Microbial control - it is essential in order to prevent the unwanted microbial contamination, transmission of diseases and infection, stop decomposition and spoilage of food.
The effects of microorganisms can often be controlled by simply limiting or inhibiting growth.
Microorganisms are controlled by means of physical agents and chemical agents.
Sterilization – the removal or destruction of all living microorganisms. It is one of the example of physical agent. It is the killing or removal of all microorganisms (including viruses)
Decontamination – the treatment of an object or surface to make it safe to handle. As a result, it needs wiping off to remove fragments before using.
Sepsis refers to the presence of pathogens in blood or tissues
Disinfection – a process that directly targets pathogens although it may not eliminate all microorganisms. It requires agents called disinfectants that actually kill microorganisms or severely inhibit their growth
Antisepsis is the prevention of infection
Microbial control means to kill or to inhibit the growth of microorganisms
Heating is the most common method used for killing microbes, including the most resistant forms, such as endospores. Liquids or gases can be sterilized by filtration.
asepsis means the absence of pathogens
Decimal Reduction Time is quantified by the time required for a 10-fold reduction in the viability of a microbial population at a given temperature
Heat killing proceeds more rapidly as the temperature rises.
Time and temperature are directly proportional with each other.
Physical methods are used extensively in industry, medicine, and the home
Physical methods can be classified into three classes :
heat
radiation
filtration
Heat – the most widely used method of physically treating an object or substance to render it sterile
There are two factors that determine the effectiveness of heat sterilization: time and temperature.
Higher temperature and shorter time are required to kill pathogens.
Thermal death time is the time it takes to kill all cells at a given temperature
The longer time is required to kill all cells in a large population than in a small one
Moist heat – has more penetrating power and inhibits growth or kills cells more quickly than does dry heat.
Autoclave – sealed heating device that uses steam under pressure to kill microorganisms
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
Flash Pasteurization – 71°C for 15 seconds, after which it is rapidly cooled.
Ultrahigh Temperature (UHT) pasteurization of milk requires heat treatment at 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 heatresistant glass materials
Flaming – accomplished by holding the end of the loop or forceps in the yellow portion of the gas flame; flaming he surface metal forcep and wire bacteriologic loops is an effective way to kill microorganisms
What type of heat sterilization is this?
A) dry heat strerilization
Identify the following sterilization methods
A) incineration
B) flaming
Identify the type of radiation
A) ultraviolet radiation
Ionizing Radiation – electromagnetic radiation of sufficient energy to produce ions and other reactive molecular species from molecules with which the radiation particles collide
Depth filters – important in biosafety applications such as in a biological safety cabinet
Membrane filters – most common filters used for liquid sterilization
Nucleopore filters – commonly used to isolate specimens for scanning electron microscopy (SEM)
Types of filters:
depth filter
membrane filters
nucleopore filters
Filtration - Used to separate cells, larger viruses, bacteria, certain microbes from liquids or gases in which they are suspended
Filtration - A unique method of sterilization as it removes contaminants instead of killing them