The mechanism of action of some antibacterial agents

Metabolic extract of the endophytic fungus Flavodon flavus isolated from Justicia brandegeana in the control of Alicyclobacillus acidoterrestris in commercial orange juice

In this work, the antibacterial activity of a crude extract of the endophytic fungus Flavodon flavus (JB257), isolated from leaves of Justicia brandegeana, was evaluated against both the vegetative and sporulated forms of Alicyclobacillus acidoterrestris. The microdilution technique was performed in order to determine the antibacterial activity of the crude extract alone as well as in combination with the bacteriocin, nisin. The minimum inhibitory concentration (MIC) of the crude extract and nisin alone against A. acidoterrestris vegetative forms were 250 μg/mL and 31.5 μg/mL, respectively, while the minimum bactericidal concentrations (MBC) were 1000 μg/mL and 62.5 μg/mL,respectively. For A. acidoterrestris spores, treatment with the crude extract at a concentration of 500 μg/mL caused a 47% reduction in growth, while nisin at 62.5 μg/mL could reduce 100% of the growth. The in vitro evaluation of the crude extract combined with nisin against A. acidoterrestris by the Checkerboard method showed a synergistic interaction between the two compounds. In addition, greater selectivity towards bacterial cells over host cells, a human hepatocyte cell line, was achieved when the crude extract was combined with nisin, Using scanning electron microscopy, interferences in the cell membrane of A. acidoterrestris could be observed after treatment with the crude extract. The results presented in this study indicate that the crude extract of the endophyte F. flavus has biotechnological potential in the food industry, especially for the treatment of orange juices through the control of A. acidoterrestris.

Cationic Polymers with Tailored Structures for Rendering Polysaccharide-Based Materials Antimicrobial: An Overview

Antimicrobial polymers have attracted substantial interest due to high demands on improving the health of human beings via reducing the infection caused by various bacteria. The review presented herein focuses on rendering polysaccharides, mainly cellulosic-based materials and starch to some extent, antimicrobial via incorporating cationic polymers, guanidine-based types in particular. Extensive review on synthetic antimicrobial materials or plastic/textile has been given in the past. However, few review reports have been presented on antimicrobial polysaccharide, cellulosic-based materials, or paper packaging, especially. The current review fills the gap between synthetic materials and natural polysaccharides (cellulose, starch, and cyclodextrin) as substrates or functional additives for different applications. Among various antimicrobial polymers, particular attention in this review is paid to guanidine-based polymers and their derivatives, including copolymers, star polymer, and nanoparticles with core-shell structures. The review has also been extended to gemini surfactants and polymers. Cationic polymers with tailored structures can be incorporated into various products via surface grafting, wet-end addition, blending, or reactive extrusion, effectively addressing the dilemma of improving substrate properties and bacterial growth. Moreover, the pre-commercial trial conducted successfully for making antimicrobial paper packaging has also been addressed.

Selfprotective smart orthopedic implants

In this review, we discuss current advances leading to an exciting change in implant design for orthopedic surgery. The initial biomaterial approaches in implant design are being replaced by cellular-molecular interactions and nanoscale chemistry. New designs address implant complications, particularly loosening and infection. For infection, local delivery systems are an important first step in the process. Selfprotective 'smart' devices are an example of the next generation of orthopedic implants. If proven to be effective, antibiotics or other active molecules that are tethered to the implant surface through a permanent covalent bond and tethering of antibiotics or other biofactors are likely to transform the practice of orthopedic surgery and other medical specialties. This new technology has the potential to eliminate periprosthetic infection, a major and growing problem in orthopedic practice.

Astonishing diversity of natural surfactants: 4. Fatty acid amide glycosides, their analogs and derivatives

FA amide glycosides are of great interest, especially for the medicinal and pharmaceutical industries. These biologically active natural surfactants are good prospects for future chemical preparation of compounds useful as antibiotics, anticancer agents, or for industry. More than 200 unusual and interesting natural surfactants, including their chemical structures and biological activities, are described in this review article.

Influence of Satellite Groups on Telechelic Antimicrobial Functions of Polyoxazolines

The antimicrobial activity of poly(alkyloxazoline) telechelics with one quaternary N,N-dimethyldodecylammonium (DDA) end group was found to be greatly controlled by the non-bioactive distal end group, the so-called satellite group. In systematic investigations, the nature of the latter groups was varied to explore the mechanism of the satellite effect. To this end, poly(2-alkyl-1,3-oxazoline)s (alkyl = ethyl, methyl) with a DDA-group at the terminating end and varying alkyl, aminoalkyl, and polyphenyloxazoline block satellite groups, have been synthesized. Poly(oxazoline) derivatives with polydispersity indices of 1.06-1.20 and molecular weights from 2,200 to 12,800 g . mol(-1) could be obtained. The macromolecular structures have been confirmed by NMR spectroscopy and ESI-MS measurements. The polymers were investigated with regard to their antibacterial efficiency towards the Gram-positive bacterium Staphylococcus aureus and the Gram-negative bacterium Escherichia coli. It was found that the introduction of alkyl chain satellites of 4-10 carbon atoms in length afforded antimicrobial activity of the polymers against both microbes that was about 2-3 times higher than that of the well-known structurally comparable low molecular weight biocide, dodecyltrimethylammonium chloride (DTAC). Based on the antimicrobial effects of the investigated polymers, a mechanism for the satellite effect was proposed.

The use of locally delivered chlorhexidine in the treatment of periodontitis. Clinical results

Since the advent of a nondegradable controlled local delivery of antibiotics in 1979, several second generation systems have been developed. Second generation systems have attempted to improve on the early system. Chlorhexidine has been used effectively for over 30 years as an antiseptic. In the early 1970s, chlorhexidine gluconate was incorporated at 0.2% into mouthrinses in Europe and in 1986 it was incorporated at 0.12% in a mouthrinse in the United States. Since these mouthrinses were effective in reducing the supragingival flora, had a high safety margin, and had no reported bacterial resistance, chlorhexidine offered a therapeutic advantage for a local delivery system. This system was developed and studied. This report will discuss this new biodegradable system containing chlorhexidine gluconate as the active agent (PerioChip). Pharmacokinetics of the system and a review of the multicenter studies in Europe and the United States are discussed. In these randomized clinical trials the chlorhexidine chip has been shown to enhance the effects of scaling and root planing. Chlorhexidine chip in conjunction with scaling and root planing, when compared to scaling and root planing alone, has shown significant improvement in probing pocket depth reduction, probing attachment level and bleeding on probing. This delivery system, in combination with scaling and root planing, has also resulted in significantly more probing depth reductions of 2 mm or more. The system is safe and efficacious. Placement of the chip is usually done in less than 1 min, it requires no retention system, biodegrades, and does not require a follow-up dental appointment.

Relationship of chemical structure and antimicrobial activity of alkyl amides and amines

Contrary to the limited effects of alkyl amides and their corresponding N-derivatives, alkyl amines affected both gram-positive and gram-negative organisms. As with other alkyl derivatives the most sensitive gram-negative bacteria were usually more resistant than the most resistant gram-positive bacteria. Compounds with a chain-length of 11 to 15 are most active. Although some of the general properties relating the activity of fatty acids to their antimicrobial action are similar to those of amine compounds, the amines are unique in that monounsaturation does not increase compound activity. The possible modes of action of these compounds are discussed.

Aspects of the mechanism of action of some cephalosporins

Cephaloridine and cephalexin had no effect on ribonucleic acid (RNA), deoxyribonucleic acid (DNA), or protein synthesis in Escherichia coli. However, cephalosporin 7/30 [7-(S-benzylthioacetamido)-cephem-3-ylmethyl-N -dimethyldithiocarbamate-4-carboxylic acid] and dimethyldithiocarbamate (DMDT), which occupies the side chain at position 3 in the 7/30 molecule, inhibited protein synthesis (and, to a lesser extent, RNA and DNA syntheses) in E. coli and had an inhibitory effect on the growth of Saccharomyces carlsbergensis. A bioautograph technique showed that two inhibitory spots were obtained with 7/30 but only one such spot with cephaloridine. Release of DMDT onto or in the bacterial cell may be responsible for "unusual" mode of action of cephalosporin 7/30.