6.9 Control of Harmful Bacteria

Introduction

Harmful bacteria cause diseases, spoil food, and decay materials. To control harmful bacteria, various chemical and physical methods are used. These methods inhibit the growth of bacteria or kill them. Understanding these methods is important for healthcare, food production, and sanitation.

Definition

Control of Harmful Bacteria: Control of harmful bacteria refers to the use of chemical and physical methods to inhibit the growth of bacteria or kill them.

In simple words: Controlling harmful bacteria means using chemicals and physical methods to stop them from growing or to kill them.

Core Concept

• Harmful bacteria can be controlled by:
• Chemical methods involve the use of chemical agents to inhibit the growth or kill bacteria.
• Physical methods involve the use of physical agents like heat, radiation, and filtration.

Detailed Explanation

Chemical Methods to Control Bacteria

Chemical methods to control bacteria are essential in various settings, including healthcare, food production, and sanitation. These methods involve the use of chemical agents to inhibit the growth or kill bacteria.

Here are common chemical methods for bacterial control:

1. Disinfectants

• Definition: Disinfectants are chemicals used to kill or inhibit the growth of bacteria on surfaces and inanimate objects.
• Use: Commonly used in hospitals, laboratories, and households.
• Examples: Bleach (sodium hypochlorite), hydrogen peroxide, quaternary ammonium compounds.

2. Antiseptics

• Definition: Antiseptics are similar to disinfectants but are designed for use on living tissues, such as skin and mucous membranes, to prevent or treat bacterial infections.
• Examples: Alcohol-based hand sanitizers, iodine-based antiseptics, hydrogen peroxide.

3. Preservatives

• Definition: Chemical preservatives are used in food and cosmetic products to inhibit the growth of bacteria and other microorganisms, prolonging the product's shelf life.
• Examples: Sodium benzoate, potassium sorbate, parabens.

4. Chemical Agents in Water Treatment

- Definition: Chlorine and chloramine are commonly used chemicals in water treatment facilities to disinfect drinking water and control bacterial growth in water distribution systems.

5. Chemotherapy

• Definition: Chemotherapy involves the use of chemicals to treat bacterial infections.
• Use: Often used when antibiotics are ineffective.
• Examples: Drugs like sulfonamides or nitrofurans.

Physical Methods to Control Bacteria

Physical methods to control bacteria are essential in various settings, including healthcare, food production, and sanitation. These methods involve the use of physical agents to inhibit the growth or kill bacteria.

Here are common physical methods for bacterial control:

1. Sterilization Process

• Definition: Sterilization employs physical agents like steam, dry heat, gas, filtration, and radiation to effectively control bacteria.
• Use: Destructive to all life forms; used for sterilizing surgical instruments.
• Application: Used on a large scale to preserve food items such as milk and meat.

2. High Temperature

• Definition: High temperatures, both dry and moist heat, are employed in microbiological laboratories to control microbes.
• Mechanism:
• Moist heat: Causes protein coagulation and microbial death.
• Dry heat: Leads to the oxidation of microbial constituents, ultimately killing them.

3. Radiation

• Definition: Certain electromagnetic radiations, particularly those below 300 nm, are effective in eradicating microorganisms.
• Example: Gamma rays are commonly used for sterilization purposes.

4. Membrane Filter

- Definition: Heat-sensitive compounds like antibiotics and serums can be sterilized using membrane filters, ensuring their purity and safety.

5. Pasteurization

• Definition: Louis Pasteur introduced pasteurization as a process to eliminate microorganisms through controlled heating.
• Application: Applied at temperatures sufficient to kill non-spore-forming bacteria.
• Examples:
• Pasteurization of milk at 71°C for 15 seconds or 62°C for 72 minutes.
• Importance: Maintains the taste of the treated product while reducing the risk of diseases like typhoid and tuberculosis.

6. Low Temperature

• Definition: Food preservation is achieved by storing it at temperatures between 10°C to 15°C.
• Application: Extends the shelf life of various items such as milk, vegetables, cheese, and meat.

7. Freezing

• Definition: Food can be preserved for weeks to months by subjecting it to freezing temperatures ranging from −10°C to −18°C.
• Application: Commonly frozen items include meat and vegetables.

8. Drying

• Definition: Dehydration, or the removal of water, prevents bacterial growth in food items.
• Examples: Dried milk and dried meat are examples of products that undergo this preservation method, ensuring their long-term storage without spoiling.

Summary Table of Chemical Methods

Summary Table of Physical Methods

Intermediate Level

Chemical Methods in Detail

Physical Methods in Detail

Comparison of Chemical and Physical Methods

Important Points

• 1. Chemical methods to control bacteria are essential in various settings, including healthcare, food production, and sanitation.
• 2. These methods involve the use of chemical agents to inhibit the growth or kill bacteria.
• 3. Common chemical methods for bacterial control:
• - Disinfectants: Disinfectants are chemicals used to kill or inhibit the growth of bacteria on surfaces and inanimate objects. They are commonly used in hospitals, laboratories, and households. Common disinfectants include bleach (sodium hypochlorite), hydrogen peroxide, and quaternary ammonium compounds.
• - Antiseptics: Antiseptics are similar to disinfectants but are designed for use on living tissues, such as skin and mucous membranes, to prevent or treat bacterial infections. Examples include alcohol-based hand sanitizers, iodine-based antiseptics, and hydrogen peroxide.
• - Preservatives: Chemical preservatives are used in food and cosmetic products to inhibit the growth of bacteria and other microorganisms, prolonging the product's shelf life. Examples include sodium benzoate, potassium sorbate, and parabens.
• - Chemical Agents in Water Treatment: Chlorine and chloramine are commonly used chemicals in water treatment facilities to disinfect drinking water and control bacterial growth in water distribution systems.
• - Chemotherapy: Chemotherapy involves the use of chemicals to treat bacterial infections. It is often used when antibiotics are ineffective, and it may include drugs like sulfonamides or nitrofurans.
• 4. Physical Methods to Control Bacteria:
• - Sterilization Process: Sterilization employs physical agents like steam, dry heat, gas, filtration, and radiation to effectively control bacteria. This process is destructive to all life forms and finds application in sterilizing surgical instruments. Additionally, it is used on a large scale to preserve food items such as milk and meat.
• - High Temperature: High temperatures, both dry and moist heat, are employed in microbiological laboratories to control microbes. Moist heat causes protein coagulation and microbial death, while dry heat leads to the oxidation of microbial constituents, ultimately killing them.
• - Radiation: Certain electromagnetic radiations, particularly those below 300 nm, are effective in eradicating microorganisms. Gamma rays, for instance, are commonly used for sterilization purposes.
• - Membrane Filter: Heat-sensitive compounds like antibiotics and serums can be sterilized using membrane filters, ensuring their purity and safety.
• - Pasteurization: Louis Pasteur introduced pasteurization as a process to eliminate microorganisms through controlled heating. It's applied at temperatures sufficient to kill non-spore-forming bacteria, as seen in the pasteurization of milk at 71°C for 15 seconds or 62°C for 72 minutes. Importantly, pasteurization maintains the taste of the treated product while reducing the risk of diseases like typhoid and tuberculosis.
• - Low Temperature: Food preservation is achieved by storing it at temperatures between 10°C to 15°C. This method extends the shelf life of various items such as milk, vegetables, cheese, and meat.
• - Freezing: Food can be preserved for weeks to months by subjecting it to freezing temperatures ranging from −10°C to −18°C. Commonly frozen items include meat and vegetables.
• - Drying: Dehydration, or the removal of water, prevents bacterial growth in food items. Dried milk and dried meat are examples of products that undergo this preservation method, ensuring their long-term storage without spoiling.
• 5. Science, Technology and Society Connections: Justify why it is important to disinfect hands and operation table before a surgery?

Remember

• - Chemical methods = disinfectants, antiseptics, preservatives, water treatment, chemotherapy.
• - Physical methods = sterilization, high temperature, radiation, membrane filter, pasteurization, low temperature, freezing, drying.
• - Pasteurization = 71°C for 15 seconds or 62°C for 72 minutes.
• - **Freezing** = −10°C to −18°C.
• - **Low temperature** = 10°C to 15°C.
• - Disinfectants = surfaces and inanimate objects.
• - Antiseptics = living tissues.
• - Preservatives = food and cosmetics.
• - Chemotherapy = treat bacterial infections.

Common Mistakes

• 1. Confusing disinfectants and antiseptics – Disinfectants = surfaces and inanimate objects; Antiseptics = living tissues.
• 2. Thinking preservatives are only for food – Preservatives are also used in cosmetics.
• 3. Forgetting the temperatures for pasteurization – 71°C for 15 seconds or 62°C for 72 minutes.
• 4. Confusing low temperature and freezing – Low temperature = 10°C to 15°C; Freezing = −10°C to −18°C.
• 5. Thinking sterilization only uses heat – Sterilization uses steam, dry heat, gas, filtration, and radiation.
• 6. Forgetting the role of radiation – Gamma rays are used for sterilization.
• 7. Confusing the chemical and physical methods – Chemical methods use chemicals; Physical methods use physical agents.
• 8. Thinking all bacteria are killed by the same method – Different methods are used for different purposes.
• 9. Forgetting the role of membrane filters – Membrane filters are used for heat-sensitive compounds.
• 10. Thinking pasteurization kills all bacteria – Pasteurization kills non-spore-forming bacteria.
• 11. Confusing the types of heat – Moist heat = protein coagulation; Dry heat = oxidation.
• 12. Thinking chemotherapy is only for cancer – Chemotherapy is also used to treat bacterial infections.

Quick Revision

• Chemical methods to control bacteria are essential in various settings, including healthcare, food production, and sanitation.
• These methods involve the use of chemical agents to inhibit the growth or kill bacteria.
• Common chemical methods for bacterial control:
• Disinfectants: Disinfectants are chemicals used to kill or inhibit the growth of bacteria on surfaces and inanimate objects. They are commonly used in hospitals, laboratories, and households. Common disinfectants include bleach (sodium hypochlorite), hydrogen peroxide, and quaternary ammonium compounds.
• Antiseptics: Antiseptics are similar to disinfectants but are designed for use on living tissues, such as skin and mucous membranes, to prevent or treat bacterial infections. Examples include alcohol-based hand sanitizers, iodine-based antiseptics, and hydrogen peroxide.
• Preservatives: Chemical preservatives are used in food and cosmetic products to inhibit the growth of bacteria and other microorganisms, prolonging the product's shelf life. Examples include sodium benzoate, potassium sorbate, and parabens.
• Chemical Agents in Water Treatment: Chlorine and chloramine are commonly used chemicals in water treatment facilities to disinfect drinking water and control bacterial growth in water distribution systems.
• Chemotherapy: Chemotherapy involves the use of chemicals to treat bacterial infections. It is often used when antibiotics are ineffective, and it may include drugs like sulfonamides or nitrofurans.
• Physical Methods to Control Bacteria:
• Sterilization Process: Sterilization employs physical agents like steam, dry heat, gas, filtration, and radiation to effectively control bacteria. This process is destructive to all life forms and finds application in sterilizing surgical instruments. Additionally, it is used on a large scale to preserve food items such as milk and meat.
• High Temperature: High temperatures, both dry and moist heat, are employed in microbiological laboratories to control microbes. Moist heat causes protein coagulation and microbial death, while dry heat leads to the oxidation of microbial constituents, ultimately killing them.
• Radiation: Certain electromagnetic radiations, particularly those below 300 nm, are effective in eradicating microorganisms. Gamma rays, for instance, are commonly used for sterilization purposes.
• Membrane Filter: Heat-sensitive compounds like antibiotics and serums can be sterilized using membrane filters, ensuring their purity and safety.
• Pasteurization: Louis Pasteur introduced pasteurization as a process to eliminate microorganisms through controlled heating. It's applied at temperatures sufficient to kill non-spore-forming bacteria, as seen in the pasteurization of milk at 71°C for 15 seconds or 62°C for 72 minutes. Importantly, pasteurization maintains the taste of the treated product while reducing the risk of diseases like typhoid and tuberculosis.
• Low Temperature: Food preservation is achieved by storing it at temperatures between 10°C to 15°C. This method extends the shelf life of various items such as milk, vegetables, cheese, and meat.
• Freezing: Food can be preserved for weeks to months by subjecting it to freezing temperatures ranging from −10°C to −18°C. Commonly frozen items include meat and vegetables.
• Drying: Dehydration, or the removal of water, prevents bacterial growth in food items. Dried milk and dried meat are examples of products that undergo this preservation method, ensuring their long-term storage without spoiling.
• Science, Technology and Society Connections: Justify why it is important to disinfect hands and operation table before a surgery?

60-Second Revision

• Chemical methods = disinfectants, antiseptics, preservatives, water treatment, chemotherapy.
• Physical methods = sterilization, high temperature, radiation, membrane filter, pasteurization, low temperature, freezing, drying.
• Pasteurization = 71°C for 15 seconds or 62°C for 72 minutes.
• **Freezing** = −10°C to −18°C.
• **Low temperature** = 10°C to 15°C.
• Disinfectants = surfaces and inanimate objects.
• Antiseptics = living tissues.
• Preservatives = food and cosmetics.
• Chemotherapy = treat bacterial infections.
• Warning: Disinfectants are for surfaces; antiseptics are for living tissues. Pasteurization kills non-spore-forming bacteria. Freezing is −10°C to −18°C. Low temperature is 10°C to 15°C. Sterilization uses steam, dry heat, gas, filtration, and radiation. Gamma rays are used for sterilization. Membrane filters are for heat-sensitive compounds. Chemotherapy treats bacterial infections. Disinfect hands and operation table before surgery to prevent infections.