disinfection and sterilization

Question 1

disinfectant slection criteria

Answer 1

• fast acting in the presence of organic substances
• effective against all types of infectious agents without destroying tissue
• easily penetrate material to be disinfecting without damaging or discolouring it
• easy to prepare, stable when exposed to light, heat and other factors

Question 2

methods of sterilization

Answer 2

dry heat- hot air oven- used for glassware, instruments, paper wrapped articles, oils, waxes and powders- 160 for 2 hrs or 170 for 1 hr

moist heat: autoclave and pressure cooker. used for culture media, water containing materials and lab waste.

incineration: burns and physcially destroys living organsism, inoculating loops and lab waste

filtration: used in media prep , filtering delicate supplements that are inactivated by autoclaving(carbs, antibiotics)

UV- used additionally with other methods, sterilize workspaces and tools, germicidal wavelengths 185nm-265nm.

Question 3

autoclave temp and time

Answer 3

121 celcius and 15 mins

Question 4

2 types of autoclaves

Answer 4

porous load autoclaves - modern, fast, reliable efficient, air removed by partial vacuum, admitting steam and reppeating, short cycles

downward displacment autocalve- air removed by dilution in turbulent steam flow, long cycles, inefficient