Microorganisms killing

Simultaneous treatment of water with UV and ozone results in higher microorganism kill than independent treatment with both UV and ozone. 

Vaccines may be considered as representing live microorganisms, killed miciooiganisms or purified bacterial and viral components (component vaccines). These vaccine classes have been deseribed in detail in Chapter 15. Some additional points about their use are diseussed below. 

Dry-heat processes kill microorganisms primarily through oxidation. The amount of moisture available to assist sterilization in dry-heat units varies considerably at different locations within the chamber and at different time intervals within the cycle. Also, the amount of heat available, its diffusion, and the environment at the spore/air interface all influence the microorganism kill rate. Consequently, cycles tend to be longer and hotter than would be expected from calculations to ensure that varying conditions do not invalidate a run. In general, convection dry-heat sterilization cycles are run above 160°C [37],... 

These consist of microorganisms killed by heat or chemicals. Killed vaccines usually require a primary series of two-three doses of vaccine to produce an adequate antibody response and generally booster dose is required. The duration of immunity varies from months to years, (e.g. in case of polio vaccine) The examples are ... 

In this chapter, the mechanisms of UV disinfechon will be presented. A mathematical description of microorganism killing by UV radiation is given. Design approaches of disinfection systems are demonstrated. Case studies will also be presented at the end of this chapter. 

Water treatment plants employ both primary and secondary disinfection (a) Primary disinfection achieves the desired level of microorganism kill or inactivation and (b) secondary disinfection ensures a stable residual concentration of disinfectant in the finished water to prevent microbial growth in the distribution system (4,7,14,17,18). 

Microorganisms killed Most vegetative bacteria Most vegetative bacteria including All microorganisms unless extreme... 

Plug-flow reactors have a decreasing concentration gradient from inlet to outlet, which means that toxic compounds in the feed remain undiluted during their passage along the reactor, and this may inhibit or kill many of the microorganisms within the... 

Other Properties. Polyester fibers have good resistance to uv radiation although prolonged exposure weakens the fibers (47,51). PET is not affected by iasects or microorganisms and can be designed to kill bacteria by the iacorporation of antimicrobial agents (19). The oleophilic surface of PET fibers attracts and holds oils. Other PET fiber properties can be found ia the Hterature (47,49). 

Vaccines can be roughly categorized into killed vaccines and Hve vaccines. A killed vaccine can be (/) an inactivated, whole microorganism such as pertussis, (2) an inactivated toxin, called toxoid, such as diphtheria toxoid, or (J) one or more components of the microorganism commonly referred to as subunit vaccines. The examples are capsular polysaccharide of Streptococcus pneumoniae and the surface antigen protein for Hepatitis B vims vaccine. 

Control of Microorganisms. Treatment-regime tests with Ca(OCl)2 and chloroisocyanurates killed all pathogenic bacteria, including the... 

Pasteurization does not mean sterilization of the beer, ie, killing all microorganisms, but rather a reduction and inactivation of the microorganisms. The result of the heat treatment depends not only on time and temperature, but also on the number of microorganisms present. It is important that tanks. 

Germicidal Properties. The germicidal activity of aqueous chlorine is attributed primarily to HOCl. Although the detailed mechanism by which HOCl kills bacteria and other microorganisms has not been estabUshed, sufficient experimental evidence has been obtained to suggest strongly that the mode of action involves penetration of the cell wall followed by reaction with the enzymatic system. The efficiency of destmction is affected by temperature, time of contact, pH, and type and concentration of organisms (177). 

Antiseptic. An antiseptic is a chemical substance that prevents or inhibits the action or growth of microorganisms but may not necessarily kill them, and is used topically on living tissue. The distinction between a disinfectant and an antiseptic is that the former is expected to kill all vegetative cells and is used only on inanimate objects, whereas the latter may not kill all cells and is used on the body. 

Biocide is an antimicrobial agent that kills or inhibits the growth of microorganisms. 

Sporicide kills (inactivates) bacterial spores, and is therefore expected to kill all other microorganisms of less resistance. According to the AO AC International it may not kill 100% of the spores, and therefore may not be as powerful as a sterilant. However, according to the EPA, sporicide and sterilant are considered identical. 

Bactenostat, fungistat, etc, are agents that only claim to inhibit, not necessarily kill, microorganisms. In some cases, if they prevent proliferation of microorganisms for sufficient time, these agents may serve as effectively as if they killed the microorganisms. 

Chlorine Dioxide. Like ozone, chlorine dioxide [10049-04-4] is a powerflil oxidant. It is usually generated as used. It has been used for disinfecting drinking water and bleaching paper pulp. Its effectiveness in killing microorganisms is well documented (305,306), and it has received recent study as a gas to sterilize medical devices. It requites 50% rh or higher to be effective. Bacterial cells had a D-value of 2.6 min and spores of 24 min (307). 

Hypochlorous acid and hypochlorite ion are known as free available chlorine. The chloramines are known as combined available chlorine and are slower than free chlorine in killing microorganisms. For identical conditions of contact time, temperature, and pH in the range of 6 to 8, it takes at least 25 times more combined available chlorine to produce the same germicidal efficiency. The difference in potency between chloramines and HOCl can be explained by the difference in their oxidation potentials, assuming the action of chloramine is of an electrochemical nature rather than one of diffusion, as seems to be the case for HOCl. 

Disinfection The process designed to kill most microorganisms in wastewater, including essentially all pathogenic (disease-causing) bacteria. There are several ways to disinfect, with chlorine being the most frequently used in water and wastewater treatment plants. 

Flame the neck of the flask and the cotton plug before inserting the plug back in the flask. Also, flame the loop to kill residual microorganisms. 

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