Exercise VI- Inhibition and Destruction of Microorganisms by Physical Agents

STERILIZATION

All forms of microbial life including bacterial spores are killed

DISINFECTION

pathogenic organisms but not necessarily all microorganisms or spores and destroyed

• BOILING

• 80°C

• PASTEURIZATION

DISINFECTION: PHYSICAL AGENTS

• MOIST HEAT

• DRY HEAT

STERILIZATION: PHYSICAL AGENTS

MOIST HEAT

• steam under pressure —- Autoclave

• Shorter sterilization time

kills by coagulation of proteins

Action of moist heat

DRY HEAT

• Longer exposure time and temperature

• Hot air oven

121oC at 15psi for 15-20 minutes

this type of autoclave is used to sterilize medical liquids and instruments

132oC at 15psi for 30-60 minutes

used for infectious medical waste

Quality Control (QC)

done to ensure that sterilization is effective using Bacillus stearothermophilus in vials or spore-strip sets

causes protein oxidation

Action of dry heat

can cause increased levels of electrocytes

lethal effects of dry heat

HOT AIR OVEN

• destruction of microorganisms including spores

• 160oC to 180oC for 1.5-3 hours

• Used for sterilization of glassware for lab use

CLEAR

No microorganisms in the tube, not inoculated

TURBIDITY

Indication of growth, after the nutrient broth is inoculated with microorganism.

Antisepsis

prevention of infection or sepsis

Microbicidal agents

• kill microorganisms

• germicide, bactericide, fungicide, algicide, viricide, sporicide

Bacteriostatic

• do not kill but prevent growth

• fungistatic, bacteriostatic

• population size

• population composition

• concentration or intensity of an antimicrobial agent

• duration of exposure

• temperature

• local environment

• presence of organic material

• compatibility of disinfectants and sterilant

Factors influencing the degree of destruction:

Turbidity

In nutrient broth, what is the indication of bacterial growth after it has been inoculated with microorganism?

Control, 800C, and Boling

In this test, each test tubes are labelled as Control, 80C, boiling, autoclave, and hot air oven, and the organism used is Bacillus subtilis; Which test tube would show bacterial growth?

80°C, bliling, autoclave, hot air oven

In this test, each test tubes are labelled as Control, 80C, boiling, autoclave, and hot air oven, and the organism used is Escherichia coli; Which test tube would show no bacterial growth?