Disinfectants exposure time

Liquid sterilants are known to corrode the metal parts of articles and instmments that are to be sterilized, although articles composed exclusively of glass or certain type of corrosion-resistant metal alloys can be safely processed. Because the degree of corrosion is related to length of exposure, many articles are merely disinfected in a shorter exposure time. Disinfection may be suitable for certain appHcations. The safety of using Hquid sterilants must be judged by a qualified microbiologist. 

It has also been demonstrated that the germicidal effectiveness of free and combined chlorine is markedly diminished with decreasing water temperature. In any situation in which the effects of lowered temperature and high pH value are combined, reduced efficiency of free chlorine and chloramines is marked. These factors directly affect the exposure time needed to achieve satisfactory disinfection. Under the most ideal conditions, the contact time needed with free available chlorine may only be on the order of a few minutes combined available chlorine under the same conditions might require hours. 

UV dose is the most important operational parameter in the UV disinfection. It can be calculated by the UV intensity multiplied by the exposure time (3,11,19). If the UV intensity is independent of time, the UV dose can be calculated by the following equation ... 

Determination of volume of water to be disinfected based on the exposure time and flow rate. 

In recognition of the need for broad spectrum hand disinfectants, new formulations of sanitary mbs have been tested for vimcidal activity. Enveloped vimses including VACV were exposed to three common alcohol-based sanitary mbs containing at least 75% alcohol, at exposure times of 15, 30 and 60 s. Significant viral inactivation (>4 log 10 steps) after 15 s with infectivity reduced to below detectable levels [65], In an earlier study, Schumann and Grossgebauer [95] observed complete disinfection of VACV from hands using 70% isopropyl-alcohol with a 2-5 min exposure. Similarly, VACV embedded in rabbit dermal scabs were completely inactivated after 3 h exposures in... 

These agents can kill mycobacterium (TB), many, but not all, types of virus s fungi, and vegetative bacteria. These disinfectants can t kill bacterial spores in any practical exposure time. Examples of intermediate-level disinfectants include phenols, alcohols, iodophors, and combinations of isopropanol and QACs. Noncritical instruments and environmental surfaces may require disinfection with intermediate-level disinfectants. The correct application of intermediate-level disinfectants is for such noncritical items as floors and countertops, patient room furniture, instruments that contact only intact skin, and plastic or metal machine housings that do not directly contact patients. 

Disinfectants must contact the exterior and interior surfaces of an instrument for proper recommended exposure time and temperature. Some agitation and physical positioning may help till the interior lumen of hollow instruments and dislodge air pockets. Disinfectants can kill microbes or cells of a mucous membrane. Therefore, rinse away all disinfectants from instruments with copious amounts of sterile water. Use a double- or triple-rinse technique with smaller volumes of sterile water. Each rinse removes about 90% of the disinfectant. A double-rinse removes 99%, and a triple-rinse removes 99.9% of the disinfectant. A flowing rinse where sterile water pours over an instrument is more effective than a static rinse where the instrument is soaked in a container. 

It is impossible to provide detailed and predictable protocols for disinfection of biofilms in various situations which can be generalized. In principle, biocides can be effective against biofilms. However, this has to be verified in given situations and it has to be taken into consideration that the three crucial factors for biocide efficacy, i.e., concentration, exposure time and temperature, have to be optimised in order to achieve the required efficacy. It will be important to verify the effect. In order to do so, it is necessary to perform the assessment with intact biofilms and not with removed and suspended biofilm organisms as these will be much more susceptible to the biocide. 

Since the direct estimation of microbial numbers by conventional culturing methods is time-consuming and well affected by environmental conditions (18), a simple test for the most resistant enzyme activity is appropriate on a routine basis. If enzyme activity is detected, it can be assumed that the heat treatment was inadequate (4,15). Appropriately, GFPuv can be employed as a BI in thermal processes (blanching, pasteurization, disinfection) at temperatures >75°C for products at pH > 5.5, with the inactivation of GFPuv shown to be directly related to the time of exposure to moist heat and pH. 

Example 2.1 An experimenter challenges a benzalkonium chloride disinfectant with 1 X 10 Staphylococcus aureus bacteria in a series of timed exposures. As noted earlier, exponential microbial colony counts are customarily linearized via a logio scale transformation, which has been performed in this example. The resultant data are presented in Table 2.1. 

Staphylococcus species are relatively more resistant to heat, as well as various topical disinfectants and topical antimicrobials, than are most other pathogenic bacteria [4,5]. For example, many species of bacteria are killed when exposed to 60°C temperature for 30 minutes. However, comparable microbial reductions in Staphylococcus spp. may require exposure to a temperature of 80°C for 1 hour. And unlike many other pathogenic microorganisms. Staphylococcus spp. will grow at 45°C, are relatively resistant to drying, and can remain viable for extended periods of time. 

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