Antimicrobial action of silver nitrate

Silver nitrate 3 mug/ml prevented the separation into two daughter cells of sensitive dividing cells of Pseudomonas aeruginosa growing in nutrient broth plus the chemical. Cell size of sensitive cells was increased and the cytoplasmic contents, cytoplasmic membrane and external cell envelope structures were all abnormal. P. aeruginosa cells grown in the presence of silver nitrate 9 mug/ml showed all these changes to a marked degree except inhibition of cell division was not observed. Silver nitrate (1.5 mug/ml) in distilled water inactivated bacteriophage T2 particles as determined by their infectivity to Escherichia coli B cultures. Lysozyme (50 mug/ml) reduced, and sodium chloride (0.9%) blocked this activity.     

Antimicrobial action of novel chitin derivative

Aminoethyl-chitin (AEC) was synthesized in an attempt to both increase solubility of chitin in water and biological activity. AEC was obtained by grafting 2-chloroethylamino hydrochloride onto chitin at C-6 position. The structure of AEC was elucidated FT-IR and (1)H NMR spectroscopy, and its antimicrobial activity was investigated using three Gram-positive and Gram-negative bacteria. The integrity of the cell membranes of the representatives E. coli and S. aureus was investigated by determining the release of intracellular components of cells. When treated with AEC, release of 260 nm absorbing materials quickly increased both E. coli and S. aureus, but absorbance value was different due to the difference in cell structures. For detailed study, outer membrane (OM) and inner membrane (IM) permeabilization assay were performed using the fluorescent probe 1-N-phenylnaphthylamine (NPN) and the release of cytoplasmic beta-galactosidase activity. The results showed that AEC rapidly increased NPN uptake and the release of cytoplasmic beta-galactosidase via increasing the permeability of OM and IM. In addition, cytotoxic effect of AEC was assessed using human lung fibroblast (MRC-5) cell line, and AEC showed less toxic against MRC-5.     

Antimicrobial action and efficiency of silver-loaded zeolite X

Aims: To synthesize silver-loaded zeolite X and establish the extent to which it persist in its antimicrobial action against strains of Escherichia coli K12W-T, Pseudomonas aeruginosa NCIMB8295 and Staphylococcus aureus NCIMB6571. Methods and Results: The antimicrobial action and efficacy of silver-loaded zeolite X on Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa were investigated. Zeolite X was synthesized and loaded with Ag⁺ by ion exchange. This resulted in 2·0% (w/w) loading of Ag⁺ in the zeolite framework and 5·8% (w/w) on the zeolite. Escherichia coli and Pseudomonas aeruginosa and Staphylococcus aureus suspended in tryptone soya broth were exposed to 0·15, 0·25, 0·5 or 1·0 g l⁻¹ of silver-loaded zeolite X for a period up to 24 h. No viable cells were detected for any of the three micro-organisms within 1 h. Silver-loaded zeolite X, retrieved three times from the first exposure cultures, was washed with de-ionized water and added to fresh bacterial suspensions. The results showed that the silver-loaded zeolite X retained its antimicrobial action. Conclusions: Silver-loaded zeolite X persisted in its antimicrobial action against all three micro-organisms. Significance and Impact of the study: The results are significant for the longevity of antimicrobial action of silver-loaded zeolite X.     

Biosynthesis of penitrems and roquefortine by Penicillium crustosum

Roquefortine and the penitrems were biosynthesised concurrently at an approximately equimolar rate by Penicillium crustosum after growth and sporulation. [14C]mevalonic acid was incorporated (15% efficiency) into the isoprenoid regions of the penitrem and roquefortine molecules to an extent consistent with their 6:1 molar ratio of isoprenoid components. [14C]penitrem A (specific activity, 3.4 X 10(2) mu Ci mmol-1) and 14C-penitrems B, C, and E readministered to young cultures were metabolically interconverted, indicating considerable metabolic flux, though generally directed towards penitrem A as the end product and suggesting a metabolic grid for the penitrem metabolites. Addition of bromide to the medium preferentially favored the production of bromo-analogs rather than the usual chloropenitrems.     

Antimicrobial action spectrum of triterpene and steroid glycosides]

Antimicrobial activity of 9 triterpene glycosides of the plant and animal origin was studied. It was found that saponins inhibited the fungal growth to different extents and had no activity against grampositive and gramnegative bacteria. Triterpene glycosides of the animal origin, i.e. holoturins A and B, stichoposids A and C had the most pronounced antifungal activity as compared to the saponins isolated from plants. Changes in the length of the carbon chain from 2 to 6 monosugars had no significant effect on the activity of the triterpeneglycosides studied.     

Antimicrobial action of Lentinus edodes juice on human microflora

The action of the juice of Shiitake mushroom (L. edodes) on pathogenic and opportunistic microorganisms, detected in cases of considerable dysbiotic changes (Escherichia coli O-114, Staphylococcus aureus, Enterococcus faecalis, Candida albicans), as well as on some bacterial eubiotic producer strains (Escherichia coli M-17, Bifidobacterium spp., Lactobacillus spp.). The juice of this mushroom at a concentration of 5% from the volume of the nutrient medium was found to produce a pronounced antimicrobial effect with respect to C. albicans, S. aureus, E. faecalis, E. coli O-114 and to stimulate the growth of E. coli M-17. Bifidobacteria and lactobacteria exhibited resistance to the action of L. edodes juice.     

Biosynthesis of penitrems and roquefortine by Penicillium crustosum.

Roquefortine and the penitrems were biosynthesised concurrently at an approximately equimolar rate by Penicillium crustosum after growth and sporulation. [14C]mevalonic acid was incorporated (15% efficiency) into the isoprenoid regions of the penitrem and roquefortine molecules to an extent consistent with their 6:1 molar ratio of isoprenoid components. [14C]penitrem A (specific activity, 3.4 X 10(2) mu Ci mmol-1) and 14C-penitrems B, C, and E readministered to young cultures were metabolically interconverted, indicating considerable metabolic flux, though generally directed towards penitrem A as the end product and suggesting a metabolic grid for the penitrem metabolites. Addition of bromide to the medium preferentially favored the production of bromo-analogs rather than the usual chloropenitrems.     

Antimicrobial action of nisin against Salmonella typhimurium lipopolysaccharide mutants.

The antimicrobial activity of nisin against outer membrane lipopolysaccharide mutants of Salmonella typhimurium LT2 was investigated. Nisin sensitivity was associated with the extent of saccharide deletions from the outer membrane core oligosaccharide. The results indicated that the core oligosaccharide in lipopolysaccharide plays a role in nisin sensitivity.     

Antimicrobial action of nisin against Salmonella typhimurium lipopolysaccharide mutants.

The antimicrobial activity of nisin against outer membrane lipopolysaccharide mutants of Salmonella typhimurium LT2 was investigated. Nisin sensitivity was associated with the extent of saccharide deletions from the outer membrane core oligosaccharide. The results indicated that the core oligosaccharide in lipopolysaccharide plays a role in nisin sensitivity.     

Antimicrobial action of achacin is mediated by L-amino acid oxidase activity

Achacin is an antibacterial glycoprotein purified from the mucus of the giant snail, Achatina fulica Férussac, as a humoral defense factor. We showed that achacin has L-amino acid oxidase activity and can generate cytotoxic H(2)O(2); however, the concentration of H(2)O(2) was not sufficient to kill bacteria. The antibacterial activity of achacin was inhibited by various H(2)O(2) scavengers. Immunochemical analysis revealed that achacin was preferentially bound to growth-phase bacteria, accounting for the important role in growth-phase-dependent antibacterial activity of achacin. Achacin may act as an important defense molecule against invading bacteria.     

Factors contributing to roquefortine yield variability during cultivation of penicillium roquefortii

Variability in the roquefortine yield was shown to be associated with its consumption by the mycelium during isolation of the end product, which depended on temperature, time of culture liquid storage, and biomass concentration. This was also related to the presence in chloroform of chlorocarbonic acid ethyl ester that reacted with roquefortine.     

Antimicrobial peptides: the mode of action and perspectives of practical application

This review deals with antimicrobial peptides (AMPs) that demonstrate antibacterial, antiviral, and antifungal activity. It considers structure and mechanism of AMP interaction with lipid membrane and intracellular targets of pathogens. Special attention is paid to modern state and perspectives of AMP practical application and also to approaches that increase efficacy and reduce toxicity of AMP by chemical modification of their structure.     

Antimicrobial mechanism of action of surfactant lipid preparations in enteric Gram-negative bacilli

Two surfactant lipid preparations (SLPs) were investigated to determine their mechanism of antimicrobial action. 8N8, a water-in-oil emulsion, and W60C, a liposome, both have bactericidal activity against Gram-positive bacteria and non-enteric Gram-negative bacteria. Additionally, W60C is bactericidal for enteric Gram-negative bacilli when suspended in deionized water. Zeta potential measurements suggested that the resistance of Gram-negative bacilli to 8N8 might be caused by ionic repulsion. Addition of 50 micromol 1(-1) ethylene diamine tetra acetic acid in 100 mmol 1(-1) Tris buffer to either SLPs yielded efficient bactericidal activity against Gram-negative bacilli. This appeared to be due to disruption of the outer membrane and the chelation of divalent cations, as the addition of excess calcium inhibited the antimicrobial effect. Electron microscopy studies documented that 8N8 disrupts the bacterial cell wall, lysing the bacteria, while W60C fuses and internalizes within the cell, causing damage without immediate cell lysis. Understanding the mechanisms of action of these biocidal formulations will help to produce improved formulations with broader spectra of activity.     

Antimicrobial evaluation and action mechanism of pyridinium-decorated 1,4-pentadien-3-one derivatives

A type of pyridinium-decorated 1,4-pentadien-3-one derivatives possessing flexible alkyls were designed and synthesized by integrating the key scaffolds of pyridinium cations and 1,4-pentadien-3-one skeleton in a single molecular architecture. Antimicrobial bioassays indicated that some of the target molecules exerted considerable bioactivities against six phytopathogenic strains, especially for Xanthomonas oryzae pv. oryzae, the minimal EC₅₀ value can reach to 0.504?µg/mL. A plausible action mechanism for this kind of compounds was proposed and confirmed by employing fluorescent spectroscopy, fluorescence microscopy, and scanning electron microscopy. We anticipated that this finding can promote high-efficient lead compounds discovery in the research of antimicrobial chemotherapy.     

Antimicrobial action of palmarosa oil (Cymbopogon martinii) on Saccharomyces cerevisiae

The essential oil extracted from palmarosa (Cymbopogon martinii) has proven anti-microbial properties against cells of Saccharomyces cerevisiae. Low concentrations of the oil (0.1%) inhibited the growth of S. cerevisiae cells completely. The composition of the sample of palmarosa oil was determined as 65% geraniol and 20% geranyl acetate as confirmed by GC-FTIR. The effect of palmarosa oil in causing K(+) leakage from yeast cells was attributed mainly to geraniol. Some leakage of magnesium ions was also observed. Blocking potassium membrane channels with caesium ions before addition of palmarosa oil did not change the extent of K(+) ion leakage, which was equal to the total sequestered K(+) in the cells. Palmarosa oil led to changes in the composition of the yeast cell membrane, with more saturated and less unsaturated fatty acids in the membrane after exposure of S. cerevisiae cells to the oil. Some of the palmarosa oil was lost by volatilization during incubation of the oil with the yeast cells. The actual concentration of the oil components affecting the yeast cells could not therefore be accurately determined.     

Antimicrobial peptides (AMPs): peptide structure and mode of action

Antimicrobial peptides (AMPs) have been isolated and characterized from tissues and organisms representing virtually every kingdom and phylum. Their amino acid composition, amphipathicity, cationic charge, and size allow them to attach to and insert into membrane bilayers to form pores by 'barrel-stave', 'carpet' or 'toroidal-pore' mechanisms. Although these models are helpful for defining mechanisms of AMP activity, their relevance to resolving how peptides damage and kill microorganisms still needs to be clarified. Moreover, many AMPs employ sophisticated and dynamic mechanisms of action to carry out their likely roles in antimicrobial host defense. Recently, it has been speculated that transmembrane pore formation is not the only mechanism of microbial killing by AMPs. In fact, several observations suggest that translocated AMPs can alter cytoplasmic membrane septum formation, reduce cell-wall, nucleic acid, and protein synthesis, and inhibit enzymatic activity. In this review, we present the structures of several AMPs as well as models of how AMPs induce pore formation. AMPs have received special attention as a possible alternative way to combat antibiotic-resistant bacterial strains. It may be possible to design synthetic AMPs with enhanced activity for microbial cells, especially those with antibiotic resistance, as well as synergistic effects with conventional antibiotic agents that lack cytotoxic or hemolytic activity.     

Antimicrobial polymers: mechanism of action,factors of activity,and applications

Complex epidemiological situation, nosocomial infections, microbial contamination, and infection risks in hospital and dental equipment have led to an ever-growing need for prevention of microbial infection in these various areas. Macromolecular systems, due to their properties, allow one to efficiently use them in various fields, including the creation of polymers with the antimicrobial activity. In the past decade, the intensive development of a large class of antimicrobial macromolecular systems, polymers, and copolymers, either quaternized or functionalized with bioactive groups, has been continued, and they have been successfully used as biocides. Various permanent microbicidal surfaces with non-leaching polymer antimicrobial coatings have been designed. Along with these trends, new moderately hydrophobic polymer structures have been synthesized and studied, which contain protonated primary or secondary/tertiary amine groups that exhibited rather high antimicrobial activity, often unlike their quaternary analogues. This mini-review briefly highlights and summarizes the results of studies during the past decade and especially in recent years, which concern the mechanism of action of different antimicrobial polymers and non-leaching microbicidal surfaces, and factors influencing their activity and toxicity, as well as major applications of antimicrobial polymers.