Sterilization And Disinfectant Flashcards
1
Q
What is sterilisation?
A
The process of destruction of all forms of life, including spores.
2
Q
What disinfection?
A
The process of destruction of only pathogenic microorganisms from inanimate objects.
3
Q
Antisepsis?
A
Disinfection of living tissues
4
Q
Father of antisepsis surgery?
A
Joseph Lister-introduced phenol during world war for antiseptic
5
Q
Order of susceptibility to methods of sterilisation and disinfection?
A
Most resistant
Prions-bacterial spores-cysts of Protozoa-non envelope virus-mycobacteria-fungi-GP bacteria -gram negative bacteria - envelope viruses
6
Q
Physical methods?
A
- heat(most reliable)
- radiation
- filtration
7
Q
Type of heat sterilisation?
A
- dry heat
- moist heat
8
Q
Dry heat mechanism of action?
A
- denaturation of protein
- oxidative damage
- raising the electrolytes to toxic levels
9
Q
Types of dry heat?
A
- Flaming
- Red heat
- Incineration
- Hot air oven
10
Q
Flaming?
A
Slides, covers lips and mouths of test tubes can be disinfected by passing them through flame a few number of times.
11
Q
Red heat?
A
- effective sterilisation of articles that can be heated to redness in flame
- eg. straight wires, inoculating loops, tips of forceps, searing spatulas
12
Q
Incineration?
A
- sterilization along with significant reduction in volume -80-85 %( for final disposal) of infectious hospital waste
- animal carcasses
- human pathological material
- soiled bedding and dressing
- cytotoxic drugs
13
Q
Chambers in the incinerator?
A
- primary : temperature 650-750 Celsius
- secondary : temperature 1050-1100 Celsius
14
Q
Hot air oven introduced by?
A
Louis Pasteur
15
Q
Hot air oven?
A
- used for sterilization of
- all metallic instrument
- glassware
- cotton swabs
- oils, jellies, powder and waxes
16
Q
Temperature for hot air oven?
A
-160 Celsius for 1 hour
- 150 Celsius for 115 min
170 Celsius for 40 min
17
Q
Efficacy of hot air oven?
A
- physical : temperature chart recorder
- chemical : Browne’s tube no. 3
- biological : clostridium tetani / bacillus subtilis spore
18
Q
Mechanism of moist heat?
A
- denaturation and coagulation of Protein
19
Q
Temperature for moist heat
A
Can be used
- below 100 C
- at 100 C
- above 100 C
20
Q
Moist heat less than 100?
A
- Pasteurisation _ disinfection of milk
- Serum bath
- Vaccine bath
- Inspissation
21
Q
3 methods of pasteurisation ?
A
- Holder method : moist heat at 63 C for 30 min
- Flash method : moist heat at 72 C for 15-20sec followed by rapid cooling to temperature less than 13 C
- Ultra high temp : moist heat at 149 C for 0.5 sec
22
Q
Efficacy testing of pasteurisation?
A
- coliform test(best method) : since coliforms ( e.coli , klebsiella, enterobacter) are easily destroyed by pasteurisation, their presence in pasteurised product usually indicated inadequate pasteurisation process.
- Phosphatase test (commonly used): phosphatase is present in raw milk that is inactivated when the proper time and temperature combination are reached for adequate pasteurisation.
23
Q
What is the substrate for the phosphatase enzyme?
A
Disodium phenyl phosphate
24
Q
Serum bath?
A
Serum or body fluids containing coagulase proteins can be sterilised by heating for 1 hour at 56 C in a water bath for several successive days.
25
Vaccine bath ?
To inactivate non- sporting bacteria for preparation of vaccines, vaccine bath at 60 C for 1 hour is used
26
What is inspissation? Eg?
Moist heat at 80-85 C for hour for 3 consecutive days.
Egg and serum containing media are sterilised by inspissation
27
Principles of inspissation?
The first exposure kills the vegetative forms, in the interval between the heating the spores germinate which are then killed on subsequent heating.
28
Moist heat - at 100 C?
Tyndallisation ?fractional sterilization
- moist heat at 100 C for 2 hour for 3 consecutive days
- Koch and Arnold steam steriliser is used for sterilization of
* sugar solution
* gelatin containig media
* TCBS, XLD
* DCA, and selenite F broth
29
Moist heat above 100 C?
Autoclave
30
Principle of autoclave?
Use of saturated steam under pressure
31
Autoclave temp
Moist heat at 121 C x 15-20 min (15psi)
Moist heat at 134 C x 3 min ( 30 psi)
32
Components of autoclave?
- vessel made up of gunmetal/ stainless steel, has perforated tray for steam entry
- heating element below the perforated tray
- lid with a discharge tap, a pressure gauge and a safety valve
33
Uses of autoclave?
Sterilisation of
- metallic instrument ( non-sharp)
- microbiological culture media
- plastic container/ pipettes/ tubes
34
Efficacy of autoclave?
- physical : temperature chart recorder
- chemical : Browne’s tube no.1, bowie dick tapes
- biological : bacillus stearothermophilus spores
35
Radiation?
- non-ionising :UV rays
| - ionising : gamma rays
36
Non ionising UV rays generated by........ its wavelength?
- generated by tungsten filament mercury lamps
| - 220-280nm wavelength
37
Disadvantages of UV rays?
- not sporocidal
- poor penetration
- only use as surface disinfection of hospital corridor,hospital wards
38
Gamma rays sterilization aka?
Also called as cold sterilisation
39
Gamma radiation produced by?
Nuclear disintegration of radioactive isotopes Co60 or Cs137
40
Mechanism of action of gamma rays?
By causing DNA damage
41
Gamma rays characteristics
- highly penetrating
| - sporocidal
42
Gamma rays use?
Sterilisation of
- disposables ( syringes, gloves, petri plates)
- hormones, glassware, fabrics
- cardia implants, pacemakers
- orthopaedic implant
- sutures
- IV cannula
- Foley’s catheter
43
Efficacy testing of gamma radiation?
By spores of bacillus pumilus
44
Filtration use for?
Used for removal of microbes from solution that are heat sensitive
-serum, antibiotic solution, sugar solution, urea solution and vaccines
45
Pore size of standard bacterial filters ?
0.2-0.45microns
46
Various types of filter ?
- earthenware filters
- asbestos filters
- sintered glass filters
- membrane filters
47
Earthen ware filter?
- made of porcelain or diatomaceous earth
- shaped as candles
Eg. Mandler, Pasteur-Chamberland, Berkefeld
48
Asbestos filters?
- made up of magnesium, trisilicate
- shaped in the form of disc
- eg. Seitz filter
49
Sintered glass filter?
- made by fusion of powdered glass
| - shaped as disc
50
Membrane filter?made up? Types? Eg?
- made of cellulose ester (nitrate/ diacetate) or polycarbonate)
- two types
* capillary pore membranes : pores produced by radiation
* labyrinthine pore membranes : made by forced evaporation of solvents
Eg : millipore
51
High level disinfectant( chemisterilant) organisms and eg?
```
+
Bacteria
Fungi
Virus
Mycobacterium
Spores
```
Eg : aldehyde , plasma , ETO
52
Intermediate level disinfectant organisms and eg?
```
+
Bacteria
Fungi
Virus
Mycobacteria
```
+/-
Spores
Ed : phenol , halogen
53
Low level disinfectant organisms and eg?
+
Bacteria
Fungi
+/-
Virus
Mycobacteria
-
Spores
Eg : alcohol, surface acting agents
54
What chemical disinfectant active in the presence of organic matter?
Phenol & aldehyde
55
Alcohols Mechanism of action?
Dehydrate cells, disrupt membranes and cause coagulation of protein
56
Eg of Alcohol?
- ethyl alcohol
- isopropyl alcohol
- methyl alcohol
These are use in conc of 60-80 %
- 70 % ethyl alcohol (spirit) is used as skin antiseptic
- isopropyl alcohol is more bactericidal and less volatile is used as a hand disinfectant
57
Aldehyde MOA?
Acts through alkylation of amino-, carboxyl-, and hydroxyl group in protein and damage nucleic acids
58
Eg of aldehydes?
Formaldehyde, gluteraldehyde, orthopthaldehyde
59
Formaldehyde?
- generally available in 37-40 %
- used for fumigation of rooms, chambers, OT, biological safety cabinets, wards, sick rooms
- duckering -disinfection of animal wool and animal hair/bristles
- preserves animal specimens and culture
- disadvantage : irritant and toxic
60
Gluteraldehyde/cidex -2%?
- sterilisation(6-8hrs) and disinfection(20-25min) of heat sensitive instrument like cystoscope, bronchoscope, laparoscopies, centrifuges, anaesthetic equipment, endotracheal tubes, dialyzers
- shelf life of 14 days
61
Orthophthaldehyde (OPA)-0.55%? Advantage over cidex?
Used similar to cidex
Advantages over cidex
- stable at wide pH range
- less vapour property-nonirritant
- better odour
- better mycobactericidal activity
62
Halogens?MOA?
- chlorine
- iodine
MOA: Oxidation of essential sulfhydryl groups of enzymes
63
Chlorine compound?
- chlorine tablets are used for water disinfection ( water supplies, swimming pools)
- household bleach (5-6 % sodium hypochlorite) - to use to disinfect floors in a stock dilution of 1 : 10 water and infectious spills
64
Iodine?
Tincture of iodine (2 % iodine in 70% alcohol) used as an antiseptic.
65
What is iodophors ?
Iodine coated onto a neutral carrier molecules like pollyvinylpyrrolidone for sow release and less irritation. 10 % for skin antisepsis
66
Phenolics-coal tar derivatives?MOA? Constitution? Use?disadvantage?
MOA : disrupt cell membrane and denature protein
Constitution : 5% phenol
1-4 % creosol
2-5 %lysol
Use
- disinfection of ward floors
- discarding jars in laboratories
- disinfection of bedpans
Disadvantage : not use as skin antiseptic because they are skin corrosive
67
Chlorinated biphenolics?
- are less toxic and irritant
- they are less active and more readily inactivated by organic matter
- eg: hexachlorophene, chlorhexidine, chloroxylenol, triclosan
- used for skin antisepsis
68
What is dettol?
10% chloroxylenol
69
What is savlon?
Savlon is a mixture of chlohexidine with cetrimonium bromide
70
Surface acting agents? MOA?
MOA: lower surface tension and thereby disrupt microbial membrane.
- cationic surface active agents ( fat soluble part) is positively charged.
Eg : quaternary ammonium compound, cetrimide and benzalkonium chloride
-soaps are an ionic surface active agents
71
Ethylene oxide / ETO gas.MOA? Uses?
- MOA : alkylation agent
- highly effective chemisterilant
- used in the form of gas
- used to sterilise heat labile/ moisture sensitive articles such as beddings, rubber objects, plastics, disposable gloves, syringes and petridishes, prosthesis,complex apparatus like heart-lung machines, respiratory and dental equipment.
72
Types of ETO sterilisers ?
- cold cycle( 37-44 C)
| - hot cycle (55 C)
73
Steps in a step of ETO sterilisation?
- preconditioning
- exposure to gas
- post conditioning to remove the toxic vapours
74
Efficiency test for ETO gas?
Efficiency test is done using Bacillus globigus/ Bacillus subtilis var niger/ bacillus atrophaeus
75
Disadvantages of ETO sterilisation?
- irritant to skin and mucous membrane
- carcinogenic
- inflammable
- toxic ( cataracts and neurological disturbances)
76
Plasma (VHP) sterilisation ?
- a plasma is essentially an excited gas (hydrogen peroxide) produced by adding energy (radio frequency or microwaves)
- production of free oxygen radicals within a plasma field and thereby disrupt the metabolism of microorganisms
77
Time for one cycle of plasma steriliser?steps?temperature?
60-75mins
Steps
- vacuum phase
- injection phase
- diffusion phase
- plasma phase
- vent phase
Temperature maintained between 30-60 C
78
Characters of VHP? Efficacy?
- a safe, non toxic method of sterilisation of heat- sensitive plastics and surgical instrument
- cant be used for liquid and cellulose-based materials( such as paper) and linen
- instrument should be provided dry for sterilisation
- efficacy -spores of bacillus stearothermophilus
79
Spaulding classification?
- Dr. E. H. Spaulding divides medical devices into categories based on the risk of infection involved with their use
* critical : a device that enters normally sterile tissue or vascular system
: such device should be sterilised before use
* semi critical : a device that comes into contact with intact mucous membrane and does not ordinarily penetrates sterile tissue
: these devise should receive at least high level of disinfection
* non critical : devices that do not ordinarily touch the patient or touch only intact skin
: these device should be cleaned by low level disinfection
80
What is phenol coefficient?
- efficacy of phenol is compared with the new disinfectant
- a series of dilution of phenol and the disinfectant being tested are prepared
- a standard amount of Salmonella typhi or S. aureus are added to each dilution and incubated
- at 5 min interval, samples are with drawn from each dilution and inoculated on a growth medium
- the highest dilution that kills the bacteria after 10 min exposure, but not at 5 min is used to calculate the phenol co-efficient
P.C = dilution of test disinfectant /
Dilution of phenol
