METHODS OF MICROBIAL CONTROL

Question 1

refers to the complete destruction and removal of all forms of microbial life, including their spores

Answer 1

Sterilization

Question 2

destruction and removal of pathogens but not necessarily all microorganisms and their spores

Answer 2

Disinfection

Question 3

Use of moist heat, use of dry heat, filtration, and exposure to ionizing radiation

Answer 3

PHYSICAL METHODS OF STERILIZATION

Question 4

AUTOCLAVE sterilize used and unused media

Answer 4

• 121c 15 psi, 15-30 minutes:

Question 5

Autoclave to sterilize medical waste

Answer 5

132C, 15 psi, 30-60 minutes

Question 6

Autoclave Indicator

Answer 6

Bacillus stearothermophilus (New taxonomy: Geobacillus
stearothermophilus)

Question 7

Autoclave principle

Answer 7

Steam underpressure

Question 8

Not killed by autoclaving are:

Answer 8

Prions (infectious protein particles said to
cause neurologic diseases in animals and man; Mad cow disease and
CJD)

Question 9

• Intermittent or fractional sterilization (process is not continuous; done for several days)
• Uses: flowing steam
• Equipment used is Arnold sterilizer
• 100c for 30 minutes, for 3 consecutive days

Answer 9

Tyndalization

Question 10

• Intermittent or fractional sterilization
• Principle: thickening through evaporation
• For sterilizing media with increased protein, like: Lowenstein-Jensen media (contains egg; for M. tuberculosis)
• 75-80c for 2 hours, for 3 consecutive days

Answer 10

Inspissation

Question 11

Fractional sterilization will kill:

Answer 11

o 1st day: Vegetative cells
o 2nd day: Spores
o 3rd day: Remaining cells

Question 12

Dry heat

Answer 12

Oven
Incineration
Direct flamming
Cremation

Question 13

• Often used in a microlaboratory
• 160-180c for 1-2 hours
• Used to sterilize glasswares
• Indicator: Bacillus subtilis var. niger

Answer 13

Oven

Question 14

• Temperature to burn materials into ashes is 300-400c
• To dispose hazardous waste: 870-980c
• Not done in the Philippines because it is not environment friendly
• Dry sterilization method that can eliminate prions

Answer 14

Incineration

Question 15

• For loops and needles

Answer 15

Direct flamming

Question 16

• Burning of the body into ashes
• To control disease

Answer 16

Cremation

Question 17

• For materials that are heat-sensitive
• For antibiotic solutions, toxic chemicals

Answer 17

Filtration

Question 18

• Consist of granular material
• i.e. Berkefield filter, asbesto

Answer 18

Depth filter

Question 19

• These are porous membranes 0.1mm thick to sterilize
  culture media, antibiotics
• Composed of cellulose acetate and polycarbonate

Answer 19

Membrane filter

Question 20

filter with a pore diameter of 0.22µm can give 100% sterility

Answer 20

Millipore filter

Question 21

Can remove objects larger than 0.3µm

Answer 21

Hepa filter

Question 22

• Exposure to gamma rays
• Sterilize disposable gloves, catheters, and syringes
• Indicator: Bacillus pumilus

Answer 22

IONIZING RADIATION/COLD STERILIZATION

Question 23

CHEMICAL METHODS OF STERILIZATION

Answer 23

-ETHYLENE OXIDE (GAS STERILANT)
-FORMALDEHYDE VAPOR AND VAPOR PHASE HYDROGEN PEROXIDE
-GLUTARALDEHYDE (2%)
-PERACETIC ACID

Question 24

use of glutaraldehyde or peracetic acid

Answer 24

Cold sterilization

Question 25

Chemical sterilants a.k.a biocides

Answer 25

Take note

Question 26

- Purpose: remove pathogens in food - 63c, 30 minutes (low temperature holding): VAT pasteurization or batch method - 72c 15 seconds: High temperature short time (HTST) or Flash method - 140c, 3 seconds: Ultra-High temperature short time

Answer 26

Pasteurization

Question 27

- 100c, 15-30 minutes - For surgical instruments

Answer 27

Boiling

Question 28

- Non-ionizing radiation using UV light

Answer 28

UV

Question 29

chemical germicide for use on the skin or tissue and not to be substituted for a disinfectant

Answer 29

Antiseptic

Question 30

- Alcohols- Commonly used antiseptic (but not the best): 70% ethyl alcohol or isopropyl alcohol - Iodophors *Regarded as the best antiseptic *Iodine + detergent - Chlorhexidine - Hexachlorophene - 10% hydrogen peroxide is used for cleansing of wounds

Answer 30

Antiseptic

Question 31

is more effective than 95% EA as disinfectant

Answer 31

70% ethanol

Question 32

- Ethyl alcohol and isopropyl alcohol are non-sporicidal - Iodine is prepared as tincture with alcohol or as an iodophor

Answer 32

Take note

Question 33

for non-living things; for surfaces, used to remove blood spills - Halogens (chlorine, iodine, fluorine) - Heavy metals - Aldehydes

Answer 33

Disinfectants

Question 34

QUATS – Quaternary Ammonium Compounds o i.e. Benzalkonium chloride/zephiran o P. aeruginosa grown in ammonium acetate media is said to be resistant to QUATS - Phenolics

Answer 34

Disinfectants.

Question 35

- Best disinfectant for blood spillage sodium hypochlorite/ household bleach/ Clorox (10-30 minutes contact); the CDC recommends 1:10 dilution of bleach - If not available, can be used as substitute is vinegar

Answer 35

Take note

Question 36

: require that blood and body fluids from every patient be treated as potentially infectious; set of preventive measures applied to all patients designed to reduce risk of infection in health care setting based on the premise that all blood and other body fluids are infectious

Answer 36

Standard precaution

Question 37

: precaution on all human blood and all other body fluids that contain visible blood; set of preventive measures designed to reduce transmission of blood-borne pathogens

Answer 37

Universal precautions

Question 38

Examples of bacteria which remain active in a dry environment:

Answer 38

- N. gonorrhoeae: viable for 1 hour - M. tuberculosis: viable for several months - Bacillus and Clostridium: viable for 10 years