Chapter 11

Sterilization (Definition)

- A process that destroys or removes all viable microorganisms, including viruses. - The removal or destruction of all viable microbes.

Antiseptics (Definition)

- Chemical agents called antiseptics are applied directly to exposed body surfaces, wounds, and surgical incisions to destroy or inhibit vegetative pathogens. Examples: Iodine/alcohol swabs before IV, hydrogen peroxide in a wound, and handwashing with germicidal soap.

Microbistatic (Definition)

- Cold temperatures (refrigeration or freezing) are microbistatic and are commonly used to preserve food, media, and cultures.

Mode of action (Dry heat)

- Denotes air with a low moisture content that has been heated by a flame or electric heating coil. - Dehydrates the cell, removing the water necessary for metabolic reactions, and it alters protein structure. - However, the lack of water actually increases the stability of some protein conformations, necessitating the use of higher temperatures.

Pasteurization

- Heat is applied to kill potential agents of infection and spoilage without destroying the food flavor or value. Two types 1. Batch method (63C-66C for 30 minutes) 2. Flash method (71.6C for 15 seconds) - Not sterilization: Kills non-spore-forming pathogens and lowers overall microbe count. - Does not kill endospores or many nonpathogenic microbes.

Sanitization (Definition)

- In many cases, it is more important to focus on reducing the size of a microbial population, or its microbial load. - Refers to any cleansing technique that removes debris, microorganisms, and toxins, and in this way reduces the potential for infection and spoilage. Examples include Soaps and detergents.

Mode of action (Moist Heat)

- Occurs in the form of hot water, boiling water, or steam (60-135C) - Moist heat operates at lower temperatures and shorter expsure times to acheive the same effectiveness as dry heat. - Most microbicidal effects are due to coagulation and denaturation of proteins.

Agents That Affect Protein and nucleic Acid Synthesis

- Prevention of replication, transcription, and translation! - Protein: Denaturation

The Effects of Agents on the Cell Wall

- Several types of chemical agents damage the cell wall by blocking ts synthesis, digesting it, or breaking down its surface. - A cell deprived of a functioning cell wall becomes fragile and is lysed. - Examples of this mode of action include some antimicrobial drugs (penicillins) that interfere with the synthesis of the cell wall in bacteria. - Detergents and alcohol can also disrupt cell walls, especiall in gram (-) bacteria.

Ionizing radiation (Definition) Give one example

- Such as gamma rays and X rays, has deep penetrating power and works by causing breaks in the DNA of target organisms. Example: Preserving food such as rasberries.

Moist Heat Methods of Disinfection (Autoclave)

- Uses increased pressure and temperature (steam) to effectively disinfect and sterilize in an autoclave. - Denatures proteins

Nonionizing radiation (Definition) Give one example

- Uses ultraviolet waves with very little penetrating power and works by crating dimers between adjacent pyrimidines, which interferes with replication. Example: Sterilizing air, water or surfaces, such as mechanical ventilation.

Autoclaves (Definition) Sterilization or Disinfectant?

- Utilize steam under pressure to sterilize heat-resistant materials, whereas intermittent sterilization can be used to sterilize more delicate items. - Form of sterilization

Least Resistance (Relative Resistance of Microbes)

- Vegetative Cells - Fungal spores and hyphae, yeast - Enveloped viruses - Protozoan trophozoites

Antimicrobial agents mode of action (Cell wall and Cell membrane)

1. The cell wall: Chemical agents damage the cell wall by blocking its synthesis, digesting it, or breaking down its surface. Examples include penicillins, detergents, and alcohols, especially in gram (-) bacteria. 2. The cell membrane: The cell membrane provides a two way transport, when this is disrupted, important products can seep out and dangerous chemicals can seep in. - Chemicals called surfactants works as microbicidal agents because they lower the surface tension of cell membranes. Surfactants are polar molecules such as detergents with hydrophilic and hydrophobic regions that can physically bind to the lipid layer and penetrate the internal hydrophobic region of membranes. - Alcohols exert a related effect.

What two genera are bacterial endospores?

1. Bacillus 2. Clostridium

Detergents and Soaps

1. Cationic detergents known as quaternary ammonium compounds (quats) act as surfactants that alter the membrane permeability of some bacteria and fungi. They are not sporicidal. 2. Soaps have little microbicidal activity but, rather, function by removing grease and soil that contain microbes.

The cellular targets of physical and chemical agents fall into four general categories which are...

1. Cell walls 2. Cell membranes 3. Protein and nucleic acid synthesis 4. Protein structure and function

What are the six factors that affect death rate?

1. Number of microorganisms 2. Nature of microorganisms in the population 3. The temperature and pH of the environment. 4. The concentration (dosage, intensity) of the agent. 5. The mode of action of the agent. How does it kill or inhibit microorganisms? 6. Presence of solvents, interfering organic matter, and inhibitors. Saliva, blood, and feces can inhibit the actions of disinfectants and ever of heat.

Lyophilization (Definition)

A common method of preserving microorganisms and other cells in a viable state state for many years. - Freeze drying/preservation.

What are the modes of action of antimicrobial agents?

Agents affect cell wall synthesis, membrane permeability, and protein and nucleic acid synthesis and function.

An blank agent is applied to living tissue to destroy or inhibit microbial growth

Antiseptic

Iodophors, antibacterial soap, and chlorhexidine would be an example of?

Antiseptic

Blank agents inhibit or prevent the growth of bacteria on tissues or on other objects in the environment

Bacteriostatic

Incineration (Definition)

Can be carried out using a Bunsen burner or incinerator. Temperatures range between 800 C and 6500 C.

A blank agent is used on inanimate objects to destroy vegetative pathogens but not bacterial endospores.

Disinfectant

What property does an endospore have?

Endospores are heat resistant!

Describe how alcohol is a useful for microbial control. What is a specific term associated with the process?

Ethyl and isopropyl alcohol, in concentrations of 50% to 90%, are useful for microbial control. Alcohols act as surfactants, dissolving membrane lipids and coagulating proteins of vegetative bacterial cells and fungi. They are not sporicidal.

How agents Affect the Cell Membrane

If the membrane is disrupted, a cell loses its selective permeability and can neither prevent the loss of vital molecules nor bar the entry of damaging chemicals. - Chemicals called surfactants work as microbicidal agents because they lower the surface tension of cell membranes. Surfactants are polar molecules such as detergents with hydrophilic and hydrophobic regions that can physically bind to the lipid layer and penetrate the internal hydrophobic region of membranes. - In effect, this process "opens up" the once tight interface, leaving leaky spots that allow harmful chemicals to seep into the cell and important ions to seep out.

Dessication (Definition) Also, what is another term for this?

Lead to (often temporary) metabolic inhibition by reducing water in the cell. - Lyphophilization is a form of this. Freeze drying/preserving

Blank agents are primarily inhibitors that slow microbial growth.

Microbistatic

An antimicrobial agent's adverse effect on cells is known as its

Mode of action

Highest Resistance (Relative Resistance of Microbes)

Prions and Bacterial Endospores

Blank reduces microbial number on inanimate objects to safe levels by physical or chemical means.

Sanitization

Dishwashing, laundering clothes would be an example of?

Sanitization

Infected wounds, or blood infection would be an example of?

Sepsis

Thermal death time (TDT)

Shortest length of time required to kill all test microbes at a specified temperature - Variable: Time - Constant: Temperature

Microbiostatic

Slows the growth of microbes - Examples include refrigeration and freezing temperatures.

Blank agents destroy all viable organisms, including viruses.

Sterilatization

Autoclaving, ionizing radiation would be an example of?

Sterilization

Pasteurization (Definition) Sterilization or Disinfectant?

Subjects liquids to temperatures below 100 degrees Celsius and is used to lower the microbial load in liquids. Boiling water can be used to destroy vegetative pathogens in the home. - Disinfectant

Disinfection (Definition)

The destruction or removal of vegetative pathogens but not bacterial endospores. Usually used only on inanimate objects

Thermal death point (TDP)

The lowest temperature required to kill all microbes in a sample in 10 minutes. - Variable: Temperature - Constant: Time

Placing food in the refrigerator would be an example of microbialstatic agent? True of False?

True