Microbiology ch 9: Chemical and Physical Control of Microbes

Sterilization

Removal/destruction of all viable microbes

Disinfection

Use of chemical or physical agents to inhibit microbes on physical objects

Decontamination/Sanitation

Mechanical removal of microbes and debris

Antisepsis/Degermination

Reduces the number of microbes on living tissue

Pasterization

Use of heat to kill spoilage microbes in food and beverages

-cide

Ending that means “kills”

-stasis/-static

ending that means “prevents new growth”

Sepsis

Growth of microbes in blood/tissues

Number, type, pH, temp, concentration of agent, mode of action of agent, presence of solvents

Factors that affect microbial death

Damage to cell wall/membranes or proteins/nucleic acids

Actions of antimicrobial agents

Leaking and/or lysis

Results from damage or alteration to cell wall/membrane

Inhibits reproduction and enzymes, kills cell

Results of damage to proteins and nucleic acid

Thermal death point

Lowest temperature that kills all cells in a sample in 10 minutes

Thermal death time

Shortest time needed to kill a specific organism at a specific temperature

Moist heat

Type of heat that is effective at lower temps and needs less time to kill microbes

Dry heat

Type of heat that needs higher temperatures and more time to kill microbes

Autoclave

Steam under pressure

Cold and dessication

Slows growth in microbes

Ionizing radiation

Higher power radiation, can sterilize, penetrates surface

Non-ionizing radiation

Type of radiation that is lower power, can disinfect, and does not penetrate surface

UV

Type(s) of non-ionizing radiation

Gamma rays and X-rays

Type(s) of ionizing radiation

Denaturation of proteins and removal of water

How does heat damage microbes

Filtration

Fluid or gas through a sieve to remove microbes, can sterilize things that cannot be heated

Osmotic pressure

Use of high concentrations of salt or sugar to kill pathogens

Aqueous solutions

Solutes dissolved in pure water

Tinctures

Solutes dissolved in alcohol or water/alcohol mixture

Sterilants and Non-sterilants

Categories of chemical agents

Halogens, oxidizing agents, aldehydes, gases

Types of sterilants

Alcohols, phenolics, surfactants, heavy metals, enzymes

Types of non-sterilants

Alcohols

Dissolves/denatures cell membrane and denatures proteins, evaporates quickly