Antimicrobial activity mechanism

The mechanism of action of quats has been widely studied. It is generally agreed that their iateraction with the bacterial cell membrane is the primary event resulting ia antimicrobial activity (16,17). 

Other Nitrogen Compounds. The basis of the sophisticated nitrogen compounds Hsted in Table 10 is the reaction of formaldehyde with amino compounds. A significant amount of Hterature details investigation of the mechanism of action, particularly whether or not the antimicrobial activity depends on decomposition to formaldehyde (40—42). These compounds tend to have substantial water solubiUty and are more effective against bacteria than fungi and yeasts. Key markets for these compounds are metalworking fluids, cosmetics, and in-can preservation of paints (see Alkanolamines Amines, fatty amines). 

This wide range of pharmacokinetic properties, along with thek ease of administration, broad spectmm antimicrobial activity, and noninterference with host-defense mechanisms is responsible for thek widespread use five decades after thek discovery. 

The threat of accidental misuse of quaternary ammonium compounds coupled with potential harmful effects to sensitive species of fish and invertebrates has prompted some concern. Industry has responded with an effort to replace the questionable compounds with those of a more environmentally friendly nature. Newer classes of quaternaries, eg, esters (206) and betaine esters (207), have been developed. These materials are more readily biodegraded. The mechanisms of antimicrobial activity and hydrolysis of these compounds have been studied (207). AppHcations as surface disinfectants, antimicrobials, and in vitro microbiocidals have also been reported. Examples of ester-type quaternaries are shown in Figure 1. 

Additional hypotheses for their mechanism of action have more recently been proposed. It is well known that proanthocyanidins are able to complex metals through their ortho-diphenol groups. This property is often viewed as imparting negative traits (e.g., reduction of the bioavailability of essential mineral micronutrients, especially iron and zinc) [87]. Since iron depletion causes severe limitation to microbial growth, their ability to bind iron has been suggested as one of the possible mechanisms explaining the antimicrobial activity of proanthocyanidins [88] (Table 1). 

The antimicrobial activity of Bi(III) against the bacterium Helicobacter pylori appears to be important for its antiulcer activity (458). This organism may be involved in other conditions such as cancer. The mechanism of antimicrobial activity may involve interference in Fe(III) or Zn(II) biochemical pathways. Bismuth(III) is not known to bind to DNA. Attempts to synthesize new Bi(III) complexes with activity against H. pylori include those of Keppler et al. (459), who have found that Bi(III)-tropolonato complexes such as 98 are highly active... 

In addition to the cathelicidins and defensins, humans also utilize a variety of other host defense peptides. Examples of these include the anionic dermcidins, found in human sweat and possessing potent antimicrobial activity in a broad range of pH and salt concentrations, and the histatins, a histidine-rich host defense peptide family found in humans and higher primate species. The histatins are normally found in saliva and utilize an alternative mechanism to bacterial membrane lysis for their antimicrobial activity. ... 

The recent elucidation of the immunomodulatory activities of host defense peptides is perhaps the most intriguing to the development of these molecules as therapeutics. Importantly, many peptides that have been demonstrated to be devoid of antimicrobial activity under physiological conditions have maintenance of immunomodulatory activities. That host defense peptides have also recently been demonstrated to bridge innate and adaptive immune responses and as well act as adjuvants extends their therapeutic potential beyond the resolution of infection. Recent investigations have also sought to define the cell receptors involved in the immunomodulatory activities of host defense peptides in an effort to define the mechanism of action of these molecules and further the understanding of how these molecules are able to elicit such a broad range of... 

The first completely synthetic monocyclic beta-lactam antibiotic was aztreonam. The antimicrobial activity of this drug is exhibited mainly with respect to a broad spectrum of aerobic Gram-negative bacteria. It is resistant to beta-lactamases and does not induce their formation. The mechanism of its action is identical to that of other beta-lactam antibiotics with respect to Gram-negative bacteria. PBP are inactivated in the presence of aztreonam. 

Key words alkaloids, antimicrobial activity, anti-parasitic activity, biology, cytotoxicity, DNA, endogenous security mechanism, estrogenic effect, evolution, genes, haemoglobinization, immune system, inhibitor, locoism, narcotics, regulation, stimulator... 

Although all tetracyclines have a similar mechanism of action, they have different chemical structures and are produced by different species of Streptomyces. In addition, structural analogues of these compounds have been synthesized to improve pharmacokinetic properties and antimicrobial activity. While several biological processes in the bacterial cells are modified by the tetracyclines, their primary mode of action is inhibition of protein synthesis. Tetracyclines bind to the SOS ribosome and thereby prevent the binding of aminoacyl transfer RNA (tRNA) to the A site (acceptor site) on the 50S ri-bosomal unit. The tetracyclines affect both eukaryotic and prokaryotic cells but are selectively toxic for bacteria, because they readily penetrate microbial membranes and accumulate in the cytoplasm through an energy-dependent tetracycline transport system that is absent from mammalian cells. 

Mechanism of Action A biologic response modifier that induces activation of macrophages in blood monocytes to phagocytes, which is necessary in the body s cellular immune response to intracellular and extracellular pathogens. Enhances phagocytic function and antimicrobial activity of monocytes Therapeutic Effect Decreases signs and symptoms of serious infections in chronic granulomatous disease. Pharmacokinetics Slowly absorbed after subcutaneous administration. Half-life 0.5-1 hr. 

Mechanism of Action An antitubercular that inhibits DNA-dependent RNA polymerase, an enzyme in susceptible strains of Escherichia coli and Bacillus subtilis. Rifabutin has a broad spectrum of antimicrobial activity including against mycobacteria such as Mycobacterium avium complex (MAC). Therapeutic Effect Prevents MAC disease. 

However the mechanism of the antimicrobial effect of silver nanoparticles is not well understood. It has been recently reported that Nanosilver represents a special physicochemical system which confers its antimicrobial activities via Ag-t [11]. According to Morones et al., the bactericidal effect of silver nanoparticles on microorganisms is connected not merely with the release of silver ions in solution [12]. Silver nanoparticles can also be attached to the surface of the cell membrane and drastically distnrb its proper function [12]. They could also penetrate inside the bacteria and canse farther damage by interacting with sulfur and phosphorus-containing componnds snch as DNA. 

The nitro group of metronidazole is chemically reduced in anaerobic bacteria and sensitive protozoans. Reactive reduction products appear to be responsible for antimicrobial activity. The mechanism of tinidazole is assumed to be the same. 

Benzoyl peroxide is an effective topical agent in the treatment of acnevulgaris. It penetrates the stratum corneum or follicular openings unchanged and is converted metabolically to benzoic acid within the epidermis and dermis. Less than 5% of an applied dose is absorbed from the skin in an 8-hour period. It has been postulated that the mechanism of action of benzoyl peroxide in acne is related to its antimicrobial activity against P acnes and to its peeling and comedolytic effects. 

Azelaic acid is a straight-chain saturated dicarboxylic acid that is effective in the treatment of acnevulgaris (in the form of Azelex) and acne rosacea (Finacea). Its mechanism of action has not been fully determined, but preliminary studies demonstrate antimicrobial activity against P acnes as well as in vitro inhibitory effects on the conversion of testosterone to dihydrotestosterone. Initial therapy is begun with once-daily applications of the 20% cream or 15% gel to the affected areas for 1 week and twice-daily applications thereafter. Most patients experience mild irritation with redness and dryness of the skin during the first week of treatment. Clinical improvement is noted in 6-8 weeks of continuous therapy. 

Plants have evolved different mechanisms to protect themselves against a great variety of invasive pathogens. As a part of the defense, plants produce a number of secondary metabolites with antimicrobial activity. Many of these compounds are produced constitutively, being present in healthy plants as normal metabolic products. VanEtten et al. proposed the term "phytoanticipin" to define these preformed antimicrobial... 

It has been postulated that the mechanism of action of benzoyl peroxide in acne is related to its antimicrobial activity against P acnes and to its peeling and comedolytic effects. 

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