Control Microbe Growth

•Daily life

•Hospitals

•Microbiology laboratories

•Food production industry

•Other industries

Removal or destruction of all forms of microbial life

Control directed at destroying harmful microorganisms. Destruction of vegetative pathogens on inert surface

Destruction of vegetative pathogens on living tissue

Object or area is free of pathogens

Mechanical removal of most of the microbes in a limited area

any cleansing technique that mechanically removes microbes

inhibition of growth and multiplication of bacteria

kills microorganisms with exception of endospores

•Type of microbe – ‘tough bugs’

•Number of microbes present

• •Environmental conditions
• –Organic material present?
• –Temp & pH (warm disinfectant vs
• cold?)

•Potential risk of infection

Most resistant: Prions, endospores, mycobacteria

Most susceptible: Enveloped viruses, G+ bacteria, non-enveloped viruses

Without a lipid envelope

•Protein capsid

With a lipid envelope covering the outside of the virus

•Phospholipid envelope

Moist heat: lower temperatures and shorter exposure time; coagulation and denaturation of proteins

•Boiling

•Autoclaving

•Commercial canning

•Pasteurization

• •Boiling at 100oC for 30 minutes to destroy
• non-spore-forming pathogens

•Disinfection

• •Pasteurization – heat is applied to kill potential
• agents of infection and spoilage without destroying the food flavor or value

• •Dry heat: uses higher temperature than
• moist heat

•Hot oven (hot-air sterilization)

•Direct flaming

•Filter size excludes microbes (≤0.22 mm)

•Used for heat-sensitive liquids

–Ex. Antibiotics, vitamins, amino-acids

• •HEPA filters: high-efficiency particulate
• air filters (0.3 mm)

•Infection-control rooms or laboratories

Gamma rays

•Produces reactive molecules that damage DNA

•Hydroxyl radicals, superoxide

•Used for sterilization of plastic disposables, Petri dishes

•Used in food preservation

UV light

• •Little penetrating power -  must be directly
• exposed

•Damages DNA

•“Germicidal lamps”

• controls fungi, and some bacterial growth
• in foods & cosmetics

•found naturally in cranberries, prunes, apples, cinnamon, cloves

Benzoic acid - naturally occurring compound; totally safe and has no adverse health implications

Benzene - known carcinogen