Methods Of Sterilisation

Question 1

Materials to be sterilised in red heat,flaming, incineration, hot air oven respectively

Answer 1

*inoculating wires, tips of forceps and needles
*glass slides,scalpels, mouth of culture tubes
*soiled dressings, animal carcasses bedding,pathological materials
*glassware, surgical instruments, chemicals

Question 2

Sterilizing agents

Answer 2

Physical agents-dry heat ,moist heat,filtration, radiation
Chemical agents-dyes,alcohols,aldehydes,phenols,halogens

Question 3

Most reliable method if sterilization

Answer 3

Heat-exposing them to low heat or exposing them for longer periods

Question 4

Factors influencing sterilization by heat

Answer 4

-nature of heat
-temperature and time
-no of microorganisms
-type of materials from which organism should be eradicated
-characteristics of organism,species,strains,presence of spores

Question 5

Dry heat
Flaming

Answer 5

To sterilize inoculating loop/wire,tip of forceps,searing spatulas
-hold the substances over bunsen flame till they become red-hot
-put inoculating wires on disinfectant if any infective material is present to prevent spreading

Question 6

Dry heat
Incineration

Answer 6

Terminal sterilization to destroy biomedical wastes
To sterilize-plastic such as PVC and polyethene

Question 7

Dry heat
Hot air oven

Answer 7

Most widely used method
-through conduction
-heat absorbed by surface of the substance a
,then it reaches the centre till heat reaches the entire item
Holding period-160 oC
Substances-glassware,forceps,scissors, scalpes, all glass syringes
Pharmaceuticals-liquid paraffin,dusting powder,fats ,grease
-oven heated by electricity

Question 8

Principle of hot air oven

Answer 8

-fan fitted inside for even distribution of air and elimination of air pockets
-free circulation of air bw the substances
-allow cooling of oven for 2 hours before opening door to avoid crack due to sudden cooling

Question 9

Substances to be used in hot air oven

Answer 9

Glassware-perfectly dry before placing
Test rube and flask-wrapped in craft paper
Sharp instruments sterilize at 150oC

Question 10

To control sterilization

Answer 10

Physical-using thermocouple
Chemicals -brownes tube ,cmplte sterilization
Biological -heat resistant spores of clostridium tetani/bacillus subtitles,sub sp Niger to indicate efficiency

Question 11

Moist heat

Answer 11

Pasteurization
Inspissation

Question 12

Moist heat
Pasterisation

Answer 12

2 methods followed by heating at 13oC
Holder method -milk heated at 63oC for 30 min,coxiella burnetti survives
Flash process-heated at 72oC for 15 to20 s

Destroying non sporing bacteria,mycobacteria,brucellae, salmonallae

Question 13

Moist heat
Inspissation

Answer 13

Media-lowenstein Jenson
Loefflers serum
-heating 80 to 85 oC for 1/2 hour on 3successive days in inspissator

Question 14

Usage of vaccine bath

Answer 14

Bacterial vaccines-60oC for 1 hour
Serum or body fluids containing coagulable protein- 56oC in successive days

Question 15

At temp 100oC

Answer 15

Boiling
Tyndallysation
Steam sterilizer

Question 16

Above 100oC

Answer 16

Autoclave-steam sterilizer

Question 17

Temp at 100oC
Boiling

Answer 17

To kill bacteria
At 90 to 100oC
Principle -material immersed in water for 10 to 30 min
Lid of sterilizer should not open
Add 2%na nahc03 to make water soft and the process smooth
Don’t use hard water

Not for-instruments for surgical procedures

Question 18

Steam sterilizer at100oC

Answer 18

To sterilize culture media-atmosphere of free steam
Not at high temp
Steamer used-koch or Arnold

Question 19

At temp 100oC
Tyndallisation

Answer 19

Media with sugars or gelatin
100oC for 20 min
Principle
On first exposure kills bacteria and spores (fav medium) again germinate and be killed in subsequent exposure to 100oC for 20 min