Microbial Control and Destruction

Cards (51)

  • 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 :
    1. heat
    2. radiation
    3. 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:
    1. depth filter
    2. membrane filters
    3. 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