Micropara Lecture 4

• •Microbial Control or Control of Microbial Growth

  means to inhibit or prevent growth of microorganisms.
• • Sterilization


  removal or destruction of all microbes
• • Aseptic


  -aiming at the complete elimination of harmful microorganisms.
• Disinfection


  The process of cleaning something with theaid of physical or chemical agents, in order to destroy pathogens
• Antisepsis/Antiseptic/Germicide


  "against putrefaction"
• Degerming


  Method of remove most (but not all) microbes from the skin's surface.
• Sanitization


  disinfecting places and utensils used by the public.
• Sanitizer


  agent that reduces the microbial population to safe level.
• • Antimicrobial agents agents that inhibit the growth or completely destroy the life of microorganism
• Anti-microbial agents could be Physical agents Chemical agents Chemotherapeutic agents
• Decontamination


  process of cleansing an object or substance to remove contaminants
• -static/-stasis


  indicates that a chemical or physical agent inhibits microbial metabolism and growth but does not kill microorganisms.
• o-cide/-cidal


  agents that destroy or permanently inactivate a particular type of microorganism.
• Heat sterilization


  Divided into Moist heat and Dry heat
• Moist Heat

  Autoclaving• - steam under pressure• -121 °C, 15 psi, 10 – 15 minutes, Boiling• -commonly employed but incompletely effective.• 100°C, Free flowing steam (Arnold sterilizer)• also known as Intermittent sterilization or Tyndallisation or fractionation- consist of heating 80 to 100 ° C for 30 mins. For 3 consecutive days first heating: vegetative cells and some spores will be killed, subsequent heating: more resistant spore, Pasteurization - Use of mild heating to kill bacteria.
• • Dry heat - fosters the oxidation of metabolic and structural chemicals. 1. Flaming used in bacteriological loop and needles 2. Hot air oven for glassware, Petri dishes, pipettes, flasks - 180 °C for 1 – 2 hours160-165°C for 2 hours170-180°C for 1 hour 3. Incineration (Burning) process that involves combustion
• Cold


  Low temperature, •inhibit microbial growth
• Lyophilization


  Freeze-drying method
• Deep-freezing


  • 50 °C to -95 °C
• Refrigeration

  2°C to 7°C
• Desiccation


  Absence of water or moisture The process of extreme drying
• Desiccator


  A common use is to protect chemicals which are hygroscopic or which react with water from humidity
• Desiccant


  a hygroscopic substance used as a drying agent
• High Osmotic pressure


  Use of high salt or sugar concentration to create hypertonic environment to cause plasmolysis
• • Osmotic pressure is an important factor that affects cell.
• • Osmosis is the net movement of solvent molecules through a partially permeable membrane into a region of higher solute concentration
• • Radiation sterilization electromagnetic radiation (U.V., X-rays)- damages DNA
• Ionizing radiation - generates electrons, hydroxyl radicals, etc.• - alters DNA, cell death
• Non-ionizing radiation UV light, visible light, infrared, radio wave, microwave (weak)
• Filter sterilization


  consist of pores too small for passage of microorganisms but large enough to allow the passage of gas o liquid.
• • Membrane Filter (composed of polymers with high tensile strength) • Nucleation tuck filter (Nucleopore) • Seitz filter (disks of asbestos-cellulose mixture) • - Chamberland filter (unglazed porcelain) • - Barkefeld filter (diatomaceous earth)
• Ultrasonic and Sonic Vibration 


  Vibration periodic back-and-forth motion of the particles
• Chemical methods Mode of action 1. Damage to cell wall or inhibition of cell wall

  synthesis

  2. Alteration of the:

  -cytoplasmic membrane permeability.

  - physical and chemical state of proteins and

  nucleic acid.

  4. Inhibition of :

  - enzyme function.

  - protein and nucleic acid synthesis.
• NON-SELECTIVE Method


  PHENOL, PHENOLICS, ALCOHOLS, HALOGENS, OXIDIZING AGENTS, SURFACTANTS, SOAPS AND DETERGENTS, ALDEHYDES, GASEOUS AGENTS
• SELECTIVE Method


  ANTIBIOTICS, ANTI-viral drugs, Anti-protozoan drugs, Anti-helminthic drugs
• •Microbial Control or•Control of Microbial Growth

  means to inhibit or prevent growth of microorganisms.
• two basic control affected

  •(1) by killing microorganisms• (2) by inhibiting the growth of microorganisms.
• Uses of Sterilization• Laboratory


  • Culture media, reagents, containers, loops and needles, glass wares, etc.
• Medical and surgical equipment or materials used in penetrating normally sterile portions of the human body
• Filter sterilization


  -for heat-sensitive substances