wire tip of forceps and searing spatulas of milk) – Holder method (630C for 30 min) 2. Burning or Incineration – for contami- or flash process (720C for 15 sec) destroy all
nated cloth, animal carcasses and nonsporing pathogens. Coxiella burnetii is pathological materials, PVC and polythene relatively heat resistant and may survive holder (Polystyrene should autoclave) method. Also used for vaccines of non-sporing 3. Hot air oven – Most widely used method of bacteria, serum or body fluids containing
sterilization by dry heat coagulable proteins.
• Holding period of 1600C for one hour is 2. Temperature at 1000C (Boiling) – Rolling boil
used to sterilize glassware, scalpels, all (boiling for 5 - 10 minutes) will kill bacteria, but glass syringes, swabs, liquid paraffins, not spores or viruses
dusting powder, fats and grease 3. Steam at atmospheric pressure 1000C - Koch
• Sterilization control is done by spore of or Arnold steamer is usually used container non-toxigenic strain of Cl. tetani and culture media are simultaneously • For cutting instruments temperature of sterilized. Single exposure of 20 min usually
1500C for 2 hours is required ensures sterilization; but for media containing • Drawback - It has no penetrating power sugars or gelatin an exposure of 1000C for 20
so not used for bulky articles such as minutes on three successive days is used
mattresses known as Tyndallization
4. Steam under pressure = autoclave or steam
sterlizer (>1000C) - Most effective sterilizing agent for dressing, instruments, laboratory wares, media and pharmaceutical products; aqueous solutions. Sterlization control by bacillus
REVISION
AT
A
GLANCE
Filtration : Used to remove bacteria; virus isolation; testing water samples for vibrio cholera or typhoid bacilli; and obtaining bacterial toxins. Membrane filters is routinely used in water purification and analysis, sterlization and sterility testing and for preparations of solutions for parenteral use. Most widely used pore diameter is 0.22 μm.
Radiation
Non ionization Ionizing radiation
1. Infrared radiation - Form of hot air – X-rays, gamma rays (Commonly used) and cosmic rays sterlization used for rapid mass sterlization referred to as cold Sterlization
of prepacked items such as syringes and – Used for plastics, syringes, swabs, catheters, animals
catheters feeds, cardboard, oils grease, fabrics, metal foils
2. Ultraviolet radiation - For entryways, operation – Most effective but very costly theaters and laboratories
Alcohols
• MC used are ethanol and isopropyl alcohol (better).
• Both used as skin disinfectant in 70% concentration.
• Not sporicidal but active against non sporing bacteria and viruses. • Isopropyl alcohol is used for disinfection of clinical thermometers.
• Methyl alcohol effective against fungal spores and is used for treating cabinets and incubators. • Most effective skin antiseptic is alcoholic solution of chlorhexidine and iodine.
Aldehydes
• Formaldehyde : Sporicidal (Slow activity), bactericidal, virucidal. Used for sterlising instruments and heat sensitive
catheters and for fumigating wards, sick rooms and laboratories.
• Glutarldehyde : Specially effective for tubercle bacilli, viruses and fungi.
– 2% solution called Cidex used for cystoscope and bronchoscopes. Dyes
• Acridine and aniline dyes used as skin and wound antiseptic. • More active against Gram positive organism.
Halogens
• Iodine in aqueous and alcoholic solution is used widely as skin disinfectant. • Active against tubercle bacteria, viruses, spores (moderately).
• Iodophores are compounds of iodine with non ionic wetting or surface active agents. They are more active. • Chlorine is used commonly as hypochlorites.
Ethylene oxide
• Highly penetrating and highly active against all microorganism including viruses and spores. • Specially used for sterilizing heart lung machine.
Formaldehyde gas
• For fumigation of operation theatres and other rooms.
• Betapropiolactone is more efficient for fumigation than formaldehyde. Surface Active Agents
• Most important antibacterial agents are cationic surface active agents. • No action on spores, tubercle bacilli and most viruses.
SECTION
–
A
1. Which of the following is most resistant to anticeptics? [AI 08]
a) Spore b) Prion
c) Cyst d) Fungus
2. Which of the following statement is true :
a) Solid media are enrichment media [AI 07]
b) Nutrient broth is basal media c) Agar adds nutrient to media d) Chocolate agar is selective media
3. A chest physician performs bronchoscopy in the procedure room of the out patient department. To make the instrument safe for use in the next patient waiting outside, the most appropriate method to disinfect the endoscope is by :
a) 70% alcohol for 5 min [AI 03]
b) 2% glutaraldehyde for 20 min c) 2% formaldheyde for 10 min d) 1% sodium hypochlorite for 15 min
4. Heat labile instruments for use in surgical pro- cedure can be best sterlized by : [AI 03]
a) Absolute alcohol b) Ultra violet rays
c) Chlorine releasing compounds d) Ethylene oxide gas
5. Out of the following the true statement regard- ing sterlization is : [AI 97]
a) Dry heat is the best method of sterilization of liq- uid paraffin
b) All glass syringes are best sterilized by boiling at 1000C
c) Bacterial vacines are best sterilized by ethylene oxide
d) Pasteurization of milk by flash method is done by heating at 630C for 30 minutes
6. The operating temperature in an ethylene oxide sterilization during warm cycle is : [AIIMS 04]
a) 20-350C b) 49-630C c) 68-880C d) 92-1100C
7. The sterilization method for the instruments which are damaged by dry heat is : [AIIMS 95]
a) Steam b) Radiation
c) Boiling d) Burning
8. Choose the correct ones for the decreasing or- der of resistance to sterilization : [PGI Dec. 07]
a) Prions, bacterial spores, bacteria b) Bacterial spores, Bacteria, Prions c) Bacteria, Prions, Bacterial spores d) Prions, Bacteria, Bacterial spores e) Bacterial spores, prions, bacteria
9. Decreasing order of resistance to sterilization :
a) Spores, prions, non-lipid of smll virus
b) Prions, spores, enveloped viruses [PGI 07]
c) Spores, mycobacteria, lipid or medium size vi- rus
10. Sterilising agents include : [PGI 02]
a) Dry heat b) Ethylene oxide c) Ether
d) Alcohol e) Chlorohexidine
11. Which of the following can be reliably used for hand washing : [PGI 00]
a) Chlorhexidine b) Isopropyl alcohol c) Lysol
d) Cresol
e) Glutaraldehyde
12. Sporocidal disinfectant is following except :
a) Glutaraldehyde [PGI 99]
b) Formaldehyde c) Ethylene oxide d) Benzalkonium chloride
13. All are sporicidal except : [PGI 99]
a) Lysol
b) Glutaraldehyde c) Ethylene dioxide d) Formaldehyde
14. Sterlization of culture media containing serum is
by : [PGI 98] a) Autoclaving b) Micropore filter c) Gamma radiation d) Centrifugation