Micribiology - Endospores And Contol Of Microbial Growth (w20)

Question 1

What are endospores ?

Answer 1

Resting/dormant/inert form of some bacterial cells
Produced only by two Gram+ Genera: Bacillus and Clostridium

Question 2

What is sporulation ?

Answer 2

The process of endospore formation

Question 3

What is germination ?

Answer 3

The process in which endospores return to the vegetative state

Question 4

What are the 4 terms used to describe antimicrobial control measures ?

Answer 4

• sterilization
• disinfection
• sanitisation
• antimicrobial chemotherapy

Question 5

How is sterilization an antimicrobial growth measure ?

Answer 5

Sterilisation: Destroying all microbial life (including endospores)
A sterile object is totally free of viable microorganisms

Question 6

How is disinfection an antimicrobial control measure ?

Answer 6

Disinfection: Reduces the number of pathogenic microorganisms (not endospores) to the point where they no longer cause diseases
Disinfectant: agents applied on inanimate objects/surfaces (toxic to human tissue)
Antiseptic: agents applied on living tissue

Question 7

How is sanitisation an antimicrobial control measure ?

Answer 7

Sanitisation: reduces the microbes to safe levels by public health standards

Question 8

How is antimicrobial chemotherapy an antimicrobial control measure ?

Answer 8

Antimicrobial chemotherapy: Drug treatment for specific infections used internally to SELECTIVELY kill or inhibit growth of microorganisms within host tissues, targeting a unique structure of the specific microbe

Question 9

What are endospores resistant to ?

Answer 9

Desiccation, heat, chemicals and radiation

Question 10

What are the three sequential steps of germination ?

Answer 10

1) activation
2) initiation
3) outgrowth

Question 11

What happens during germination ?

Answer 11

During germination, the core is hydrated, spore coats are cracked and the cell metabolism is restored

Question 12

What disease does clostridium botulinum cause ?

Answer 12

Botulism

Question 13

What disease does clostridium perfingens cause ?

Answer 13

Gas gangrene

Question 14

What disease does clostridium tetani cause ?

Answer 14

Tetanus

Question 15

What disease does bacillus anthracite cause ?

Answer 15

Cutaneous or pulmonary anthrax

Question 16

What is the goal of an sterilization process ?

Answer 16

The goal of any sterilisation process is the destruction of bacterial endospores, viruses and cellular organisms

Question 17

What is sterilization and essential stage in ?

Answer 17

Sterilisation is an essential stage in the:
- processing of any product destined for parenteral administration
- for contact with broken skin, mucosal surfaces, or internal organs

Question 18

Death of a whole population is not instantaneous but continues in a _________ manner as the time or concentration is _______ .

Answer 18

1) logarithmic
2) increased

Question 19

What does effectiveness of the control agents depend on ?

Answer 19

Effectiveness of the control agents depends on:
- Time of exposure
- Microbial characteristics
- Number of microbes
- Environment (organic matter, temperature, biofilms)

Question 20

What effects do treatments used to control microbial death have on the microbes ?

Answer 20

Effects on the microbes
- Alternation of membrane permeability
- Protein denaturation
- Damage to nucleic acids

Question 21

What physical treatments are there to control microbial death ?

Answer 21

Physical treatments:
- Temperature
- Heat (moist and dry)
- Cold temperatures
- Filtration
- Radiations
- Osmotic pressure

Question 22

What chemical treatments are there to control microbial death ?

Answer 22

Chemical treatments :
- Alcohols
- Halogens
- Iodine
- Chlorine
- Phenolics
- Aldehydes
- Quaternary ammonium compounds
- Sterilizing gases
- Heavy metals

Question 23

What is more effective for controlling microbial death: moist or dry heat ?

Answer 23

Moist heat, which kills microbes by denaturing their proteins.

Question 24

What is autoclave ?

Answer 24

Autoclave: preferred sterilisation method, unless material is damaged by heat, moisture, or high pressure

Closed chamber with hot saturated steam under pressure

Question 25

What is pasteurization ?

Answer 25

Pasteurisation (moist heat disinfection): Developed by Louis Pasteur to prevent the spoilage of beverages. Used to reduce microbes responsible for spoilage of beer, milk, wine, juices, etc.

Question 26

What are the three methods available for pasteurization ?

Answer 26

3 Methods:
1) Classic Method of Pasteurisation: 65 o C for 30 minutes

2) Flash Pasteurisation (HTST): Used today. 72 o C for 15 seconds

3) Ultra High Temperature Pasteurisation (UHT): 140 o C for 4 seconds and then cooled quickly in a vacuum chamber. This is a sterilising method

Question 27

What do low temperatures do to microbes ?

Answer 27

• Low temperatures (< optimal temp.) slow down microbial growth
• Reduces metabolic rate of most microbes to stop their proliferation and toxin production, but often do not kill microbes
• Refrigeration temperatures (4-8 o C) are used for food preservation

Question 28

What does filtration of microbes do ?

Answer 28

Filtration: Removal of microbes by passage of a liquid or gases through membrane material with defined small pores (< microbe size)

Question 29

What is osmotic pressure in reference to microbial growth ?

Answer 29

Osmotic pressure: The use of high concentrations of salts and sugars in foods is used to increase the osmotic pressure and create a hypertonic environment.

Question 30

What is plasmolysis ?

Answer 30

When the water leaves the cell, plasma membrane shrinks away from cell wall. The cell may not die, but usually stops growing.