LESSON 13: CONTROL MICROORGANISM

Question 1

Ubiquitous and many microorganisms are associated with
undesirable consequences, such as food spoilage and disease.

Answer 1

MICROBES

Question 2

it is essential to kill a wide variety of microorganisms or inhibit their growth to minimize
their destructive effects. The goal is twofold:

Answer 2

: (a) to destroy pathogens and prevent
their transmission and
(b) to reduce or eliminate microorganisms responsible for the
contamination of water, food, and other

Question 3

Microorganisms are controlled
either by
physical agents (temperature, desiccation, osmotic pressure, radiation, and
filtration) or

Chemical agents (disinfectants, antiseptics, antibiotics, and chemotherapeutic antimicrobial chemicals).

Question 4

a process by which an article, surface, or medium is freed of all
living microorganisms either in the vegetative
or in the spore state.

Answer 4

Sterilization

Question 5

any material that has been subjected to the above process.

Answer 5

Sterile

Question 6

A chemical agent that is used to perform sterilization because of their ability y to destroy spores.

Answer 6

STERILANTS

Question 7

also called a microbicide,
is any chemical agent that kills pathogenic
microorganisms either on inanimate (nonliving) materials or on living tissue but not resistant microbial.

Answer 7

Germicide

Question 7

the use of a chemical agent that destroys or removes all pathogenic organisms or organisms capable of giving rise to infection or its harmful products (toxin) thus destroys vegetative pathogens but not bacterial endospores.

Answer 7

Disinfection

Question 8

Used only on inanimate objects because they can be toxic to human and other animal tissue, when used in HIGHER CONCENTRATION

Answer 8

Disinfectant

Question 9

Defined as the growth of microorganisms in the body or the presence of
microbial toxins in blood and other tissues

Answer 9

Sepsis

Question 10

refers to any practice that prevents the entry of infectious agents into
sterile tissues and thus

Answer 10

Asepsis

Question 11

s any cleansing technique that mechanically removes
microorganisms (along with food debris) to reduce the

Answer 11

Sanitization

Question 11

e chemical agents applied directly to the exposed body surfaces
(e.g., skin and mucous membranes), wounds, and surgical incisions to destroy or
inhibit vegetative pathogens

Answer 11

Antiseptics

Question 12

process usually involves scrubbing the skin or
immersing it in chemicals, or both. It also emulsifies oils that lie on the outer
cutaneous layer and mechanically removes potential pathogens from the outer
layers of the skin.

Answer 12

Degerming/antisepsis

Question 12

a compound (e.g., soap or detergent) that is used to perform
sanitization.
Air sanitization with ultraviolet lamps reduces airborne microbes in
hospital rooms, veterinary clinics, and laboratory installations.

Answer 12

Sanitizer

Question 13

Examples of degerming procedures are
(a) surgical hand scrub,
(b)
application of alcohol wipes to the skin, and
(c) cleansing of a wound with germicidal
soap and water

Question 14

STERILIZATION
Classified into:2.
1. Physical methods
2. Chemical method

Question 14

Methods of controlling microorganism

Answer 14

1. Sterilization
2. Disinfection
3. Antimicrobials

Question 15

Physical methods of sterilization

Answer 15

1. Sunlight
2. Heat
3. Filtration
4. Radiation
5. Sonication

Question 16

natural method of sterilization of water in tanks, rivers, and lakes.

Answer 16

Sunlight

Question 17

Direct sunlight has an active germicidal effect due to its content of ultraviolet and heat rays.

Question 18

Bacteria present in natural water sources are rapidly destroyed by exposure to sunlight.

Question 19

One of the most dependable method of sterilization.

Answer 19

Heat

Question 20

higher
temperatures (exceeding the maximum) are microbicidal, whereas
lower
temperatures (below the minimum) tend to have inhibitory or microbiostatic
effects.

Question 21

Two types: moist and dry heat.

Question 22

Sterilization by moist heat occurs

Answer 22

Hot water, boiling water, or steam (vaporized water) and the temperature usually ranges from 60 to 135°C. M

Question 22

Moist heat kills microorganisms by

Answer 22

denaturation and coagulation of proteins.

Question 23

Classification of moist heat:

Question 24

Sterilization at a temperature below 100°C: example is Pasteurization

Question 25

A technique in which heat is applied to liquids to kill potential agents of infection and spoilage, while at the same time retaining the liquid’s flavor and food value.

Answer 25

Pasteurization

Question 26

This method is extensively used for sterilization of milk and other fresh beverages, such as fruit juices, beer, and wine which are easily contaminated during collection and processing.

Answer 26

pasteurization

Question 27

Pasteurization has two methods:

Answer 27

Flash method and Holder method

Question 27

(product is exposed to heat at 72°C for 15–20 seconds followed by a sudden cooling to 13°C or lower)

Answer 27

Flash method

Question 28

(product is exposed to a temperature of 63°C for 30 minutes followed by cooling to 13°C or lower, but not less than 6°C).

Answer 28

Holder method

Question 29

Pasteurization inactivates most viruses and destroys the vegetative stages of 97–99% of bacteria and fungi, it does not kill endospores or thermoduric species (mostly nonpathogenic lactobacilli, micrococci, and yeasts)

Question 30

Sterilization at a temperature of 100°C: includes (a) boiling and (b) steam sterilizer

Question 31

Of water for 10–30 minutes kills most of the vegetative forms of bacteria but not bacterial spores thus only for disinfection.

Answer 31

Boiling

Question 32

At 100°C: substances are exposed to steam at atmospheric pressure for 90 minutes during which most vegetative forms of the bacteria except for the thermophiles are killed by the moist heat.

Answer 32

Steam sterilizer

Question 33

pasteurization inactivates most viruses and destroys the vegetative stages of 97–99% of bacteria and fungi, it does not kill endospores or thermoduric species (mostly nonpathogenic lactobacilli, micrococci, and yeasts).

Answer 33

Sterilization at a temperature above 100°C:

Question 34

Certain heat-labile substances (e.g., serum, sugar, egg, etc.) that cannot withstand the high temperature of the autoclave can be sterilized by a process of intermittent sterilization, known as

Answer 34

Tyndallization

Question 35

used most often to sterilize heat-sensitive culture media, such as those containing sera (e.g., Loeffler’s serum slope), egg (e.g., Lowenstein–Jensen’s medium), or carbohydrates (e.g., serum sugars) and some canned foods.

Answer 35

Intermittent sterilization

Question 36

Process of Tyndallization

Answer 36

Carried out over a period of 3 days and requires a chamber to hold the materials and a reservoir for boiling water. Items to be sterilized are kept in the chamber and are exposed to free to flowing steam at 100°C for 20 minutes, for each of the three consecutive days

Question 37

1st day:

Answer 37

: the temperature is adequate to kill all the vegetative forms of the bacteria, yeasts, and molds but not sufficient to kill

Question 38

2nd day:

Answer 38

The surviving spores are allowed to germinate to vegetative forms on the second day and are killed on re-exposure to steam.

Question 39

3rd day:

Answer 39

Re-ensures killing of all the spores by their germination to vegetative forms

Question 40

Makes use of air with a low moisture content that has been heated by a flame or electric heating coil. In practice, the temperature of dry heat ranges from 160°C to several thousand degrees Celsius.

Answer 40

Sterilization by dry heat

Question 41

kills microorganisms by protein denaturation, oxidative damage, and the toxic effect of increased level of electrolytes.

Answer 41

Dry heat

Question 42

Sterilization of inoculating loop or wire, the tip of forceps, searing spatulas, etc., is carried out by holding them in the flame of the Bunsen burner till they become red hot.

Question 43

Glass slides, scalpels, and mouths of culture tubes are sterilized by passing them through the Bunsen flame without allowing them to become red hot.

Question 44

Excellent method for safely destroying infective materials by burning them to ashes

Answer 44

Incineration

Question 45

Electrically heated and is fitted with a fan to ensure adequate and even distribution of hot air in the chamber.

Answer 45

Hot air oven

Question 46

remove contaminating microorganisms from solutions rather than directly destroying them.

Answer 46

Filters

Question 47

The filters are of two types:

Answer 47

(a) depth filters; ex: candle filter, asbestos filter or sintered glass filters (b) membrane filters; ex: cellulose acetate, cellulose nitrate, polycarbonate, polyvinylidene fluoride, or other synthetic materials made

Question 48

An excellent sterilizing agent with very high penetrating power. These radiations penetrate deep into objectsand destroy bacterial endospores and vegetative cells, both prokaryotic and eukaryotic but not that effective against viruses.

Question 50

Example: (a) X-rays, (b) gamma rays, and (c) cosmic rays

Question 51

from a cobalt-60 source is used for sterilization of antibiotics, hormones, sutures, catheters, animal feeds, metal foils, and plastic disposables, such as syringes, meat and other food items.

Answer 51

Gamma radiation

Question 52

Irradiation usually kills

Answer 52

Escherichia coli O157:H7, Staphylococcus aureus, Campylobacter jejuni, and other pathogens.

Question 53

Since there is no detectable increase of temperature in this method, this method is commonly referred to as

Answer 53

“cold sterilization.”

Question 54

While nonionizing radiations include infrared and

Question 55

Use of high-frequency sound (sonic) waves beyond the sensitivity of the human ear are known to disrupt cells. Sonication transmits vibrations through a water-filled chamber (sonicator) to induce pressure changes and create intense points of turbulence that can stress and burst cells in the vicinity.

Answer 55

Sonication

Question 56

Heat generated by the sonic waves (up to 80°C) also appears to contribute to the antimicrobial action.

Question 57

Gram-negative rods are most sensitive to ultrasonic vibrations.

Question 58

Gram-positive cocci, fungal spores, and bacterial spores are resistant to them

Question 59

The process of inactivating microorganisms by direct exposure to chemical or physical agents.

Answer 59

DISINFECTION

Question 59

products or biocides that destroy or inhibit the growth of microorganisms on inanimate objects or surfaces

Question 60

Disinfectants can be sporistatic but are not necessarily sporicidal.

Question 61

are biocides or products that destroy or inhibit the growth of microorganisms

Answer 61

Antiseptics

Question 62

9 Properties of ideal disinfectant

Answer 62

1. It should have a wide spectrum of antimicrobial activity. 2. It should act in the presence of organic matter. 3. It should not be toxic to human or corrosive. 4. It should be stable upon storage and should not undergo any chemical change. 5. It should be odorless or with a pleasant odor. 6. It should be soluble in water and lipids for penetration into microorganisms. 7. It should be effective in acidic as well as in alkaline media. 8. It should have speedy action. 9. If possible, it should be be relatively inexpensive.

Question 63

Action of Disinfectants

Answer 63

1. They produce damage to the cell wall and alter permeability of the cell membrane, resulting in exposure, damage, or loss of the cellular contents. 2. They alter proteins and form protein salts or cause coagulation of proteins. 3. They inhibit enzyme action and inhibit nucleic acid synthesis or alter nucleic acid molecules. 4. They cause

Question 64

Factors Influencing Activity of Disinfectants

Answer 64

1. temperature 2. types of microorganism 3. physiological state of the cell 4. environment

Question 65

1. temperature

Answer 65

Increase in temperature increases the efficiency of disinfectants.

Question 66

Vegetative cells are more susceptible than spores. Spores may be resistant to the action of disinfectants.

Answer 66

Type of microorganism:

Question 67

: Young and metabolically active cells are more sensitive than old dormant cells. Non growing cells

Answer 67

. Physiological state of the cell:

Question 68

The physical or chemical properties of the medium or substance influence rate as well as efficiency of disinfectants, e.g., pH of the medium and presence of extraneous materials.

Answer 68

Environment

Question 69

most widely used antiseptics and disinfectants in laboratories and hospitals worldwide. They are bactericidal or bacteriostatic and some are fungicidal also. They act by denaturing proteins and disrupting cell membranes. They are effective in the presence of organic material and remain active on surfaces long after application. E

Question 70

Examples

Answer 70

1. phenol 2. Crerol 3. Halogenated diphenyl compounds

Question 71

is effective against vegetative forms of bacteria but not suitable for application to skin or mucous membrane),

Answer 71

Phenol

Question 72

(are more germicidal and less poisonous than phenol but corrosive to living tissues. They are used for cleaning floors (1% solution), for disinfection of surgical instruments, and for disinfection of contaminated objects.

Answer 72

cresol

Question 73

is a solution of cresols in soap)

Answer 73

Lysol

Question 74

s (like hexachlorophene and chlorhexidine are highly effective against both Gram- positive and Gram-negative bacteria.

Question 75

They are used as skin antiseptics and for the cleaning of wound surfaces especially hexachlorophene because once applied it persists on the skin and reduces growth of skin bacteria for longer periods.

Question 76

It can cause brain damage and is now used in hospital nurseries only after a staphylococcal outbreak)

Question 77

Are fluorine, bromine, chlorine, and iodine—a group of nonmetallic elements that commonly occur in minerals, sea water, and salts.

Answer 77

Halogens

Question 78

kills not only bacterial cells and endospores but also fungi and viruses

Answer 78

chlorine

Question 79

at a concentration of 0.6–1.0 part of chlorine per million parts of water makes water potable and safe to use.

Answer 79

Chlorination

Question 80

chlorine is ineffective at an alkaline pH, less effective in the presence of excess organic matter, and relatively unstable, if exposed to light.

Question 82

rapidly penetrates the cells of microorganisms, where it apparently disturbs a variety of metabolic functions by interfering with the hydrogen and disulfide bonds of proteins. not adversely affected by organic matter and pH.

Answer 82

Iodine

Question 83

most widely used disinfectants and antiseptics effective at a concentration of 60–70% in water. They are bactericidal and fungicidal but not sporicidal or virucidal.

Answer 83

alcohol

Question 84

are the two most popular alcohol germicides. They act by denaturing bacterial proteins and possibly by dissolving membrane lipids.

Answer 84

Ethyl alcohol Isopropyl alkohol

Question 85

Is effective against fungal spores.

Answer 85

Methyl alcohol

Question 86

: are highly reactive molecules that combine with nucleic and alkylating molecules; sporicidal and can be used as chemical sterilants.

Answer 86

aldehydes

Question 87

That is usually dissolved in water or alcohol before use against bacteria, spores and viruses.

Answer 87

Folmaldehyde

Question 88

Is 40% aldehyde in aqueous solution. It is used to: 1. preserve fresh tissue specimens, 2. destroy anthrax spores in hair and wool, 3. prepare toxoids from toxins, 4. sterilize bacterial vaccines, and 5. kill bacterial cultures

Answer 88

Formalin Solution

Question 89

used for sterilization of large volume of heat-sensitive disposable items and also instruments

Answer 89

Gases

Question 90

frequently used gaseous agents

Answer 90

Ethylene oxide, formaldehyde gas, and betapropiolactone

Question 91

: such as detergents are the substances that alter energy relationship at interfaces producing a reduction in surface tension.

Question 92

are organic molecules that serve as wetting agents and emulsifiers because they have both polar hydrophilic and nonpolar hydrophobic ends thus are very effective cleansing agents

Answer 92

Surface active agents:

Question 93

They are different from soaps, which are derived from fats. Four types:

Answer 93

: (i) Cationic surface active agents ex: quaternary ammonium compounds, (ii) Anionic surface active agents, ex: soap made from saturated or unsaturated fatty acids, (iii) Nonionic surface active agents (not effective), (iv) Amphoteric or ampholytic compounds

Question 94

This group includes halogens, hydrogen peroxide, potassium permanganate, and sodium perborate. They are good disinfectants and antiseptics but are less effective in the presence of organic matter.

Answer 94

Oxidizing agents

Question 95

used extensively as skin and wound antiseptics include (a) acridine dyes and (b) aniline dyes both more active against Gram positive bacteria

Answer 95

Dyes

Question 96

Soluble salts of mercury, silver, copper, arsenic, and other heavy metals have antibacterial activity, both bactericidal and bacteriostatic. They combine with proteins, often with their sulfhydryl groups and inactivate them or may also precipitate cell proteins.

Answer 96

Heavy metals:

Question 97

(such as sulfuric acid, nitric acid, hydrochloric acid, and benzoic acid) a

Answer 97

acids

Question 98

(like potassium and sodium hydroxide and ammonium hydroxide) are germicidal in nature.

Answer 98

alkalis

Question 99

They kill microorganisms by hydrolysis and altering the medium

Answer 99

acids and alkalis