Control of growth usually involves the use of physical or chemical agents which either kill or prevent the growth of microorganisms. Agents which kill cells are called cidal agents; agents which inhibit the growth of cells without killing them are referred to as static agents.
Thus, the term bactericidal refers to killing bacteria, and bacteriostatic refers to inhibiting the growth of bacterial cells. A bactericide kills bacteria, a fungicide kills fungi, and so on. In microbiology, sterilization refers to the complete destruction or elimination of all viable organisms in or on a substance being sterilized. There are no degrees of sterilization: an object or substance is either sterile or not.
Sterilization procedures involve the use of heat, radiation or chemicals, or physical removal of cells. Methods of Sterilization Heat : most important and widely used. For sterilization one must consider the type of heat, and most importantly, the time of application and temperature to ensure destruction of all microorganisms.
Endospores of bacteria are considered the most thermoduric of all cells so their destruction guarantees sterility.
Incineration : burns organisms and physically destroys them. Used for needles, inoculating wires, glassware, etc. Boiling : o for 30 minutes. Kills everything except some endospores.
Autoclaving steam under pressure or pressure cooker Autoclaving is the most effective and most efficient means of sterilization. These two variables are extremely important. Higher temperatures ensure more rapid killing. Longer times are needed for larger loads, large volumes of liquid, and more dense materials.
Autoclaving is ideal for sterilizing biohazardous waste, surgical dressings, glassware, many types of microbiologic media, liquids, and many other things. However, certain items, such as plastics and certain medical instruments e. Furthermore, microbial control technologies can ensure that fewer natural resources are needed, because products do not need to be replaced as often.
Microbial control technologies intend to exterminate, render harmless, or prevent the spread of harmful organisms. While on the one hand the substances may be of a somewhat aggressive nature, these same substances aim to protect us against microorganisms we cannot otherwise control.
By taking appropriate measures, the microbial control technologies can be safely used. It is a priority for MCEC members to educate users on how to safely use microbial control solutions, ensuring that instructions of use are followed, and risk mitigation measures are applied preventing harm to the user, their surroundings, or the environment.
MCEC member companies also conduct extensive research to find microbial control solutions where only the unwanted microorganisms are targeted, and humans and the environment remain unharmed. There is no one-size-fits-all approach for alternative substances and identifying a substitute does not equal the replacement of one substance in all existing applications. Furthermore, substituting substances can take substantial time and resources before delivering results.
Substances need to be proven sufficiently efficient without unacceptable risk for human health or the environment for each use. For this, an extensive efficacy and toxicological data package is needed.
Furthermore, the lack of guarantee that the new substance or product will pass the scrutiny of the approval process could result in little incentive for innovation in this area. It can take up to 10 years before a new solution is accepted to market. New active substances need to undergo a thorough scrutiny first, and rightfully so. This scrutiny is largely linked to compliance with the Biocidal Product Regulation BPR which provides the framework to assess the risk and efficacy of biocidal products.
Under the Registration, Evaluation, Authorisation and Restriction of Chemicals REACH legislation, companies must demonstrate how their substance can be safely used, and they must communicate appropriate risk management measures to the users.
The term antibiotic was first used in by Selman Waksman and his collaborators in journal articles to describe any substance produced by a microorganism that is antagonistic to the growth of other microorganisms in high dilution. This definition excluded substances that kill bacteria, but are not produced by microorganisms such as gastric juices and hydrogen peroxide. It also excluded synthetic antibacterial compounds such as the sulfonamides.
Many antibacterial compounds are classified on the basis of chemical or biosynthetic origin into natural, semisynthetic, and synthetic. Another classification system is based on biological activity. In this classification, antibacterials are divided into two broad groups according to their biological effect on microorganisms: bactericidal agents kill bacteria, andbacteriostatic agents slow down or stall bacterial growth.
Joseph Lister : Joseph Lister was one of the first to use aseptic techniques during surgeries. The degree of acceptable microbial presence can differ based on the circumstances.
Sterilization as a definition means that all life was terminated, whereas sanitization and disinfection terminates selectively and partially. In general, surgical instruments and medications that enter an already aseptic part of the body such as the bloodstream, or penetrate the skin must be sterilized to a high sterility assurance level SAL.
Examples of such instruments include scalpels, hypodermic needles, and artificial pacemakers. For example, medical device manufacturers design their sterilization processes for an extremely low SAL. This is also essential in the manufacture of parenteral pharmaceuticals. Preparation of injectable medications and intravenous solutions for fluid replacement therapy requires not only a high sterility assurance level, but also well-designed containers to prevent entry of adventitious agents after the initial product sterilization.
Food preservation is another field where the presence of microorganisms is taken under consideration. The process usually involves preventing the growth of bacteria, fungi such as yeasts , and other microorganisms although some methods work by introducing benign bacteria or fungi to the food.
The rate of microbial death is used to develop standard protocols for sterilization in many industries. The rate of microbial death can be determined. It is important in order to develop standard protocols for disinfection which will facilitate the sterilization routine in many industries. The goal is to find out what is the minimum time needed to achieve acceptable level of sterilization for a specific purpose.
The killing agent can be different e. When the killing factor is heat, the phrase thermal death can be used. Thermal death time is a concept used to determine how long it takes to kill a specific bacteria at a specific temperature. It was originally developed for food canning and has found applications in cosmetics, and in producing salmonella-free feeds for animals e.
Killing curve of C. In the food industry, it is important to reduce the amount of microbes in products to ensure proper food safety. This is usually done by thermal processing and finding ways to reduce the number of bacteria in the product. Z or z-value is used to determine the time values with different D-values at different temperatures with its equation shown below:. Such death curves can be empirically established for all bactericidal agents.
This D-value is affected by pH of the product where low pH has faster D values on various foods. The D-value at an unknown temperature can be calculated knowing the D-value at a given temperature provided the Z-value is known.
The target of reduction in canning is the D reduction of Clostridium botulinum , which means that processing time will reduce the amount of this bacteria by 10 12 bacteria per gram or milliliter. A D reduction will take seconds.
0コメント