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Microbiology > General microbiology-3 > Flashcards

General microbiology-3 Flashcards

1
Q

Physical methods of sterilization

A
  1. Heat
  2. Filtration
  3. Radiation
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2
Q

Types of dry heat sterilization

A

Sunlight
Hot air oven
Incinerator
Flame burners
Candle

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3
Q

Mechanism of dry heat sterilization

A

‘CODE’
Charring
Oxidative damage
Denaturation of protein
Electrolytes increased

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4
Q

Moist heat sterilization example

A

Boiling water, Pressure cookers

Moist heat > Dry heat

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5
Q

Mechanism of moist heat sterilization

A

Coagulation and denaturation of proteins

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6
Q

What is a hot air oven?

A

A dry heat sterilization device that uses hot air (160°C) to kill microorganisms by oxidation.

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7
Q

What are the standard temperature and time settings for a hot air oven?

A

160°C – 2 hours
170°C – 1 hour
180°C – 30 minutes

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8
Q

What items can be sterilized using a hot air oven?

A

✅ Glassware (flasks, test tubes, Petri dishes)
✅ Metal instruments (forceps, scalpels)
✅ Powders (talc, zinc oxide)
✅ Oily substances and fats

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9
Q

What items cannot be sterilized in a hot air oven?

A

❌ Plastic materials (melts at high temperatures)
❌ Rubber items (gets damaged)
❌ Culture media (heat-sensitive)

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10
Q

What is the biological indicator used to check sterilization efficiency in a hot air oven?

A

Bacillus atrophaeus spores
Bacillus subtilis spores
C. tetani spores

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11
Q

What is the chemical indicator used to check sterilization efficiency in a hot air oven?

A

Browne’s tube (green spot means sterilization complete)

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12
Q

What is the temperature range used in incineration?

A

There are 2 chambers-
700-800 C
1000-1100 C

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13
Q

Uses of Incineration

A

Human anatomical waste
Animal carcasses
Hospital waste
Soiled bedding, dressings
Expired cytotoxic drugs

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14
Q

Types of moist heat sterilization

A

Below 100 C-
-Pasteurisation
-Inspissation
-Vaccine water bath

100C
- Boiling
- Tyndallization

Above 100C
- Autoclave

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15
Q

Types of pasteurization

A

Holder method &laquo_space;Flash method (kills Coxiella)

Holder- boil at 63 C for 30 mins
Flash- boil at 72 C for 20 secs, cool to <13 C

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16
Q

Inspissation

A

80 C for 20-30 mins for 3 consecutive days
Used for Loeffler’s serum slope, LJ media for TB

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17
Q

Vaccine water bath

A

60 C for 60 mins

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18
Q

Boiling vs Tyndallisation

A

Boiling- at 100 C for 15 mins
Didnt kill spores

Tyndallisation- at 100 C for 20 mins for 3 days
Spores dead

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19
Q

Autoclave settings

A

125 C for 15 mins at 15 psi
To kill prions-
134 C for 1.5 hrs

20
Q

Uses of autoclave

A

Surgical instruments
Culture media (except LJ and LSS)
Laboratory glassware
Dressings and bandages
Sutures (except catgut)
Sputum (prior to discard)

21
Q

What biological indicator is used to check autoclave efficiency?

A

Geobacillus stearothermophilus spores (heat-resistant bacteria).

22
Q

Filtration is done by

A

Seitz filter

23
Q

Sietz filter contains

A

Asbestos (carcinogenic)
Pore size: 0.22 Mc

24
Q

Uses of Sietz filter

A

Heat sensitive substances such as vaccines, antibiotics, serum, toxins, sugar solutions

25
Q

Another method of filtration

A

Air purifiers-
HEPA- High Efficiency Particulate Air Filter
ULPA- Ultra Low Particulate Air Filter

26
Q

Control of filtration

A

Brevundimonas diminuta
Serratia

27
Q

Ionizing radiation

A

Cold radiation
Eg; X rays, Gamma rays, Cosmic rays
High penetrating power
Sporicidal
Uses- Catgut sutures, grafts

28
Q

Non ionizing radiation

A

Hot radiation
Eg. UV rays, Infrared rays
Used for OT fumigation, Biosafety cabinet
Low penetrating power
Bactericidal but not sporicidal

29
Q

Control for radiation

A

Bacillus pumilus

30
Q

Types of chemical sterilization

A

Alcohol
Aldehyde
Halogens
Phenols
Plasma sterilization
Gas sterilization

31
Q

Alcohol as chemical sterilizing agent

A

Ethyl alcohol- 70%
Isopropyl alcohol- 70 to 80%
Used to clean thermometers, stethoscope

32
Q

Formaldehyde for chemical sterilization

A

Gas- OT fumigation
Formalin- store human specimens
Duckering- killing B. anthracis spores from animal wool with formaldehyde

33
Q

Glutaraldehyde as chemical sterilization agent

A

Commercial name- CIDEX
To clean bronchoscope, endoscope, laryngoscope
Except arthroscope- by plasma sterilization

34
Q

Phenol for sterilisation

A

Used as antiseptics
Phenol (5%)
Cresol (1-3%)
Lysol (2-5%)
Modified phenol:
- Chlorhexidine + Cetrimide= Savlon
- Chloroxylenol= Dettol

35
Q

Halogens used as chemical sterilization

A
  1. Chlorine- 1% sodium hypochlorite for blood spills
  2. Iodine- betadine (povidone iodine), tincture iodine (2% iodine)
36
Q

Plasma sterilization

A

A low-temperature sterilization method using hydrogen peroxide vapor and plasma to kill microorganisms.

37
Q

How does plasma sterilization kill microorganisms?

A

By generating free radicals (hydroxyl & superoxide ions) that disrupt cell membranes, DNA, and proteins.

38
Q

What materials can be sterilized using plasma sterilization?

A

Plastics
Arthroscopes, Ureteroscopes

39
Q

Biological Indicator for Plasma Sterilization

A

Geobacillus stearothermophilus spores (same as for autoclave).

40
Q

Which gas is commonly used in gas sterilization?

A

Ethylene Oxide (EtO) is the most commonly used gas for sterilization.

41
Q

MOA of Ethylene oxide (ETO)

A

Microbicidal and sporicidal

42
Q

Side effects of ETO

A

Highly irritant
Highly inflammable
Highly explosive

so, never use 100% ETO, 3-10% is enough
Mix with inert gas to prevent inflammation

43
Q

Uses of ETO

A

Cardiopulmonary machines
Pre packed syringes

44
Q

Control for ETO

A

Bacillus globigii

45
Q

Tests of Disinfectants

A
  1. Rideal Walker test/ Phenol coefficient test
    Compared with phenol.
    Disadv: we don’t know the efficacy of organic matter
  2. Modified Rideal Walker test/ Chick Martin test
    Compared in presence of Yeast, soil (organic matter)
  3. Kelsey-Sykes test/ capacity test: to check capacity of disinfectant
  4. Kelsey- Maurer test/ in use test: to check usage of disinfectant
46
Q

Sporicidal agents

A

APT EFGH
Autoclave
Plasma sterilization
Tyndallisation
ETO
Formaldehyde
Glutaraldehyde
H2O2, Hot air oven, 1% Hypochlorite

47
Q

Spaulding classification

A

Critical device- penetrates sterile sites
Use High level disinfectant (HLD)
Semi critical device- in contact with mucous membranes- Use HLD
Non critical device- in contact with skin- Intermediate/ Low level disinfectant
Non critical surfaces/ Medical equipments- computers, desks, tables- LLD

Microbiology (19 decks)

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