By T.Divya R.Manjeera Bharat Kishore.

STERILISATION AND

DISINFECTION

LABORATORY SAFETY Wear gloves Wash hands after working with

infectious materials Disinfect all instruments after use Use water to moisten specimen labels Disinfect all contaminated waste

before discarding Report to appropriate personnel all

accidents or exposures to infectious agents

STERILISATIONThe process by which an article ,surface or

medium is freed of all living microorganisms either in the vegetative or spore state.

Object of Sterilisation :Uses:- .to prevent contamination by

organisms in surgery to maintain asepsis .in food manufacture .in drug manufacture Methods :depend on purpose,material

and nature of microorganisms to be removed or destroyed

DISINFECTION :- destruction or removal of all pathogenic organisms or organisms capable of giving rise to infection.

ANTISEPSIS :- prevention of infection usually by inhibiting the growth of bacteria in wounds or tissues.

ANTISEPTICS :-chemical disinfectants which can be safely applied on skin and mucous membrane

BACTERICIDAL AGENTS or GERMICIDES :-those which are able to kill bacteria

BACTERIOSTATIC AGENTS :-prevent multiplication of bacteria which may however remain alive

CLEANING :-an important preparatory role before sterilisation by removing soil and other dust , reducing microbial burden making sterilisation more effective.

DECONTAMINATION :-process of rendering an article or area free of danger from contaminants.

A. PHYSICAL AGENTS Sunlight Drying Dry heat:flaming,incineration,hot air Moist heat :pasteurisation,boiling,steam

under pressure Filtration Radiation Ultrasonic and sonic vibrations

B. CHEMICAL AGENTS Alcohols :ethyl,isopropyl,trichlorobutan

ol Aldehydes :formaldehyde,glutaraldehyd

e Dyes Halogens Phenols Surface active agents Metallic salts Gases:ethylene

oxide,formaldehyde,betapropiolactone

1.SUNLIGHT bactericidal activity spontaneous sterilisation under

natural conditions action is due to uv rays Germicidal effect due to uv and heat

rays

2.DRYING unreliable spores are unaffected

3 .HEAT reliable Factors influencing nature of heat temperature and time no.of microorganisms present characteristics of organisms type of material from which the

organisms have to be eradicated

THERMAL DEATH TIME :-minimum time required to kill a suspension of organisms at a predetermined temperature in a specified environment.

STERILISATION TIME depends on no. of organisms in suspension spores characteristics of organisms

DRY HEAT FLAMING : bunsen flame

INCINERATION :an excellent method for safely destroying hospital wastes

INCINERATOR

HOT AIR OVEN widely used temperature 160 C time 1 hour sterilises

glassware,foreceps,scissors,scalpels,syringes,swabs

Oven is heated by electricity It is fitted with a fan for even distribution

of air Should not be overloaded Glassware should be perfectly dry before

being placed in the oven 180 C –cotton plugs get charred 150 C , 2hrs –instruments used in

ophthalmic surgery 150 C , 1hr –oils, glycerol and dusting

powder Oven is allowed to cool slowly for 2 hrs.

Sterilisation control :Spores of non toxigenic strain of

Clostridium tetani are usedPaper strips impregnated with 106

spores placed in envelopes inserted into suitable packs

sterilisation

Strips removed and inoculated into

thioglycollate or cooked meat media

Incubated for sterility test under strict anaerobic conditions for 5 days at 37 C

Brownes tube

MOIST HEAT 1. Temp. below 100 C Pasteurisation of milk : Holder method :63 C , 30

min. Flash process :72 C , 15-20

sec. Cooled quickly to 13 C

Non sporing pathogens destroyed Coxiella burnetti survives holder

method Inspissator 80 C , 5 -10 min.-

bacteria ,yeasts moulds 60 C , viruses

2. Temp. at 100 Ca) Boiling : vegetative

bacteria killed spores not killedb) Steam at atmospheric

pressure 100 C Koch or Arnold steamer

STEAMER

TYNDALLISATION or INTERMITTENT STERILISATION

100 C ,20 min , 3 successive days

C) Steam under pressure : Temp. 108 C -147 C :

dressings,instruments,laboratory ware,media,pharmaceutical products sterilised

For aqueous solutions 108 C -126 C Steam sterilisers laboratory autoclaves hospital dressing sterilisers bowl and instrument sterilisers rapid cooling sterilisers

HOSPITAL DRESSING STERILISER

INSTRUMENT STERILISER

RAPID COOLING STERILISER

PRESSURE COOKER

LABORATORY AUTOCLAVE

PRINCIPLE –Water boils when its vapour pressure equals that of the surrounding atmosphere.

e

Click icon to add picture

LABORATORY AUTOCLAVE

DEFECTS The method of air discharge is inefficient if air is not completely removed , the desired temperature is not attained There is no facility for drying the load after sterilisation and before taking it out. STERILISATION CONTROL :spores of Bacillus stearothermophilus are used

as the test organism.Spores require 121 C , 12 min. to get killed