1. Controlling of Microbial Growth
The control of microbial growth is necessary in many practical situations, and significant advances in agriculture, medicine, and food science .
Control of microbial growth means to inhibit or prevent growth of microorganisms.

2. By killing microorganisms
This control is affected in two basic ways :
By killing microorganisms By
inhibiting the growth of
microorganisms
Agents which kill cells
are called cidal agents
Agents which inhibit the growth of cells
are called static agents

3. Agents used in Controlling of Microorganisms 3 Types
I. Physical Agents
II. Chemical Agents
III. Biological Agents
1. Antiseptics
2. Disinfectants
3. Preservatives
1. Natural
2. Semisynthetic
1. Heating
3. Filtration
5. freezing
4. Pasteurization
2. Irradiation
6. Drying (removal of HOH)

4. Means using of temperature to ensure destruction of all microorganisms
Physical Agents
I Heating
Means using of temperature to ensure destruction of all microorganisms
Incineration
Boiling
Autoclaving
(steam under pressure or pressure cooker)
Dry heat
(hot air oven)
100oC for 30 minutes
temperature/pressure employed is 121oC/1.5 psi for 15 minutes
160oC/2hours or 170oC/1hour
burns organisms and physically destroys them
Kills everything
for sterilizing biohazardous waste, surgical dressings, glassware, and many types of microbiologic media, liquids, and many other things
used for glassware, metal, and objects that won't melt لا تذوب
Used for needles, inoculating wires, glassware, etc.

5. usually destroys or distorts nucleic acids
2. Irradiation
usually destroys or distorts nucleic acids
used to sterilize the surfaces of objects By
x-rays, gamma radiation and electron beam radiation are also used

6. Physical removal (exclusion) of all cells in a liquid or gas.
3. Filtration
Physical removal (exclusion) of all cells in a liquid or gas.
Used to remove the smallest known bacterial cells.

7. 4. Pasteurization
It means the use of mild heat to reduce the number of microorganisms in a product or food
Milk is usually pasteurized by heating, typically at 63°C for 30 minutes or at 71°C for 15 minutes

8. Low temperature (refrigeration and freezing)
Most organisms grow very little or not at all at 0oC. Perishable foods are stored at low temperatures to slow rate of growth and consequent spoilage (e.g. milk).

9. 6. Drying (removal of HOH)
Most microorganisms cannot grow at reduced water activity. Drying is often used to preserve foods (e.g. fruits, grains, etc.).

10. II. Chemical Agents 1. Antiseptics 2. Disinfectants 3. Preservatives
Cidal agents.
Harmless enough to be applied to the skin and mucous membrane.
Should not be taken internally.
Examples include alcohols, silver nitrate, iodine solution, alcohols, detergents.
Cidal agents.
Not safe for application to living tissues.
Used on inanimate objects such as tables, floors, utensils, etc.
Examples: hypochlorites, chlorine compounds, copper sulfate, formaldehyde, phenolic compounds and LTGP (Low Temperature Gas Plasma).
Static agents.
Used to inhibit the growth of microorg-anisms.
Most often in foods.
If eaten they should be nontoxic.
Examples are calcium propionate, sodium benzoate, nitrate and sulfur dioxide, ethylene oxide (ETO) and ozone.
used to prevents microbial reproduction
used as a disinfectant for water and food

11. III. Biological Agents
The biological agents are antimicrobial agents that kill (cidal effect) or inhibit (static effect) the growth microorganisms.
Antimicrobial agents may be of natural or synthetic origin:
1. Natural
2. Semisynthetic
Antimicrobial agents produced by microorganisms that kill or inhibit other microorganisms.
Examples are penicillin and its relatives.
Molecules produced by a microbe that are subsequently modified by an organic chemist to enhance their antimicrobial properties or to render them unique for a pharmaceutical patent.
Examples are sulfonilamides and chloramphenicol.

12. Efficiency of antibiotics
Broad spectrum
Limited spectrum
Antibiotics effective against prokaryotes which kill or inhibit a wide range of Gram-positive and Gram-negative bacteria.
Antibiotics effective against prokaryotes which kill or inhibit a single organism.
Narrow spectrum
Antibiotics effective against prokaryotes which kill or inhibit a wide range of Gram-negative or Gram-negative bacteria