Module 4 Flashcards
Why control growth of microorganisms?
- prevent spoilage of important commodities
- prevent infection
- prevent contamination of cultures, personnel, and environment
complete destruction of all microorganisms, including endospores
STERILIZATION
- killing, inhibition, or removal of pathogenic microorganisms
DISINFECTION
inanimate objects that harbor microorganisms
Fomites
Reduction of microbial population to levels considered safe by public health standards
SANITIZATION
preventing infections in living tissues using chemicals
ANTISEPSIS
Agents that carry out antisepsis
selectively effective against microorganisms; does not cause tissue damage
ANTISEPTICS
mechanical removal + use of
mild chemicals on tissues or
skin
DEGERMING
Agents Used in Microbial Control
PHYSICAL or CHEMICAL
Physical Methods to Control Microorganisms
Application of Heat
Filtration
Desiccation
Addition of Solutes
Radiation
Chemical Methods to Control Microorganisms
Antimicrobial agents
Phenols and phenolics
Alcohols
Halogens
Heavy Metals
Surfactants
Organic Acids
Alkylating Agents
Peroxygens
- MOA: denatures proteins and other cellular components
- Moist or Dry Heat
Application of Heat
- MOA: irreversible
denaturation of enzymes and
structural proteins - more effective in penetrating
cells
Moist Heat
Types of Moist Heat
Boiling
Steam under pressure
Tyndallization
Pasteurization
- kills vegetative cells and
eukaryotic spores - sterility is not achieved
Boiling
- uses autoclave or pressure
cooker - 121 ̊C, 15 psi, for 15 minutes
Steam under pressure
Indicators to ensure sterility:
autoclave tape
Geobacillus stearothermophilus spores
- intermittent or fractional sterilization
- for materials destroyed beyond 100̊C
Tyndallization
Process of Tyndallization
- heating to 100 ̊C for 15 to 30 minutes
- done for 3 consecutive days
- kill pathogens and reduce the
number spoilage
microorganisms
Pasteurization
basis of pasteurization
Coxiella burnettii
Ways of pasteurization
LTLT – 63 ̊C, 30 minutes
HTST - 72 ̊C, 15 seconds
UHT - 135 to 140 ̊C, 1 to 2 seconds
Types of Dry Heat
Direct Flame
Hot Air
- MOA: incineration or burning to ashes
- Alcohol lamps, Bunsen burner, Bactericinerator
Dry Heat – Direct Flame
- MOA: oxidation of molecular components
- 170 ̊C for at least 2 hours
- mechanical convection oven
Dry Heat – Hot Air
- Refrigeration – 4 to 7 ̊C
- Freezing - 0 ̊C and below
- MOA: decreased enzyme
activity = decrease in
metabolic activity
Low Temperature
group of organisms with the ability to grow and reproduce under low temperatures ranging from −20 °C to 10 °C
psychrophiles
- MOA: exclusion of
microorganisms - common pore size: 0.2 μm
- for heat sensitive solutions
Filtration
MOA: lowering of aw = microbiostasis
Desiccation
types of Desiccation
Drying
Freeze drying or lyophilization
- sunlight, drum drying,
spray drying, evaporation
Drying
rapid freezing then sublimation
Freeze drying or lyophilization
- MOA: osmotic shock
- increase in solutes such as
salts and sugars
Addition of Solutes