Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Microbiology > Control Of Microbial Growth > Flashcards

Control Of Microbial Growth Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

Why do we need microbial growth?

A
  • prevent cross contamination of cultures in a laboratory
  • prevent contamination of equipment used in medical and food preparation procedures
  • to increase the shelf life of food and beverages
  • to limit the detrimental effect the microbes or their metabolic products would have on us and/or our food
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is sterilisation?

A

Killing or removal of all microorganisms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is commercial sterilisation?

A

Killing clostridium botulinum endospores (no pathogens left, growth stopped)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is disinfection?

A

Removing pathogens from inanimate objects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is antisepsis?

A

Removing pathogens from living tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is degerming?

A

Removing microbes in a limited area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is sanitisation?

A

Lowering microbial counts e.g. On eating utensils

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is a biocide/germicide?

A

Kills microbes, inactivated viruses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is bacteriostasis?

A

Inhibiting, not killing, microbes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is sepsis?

A

Refers to microbial contamination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is asepsis?

A

Is the absence of significant contamination.

Asceptic techniques prevent microbial contamination of wounds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe some patterns of microbial death.

A

Population death rate is constant.

90% of population will be reduced after I minute

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are some of the factors that affect microbial death?

A
  1. Number of microbes. More time may need to be applied
  2. Environment. Organic matter, temperature, biofilms.
  3. Time of exposure
  4. Microbial characteristics
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the 3 actions of microbial control actions?

A
  1. Alteration of membrane permeability
  2. Damage to proteins
  3. Damage to nucleic acids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the 6 microbial physical control mechanisms?

A
  1. Temperature +/- moisture
  2. Filtration
  3. Desiccation (drying)
  4. Osmotic pressure
  5. High pressure
  6. Radiation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Explain the importance of heat as a microbial control mechanism

A

Heat denatures and coagulates proteins

Microbes differ in their resistance to the affects of temperature

17
Q

What is thermal death point?

A

TDP. Lowest temperature at which ALL cells in a culture are killed in 10min

18
Q

What is thermal death time?

A

TDT . Time during which ALL cells in a culture are killed

19
Q

What is decimal reduction time?

A

DRT. Time (in minutes) to kill 90% of a population at a given temperature

20
Q

Describe autoclaving

A 
Moist heat (steam) under pressure. Steam must contact the items surface
- temperature acting on items is raised by increasing the pressure around the item
15psi (103 kPa), 121 degrees centigrade for 15  minutes - kills all (except prions)
- sterilisation time depends on the volume. 10ml = 15 mins
21
Q

Describe dry heat sterilisation and the techniques used.

A 
Kills by oxidation
Dry heat
Flaming
Incineration
Hot air sterilisation
22
Q

Explain the purpose of pasteurisation

A

Kills pathogens and reduces spoilage organisms.
Equivalent treatments
63 degrees Celsius for 30 min
High temp short time. 72 degrees for 15 sec
Ultra high temp. 140 degrees for less than 1 sec
Thermoduric (heat resistant) organisms can survive and cause spoilage

23
Q

Describe how low temps suppress microbial growth

A
  1. Refrigeration. Slows metabolic activity, generally bacteriostatic, rather than bacteriocidal
  2. Freezing. Slow freezing more effective than flash freezing as forming ice crystal disrupt the cells, thawing more damaging than freezing
  3. Freeze drying. Long term preservation, decreases water availability
24
Q

Describe how filtration suppresses microbial growth

A

HEPA - removes microbes > 0.3 um
Membrane filtration removes microbes > 0.22 um
Does NOT inactivate any existing metabolic products (toxins)
Will not remove viruses

25
Q

Describe the steps of making a disk diffusion plate?

A
  1. Inoculate surface with bacteria
  2. Add disc with inhibitor /antibiotic
  3. Incubate to allow bacteria to grow while inhibitor diffuses out into medium
26
Q

What is the importance of phenols and phenolics?

A

They disrupt the plasma membranes

Exert antimicrobial activity by injuring lipid containing plasma membranes - leakage of cellular contents

27
Q

What is the importance of bisphenols?

A

Important ones are hexacholorophene and triclosan. They disrupt the plasma membranes

28
Q

What is the importance of biguanides?

A

They can refer to a molecule, or to a class of drugs based upon a molecule with amine groups that are involved
Acts on membranes by blocking lipid synthesis and disrupting plasma membranes
Often used in combination with other agents
Antiseptic uses
Disinfectant uses
Preservative uses

29
Q

Describe quats and their importance.

A

Quarternary ammonium compounds
Effective against bacteria, fungi, viruses (enveloped and non) and emoebae
Do not kill endospores or mycobacterium
Widely used in both the home an industry

30
Q

Identify the appropriate uses for the surface acting agents

A

Soap
Degerming (cleaning/washing)
Acid-anionic detergents
Quaternary ammonium compounds (cationic detergents)
Sanitising
Bactericidal, denature proteins, disrupt plasma membranes

31
Q

From most resistant to least resistant, name the microbes that influence control methods

A 
Prions
Endospores of bacteria
Mycobacterium
Cysts of Protozoa
Vegetative Protozoa
Gram negative bacteria
Fungi, including most fungal spores
Viruses without envelopes
Gram positive bacteria
Viruses with lipid envelopes
All depends on the presence of membranes being disrupted and the resistance of the membrane on what is trying to get through
32
Q

What are asceptic techniques?

A

A set of practices and procedures performed under carefully controlled conditions with the aim of minimising contamination by unwanted pathogens or cells
Eg. Culturing microorganisms, cell structure, surgery, wound care etc

33
Q

What is the importance of Ehrlich?

A

Came up with the concept that different organisms have different types of cells and therefore should have unique drug targets within those cells. That’s the magic bullet idea - kill an invading pathogen, but leave us humans alive

34
Q

What is the importance of Fleming/ Florey and Chain?

A

Fleming - Discovered the most famous magic bullet, penicillin
Florey and Chain - were able to develop this for use in the Second World War. Modern antibiotic era was born

35
Q

Define broad spectrum and narrow spectrum.

A

In relation to antibiotics that affects a broad or narrow range of gram positive or gram negative bacteria. They are called broad spectrum antibiotics

36
Q

List the 5 antibiotic modes of action

A

Can affect 5 main targets

  1. Cell wall - inhibition of cell wall synthesis
  2. Membrane - injuring the plasma membrane
  3. Protein - inhibiting protein synthesis
  4. Nucleic acids - inhibiting nucleic acid synthesis, interfere with process of DNA replication
  5. Essential metabolite. Competitively inhibited by a substance that closely resembles normal substrate for the enzyme

Microbiology (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions