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My Microbiology > Sterilization And Disinfectant > Flashcards

Sterilization And Disinfectant Flashcards

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1
Q

What is sterilisation?

A

The process of destruction of all forms of life, including spores.

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2
Q

What disinfection?

A

The process of destruction of only pathogenic microorganisms from inanimate objects.

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3
Q

Antisepsis?

A

Disinfection of living tissues

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4
Q

Father of antisepsis surgery?

A

Joseph Lister-introduced phenol during world war for antiseptic

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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

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6
Q

Physical methods?

A
  • heat(most reliable)
  • radiation
  • filtration
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7
Q

Type of heat sterilisation?

A
  • dry heat

- moist heat

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8
Q

Dry heat mechanism of action?

A
  • denaturation of protein
  • oxidative damage
  • raising the electrolytes to toxic levels
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9
Q

Types of dry heat?

A
  1. Flaming
  2. Red heat
  3. Incineration
  4. Hot air oven
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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.

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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
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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
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13
Q

Chambers in the incinerator?

A
  • primary : temperature 650-750 Celsius

- secondary : temperature 1050-1100 Celsius

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14
Q

Hot air oven introduced by?

A

Louis Pasteur

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15
Q

Hot air oven?

A
  • used for sterilization of
    • all metallic instrument
    • glassware
    • cotton swabs
    • oils, jellies, powder and waxes
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16
Q

Temperature for hot air oven?

A

-160 Celsius for 1 hour
- 150 Celsius for 115 min
170 Celsius for 40 min

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17
Q

Efficacy of hot air oven?

A
  • physical : temperature chart recorder
  • chemical : Browne’s tube no. 3
  • biological : clostridium tetani / bacillus subtilis spore
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18
Q

Mechanism of moist heat?

A
  • denaturation and coagulation of Protein
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19
Q

Temperature for moist heat

A

Can be used

  • below 100 C
  • at 100 C
  • above 100 C
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20
Q

Moist heat less than 100?

A
  1. Pasteurisation _ disinfection of milk
  2. Serum bath
  3. Vaccine bath
  4. Inspissation
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21
Q

3 methods of pasteurisation ?

A
  1. Holder method : moist heat at 63 C for 30 min
  2. Flash method : moist heat at 72 C for 15-20sec followed by rapid cooling to temperature less than 13 C
  3. Ultra high temp : moist heat at 149 C for 0.5 sec
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22
Q

Efficacy testing of pasteurisation?

A
  1. 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.
  2. 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.
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23
Q

What is the substrate for the phosphatase enzyme?

A

Disodium phenyl phosphate

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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.

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25
Q

Vaccine bath ?

A

To inactivate non- sporting bacteria for preparation of vaccines, vaccine bath at 60 C for 1 hour is used

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26
Q

What is inspissation? Eg?

A

Moist heat at 80-85 C for hour for 3 consecutive days.

Egg and serum containing media are sterilised by inspissation

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27
Q

Principles of inspissation?

A

The first exposure kills the vegetative forms, in the interval between the heating the spores germinate which are then killed on subsequent heating.

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28
Q

Moist heat - at 100 C?

A

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
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29
Q

Moist heat above 100 C?

A

Autoclave

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30
Q

Principle of autoclave?

A

Use of saturated steam under pressure

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31
Q

Autoclave temp

A

Moist heat at 121 C x 15-20 min (15psi)

Moist heat at 134 C x 3 min ( 30 psi)

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32
Q

Components of autoclave?

A
  • 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
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33
Q

Uses of autoclave?

A

Sterilisation of

  • metallic instrument ( non-sharp)
  • microbiological culture media
  • plastic container/ pipettes/ tubes
34
Q

Efficacy of autoclave?

A
  • physical : temperature chart recorder
  • chemical : Browne’s tube no.1, bowie dick tapes
  • biological : bacillus stearothermophilus spores
35
Q

Radiation?

A
  • non-ionising :UV rays

- ionising : gamma rays

36
Q

Non ionising UV rays generated by…….. its wavelength?

A
  • generated by tungsten filament mercury lamps

- 220-280nm wavelength

37
Q

Disadvantages of UV rays?

A
  • not sporocidal
  • poor penetration
  • only use as surface disinfection of hospital corridor,hospital wards
38
Q

Gamma rays sterilization aka?

A

Also called as cold sterilisation

39
Q

Gamma radiation produced by?

A

Nuclear disintegration of radioactive isotopes Co60 or Cs137

40
Q

Mechanism of action of gamma rays?

A

By causing DNA damage

41
Q

Gamma rays characteristics

A
  • highly penetrating

- sporocidal

42
Q

Gamma rays use?

A

Sterilisation of

  • disposables ( syringes, gloves, petri plates)
  • hormones, glassware, fabrics
  • cardia implants, pacemakers
  • orthopaedic implant
  • sutures
  • IV cannula
  • Foley’s catheter
43
Q

Efficacy testing of gamma radiation?

A

By spores of bacillus pumilus

44
Q

Filtration use for?

A

Used for removal of microbes from solution that are heat sensitive
-serum, antibiotic solution, sugar solution, urea solution and vaccines

45
Q

Pore size of standard bacterial filters ?

A

0.2-0.45microns

46
Q

Various types of filter ?

A
  • earthenware filters
  • asbestos filters
  • sintered glass filters
  • membrane filters
47
Q

Earthen ware filter?

A
  • made of porcelain or diatomaceous earth
  • shaped as candles
    Eg. Mandler, Pasteur-Chamberland, Berkefeld
48
Q

Asbestos filters?

A
  • made up of magnesium, trisilicate
  • shaped in the form of disc
  • eg. Seitz filter
49
Q

Sintered glass filter?

A
  • made by fusion of powdered glass

- shaped as disc

50
Q

Membrane filter?made up? Types? Eg?

A
  • 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
Q

High level disinfectant( chemisterilant) organisms and eg?

A 
\+
Bacteria
Fungi
Virus
Mycobacterium
Spores

Eg : aldehyde , plasma , ETO

52
Q

Intermediate level disinfectant organisms and eg?

A 
\+
Bacteria
Fungi
Virus
Mycobacteria

+/-
Spores

Ed : phenol , halogen

53
Q

Low level disinfectant organisms and eg?

A

+
Bacteria
Fungi

+/-

Virus
Mycobacteria

-
Spores

Eg : alcohol, surface acting agents

54
Q

What chemical disinfectant active in the presence of organic matter?

A

Phenol & aldehyde

55
Q

Alcohols Mechanism of action?

A

Dehydrate cells, disrupt membranes and cause coagulation of protein

56
Q

Eg of Alcohol?

A
  • 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
Q

Aldehyde MOA?

A

Acts through alkylation of amino-, carboxyl-, and hydroxyl group in protein and damage nucleic acids

58
Q

Eg of aldehydes?

A

Formaldehyde, gluteraldehyde, orthopthaldehyde

59
Q

Formaldehyde?

A
  • 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
Q

Gluteraldehyde/cidex -2%?

A
  • 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
Q

Orthophthaldehyde (OPA)-0.55%? Advantage over cidex?

A

Used similar to cidex

Advantages over cidex

  • stable at wide pH range
  • less vapour property-nonirritant
  • better odour
  • better mycobactericidal activity
62
Q

Halogens?MOA?

A
  • chlorine
  • iodine

MOA: Oxidation of essential sulfhydryl groups of enzymes

63
Q

Chlorine compound?

A
  • 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
Q

Iodine?

A

Tincture of iodine (2 % iodine in 70% alcohol) used as an antiseptic.

65
Q

What is iodophors ?

A

Iodine coated onto a neutral carrier molecules like pollyvinylpyrrolidone for sow release and less irritation. 10 % for skin antisepsis

66
Q

Phenolics-coal tar derivatives?MOA? Constitution? Use?disadvantage?

A

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
Q

Chlorinated biphenolics?

A
  • 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
Q

What is dettol?

A

10% chloroxylenol

69
Q

What is savlon?

A

Savlon is a mixture of chlohexidine with cetrimonium bromide

70
Q

Surface acting agents? MOA?

A

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
Q

Ethylene oxide / ETO gas.MOA? Uses?

A
  • 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
Q

Types of ETO sterilisers ?

A
  • cold cycle( 37-44 C)

- hot cycle (55 C)

73
Q

Steps in a step of ETO sterilisation?

A
  • preconditioning
  • exposure to gas
  • post conditioning to remove the toxic vapours
74
Q

Efficiency test for ETO gas?

A

Efficiency test is done using Bacillus globigus/ Bacillus subtilis var niger/ bacillus atrophaeus

75
Q

Disadvantages of ETO sterilisation?

A
  • irritant to skin and mucous membrane
  • carcinogenic
  • inflammable
  • toxic ( cataracts and neurological disturbances)
76
Q

Plasma (VHP) sterilisation ?

A
  • 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
Q

Time for one cycle of plasma steriliser?steps?temperature?

A

60-75mins

Steps

  • vacuum phase
  • injection phase
  • diffusion phase
  • plasma phase
  • vent phase

Temperature maintained between 30-60 C

78
Q

Characters of VHP? Efficacy?

A
  • 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
Q

Spaulding classification?

A
  • 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
Q

What is phenol coefficient?

A
  • 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

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