Control of Bacterial Growth

Question 1

Sterilization

Answer 1

the complete killing or removal of all living microbes, including the most resistant forms (bacterial spores)

Heating is the most common method used for killing microbes.

Question 2

Decontamination

Answer 2

the treatment of objects or surfaces to make it safe to handle

Question 3

Disinfection

Answer 3

The control directed against pathogens.

Usually refers to destruction of vegetative (Not spores) pathogens.

In practice, the term is most commonly used for using chemicals to treat inanimate surfaces or obects.

Question 4

Antisepsis

Answer 4

Application to living tissues, generally body surfaces or cavities to kill bacteria or reduce bacterial load.

Question 5

Sanitization

Answer 5

Intended to lower microbial load to minimize the disease transmission

Question 6

Sepsis

Answer 6

Greek word for decay or putrid

Indicates bacterial contamination

Question 7

Asepsis

Answer 7

The absence of bacterial contaminations.

Object or area are free of pahtogens

Question 8

Aseptic Technique

Answer 8

Important in bacteriology to prevent contamination

Question 9

Factors Affecting Microbial Death

Answer 9

1. The number of microbes:
   
   1. larger populations take longer to kill
2. Environmental Conditions:
   
   1. presence of organic matter often inhibits the action of the antimicrobial.
3. Time of exposure:
   
   1. a minimum contact time is required for efficacy of most antiseptics and disinfectant
4. Microbial Characterisitics:
   
   1. bacterial spores are the most resistant forms of bacteria and are generally affected by few biocides. Most Biocides tend to be more effective against Gram + than Gram - bacteria because there is less lipid in the cell membrane.

Question 10

Alteration of memebrane Permeability

Answer 10

The cytoplasmic membrane located inside the bacterial cell wall is the target of many control agents. The membrane has selective permeability regulating the entry of nutrients and exit of products.

Damage to the cytoplasmic membrane caused cellular contents to leak and interferes with the growth of the cell.

Question 11

Damage to Proteins

Answer 11

Altered (denaturation) or destruction of protein structures or their activites will interfere with growth of or kill the bacteria.

Chemicals or heat may disrupt bonding, which is the reason for altered structure or destruction of activities.

Question 12

Damage to nucleic acids

Answer 12

Damage to RNA or DNA by heat, chemicals, or radiation is frequently lethal to the cells and cannot carry our normal metabolic functions.

Question 13

Heat

Answer 13

Most common method for the control of microbial growth.

Kills bacteria by denaturing proteins.

Question 14

Thermal Death Point

Answer 14

As the lowest temperature at which all microorganisms in a particular liquid suspension will be killed in 10 minutes.

Question 15

Moist Heat

Answer 15

Kills microbes be denaturing protiens (coagulation), which is caused by breaking hydrogen bonds and loss of three dimensional structure of proteins.

Question 16

Boiling

Answer 16

@100C

Kills vegetative bacterial cells, but not bacterial spores. Generally done for 5-10 mins.

NOT a method of sterilization.

Question 17

Steam Under Pressure

Answer 17

Autoclave, or pressure cooker

Required to raise the temperature above 100C.

In an Autoclave, temperatire reacheds 121C becuase steam is applied under a pressure of 15psi, which is atmosphere above sea level pressure.

Higher the pressure, higher the temp.

@ 121C for 15 minutes evern bacterial spores are killed.

Perfect method for steriliziation.

Question 18

Pasteurization

Answer 18

Uses precisely controlled hfeat to reduce microbial numbers in heat sensitive liquids (milk).

Does not kill all microorganisms; hence, it is not the same as sterilization.

Question 19

Dry heat

Answer 19

NOT as effective as moist heat because moisture allows heat to penetrate better.

Kills by oxidation.

Dry sterilization is done by flaming. Incineration to sterilize contaminated materials or carcasses.

Hot-air sterilization: Done in an oven at a temperature of 170C maintanied for 2 hours will ensure sterilization.

Question 20

Radiation

Answer 20

Microwaves, ultraviolet rays, x-rays, gamma rays, and electrons are all forms of electromagnetic radiation. Radiation that kills microorganisms is of two types:

Ionizing and nonionizing.

Question 21

Ionizing Radiation

Answer 21

These have a wave length less than 1nm.

Gamma rays and X-rays have sufficient energy to produce ions and other reactive products from molecules with which radiation particles collide.

Creat electorns, hydroxyl radicals, and hydride radicals.

Question 22

Nonionizing Radiation

Answer 22

Have wave lengths greater than 1nm.

Ultraviolet rays (220-300nm)

Damages the DNA of exposed bacteria by causing bonds to form between pyrimidine bases. Particularly Thymine.

Thymine dimers inhibid DNA replication.

Question 23

Filter Sterilization

Answer 23

Involves the use of a filter with pores too small for the passage of microorganisms.

Used for sterilization of heat-sensitive liquids, like culture media.

Most common filter used is a membrane filter.

HEPA-filters can be used to remove airborne microbes.

Question 24

Phenols and Phenolics

Answer 24

Phenol was the first chemical used to control surgical infections.

Derivatives of Phenol (pheolics) contain a molecule of phenol to reduce irritation and increase antibacterial activity.

Active in the presence of organic compounds and are stable for long periods of time.

Question 25

Halogens

Answer 25

Iodine and Chlorine, alone ore as constituents of inorganic or organic compounds are effective antimicrobial agents.

Iodine: the oldest and most effective antiseptic.

Chlorine: a gas or in combination with other chemicals is also used widely.

Question 26

Alcohols

Answer 26

Kill bacteria but not endospores.

Mode of action is protein denaturation, and the disruption of cytoplasmic membranes. Dissolve lipid components

Question 27

Heavy metals and their compounds

Answer 27

Silver, Mercury, Copper, and Zinc have antibicrobial activity. Effective in small amounts.

Use is limited because of toxicity and corrosiveness,

Question 28

Surface Active Compounds

Answer 28

Also called Surfactants

decrease surface tension among molecules of a liquid. Soaps and detergents.

Useful for mechanical removal of microbes by scrubbing.

Question 29

Quanternary Ammonium Compounds

Answer 29

Cationic detergents are most widely used surface active agents.

Cleaning action is due to the positively charged milecules and mode of action is not known.

Question 30

Ozone

Answer 30

Highly reactive form of oxygen that is fenerated by passin oxygen through high-voltage discharges. Often used to supplement chlorine in the disinfection of water.

Question 31

Hydrogen Peroxide

Answer 31

Commonly used antiseptic.

Not good for open wounds because it is rapidly broken down to water and oxygen by catalase.

Question 32

Peracetic Acids

Answer 32

Effective liquid sporicide and is considered as sterilant. Kills spores withing 30 minutes,

Useful in food processing and medical equipment.

Question 33

Formaldehyde

Answer 33

Gas is an excellent disinfectant. Commonly available as formalin.

Used in preserving biological specimens and to inactivate bacteria or toxins in vaccines.

Glutaraldehyde is less irritating and more effective than formalydehyde.

Question 34

Gaseous Sterilizers

Answer 34

Chemicals are used in a closed chamber to sterilize heast sensitive materials. Most commonly used chemical is ethylene oxide.

Toxic and flamable.

Effective against all microbes and spores, but requires period of several hours 4-18 of exposure.