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Microbiology > General microbiology-3 > Flashcards

General microbiology-3 Flashcards

(47 cards)

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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

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A

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

20
Q

Uses of autoclave

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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?

Study These Flashcards
A

Geobacillus stearothermophilus spores (heat-resistant bacteria).

22
Q

Filtration is done by

23
Q

Sietz filter contains

Study These Flashcards
A

Asbestos (carcinogenic)
Pore size: 0.22 Mc

24
Q

Uses of Sietz filter

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A

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

25
Another method of filtration
Air purifiers- HEPA- High Efficiency Particulate Air Filter ULPA- Ultra Low Particulate Air Filter
26
Control of filtration
Brevundimonas diminuta Serratia
27
Ionizing radiation
Cold radiation Eg; X rays, Gamma rays, Cosmic rays High penetrating power Sporicidal Uses- Catgut sutures, grafts
28
Non ionizing radiation
Hot radiation Eg. UV rays, Infrared rays Used for OT fumigation, Biosafety cabinet Low penetrating power Bactericidal but not sporicidal
29
Control for radiation
Bacillus pumilus
30
Types of chemical sterilization
Alcohol Aldehyde Halogens Phenols Plasma sterilization Gas sterilization
31
Alcohol as chemical sterilizing agent
Ethyl alcohol- 70% Isopropyl alcohol- 70 to 80% Used to clean thermometers, stethoscope
32
Formaldehyde for chemical sterilization
Gas- OT fumigation Formalin- store human specimens Duckering- killing B. anthracis spores from animal wool with formaldehyde
33
Glutaraldehyde as chemical sterilization agent
Commercial name- CIDEX To clean bronchoscope, endoscope, laryngoscope Except arthroscope- by plasma sterilization
34
Phenol for sterilisation
Used as antiseptics Phenol (5%) Cresol (1-3%) Lysol (2-5%) Modified phenol: - Chlorhexidine + Cetrimide= Savlon - Chloroxylenol= Dettol
35
Halogens used as chemical sterilization
1. Chlorine- 1% sodium hypochlorite for blood spills 2. Iodine- betadine (povidone iodine), tincture iodine (2% iodine)
36
Plasma sterilization
A low-temperature sterilization method using hydrogen peroxide vapor and plasma to kill microorganisms.
37
How does plasma sterilization kill microorganisms?
By generating free radicals (hydroxyl & superoxide ions) that disrupt cell membranes, DNA, and proteins.
38
What materials can be sterilized using plasma sterilization?
Plastics Arthroscopes, Ureteroscopes
39
Biological Indicator for Plasma Sterilization
Geobacillus stearothermophilus spores (same as for autoclave).
40
Which gas is commonly used in gas sterilization?
Ethylene Oxide (EtO) is the most commonly used gas for sterilization.
41
MOA of Ethylene oxide (ETO)
Microbicidal and sporicidal
42
Side effects of ETO
Highly irritant Highly inflammable Highly explosive so, never use 100% ETO, 3-10% is enough Mix with inert gas to prevent inflammation
43
Uses of ETO
Cardiopulmonary machines Pre packed syringes
44
Control for ETO
Bacillus globigii
45
Tests of Disinfectants
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
Sporicidal agents
APT EFGH Autoclave Plasma sterilization Tyndallisation ETO Formaldehyde Glutaraldehyde H2O2, Hot air oven, 1% Hypochlorite
47
Spaulding classification
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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