Bacterial permeability

BPB Para-bromophenacyl bromide BPI Bacterial permeability-increasing protein... 

Chloramphenicol is able to inhibit the peptidyl transferase reaction and so bacterial protein synthesis by binding reversibly to the 50s ribosomal subunit. Resistance can occur due to the plasmid-mediated enzyme chloramphenicol acetyltransferase which inactivates the drug by acetylation. Such resistance is often a part of plasmid-mediated multidrug resistance. Resistance can also occur by an altered bacterial permeability. However in most instances resistance to chloramphenicol only develops slowly and remains partial. 

Resistance occurs by two mechanisms. Changes in bacterial permeability can hinder penetration of the drug or changes in the bacterial RNA polymerase can diminish drug binding to the enzyme. It is almost completely absorbed after oral administration with peak plasma concentrations reached after 2-A h. It... 

Resistance to the sulfonamides can be the result of decreased bacterial permeability to the drug, increased production of PABA, or production of an altered dihydropteroate synthetase that exhibits low affinity for sulfonamides. The latter mechanism of resistance is plasmid mediated. Active efflux of the sulfonamides has also been reported to play a role in resistance. The inhibitory effect of the sulfonamides also can be reversed by the presence of pus, tissue fluids, and drugs that contain releasable PABA. 

Bacterial resistance to sulfonamides can originate by random mutation and selection or by plasmid transfer of resistance it usually does not confer cross-resistance to other classes of antibiotics. Resistance to sulfonamide results from altered constitution of the bacterial cell that causes (I) a lower affinity for sulfonamides by dihydropteroate synthase, (2) decreased bacterial permeability or active efflux of the drug, (3) an alternative metabolic pathway for synthesis of an essential metabolite, or (4) an increased production of an essential metabolite or drug antagonist. Plasmid-mediated resistance is due to plasmid-encoded, drug-resistant dihydropteroate synthetase. 

Espinoza J. Anitmicrobial peptides in amniotic fluid defensins, calprotectin and bacterial permeability-increasing protein in patients with microbial invasion of the amniotic cavity, intra-amniotic inflammation, preterm labor, and premature rupture of membranes. J Matem Fetal Neonatal Med 2003 13 2-21. 

Sesquiterpenoids have been related with medicinal plants with different health applications, mainly anti-inflammatory [87], anti-HIV [88], antibacterial [89], and antitumor activity [88]. Up to date, no study has covered the biological activity of sesquiterpenoids from Vitis vinifera L grsLpes. Sesquiterpenoids such as famesol and nerolidol have been reported to have the ability to enhance bacterial permeability and susceptibility to exogenous antimicrobial compounds. These compounds increase the susceptibility of Staphylococcus aureus and Escherichia coli to antibiotics by disrupting the normal barrier function of the bacterial ceU membrane, allowing permeation into the cell of exogenous solutes such as antibiotics [90]. 

The authors gratefully acknowledge the assistance of Dr. Brian Sheldon of the Food Science Department for assisting with the bacterial permeability studies of the films and Drs. Kirin B. Wylie and Dr. Gary J. Spodnick, both of the College of Veterinary Medicine, for helping with the invitro and the vivo studies. The funds of the investigation were provided by the North Carolina State University. 

The synthetic and plasmid DNAs are mixed and join their sticky ends spontaneously. They are covalently bound together by DNA ligases, when the resulting hybrid plasmid is inserted into bacterial cells. Dilute calcium chloride solutions render the bacterial membranes permeable and allow the passage of ONA into the cells. 

Electroporation. When bacteria are exposed to an electric field a number of physical and biochemical changes occur. The bacterial membrane becomes polarized at low electric field. When the membrane potential reaches a critical value of 200—300 mV, areas of reversible local disorganization and transient breakdown occur resulting in a permeable membrane. This results in both molecular influx and efflux. The nature of the membrane disturbance is not clearly understood but bacteria, yeast, and fungi are capable of DNA uptake (see Yeasts). This method, called electroporation, has been used to transform a variety of bacterial and yeast strains that are recalcitrant to other methods (2). Apparatus for electroporation is commercially available, and constant improvements in the design are being made. 

Precipitate formation can occur upon contact of iajection water ions and counterions ia formation fluids. Soflds initially preseat ia the iajectioa fluid, bacterial corrosioa products, and corrosion products from metal surfaces ia the iajectioa system can all reduce near-weUbore permeability. Injectivity may also be reduced by bacterial slime that can grow on polymer deposits left ia the wellbore and adjacent rock. Strong oxidising agents such as hydrogen peroxide, sodium perborate, and occasionally sodium hypochlorite can be used to remove these bacterial deposits (16—18). 

Bacillus thuringiensis produces a variety of organic compounds which are toxic to the larvae of certain susceptible insect hosts. Among the toxic entities are proteinaceous crystals, probably three soluble toxins, and certain enzymes. The protein material is the major toxin active in killing lepidopterous larvae. The protein is formed by the cells apparently in close synchrony with sporulation, and its nature is a constant function of bacterial strain. The mode of action of the protein is under study. The sequence of events in the pathology observed is probably solubilization of the crystal (enzymatic or physical)—>liberation of toxic unit—>alteration of permeability of larval gut wall— change in hemolymph pH—>invasion of hemolymph by spores or vegetative cells of the bacterium. 

Vancomycin (Vancocin) acts against susceptible gram-positive bacteria by inhibiting bacterial cell wall synthesis and increasing cell wall permeability. This drug is used in the treatment of serious gram-positive infections that do not respond to treatment with other anti-infectives. It also may be used in treating anti-infective-associated pseudomembranous colitis caused by Clostridium difficile. 

Nikaido H. Vaara T. (1986) Molecular basis of bacterial outer membrane permeability. Microbiol Rev, 49, 1-32. 

Haemodialysis is the process of circulating the patient s blood through a machine via tubing composed of a semi-permeable material such that waste products permeate into the dialysing fluid and the blood then returns to the patient Haemodialysis solutions need not be sterile but must be flee flxm heavy bacterial contamination. 

The membrane is critically important in osomometry. Selection of a membrane involves reconciliation of high permeability toward the solvent with virtual impermeability to the smallest polymer molecules present in the sample. Membranes of cellulose are most widely used. Commercially Regenerated cellulose film is a common source. The undried gel cellophane film is often preferred, but the dry film may be swollen in water (or in aqueous solutions of caustic or zinc chloride ) to satisfactory porosity. Useful cellulose membranes may also be prepared by denitration of nitrocellulose films/ and special advantages have been claimed for bacterial cellulose films. The water in the swollen membrane in any case may be replaced by a succession of miscible organic solvents ending with the one in which osmotic measurements are to be made. Membranes of varying porosity may be... 

Experiments have shown that bacterial cells may penetrate a solid porous medium with at least 140-mD permeability and that a bacterial population may be established in such a medium if suitable substrates are supplied. Enhanced... 

Antibiotics are used to treat bacterial infection [41]. Some antibiotics act directly on cell membranes of micro-organisms, with consequent alteration of permeability and leakage of intracellular components. Antibiotics affect cell membranes and thus also the liquid membrane, with the possibility of change in oscillation. 

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