How is ultraviolet light used to control microorganisms

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It is able to kill all kinds of microorganisms, including drug resistant bacteria. It has a major limit! UV only works in its light path and can be blocked by objects. Make sure what you want sterilized is directly in line with the UV light. You can minimize this issue by using multiple UV bulbs to generate UV irradiation from different angles. References: You can watch the effect of UV exposure time on E. Standard Products. Discontinued Products. Agreement FAQs. Although gamma irradiation is a proven method of eliminating potentially harmful microbes from food, the public has yet to buy in.

Most of their concerns, however, stem from misinformation and a poor understanding of the basic principles of radiation. The most common method of irradiation is to expose food to cobalt or cesium by passing it through a radiation chamber on a conveyor belt. The food does not directly contact the radioactive material and does not become radioactive itself. Thus, there is no risk for exposure to radioactive material through eating gamma-irradiated foods.

Additionally, irradiated foods are not significantly altered in terms of nutritional quality, aside from the loss of certain vitamins, which is also exacerbated by extended storage. Alterations in taste or smell may occur in irradiated foods with high fat content, such as fatty meats and dairy products, but this effect can be minimized by using lower doses of radiation at colder temperatures. Department of Agriculture. The use of high-frequency ultrasound waves to disrupt cell structures is called sonication.

Application of ultrasound waves causes rapid changes in pressure within the intracellular liquid; this leads to cavitation , the formation of bubbles inside the cell, which can disrupt cell structures and eventually cause the cell to lyse or collapse. Sonication is useful in the laboratory for efficiently lysing cells to release their contents for further research; outside the laboratory, sonication is used for cleaning surgical instruments, lenses, and a variety of other objects such as coins, tools, and musical instruments.

Filtration is a method of physically separating microbes from samples. Air is commonly filtered through high-efficiency particulate air HEPA filters. HEPA filters have effective pore sizes of 0. HEPA filters have a variety of applications and are used widely in clinical settings, in cars and airplanes, and even in the home. For example, they may be found in vacuum cleaners, heating and air-conditioning systems, and air purifiers.

Figure Biological safety cabinets are a good example of the use of HEPA filters. HEPA filters in biological safety cabinet s BSCs are used to remove particulates in the air either entering the cabinet air intake , leaving the cabinet air exhaust , or treating both the intake and exhaust.

Use of an air-intake HEPA filter prevents environmental contaminants from entering the BSC, creating a clean area for handling biological materials. Use of an air-exhaust HEPA filter prevents laboratory pathogens from contaminating the laboratory, thus maintaining a safe work area for laboratory personnel.

Each class is designed to provide a different level of protection for laboratory personnel and the environment; BSC II and III are also designed to protect the materials or devices in the cabinet. Class I BSCs protect laboratory workers and the environment from a low to moderate risk for exposure to biological agents used in the laboratory.

They are gas tight, and materials entering or exiting the cabinet must be passed through a double-door system, allowing the intervening space to be decontaminated between uses.

Personnel can manipulate materials inside the Class III cabinet by using long rubber gloves sealed to the cabinet. HEPA filters are also commonly used in hospitals and surgical suites to prevent contamination and the spread of airborne microbes through ventilation systems.

HEPA filtration systems may be designed for entire buildings or for individual rooms. For example, burn units, operating rooms, or isolation units may require special HEPA-filtration systems to remove opportunistic pathogens from the environment because patients in these rooms are particularly vulnerable to infection.

Filtration can also be used to remove microbes from liquid samples using membrane filtration. Membrane filters for liquids function similarly to HEPA filters for air. Typically, membrane filters that are used to remove bacteria have an effective pore size of 0. Membrane filtration is useful for removing bacteria from various types of heat-sensitive solutions used in the laboratory, such as antibiotic solutions and vitamin solutions.

Large volumes of culture media may also be filter sterilized rather than autoclaved to protect heat-sensitive components. Often when filtering small volumes, syringe filters are used, but vacuum filters are typically used for filtering larger volumes. Membrane filters come in a variety of sizes, depending on the volume of solution being filtered. The solution is drawn through the filter by connecting the unit to a vacuum.

Which of the following methods brings about cell lysis due to cavitation induced by rapid localized pressure changes? Which of the following terms is used to describe the time required to kill all of the microbes within a sample at a given temperature?

Which of the following microbial control methods does not actually kill microbes or inhibit their growth but instead removes them physically from samples? Moist-heat sterilization protocols require the use of higher temperatures for longer periods of time than do dry-heat sterilization protocols do. Skip to main content. Control of Microbial Growth. Search for:. Using Physical Methods to Control Microorganisms Learning Objectives Understand and compare various physical methods of controlling microbial growth, including heating, refrigeration, freezing, high-pressure treatment, desiccation, lyophilization, irradiation, and filtration.

Think About It In an autoclave, how are temperatures above boiling achieved? Why is boiling not used as a sterilization method in a clinical setting? Think About It Does placing food in a refrigerator kill bacteria on the food? A Streak of Bad Potluck One Monday in spring , an Ohio woman began to experience blurred, double vision; difficulty swallowing; and drooping eyelids.

Think About It How does the addition of salt or sugar to food affect its water activity? Think About It What are two advantages of ionizing radiation as a sterilization method? How does the effectiveness of ionizing radiation compare with that of nonionizing radiation? This video shows how BSCs are designed and explains how they protect personnel, the environment, and the product. Think About It Would membrane filtration with a 0. Name at least two common uses of HEPA filtration in clinical or laboratory settings.

Summary: Physical Methods to Control Microorganisms The tables below summarize the physical methods of control discussed in this section. Table 1. Control Methods Using Pressure Method Conditions Mode of Action Example Uses High-pressure processing Exposure to pressures of — MPa Denatures proteins and can cause cell lysis Preservation of food Hyberbaric oxygen therapy Inhalation of pure oxygen at a pressure of 1—3 atm Inhibits metabolism and growth of anaerobic microbes Treatment of certain infections e.

Control Methods Using Dessication Method Conditions Mode of Action Example Uses Simple desiccation Drying Inhibits metabolism Dried fruits, jerky Reduce water activity Addition of salt or water Inhibits metabolism and can cause lysis Salted meats and fish, honey, jams and jellies Lyophilization Rapid freezing under vacuum Inhibits metabolism Preservation of food, laboratory cultures, or reagents Table 5.

Control Methods Using Radiation Method Conditions Mode of Action Example Uses Ionizing radiation Exposure to X-rays or gamma rays Alters molecular structures, introduces double-strand breaks into DNA Sterilization of spices and heat-sensitive laboratory and medical items; used for food sterilization in Europe but not widely accepted in US Nonionizing radiation Exposure to ultraviolet light Introduces thymine dimers, leading to mutations Surface sterilization of laboratory materials, water purification Table 6.

After significant research, development and validation, the appropriate combination of technologies and materials have been identified and are now ready to easily integrate into existing products to make disinfection easy.

The breakthrough produced a technology that effectively kills bacteria and viruses in the air and on surrounding surfaces. Violet Defense Technology represents a significant breakthrough in germicidal protection for the world and is protected by an extensive US and international patent portfolio. Food and Drug Administration or the U.