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Microbiology > Lecture 7 > Flashcards

Lecture 7 Flashcards

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Biology 101 flashcards
1
Q

What is binary fission?

A

Asexual reproduction in unicellular organisms in which a single cell divides to form two new cells.

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2
Q

Describe bacterial growth in the lag phase.

A

Also called inoculum–bacteria resumes growth slowly over 0 to 5 hours.

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3
Q

What step comes after the lag phase? Describe it.

A
  • The exponential phase
  • lasts from hour 5 to 10
  • rapid growth occurs here
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4
Q

When is the stationary phase entered?

A

When foodstuff is exhausted or toxic material accumulates, they enter the stationary phase (hour 10 onward). During this phase, bacterial cultures may lose their viable count (often without losing cell integrity–maintaining a constant total count).

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5
Q

What is the generation time for Meningococcus in CSF?

A

25 minutes

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6
Q

What is generation time in Mycobacteria in the alveoli?

A

24 hours

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7
Q

What is the phase of bacterial growth decrease called?

A

The stationary phase

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8
Q

How often can bacteria readily increase in number by 100 million fold?

A

24 hours

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9
Q

What is an invasive infection?

A

The explosiveness of exponential growth means that even a small number of bacteria can rapidly initiate an invasive infection.

Ex: Meningococci grow so quickly in a child’s CSF that the physician must intervene with great speed to avoid a fatal outcome of acute bacterial meningitis.

However, Mycobacteria divide every 24 hours–the disease is chronic and takes a considerable time to be manifested.

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10
Q

A very short generation time and huge numbers of bacteria mean what?

A

Mutations in the bacteria are a more significant means of adaptation.

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11
Q

Cessation of growth of some bacterial species (Clostridium) initiates what?

A

Sporulation

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12
Q

Dipicolinic acid in the core means the bacteria has what characteristic?

A

It is highly resistant to physical stresses (heat, bactericidal agents)

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13
Q

During sporulation, the “mother cell” does what?

A

It lyses

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14
Q

During the germination of spores, what is in the cytoplasmic contents?

A

It is released containing large amounts of toxins (tetanus, botulism, gas gangrene)

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15
Q

Can bacteria cause damage to their host even when they are not growing? Explain.

A

Yes.

  • They are still immunogenic and can elicit immune responses with beneficial and detrimental results
  • Production of toxins (hemolysis in gram + bacteria) often starts or accelerates when bacteria enter the stationary phase.
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16
Q

What do gram negative bacteria release?

A

OM-associated LPS (endotoxin) into the circulatory system it has cascade effects causing sepsis

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17
Q

Is inflammation good locally or systemically?

A

Locally only–systemic is deadly

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18
Q

How is sterilization defined?

A

The complete absence of life or of viable, growing organisms.

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19
Q

What is sterilization needed for?

A

Necessary for surgical garments, instruments, media, bacteriological glassware, etc.

20
Q

What kind of equipment can’t be sterilized?

A

heat sensitive equipment (fiberoptic scopes)

21
Q

What is an autoclave?

A

The best and easiest method for sterilizing reagents and tools

22
Q

What are the two types of autoclaves?

A
  • bench top autoclave (small labs)

* walk in autoclave (large companies)

23
Q

What can slow exhaust autoclaves sterilize?

A

liquids

24
Q

What can fast exhaust autoclaves sterilize?

A
  • glassware

* instruments

25
Q

What temperature, PSI, and length of time should an autoclave run?

A
  • Temp at 121
  • PSI at 15
  • 15 minutes
26
Q

Why is steam under pressure used for sterilization?

A

Steam helps distribute heat which kills bacteria more efficiently when moist.

27
Q

What type of kinetics does sterilization (steam under pressure) follow?

A

Time-kill kinetics (time dependent and initial bacterial load dependent)

28
Q

In sterilization, what is filtration?

A

It is the limiting of the pore size small enough to catch all pathogens

29
Q

In sterilization, radiation is good for what?

A

It may be a dangerous source material but may be good for foods.

30
Q

What is disinfection?

A

Implies the killing or removal of potentially pathogenic organisms which contaminate skin, surfaces, instruments.

Also defined as the use of antimicrobial agents to destroy microorganisms.

31
Q

How can disinfection be achieved?

A

By chemical means mostly

32
Q

Which is more effective, disinfection or sterilization?

A

Sterilization

33
Q

What is pasteurization?

A

It disinfects at 65C so it does not destroy taste of food.

34
Q

In a large plant, what temperature and time is milk put through disinfection?

A

In large plants 161F for 15 seconds. (flash pasteurization that kills microbes)

In small plants 145F for 30 minutes.

35
Q

Why is disinfection necessary?

A

To treat foods to get rid of microbial spores or other infections. It is to control pathogens to control infections.

36
Q

How do alcohols act as a disinfectant?

A

Primary action is disruption of cell membranes.

37
Q

How do detergents act as a disinfectant?

A

Surface active agents disrupt cell membranes.

38
Q

How do phenols act as a disinfectant?

A

They act as cell membrane and protein denaturant.

39
Q

How do halogens act as a disinfectant?

A

They are oxidizing agents that are particularly effective against sulfhydryl groups of proteins.

40
Q

How do heavy metals act as a disinfectant?

A

These agents bind to sulfhydryl groups of bacterial proteins, blocking enzyme activity.

41
Q

How does hydrogen peroxide act as a disinfectant?

A

They are potent oxidizing agent, but less effective against bacteria rich in catalase.

42
Q

How do formaldehyde and glutaraldehyde act as a disinfectant?

A

They are potent alkylating agents, particularly of NH2 and OH groups on proteins and nucleic acids.

43
Q

How does ethylene oxide act as a disinfectant?

A

It is a potent alkylating agent, but in gaseous form. It is probably second to autoclaving in popularity but used for heat sensitive materials such as plastics and tubing (heat sterilization would destroy the product, so this is used instead).

44
Q

Chlorhexidine belongs to what group of chemical disinfectants? What is it used for?

A
  • Antiseptic antibacterial agents
  • It is used to clean the skin after an injury, before surgery, or before an injection
  • used to clean hands before a procedure
  • works by killing or preventing the growth of bacteria on the skin
45
Q

Production of exotoxins and other toxic byproducts from bacterial metabolism is accelerated when bacteria enter which of the following phases of growth?

A

Stationary phase

46
Q

Which disinfectant would be most appropriate to use in the sterilization of heat sensitive medical equipment?

A

Ethylene Oxide

47
Q

To effectively and safely pasteurize milk products, large milk processing plants will heat large vats of raw milk at _____ F for _____ time.

A
  • 161 F

* 15 seconds

Microbiology (10 decks)

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