1. Muhammad Suleman Kamran Rasool Fatima Amjad Aysha Imtiaz

2.  Control of microbial growth means "Preventing the growth of microbes"  Very important in microbiology experiments  Preventing growth of undesirable microorganisms

3. Control Killing microorganisms Preventing their growth

4.  Sterilization – a process that destroys all viable microbes, including viruses & endospores  Disinfection – a process to destroy vegetative pathogens, not endospores  Sanitization – any cleansing technique that mechanically removes microbes  Degermation – reduces the number of microbes

5.  Cell Wall  Cell Membrane  Proteins  Nucleic Acid (DNA and RNA)

6. Physical Control Chemical Control

8.  Heat  Cold temperature Treatment  Desiccation  Radiation  Filtration

9.  Thermal death time Minimum amount of time required to kill microorganisms at a given temperature  Thermal death point The lowest temperature at which all microorganisms are killed in 10 minutes  Decimal reduction time. The time for destruction of 90 percent of the microbial population

10.  Moist heat – use of hot water or steam  Vegetative cell with in 2-3 mins  Bacterial spores 2-3 hours  Mode of action – denaturation of proteins, destruction of membranes & DNA  Autoclave  Intermittent Sterilization  Pasteurization  Boiling

11.  Dry Heat  Oxidation of organic molecules  Denatures proteins (cell destroyed)  Incineration  Heat treatment from flame or heating coil  Flame of Bunsen burner is 1,870 degrees Celsius.  Furnaces/incinerators burn from 800-6,500 degrees Celsius

12.  Dry Ovens  Heat is circulated in an enclosed compartment  Sterilization requires 150-180 degrees Celsius for 2 to 4 hours (destroys spores)

13.  Microbiostatic- Slow growth of microbes  Refrigeration  4°C Static, except for psychrotrophs  short term food preservation  Freezing  –20°C or lower (liquid nitrogen -196°C)  static to many microbes  long term food preservation (-20°C) or specimen storage (-80 to -196°C)  used to preserve foods and culture media

14.  Removal of water  Stops growth  Not effective  Microbes regrow on reintroduction of water

15.  Removal of microbes by passing through a filter  Used to sterilize  heat sensitive liquids  Air in hospital units  HEPA Filters in BSL-3

16. Ionizing Radiations Non-Ionizing Radiations

17.  Ionizing Radiation  Highly penetrating  Break DNA backbone  used to sterilize food products and medical instruments  X-rays, gamma Rays

18.  Non-ionizing Radiation  less penetrating power  form T-T Dimers, disrupt DNA structure  Used to sterilize air and solid surfaces  UV Rays

20.  For evaluating the disinfectant or chemical agent  Dip metal rings into broth cultures of the organisms.  a disk of filter paper is soaked with a chemical  placed on an inoculated agar plate  a clear zone of inhibition indicates effectiveness.

22.  Halogens  Phenolics  Alcohols  Hydrogen peroxide  Detergents & soaps  Heavy metals  Aldehydes

24.  Chlorine  Denaturation of proteins (by disrupting disulfide bonds)  Calcium hypochlorite : disinfect equipment  As a gas, maintain low microbial count in water  Iodine  Denatures proteins  Sporicidal  Degerming agent and disinfectant  Surface active agent

25.  Disrupt cell membrane (precipitate proteins)  Bactericidal, viricidal but not sporicidal  Best for disinfecting things like pus and saliva  Triclosan  added to soaps as antibacterial agent

26.  Applicable for bacterial and fungi hazardous effects but not sporicidal  70 % Ethyl alcohol & isopropyl is widely used.  Act as surfactants  dissolves membrane lipids  coagulates proteins of vegetative bacterial cells and fungi  Evaporates quickly  Useful in degerming the skin before injections

27.  Weak solution (3%) to strong solution (25%)  Produce highly reactive hydroxyl-free radicals  damage protein & DNA  interaction with catalase (at injured part)& decomposes to O 2 gas  decomposes to O 2 gas – toxic to anaerobes  Strong solutions are sporicidal

28.  Detergents  Quaternary ammonia cations  Act as surfactant  Not sporicidal  Soaps  Mechanically remove particles containing microbes  Grease and oils

29.  Glutaraldehyde & formaldehyde  Kill microbes by alkylating protein & DNA  glutaraldehyde in 2% solution (Cidex)  used as sterilant for heat sensitive instruments  formaldehyde  disinfectant, preservative  toxicity limits use

30.  Solutions of silver & mercury  kill vegetative cells in low concentrations by inactivating proteins.  Bind to the active site of important enzymes  Oligodynamic action  Not sporicidal  Eg. silver nitrate

31.  Ethylene oxide, propylene oxide, betapropiolactone & chlorine dioxide  Strong alkylating agents  Stop DNA-RNA synthesis  Stop Protein Synthesis  Disrupt protein structure  Sporicidal

32.  Microbes are found everywhere in environment  Their control is most important  By killing  By stopping Growth  Microbial Death refers to complete loss of reproductive ability of microbes even under optimum conditions  Different Methods to control  Physical Methods  Chemical Methods INTERESTING FACT!!!!!  Deinococcus radiodurans can withstand blasts of radiation 1,000 times greater than what would kill a human being.