Bacteria bactericidal effect

Significant concentrations of silver occur only in some mine and industrial wastewaters (particularly the photographic industry). In natural waters it is present in trace amounts only. Slightly higher concentrations of silver can be found in the waters which were disinfected by silver ions because of their oligodynamic properties. Water in contact with silver or its slightly soluble compounds shows a decrease in the concentration of bacteria. Bactericidal effects are explained by the reaction of Ag" " ions with proteins of living matter such effects are observed at concentrations as low as 25 pg 1. ... 

Bactericides are substances that destroy bacteria, and they can be used in various ways. They may be incorporated into the soluble-oil concentrate, either at concentrations suitable to protect the oil in storage, or at levels sufficient to provide a persistent bactericidal effect on the emulsion in service. The cost of providing sufficient bactericide to cover the use of the soluble oil at a high dilution might prove prohibitive. Continued use of the same bactericide may produce resistant strains of bacteria. 

The fluoroquinolones exert their bactericidal (bacteria-destroying) effect by interfering with an enzyme (DNA gyrase) needed by bacteria for the synthesis of DNA. 

Pure Ti02 was recently reported to be active in the disinfection of water contaminated by spores of the type Fusarium solani [142], Bacillus anthracis [143], or Cryptosporidium parvum oocysts [144], or when supported as nanocomposites on zeolite H(i for E. coli deactivation [145], and it found applications in water treatment as a replacement for chlorine. Ag-Ti02 immobilized systems were used for inactivation of bacteria, coupling the visible light response of the system and the strong bactericidal effect of Ag [146]. Silver was deposited on hydroxyapatite to form nanocomposites with a high capacity for bacterial adsorption and inactivation [147], or used for airborne bacterial remediation in indoor air [148],... 

In bacteria (Escherichia coli), paraquat is concentrated, reduced to the monocation radical, and combines with molecular oxygen to produce the superoxide radical within the cell. Copper and iron are essential mediators in bactericidal effects. The cytoplasmic membrane is the target organelle in paraquat toxicity to E. coli, and extent of damage correlates positively with levels of these metals (Kohen and Chevion 1988). 

An in vitro investigation into the bactericidal effects of a dental ultrasonic descaler on bacterial biofilms using Actinobacillus actinomycctcmcomitans and Porphyromonas gin-givalis has been reported [49]. Suspensions of the bacteria were subjected to the vibrations of a Cavitron PI insert for 2.5 and 5.0 min in an acoustically-simulated model substrate. A 60 % kill rate was achieved at a temperature of around 50 °C which constituted an alternative treatment for bacterial biofilms. This study suggested that a similar approach could be used in the clean-up of a range of biofQms considered to be the cause of a range of environmental hazards. 

The effect of antibacterial drugs can be observed in vitro (3). Bacteria multiply in a growth medium under control conditions. If the medium contains an antibacterial drug, two results can be discerned 1. bacteria are killed—bactericidal effect 2. bacteria survive, but do not multiply-bacteriostatic effect Although variations may occur under therapeutic conditions, different drugs Lullmann, Color Atlas of Pharmacology... 

The formation of sulfa drugs is another excimple of a multistep synthesis. The sulfa drugs cire bactericides, effective c ainst a wide variety of bacteria because they mimic p-aminobenzoic acid (Figure 13-48). Many bacteria require p-aminobenzoic acid, which they cire unable to synthesize, and need to synthesize folic acid. Many types of sulfa drugs exist, and most of them involve the substitution of one of the hydrogen atoms on the -SO2-NH2. Prontosil (Figure 13-49) was the first commercially available sulfa drug. The metabolism of prontosil produced sulfanilamide. 

Several experiments have shown the bactericidal effect of fluoride ions at high concentrations [180,181]. This effect generally occurs at concentrations well above those generally observed in saliva however, the use of fluoridated toothpaste or dental topical applications of fluoride may temporarily elevate the fluoride concentration in the oral cavity to bactericidal levels. It has been demonstrated that fluoride affects the metabolism of oral bacteria and reduces its acid tolerance. It is most effective at acidic pH values and, for example, fluoride levels as low as 0.1 mM can cause the complete arrest of glycolysis by Steptococcus mutans. It has been suggested that modifying the biological fluids related to the presence... 

Mechanism of Action An anti-infective that acts upon cell wall and cell membrane. Releases silver slowly in concentrations selectively toxic to bacteria. Therapeutic Effect Produces bactericidal effect. 

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. 

For Salmonella, at the lower initial bacteria level (104), the following log reductions were recorded 0.78 at 0 minutes, 1.11 at 20 minutes, 1.08 at 60 minutes, and 1.23 at 240 minutes. Thus, at 4 hours (240 minutes), the ratio of the initial bacteria count in the control to bacteria in the sample treated with 32 ppm silver is 101 23. For the higher initial bacteria level (106), the following log reductions were recorded 0.86 at 0 minutes, 0.95 at 20 min, 0.98 at 60 min and 1.17 at 240 min. The results indicate that the 32 ppm silver embodiment of this invention shows an effective bactericidal effect for Salmonella on beef steak. It will be appreciated that disinfecting a meat surface is an extreme challenge for any disinfectant. 

In addition to this, other actions take place involving a diminution in the number of bacteria,1 although sometimes there is an initial rise, followed by decline. The bactericidal effects are induced by a variety of causes, the more important of which are ... 

Molnar et al. [69] studied antibacterial effect and plasmid curing property of several phenothaizines and tried to correlate these functions with respect to their chemical structure. They observed that diethazine, amitriptyline, and impipramine showed bacteriostatic and bactericidal effect on different bacteria. Chlorpromazine sulfoxide and fluorescein were ineffective even at 1000 Ag/ml. The antibacterial compounds deleted at 40-70% frequency the F lac-t- plasmid of Escherichia coli K12 Le-140. Similar plasmid elimination potentiality by phenothiazines was reported by the same group of authors in 1982 [72],... 

Inhibitions of cell wall biosynthesis can be determined independently from DNA, RNA and protein biosyntheses. They will usually have been signaled by bactericidal effects and lysis of the test culture. In many instances, inhibition of cell wall synthesis results in the progressive accumulation of intermediates which can be assayed colorimetrically64, 6J) for N-acylaminohexose in acid-soluble fractions of the test bacteria. 

Advanced wound management products containing silver have been developed to treat difficult-to-heal wounds, chronic ulcers, and extensive burns. Odor absorbing dressings adsorb polarized bacteria onto the surface of the charcoal cloth used in the formulation. The silver present in the dressing exerts a bactericidal effect that gradually diminishes as wound exudate saturates the material. 

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