Control of Microbial Growth

Physical and chemical methods of microbial control that kill the targeted microorganism are identified by the suffix -cide (or -cidal). The prefix indicates the type of microbe or infectious agent killed by the treatment method: bactericides kill bacteria, viricides kill or inactivate viruses, and fungicides kill fungi. Other methods do not kill organisms but, instead, stop their growth, making their population static; such methods are identified by the suffix - stat (or -static). For example, bacteriostatic treatments inhibit the growth of bacteria, whereas fungistatic treatments inhibit the growth of fungi. Factors that determine whether a particular treatment is -cidal or -static include the types of microorganisms targeted, the concentration of the chemical used, and the nature of the treatment applied.

• Heat is a widely used and highly effective method for controlling microbial growth. 
•  Dry-heat sterilization protocols are used commonly in aseptic techniques in the laboratory. However, moistheat sterilization is typically the more effective protocol because it penetrates cells better than dry heat does.
• Pasteurization is used to kill pathogens and reduce the number of microbes that cause food spoilage. Hightemperature, short-time pasteurization is commonly used to pasteurize milk that will be refrigerated; ultrahigh temperature pasteurization can be used to pasteurize milk for long-term storage without refrigeration.
• Refrigeration slows microbial growth; freezing stops growth, killing some organisms. Laboratory and medical specimens may be frozen on dry ice or at ultra-low temperatures for storage and transport.
• High-pressure processing can be used to kill microbes in food. Hyperbaric oxygen therapy to increase oxygen saturation has also been used to treat certain infections.
• Desiccation has long been used to preserve foods and is accelerated through the addition of salt or sugar, which decrease water activity in foods.
• Lyophilization combines cold exposure and desiccation for the long-term storage of foods and laboratory materials, but microbes remain and can be rehydrated.
• Ionizing radiation, including gamma irradiation, is an effective way to sterilize heat-sensitive and packaged materials. Non-ionizing radiation, such as ultraviolet light, is unable to penetrate surfaces but is useful for surface sterilization.
• HEPA filtration is commonly used in hospital ventilation systems and biological safety cabinets in laboratories to prevent transmission of airborne microbes. Membrane filtration is widely used to remove bacteria from heat-sensitive solutions.

Attribution: "Microbiology for Allied Health Students" by Molly Smith and Sara Selby is licensed under CC BY 4.0