Neutralizing agents, antimicrobial

Textile Finishing. Polyethyleneimine-A/-methylolurea derivatives improve the crease and wear resistance of cotton (429,430). The adhesion between individual wool fibers is improved by pretreatment with amines, which leads to improved shrink resistance (431). An antimicrobial finish can be appHed to cotton by using a combination of PEI and ureas to bind zinc pyrithione to the fabric (432). After wool has been provided with a flameproof finish using fluorozirconate or fluorotitanate, the wool can be neutralized with PEI (433). Conventional neutralizing agents caimot be used for this purpose since they impair the flameproof characteristics of the impregnated fabric. 

Table 11.4 Neutralizing agents for some antimicrobial agents"...

Several factors influence the antimicrobial activity of silver salts [19]. Silver has a marked tendency to adsorb to surfaces and bactericidal activity is reduced in the presence of phosphates, chlorides, sulphides and hard water. Activity is increased as the temperature is raised (Q,o = 1.6, that is, a 1.6-fold increase in activity per 10°C rise in temperature) and is pH-dependent, increasing with increasing pH [19, 20]. Sodium thioglycol-late has been recommended as a suitable neutralizing agent for use in... 

Test Method. Microorganisms are exposed to the test materials for proposed time intervals of 0, 3, 6, 9, 12, 15, 20, and 30 minutes. At the end of the exposure period, an appropriate neutralizing agent is used to quench antimicrobial activity chemically and/or by dilution. Microorganism populations before and after the treatment are enumerated to calculate the antimicrobial activity of the test product, expressed in a logw reduction format. 

The sulfosuccinate monoester based on undecylenic acid monoethanolamide and its antimicrobial properties was described shortly before [12]. In comparison of shampoos containing different antidandruff agents, this sulfosuccinate s performance was favorably evaluated [13]. It was neutral with respect to lipid replacement on scalp and forehead after application of the respective shampoo. This undecylenic acid-based sulfosuccinate was also found to reduce dandruff formation in another investigation [14]. 

Table 1 shows known neutralizers for a variety of chemical antimicrobial agents and the reported toxidties of some chemical neutralizers to specific microorganisms. Antibiotics may not be susceptible to neutralization by chemical means, but rather by enzymatic treatment (e.g., penicillinase). These enzymes may be used where required (for P-lactum antibiotics). 

Antimicrobial agents with high r values are rapidly neutralized by dilution, while those with low T values are not good candidates for neutralization by dilution. 

According to the type of antimicrobial agent, the neutralizers shown in Table 1 should be added. 

If the solution has insufficient neutralizing capacity, the concentration of polysorbate 80 or lecithin may be increased. Alternatively, according to the type of antimicrobial agent, the neutralizers listed in Table 1 should be added. 

Compared with suspended (planktonic) cells, bacteria on surfaces as biofilms are invariably phe-notypically more resistant to antimicrobial agents. With biofilms, suspension tests can be modified to involve biofilms produced on small pieces of an appropriate glass or metal substrate, or on the bottom of microtitre tray wells. After being immersed in, or exposed to the disinfectant solution for the appropriate time interval, the cells from the biofilm are removed, e.g. by sonication, and resuspended in a suitable neutralizing medium. Viable counts are then performed on the resulting planktonic cells. 

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