Microbial Control

• Microbial control is essential to prevent unwanted microbial contamination, transmission of diseases and infection, stop decomposition and spoilage of food
• Sterilization is the removal or destruction of all living microorganisms
• Decontamination is the treatment of an object or surface to make it safe to handle
• Disinfection is a process that directly targets pathogens although it may not eliminate all microorganisms
• Sepsis is the presence of pathogens in blood or tissues
• Asepsis is the absence of pathogens
• Antisepsis is the prevention of infection
• Microbial control is to kill or to inhibit the growth of microorganisms
• Heating: The most common method used for killing microbes, including the most resistant forms, such as endospores
• Decimal reduction time is the time required for a 10-fold reduction in the viability of a microbial population at a given temperature
• Time and temperature is directly proportional with each other
• Thermal death time is the time it takes to kill all cells at a given temperature
• Moist heat: Has more penetrating power and inhibits growth or kills cells more quickly than dry heat
• Autoclave: Sealed heating device that uses steam under pressure to kill microorganisms, Steam under a pressure of 1.1 kg/cm2 (15 lb/in2), which yields a temperature of 121°C for 15 mins, It is not the pressure inside the autoclave that kills the microorganisms but the high temperatures that are achieved when steam is placed under pressure
• Pasteurization: Uses heat to significantly reduce rather than totally eliminate the microorganisms found in liquids, such as milk, Flash Pasteurization - 71°C for 15 seconds, after which it is rapidly cooled, Ultrahigh Temperature (UHT) pasteurization of milk - 135°C for 1–2 sec and actually sterilizes the milk such that it can be stored at room temperature for long periods without spoilage
• Dry heat: Effective sterilization of metals, glasswares, some powders, oils and waxes, Incineration (burning) - effective means of destroying contaminated disposable materials; intense heat ignites and reduces microbes to ashes and gas; limited to metals and heat-resistant glass materials, Flaming - accomplished by holding the end of the loop or forceps in the yellow portion of the gas flame; flaming the surface metal forcep and wire bacteriologic loops is an effective way to kill microorganisms
• Dry heat sterilization: Using a Bunsen burner flame, Using an electrical heating device
• Ultraviolet (UV) radiation: Useful for disinfecting surfaces and air, Widely used to decontaminate and disinfect the work surface of laboratory laminar flow hoods equipped with a "germicidal" UV light, air circulating in hospital and food preparation rooms, Has very poor penetrating power, limiting its use to the disinfection of exposed surfaces or air rather than bulk objects such as canned foods or surgical clothing
• Ionizing radiation: Electromagnetic radiation of sufficient energy to produce ions and other reactive molecular species from molecules with which the radiation particles collide
• Filtration: Used to separate cells, larger viruses, bacteria, certain microbes from liquids or gases in which they are suspended, A unique method of sterilization as it removes contaminants instead of killing them, Cotton plug in test tube, flask, pipette is a good filter for preventing the entry of microbes, Dry gauze and paper mask prevent the outward passage of microbes from the mouth and nose, protects from inhaling airborne pathogens and foreign particles that could damage the lungs
• Types of filters: Depth filters, Membrane filters, Nucleopore filters
• Antimicrobial agent is a natural or synthetic chemical that kills or inhibits the growth of microorganisms
• Types of antimicrobial agents: Cidal agents - kill microbes, Static agents - inhibit the growth of a microbe, Bacteriolytic agents - lysis of the bacterial cells
• Classes of chemical antimicrobial agents: Sterilants, Disinfectants, Antiseptics or germicides