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MIMM 211 > Lecture 32: Control of microorganisms > Flashcards

Lecture 32: Control of microorganisms Flashcards

1
Q

How many bacteria are estimated to be on Earth?

A

3^30

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2
Q

Rank the following items in terms of bacteria per square inch: hairbrush, kitchen floor, skin, kitchen sink, remote, sponge.

A

Least to most: remote, kitchen floor, hairbrush, kitchen sink, sponge, skin (by far the most!)

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3
Q

Why might the food industry want to control microorganisms?

A

Microbial infections caused by food can be costly for companies, and they also want to make sure that the produce can last and not spoilage due to bacterial and mould overgrowth.

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4
Q

Give 5 examples of bacterial pathogens that can contaminate food storage.

A

Salmonella, Listeria, E. Coli 0157, Campylobacter, Clostridium perfringens

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5
Q

Why might medicine and antimicrobial therapy require microorganismal control?

A

Need for a sterile environment for surgery and sterile instruments and devices. Control of airborne biohazards is necessary for immunocompromised hosts and to avoid nosocomial transmission of infections.

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6
Q

Why might environmental microbial control be necessary?

A

For potable and filtered water and for waste water management

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7
Q

What are the 4 methods that control microorganisms?

A

Antisepsis, sanitization, disinfection, and sterilization.

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8
Q

Rank the microorganismal control methods by effectiveness.

A

Antisepsis, sanitization, disinfection, and sterilization

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9
Q

How effective is antisepsis in killing bacterial pathogens (spores, non-pathogenic bacteria, and pathogenic bacteria)?

A

It reduces the microbial population, but some pathogens of all types may still survive.

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10
Q

What types of surfaces are involved in antiseptic microbial control methods?

A

It typically involves living tissues like skin and muscosa

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11
Q

Give 3 examples of antiseptic microbial control methods.

A

Mouthwash, skin antiseptic gels, and wipes

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12
Q

How effective is sanitization and disinfection in killing bacterial pathogens (spores, non-pathogenic bacteria, and pathogenic bacteria)?

A

It reduces the total microbial population to a safe public health standard by killing pathogens, but a few spores and non-pathogenic bacteria remain.

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13
Q

Give 2 examples of sanitization/disinfectants

A

Bleach and cleaners

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14
Q

How effective is sterilization in killing bacterial pathogens (spores, non-pathogenic bacteria, and pathogenic bacteria)?

A

All microoganisms and cells are killed including viruses and spores.

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15
Q

Give 4 examples of sterilization methods.

A

Heat, chemicals, radiation, and mechanically (filter).

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16
Q

What is the difference between bacteriostatic and bactericidal agents?

A

A bacteriostatic agent will halt growth without killing the bacteria, while a bactericidal agent will kill the bacteria.

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17
Q

Describe how the microbial population curve differs after the addition of a bacteriostatic drug and a bactericidal drug.

A

With the addition of a bacteriostatic drug, the population curve will stay at the same height. With the addition of a bactericidal drug, the curve will come down as all the bacteria die.

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18
Q

Describe an example of an exception involving the separation between bacteriostatic and bactericidal agents.

A

The separation between bacteriostatic and bactericidal agents doesn’t always hold true. A bacteriostatic agent at very high doses can have bactericidal effects. This can be the case for antibiotics that target replication.

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19
Q

Microbial death is usually measured on a […] scale.

A

Log

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20
Q

What is D value?

A

It is decimal reduction time. It is the amount of time required to have a log-fold reduced in microorganisms from 10^8 to 10^7. This is the amount of time required to kill 90% of microorganisms.

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21
Q

When comparing two antimicrobial agents, how can you determine which is more potent?

A

The one with a lower D50

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22
Q

Give 5 examples of influencing factors on the effectiveness of microbial control measures.

A
  • Microbial population size
  • Microbial composition
  • Concentration/potency of antimicrobial agents
  • Contact time
  • Temperature
  • Local environment: pH, organic matter
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23
Q

Among mold, viruses, bacteria, and prions, and their spores, which are the easiest and hardest to kill using a steam autoclave?

A

Easy to hard: bacteria, bacterial spores, mold, mold spores, viruses, viral spores (not killed) prions (never killed). Spores are always harder to kill than cells.

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24
Q

What are the 3 major categories of methods to control microorganisms? How are they best used?

A

Physical, mechanical, and chemical. It is common to combine several methods.

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25
Q

What type of control method is the steam autoclave? What level of control does it provide? Is it moist or dry?

A

Physical (heat-based), sterilization, moist

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26
Q

Explain how the autoclave works and what kinds of substances it sterilizes.

A

It uses steam at high pressure to sterilize liquids and solid materials. It can also kill spores above 121ºC

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27
Q

How long does it take to autoclave something?

A

15-30 mins depending on vol of material autoclaved

28
Q

Name a pro and a con of the autoclave.

A

Pro: efficient, simple, cheap, and produces no waste
Con: high pressure and humidity can damage materials

29
Q

Name 2 methods of quality control for autoclaving.

A

Geobaccilus spore biological indicator test or heat indicator strip to verify that the autoclave is still functioning correct.

30
Q

What type of control method is pasteurization? What level of control does it provide? Is it moist or dry?

A

Physical (heat-based), moist, disinfection

31
Q

What is pasteurization?

A

It is a disinfection method used for heat-sensitive products such as dairy products, eggs, wine, and beer

32
Q

How effective is pasteurization in killing bacteria?

A

It can kill non-spore forming pathogenic bacteria to reduce spoilage and risk of illness, but it does not sterilize

33
Q

What are the standard and high pasteurization settings?

A

Standard: 60ºC for 30 mins
High: 135-140ºC for 2-5 s

34
Q

Name 4 characteristics of food spoilage.

A
  • Visible growth of mould
  • Gas/odour production by overgrowth of microorganisms
  • Softening and rotting due to enzyme production and pigments
  • Growth of pathogenic bacteria such as Salmonella, E. coli, and Listeria
35
Q

What type of control of method is UV radiation? Is it ionizing or non-ionizing? What level of control does it provide?

A

Physical (radiation-based), non-ionizing, disinfection or sterilization

36
Q

How does UV radiation work?

A

It uses short-range UV-C to kill microorganisms at a short distance, but it cannot penetrate glass, plastic, or water well.

37
Q

How effective is UV radiation?

A

It can disinfect or sterilize depending on the dose, intensity, and distance from the UV source.

38
Q

Name a pro and a con of UV radiation.

A

Pro: no heat, physical, or chemical damage to products used.
Con: toxic to humans - necessitates eye and skin protection

39
Q

What types of substances is UV radiation used for?

A

Water, blood products, air, food, and beverages.

40
Q

What type of control method is gamma radiation? What level of control does it provide? Is it ionizing or non-ionizing?

A

Physical (radiation-based), disinfection or sterilization (moreso sterilization), ionizing

41
Q

How does gamma radiation work?

A

It uses biologically hazardous high frequency photons, as they can damage DNA and cell structures. It can penetrate glass and plastic and acts quickly.

42
Q

What is gamma radiation used for?

A

It is used in highly specialized sterilization facilities for medical supplies, pharmaceuticals, biologicals, and food products.

43
Q

What type of control method are antiseptics?

A

Chemical (liquid-based)

44
Q

How do antiseptics work?

A

They kill or inhibit microorganismal growth but does not sterilize.

45
Q

What type of surfaces are antiseptics typically used for?

A

Skin/tissue surfaces

46
Q

What type of control method is disinfectant?

A

Chemical (liquid-based or gas-based).

47
Q

How do disinfectants work?

A

They kill or inhibit the growth of microorganisms but do not sterilize.

48
Q

What types of surfaces are disinfectants used on?

A

Inanimate surfaces such as bathrooms or hospital equipment.

49
Q

Give 3 examples of disinfectants.

A

Bleach, chlorine, detergents, ethanol, etc…

50
Q

Are antiseptics and disinfectants specific or non-specific? Explain why.

A

Non-specific, as they are just generally toxic and disrupt cell function.

51
Q

Name the 4 categories of liquid antiseptics and disinfectants discussed and give an example for each.

A

Alcohols (ethanol), phenolics (Lysol), Aldehydes (gluteraldehyde), Halogens (bleach, chlorine)

52
Q

What is the mechanism of action for alcoholic antiseptics and disinfectants?

A

Denatures proteins, dissolves lipids in membrane

53
Q

What is the mechanism of action for phenolics and phenol derivative antiseptics and disinfectants?

A

They disrupt cell membrane and denature proteins

54
Q

What is the mechanism of action for aldehyde antiseptics and disinfectants?

A

They crosslink with nucleic acids and proteins to inactive them. They are very toxic.

55
Q

What is the mechanism of action for halogen antiseptics and disinfectants? What level of control do they provide?

A

They form hypochlorous acid (HOCl), which reacts with molecules by oxidation. This can sterilize at high concentrations, but are typically used as disinfectants. They are toxic.

56
Q

What type of control method is sterilization?

A

Chemical (gas-based)

57
Q

What are gas disinfectants and sterilizer used for?

A

They are useful for heat sensitive items.

58
Q

Give 2 examples of gas disinfectants/sterilizers?

A

Ethylene oxide and vaporized hydrogen peroxide.

59
Q

Explain the mechanism of action of ethylene oxide.

A

It has a highly reactive ring structure, so it reacts with nucleic acid and protein as a strong alkylating agent that can penetrate plastic. It is very toxic and flammable.

60
Q

Explain the mechanism of action of vaporized hydrogen peroxide.

A

It causes no damage to non living materials and has no toxic byproduct since it degrades to water and oxygen.

61
Q

Explain how liquid filtration systems work.

A

They involve the use of porous membranes for size exclusion. This allows for the sterilization of heat-sensitive liquids.

62
Q

In liquid filtration, what is the typical pore size? What types of microorganisms can that filter out? What is left behind and why?

A

<0.45-0.2 microns. This removes bacteria, fungi, and spores. It does not remove viruses, as they require a smaller pore size of <50 nm.

63
Q

What level of control does liquid filtration provide?

A

It sterilizes heat-sensitive liquids.

64
Q

Give an example of an air filtration system.

A

HEPA: High-efficiency particulate air filter.

65
Q

How big are the pores in air filtration systems?

A

0.1-0.3 microns

66
Q

What types of organisms can air filtration systems target?

A

It filters airborne fungi and bacteria (incl spores) and absorbs viruses.

67
Q

Where are air filtration systems typically used?

A

In biosafety cabinets, ventilation systems, and portable residential air filtration units.

MIMM 211 (38 decks)

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