Module 4: Microbe Control

Historical microbe control methods

salting food, smoking food, pickling food, drying food, exposure to sunlight(UV)

4 process of microbe control outside of the body

sterilization, disinfection, decontamination, antisepsis

Sterilization

destroys/removes all microbes including endospores and viruses, impractical/dangerous to do on human body

Sterilization common uses

surgical instruments, syringes

Sterilization agents/techniques

autoclave: uses high temps, high pressure, and moisture

sterilants: chemical agents

Disinfection

can be by physical or chemical means by using a disinfectant, kills vegetative pathogens but not endospores, kills most microbes which reduces contamination, used on inanimate objects

Disinfection common uses

examination tables, food prep areas, thermometers

Disinfection agents/techniques

bleach, iodine, boiling

Decontamination

also called sanitization, a cleansing technique, mechanically removes microbes and debris, used on inanimate objects and reduces contamination to safe levels

Decontamination common uses

cooking utensils, dishes, cans, bottles

Decontamination agents/techniques

sanitizer(soap/detergent), commercial dish washers(heat)

Antisepsis

also known as degermination, decontamination of living surfaces, scrub skin or immerse skin in chemicals

Sepsis

growth of microbes in blood and other tissues

Asepsis

practice of preventing entry of infectious agents into tissues, goal of antisepsis

Antisepsis agents/techniques

alcohol wipe, surgical hand scrub, Betadine

Antisepsis techniques

chemical agents(antiseptics) applied to body surface and surgical incisions, destroys/inhibits vegetative pathogens

Bactericide

agent that kills vegetative bacteria

Fungicide

agent that kills fungal spores

Virucide

agent that kills viruses

Sporicide

agent that kills endospores

Germicide/microbicide

agent that kills microbes

Endospores

resistant to heating, freezing, drying, radiation, and chemicals

Endospore formation stimulus

depletion of nutrients and water

Sporulation

spore formation

Sporangium

vegetative cell that has turned into sporulating cell, transformation takes 6-8 hours

Germination

spore releases vegetative cell, occurs during favorable conditions

Process of germination

endospore is exposed to water or germination agent which begins to break down the cortex, core rehydrates and takes up nutrients, bacteria grows out of endospore coat

Medical significance of endospores

some diseases are related to the persistence and resistance of spores; they enter tissues, germinate, and cause disease; makes sterility and cleanliness hard because they resist ordinary cleaning methods

Medically significant bacteria with endospores

Bacillus anthracis: anthrax

Clostridium tetani: tetanus

C. botulinum: botulism

Killing endospores

if a process kills endospores, it will also kill vegetative cells

Cellular targets of physical and chemical agents

cell wall, cell membrane, nucleic acid synthesis, and proteins

Impacts of agents on cell wall

damages cell wall by blocking its synthesis or digesting/breaking down the cell wall

cells with a damaged cell wall are fragile and can lyse easily

cell wall can be targeted and damaged by alcohols and detergents

Impacts of agents on cell membrane

disruption of cell membrane causes loss of selective permeability, loss of vital molecules, and entry of damaging chemicals

What other than cells have a membrane

animal viruses

Impact of agents on nucleic acid synthesis

no DNA leads to no replication, no RNA leads to no transcription/translation which leads to no proteins

Impact of agents on proteins

inhibiting ribosomes causes no protein synthesis, deactivate proteins through denaturation, forcing shape change, or blocking the active site of enzymes