterial inner membrane and artificial lipid vesicles, indicating that the antibacterial action is due to perturbation of bacterial cell membranes, leading to enhancement of their permeability. These results also suggest that the hydrophobic region of CEL-III, from which P332 and its analogs were derived, may play some role in the interaction with target cell membranes to trigger hemolysis.     

低聚壳聚糖美拉德衍生物抑菌性能研究

本文研究了基于与葡萄糖、麦芽糖和木糖进行美拉德反应的低聚壳聚糖衍生物的抑菌性.测定低聚壳聚糖及其衍生物对大肠杆菌和金黄色葡萄球菌的抑制效果.结果显示:壳聚糖及其衍生物对金黄色葡萄球菌的抑制作用强于对大肠杆菌的抑制作用,且随着浓度增加,对两种菌的抑菌效果增强.大多数壳聚糖衍生物的抑菌效果优于壳聚糖本身,其中CG 1∶1 8 h(低聚壳聚糖的氨基与葡萄糖的羰基的物质量比为1∶1,反应8h)的抑菌效果最好,CM 1∶3 8 h(低聚壳聚糖的氨基与麦芽糖的羰基的物质量比为1∶3,反应8 h)抑菌性最差,这可能与参加反应的还原糖种类、反应物比例以及反应时间相关.