METHODS OF MICROBIAL CONTROL (DISINFECTION AND STERILIZATION))

Question 1

• a Greek Physician (460-377 BC) Disproved the idea that disease was a punishment for sins
• He advocated irrigation of wounds with wine or boiled water foreshadowing antisepsis

Answer 1

Hippocrates

Question 2

a Greek Doctor who practiced medicine in Rome, boiled instruments used in caring wounded Roman gladiators.

Answer 2

Galen

Question 3

a German Physician, and regarded as “saviour of mothers” who advocated the use of hand disinfection using chlorine lime solutions in obstetrics clinics. He is considered an early pioneer of antiseptic procedures.

Answer 3

Ignaz Semmelweiz

Question 4

French Chemist and Microbiologist conducted
experiments that proved germs as causes of certain diseases

Answer 4

Louis Pasteur

Question 5

a British Surgeon reduced the mortality rate of his patients by using a carbolic solution spray. He used it on wounds, on equipment in contact with wound, and on hands of the operating team.

Answer 5

Joseph Lister

Question 6

What is the difference between
STERILIZATION and DISINFECTION?

Answer 6

Sterilization: Complete destruction of ALL FORMS of microbial life of including endospores. An All or nothing process

Disinfection: Elimination of a defined scope of microorganisms, including some endospores

Question 7

What is the difference between
DISINFECTANT and ANTISEPTIC?

Answer 7

Disinfectant: Chemical agents applied to inanimate objects

Antiseptic: Chemical agents applied to the skin for the purpose of eliminating or reducing the number of bacteria present. It does not kill endospores.

Question 8

Complete destruction of ALL FORMS of microbial life of including endospores. An All or nothing process

Answer 8

sterilization

Question 9

Elimination of a defined scope of microorganisms, including some endospores

Answer 9

disinfection

Question 10

Chemical agents applied to inanimate objects

Answer 10

Disinfectant

Question 11

Chemical agents applied to the skin for the purpose of eliminating or reducing the number of bacteria present. It does not kill endospores.

Answer 11

Antiseptic

Question 12

Microbial factors that contribute to their varied resistance

Answer 12

Endospores of bacteria
Cell wall of Mycobacteria
Viruses with lipid envelopes
Organisms that form biofilm
Prions

Question 13

what will happen if there are presence of organic matter during disinfection

Answer 13

May inactivate disinfectants

May prevent full penetration and contact of disinfectant to the surface to be disinfected

Question 14

The critical aspect in sterilization and disinfection

Answer 14

Contact time

Question 15

factor that influence the degree of killing that has has a parallel relationship with effectiveness

Answer 15

temperature

Question 15

Contact time can be influenced by:

Answer 15

▪ Bio burden of the material to be disinfectedor sterilized
▪ Type of microorganisms
▪ Presence of organic material
▪ Temperature at which the disinfectant is used

Question 16

factor that influence the degree of killing that affects the effectiveness of a disinfectant

Answer 16

pH

Question 16

disinfectants should be used at what temperature

Answer 16

20-22C

Question 17

Disinfecting biofilms may require increased
disinfectant’s/sterilant’s:

Answer 17

▪ Concentration
▪ Contact time

Question 17

factor that influence the degree of killing that is a community covered with a protective material that
shields them from external factors

Answer 17

Biofilm

Question 18

what is the common mistake when using disinfectants

Answer 18

two disinfectants are better
than 1

Question 19

• Materials that invade sterile tissues or enter the vascular system
• May produce infection if contaminated

What is the type of disinfection/sterilization?

Answer 19

Critical materials; Sterilization

Question 20

Materials that come in contact with mucus membranes and non-intact skin

What is the type of disinfection/sterilization?

Answer 20

Semi-critical materials; High level disinfection agents

Question 21

Iodine containing. Used at 0.1-0.2% concentration. Some iodine containing disinfectants can also be used as antiseptic agents.

What is the disinfection level and the agent used?

Answer 21

Low; Iodine

Question 21

Objects that come in contact with intact skin but not mucus membranes What is the type of disinfection/sterilization?

Answer 21

Non-critical materials; Intermediate to low level disinfection

Question 22

Biological detergent contains enzymes, non-biological does not. Used to remove soil and surface debris from items. What is the disinfection level and the agent used?

Answer 22

Basic cleaning; Detergent

Question 23

Used on hard surfaces as a disinfectant or on the skin as an antiseptic. Greater than 70% v/v solution required. Denatures cell membranes and dehydrates cells. What is the disinfection level and the agent used?

Answer 23

Intermediate; Alcohol

Question 24

10% concentration required. 2 types of bleach: CHLORINE AND PEROXIDE. Both peroxide and chlorine bleaches can corrode metal objects if left in contact for too long. Can irritate skin and mucous membranes. What is the disinfection level and the agent used?

Answer 24

Intermediate to low; Bleach

Question 25

0.2% concentration required for HLD. Corrosion of metal objects can occur with long contact time. Environmentally safe waste produced after processing. What is the disinfection level and the agent used?

Answer 25

High to intermediate; Peracetic acid

Question 26

0.2% concentration required for HLD. Can irreversibly bin proteins to the surface of processed objects, thorough washing required before sterilant treatment. Can irritate skin and mucous membranes. What is the disinfection level and the agent used?

Answer 26

High; Glutaraldehyde

Question 27

Enumerate the factors that influence the degree of killing

Answer 27

Concentration of disinfectants Presence of organic matter Nature of surface to be disinfected Temperature Contact time pH Biofilms Compatibility of disinfectants

Question 28

What method only destroys vegetative bacteria and what is its temperature and contact time?

Answer 28

Boiling; 100 degreed celsius, 10-15 minutes

Question 29

what is the temperature and contact time of autoclave for sterilization of culture media, utensils, glass pipettes, and instruments for assays

Answer 29

-121 degrees celsius, 15psi, 15 minutes

Question 30

Method that is the fastest and simplest method of sterilization that kills organisms, including spore-forming bacteria except PRIONS.

Answer 30

Autoclave

Question 30

What is the principle of autoclave

Answer 30

moist heat or steam under pressure

Question 31

what is the temperature and contact time of autoclave for decontamination of medical wastes and used instruments.

Answer 31

-132 degrees celsius, 15psi, 30-60 minutes

Question 32

what is the biologic indicator in autoclave

Answer 32

Geobacillus stearothermuphilus

Question 32

Method that is used in the sterilization of high-protein culture media such as Lowenstein Jensen medium for Mycobacteria

Answer 32

Inspissation

Question 33

Mode of action of inspissation

Answer 33

Thickens the medium through evaporation

Question 34

Method used to sterilize milk, dairy products, and alcoholic beverages, eliminates food borne pathogens and organisms responsible for spoilage, cannot eliminate bacterial spores.

Answer 34

Pasteurization

Question 34

Temperature and contact time of inspissation

Answer 34

75-85 degrees, 2 hours, 3 consecutive days

Question 35

Method that uses dry heat in killing microorganisms through protein denaturation. Suitable for the sterilization of heat-stable objects not penetrated by moist heat. Used to sterilize glasswares, oil products, petrolatum, or powders.

Answer 35

Oven

Question 35

Temperature and contact time of oven

Answer 35

160-170 degrees, 1.5-2 hours

Question 35

Method that is used in direct heating. Sterelizes inoculating loops and needles

Answer 35

Flaming

Question 36

Biologic indicator in oven

Answer 36

Bacillus subtilis var. niger

Question 37

Temperature for hazardous materials in Incineration

Answer 37

870-980 degrees celsius

Question 37

Most common method for treating infectious wastes and infected laboratory animal. Destroys prions. Burns materials into ashes at 300-400 degrees celsius.

Answer 37

Incerination

Question 38

Method used to control the spread of communicable diseases

Answer 38

Cremation

Question 39

Temperature in cremation

Answer 39

1800 degrees farehnheit (982 degrees celsius)

Question 40

Method of choice for the sterilization of heat-sensitive compounds or solutions such as antibiotic solutions, toxic chemicals, radioisotopes, vaccines and carbohydrates.

Answer 40

Filtration

Question 41

What type of filtration uses cellulose acetate/cellulose nitrate membrane with a vacuum

Answer 41

liquid filtration

Question 41

WHAT CHEMICAL METHOD? - Precipitates bacterial protein - Kills bacteria - Irreversible

Answer 41

Bactericidal

Question 41

What type of filtration uses 0.45um and 0.80um pores membrane filters

Answer 41

Filtration of bacteria, yeast, and molds

Question 41

What type of filtration uses HEPA filters that remove organisms larger than 0.3um from isolation rooms, operating rooms, and biological safety cabinets.

Answer 41

Air filtration

Question 41

Method that uses low energy and is used to sterilize exposed surface air, operating rooms, biosafety cabinets, nurseries, and cafeterias.

Answer 41

Non-ionizing radiation

Question 41

Method that has a short wavelength, and has high energy. Destroys vegetative cells and endospores of both prokaryote and eukaryote cells. Used to sterilize disposable supplies.

Answer 41

Ionizing radiation

Question 42

WHAT CHEMICAL METHOD? - Applied typically to the skin - Inhibits sepsis formation

Answer 42

Antiseptic

Question 42

WHAT CHEMICAL METHOD? - Applied to inanimate objects

Answer 42

Disinfectant

Question 42

WHAT CHEMICAL METHOD? - Inhibits the growth of microorganisms - Reversible

Answer 42

Bacteriostatic

Question 42

WHAT CHEMICAL METHOD? MOA: inactivation of proteins and nucleic acids Has irritable factor and carcinogenic - not recommended for routine disinfection and sterilization

Answer 42

Formaldehyde

Question 43

WHAT CHEMICAL METHOD? MOA: inactivation of DNA or RNA Rapid killing action, not activated by organic matter, but does not penetrate organic matter well. Used as sterilant or disinfectant depending on the CONTACT TIME

Answer 43

glutaraldehyde

Question 43

WHAT CHEMICAL METHOD? MOA: denaturation of protein, dissolution of lipid membrane, and dehydration of cells Has excellent in-vitro activity against most gram-positive and gram-negative bacteria Used both as antiseptic and disinfectant

Answer 43

Alcohol

Question 44

WHAT CHEMICAL METHOD? MOA: Free iodine degrades microbial cell walls and cytoplasm, denatures and coagulates chromosomal materials. Used as skin preparation agents for blood collection sites.

Answer 44

Halogens

Question 45

WHAT CHEMICAL METHOD? MOA: antibacterial effect is attributed to the oxidative effects of hypochlorous acids formed when chloride ions are dissolved in water Inexpensive and has a broad spectrum activity Oldest and most commonly used disinfectants

Answer 45

Chlorine and chlorine compounds

Question 46

WHAT CHEMICAL METHOD? MOA: destroys plasma membranes and denatures cell proteins Has a broad spectrum activity, but not sporicidal Effective in the presence of organic matter and remains active for long periods of time when applied on surfaces The first widely used disinfectant and antispetic

Answer 46

Phenol and Phenolic compounds

Question 46

Most commonly used gas for sterilization MOA: alkylation of nucleic acids in the spore and vegetative cells

Answer 46

Ethylene Oxide

Question 46

Active against all vegetative microorganisms and fungal spores Used to sterilize medical equipment

Answer 46

Peracetic acid

Question 46

WHAT CHEMICAL METHOD? MOA: disrupts cell membranes of bacteria resulting in leakage of cell contents Used as surface-active agents Inactivated by organic matter

Answer 46

Quaternary Ammonium Compounds

Question 47

Combined H2O2 and peracetic acid vapors is used in the pharmaceutical and medical devices industries.

Answer 47

Hydrogen peroxide and peracetic acid

Question 48

Active against all vegetative microorganisms, bacterial endospores, and fungal spores. Used as sterilant in the pharmaceutical and medical devices industries.

Answer 48

Hydrogen peroxide

Question 49

Sporicidal disinfectants

Answer 49

Glutaraldehyde Hydrogen peroxide Ethylene oxide Combined Hydrogen peroxide and peracetic acid

Question 50

Disinfectants inactivated by organic matter

Answer 50

Alcohol Chlorine and Chlorine compounds Quaternary Ammonium Compounds

Question 51

What number of biosafety level where organisms with known potential of infecting healthy individuals

Answer 51

BSL 1

Question 52

What number of biosafety level where organisms acquired through ingestion, percutaneous, and mucous membrane exposure

Answer 52

BSL 2

Question 53

What number of biosafety level where organisms possible for aerosol transmission

Answer 53

BSL 3

Question 54

What number of biosafety level where organisms that may expose extreme risk to laboratory workers and may cause life threatening disease

Answer 54

BSL 4

Question 55

Category where agents that pose the greatest health threat, easily transmitted, highly infectious, and high mortality rate

Answer 55

Category A

Question 55

Category where moderately easy to disseminate or transmit. Moderate morbidity and low mortality

Answer 55

Category B

Question 56

Category where organisms that can be engineered for mass destruction in the future. High mortality and morbidity rates.

Answer 56

Category C