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Introductory Microbiology > Microbial Control > Flashcards

Microbial Control Flashcards

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1
Q

What is sterilization

A

The killing or removal of ALL viable organisms ( including endospores)

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2
Q

Is clean and sterilized is the same

A

Hands can be clean, but not sterile

The cloth coming from autoclave can be dirty, but sterile

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3
Q

What is inhibition

A

Effectively limit microbial growth. We are not necessarily killing them. We just stop them from multiplying

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4
Q

What is decontamination

A

The treatment of an object to make it safe to handle ( removing food from the table)

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5
Q

What is disinfection

A

Directly targets the removal of all pathogens, not necessarily all microorganisms

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6
Q

Physical methods for antimicrobial control

A

Heat
Radiation
Filtration

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7
Q

Chemical methods for killing microbes are also called

A

Antimicrobes

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8
Q

What antimicrobes are used on external surfaces and internally

A

External: sterilants,disinfectants, antiseptics
Internally: antibiotics,antiviruls,antifungals

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9
Q

What is the most widely used physical control for controlling microorganisms

A

Heat

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10
Q

High temperatures ___ macromolecules

A

Denature

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11
Q

What is decimal reduction time?

A

Amount of time required to reduce viability tenfold ( from 100% to 10%)

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12
Q

The decimal reduction time is ___ correlated with the temperature

A

Inversely

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13
Q

The time necessary to kill a defined fraction is dependent of ____

A

The initial cell concentration

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14
Q

What will be the difference in decimal reduction time between mesophile and thermophile

A

Mesophile will have lower decimal time at lower temperatures, comparing to thermophile

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15
Q

What is the thermal death time

A

the time needed to kill all cells at a given temperature.

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16
Q

Thermal death time depends on

A

The population size of the microorganism tested, so you need to standardize the starting number of cells to be able to compare the sensitivity of different microorhanisms

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17
Q

What is the issue with endospores

A

They can resist the temperatures that will kill microorganisms. 5 min in boiling water for a decimal reduction

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18
Q

What is the autoclave

A

A sealed device that uses steam under pressure. it allows temperature of water to get above 100 C without boiling

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19
Q

What is the time and temperature for sterilization in autoclave

A

121 C in 10-15 minutes

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20
Q

What kills the microorganism in the autoclave

A

Not the pressure, but the temperature

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21
Q

What should you remember with autoclave and big objects

A

The object is a little colder than the environment and thus more time is required

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22
Q

What is Pasteurization

A

The process of using precisely controlled heat to reduce the microbial load in heat-sensitive liquids. It does not kill all microorganisms

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23
Q

What is the purpose of pasteurization?

A

Reduces the microbial load, increases the shelf life of the product

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24
Q

Pasteurization reduces what kinds of pathogens

A 
Listeria monocytogenes
Salmonella enterica
Campylobacter
E.coli
Mycobacterium
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25
Q

The time and temperature for flash and bulk pasteurization

A

Flash: 72 C for 15 sec
Bulk: 65 C , 30 min

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26
Q

The principle of pasteurization

A

At first it is heated for a short period of time and then quickly cooled. Can be heated more for the milk that will undergo further processing

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27
Q

What radiation can reduce microbial grwoth

A 
Microwaves
UV
X-rays
gamma rays
electrons
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28
Q

What does UV do to microorganisms

A

UV has enough energy to cause modifications and breaks in DNA, which inhibit replication, transcription and cause death

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29
Q

What is the barrier for UV light

A

Cannot penetrate solid,opaque or light-absorbing surfaces. Can sterilize only the top layer

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30
Q

UV light is useful for sterilization of

A

Water and Air

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31
Q

What is ionizing radiation

A

-Electromagnetic radiation that produces ions and other reactive molecules

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32
Q

How ionizing radiation stop the growth of microorganisms

A

Generates electrons and hydroxyl radicals that cause damage to DNA and proteins

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33
Q

What emits electrons and gamma rays

A

Electrons by cathode ray tubes

Gamma rays by radioisotopes

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34
Q

What rays have the highest energy

A

Gamma rays

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35
Q

What is specific about Deinococcus radiodurans

A

It does not have spores

But it has multiple copies of its genome, so as soon as one copy get damaged or destroyed, it has back up

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36
Q

Filtration is used on

A

Sensitive liquids and gases

Pores of filter are too small for organisms, but big enough for liquids and gases

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37
Q

What is depth filters

Where it is used and examples

A

Fibrous sheet or mat made from an array of fiber ( paper or glass)
Used to sterilize liquid,air
HEPA filters

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38
Q

Mmebrane filters: what is it and how it can be speeded up

A

It functions like a sieve. it has nucleopores as a filter. Can be speeded up by syringe, pump, or vacuum

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39
Q

Antimicrobial agents can be classified as

A
  • Bacteristatic: inhibit growth of microorganisms
  • Bacteriocidal: kill microorganisms
  • Bacteriolytic: kill microorganism by inducing lysis
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40
Q

What is MIC

A

Minimum inhibitory concentration - the smallest amount of an agent needed to inhibit growth of a organism

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41
Q

What is MLC

A

Minimum lethal concentration- the lowest concentration of an agent that kills a test organism

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42
Q

What is MBC

A

Minimum bacteriocodal concentration - the lowest concentration of an agent that kills a test bacterium

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43
Q

To see MBC we need to

A

to plate on agar to see the growth

44
Q

What is disc diffusion assay

A

Antimicrobial agent added to filter paper disc. MIC is reached t some distance from the disc

45
Q

What is the zone of inhibition

A

Area of no growth around the disc

46
Q

What kind of method is disc diffusion assay

A

Semiquantitative way

The bigger the zone of inhibition-> the more susceptible to the agent

47
Q

What does it mean superficial bacterial infections

A

outside of the body, on the skin

48
Q

Two categories of the antimicrobial agents

A

Products used to control microorganisms in commercial and industrial applications ( air-conditioning,textile,etc.)
-Products designed to prevent growth of human pathogens in inanimate environments and on external body surfaces

49
Q

What is a sterilants

A

They destroy all forms of microorganisms, including endospores. Called COLS STERILIZATION in contrast to autoclave

50
Q

What is disinfectants/sanitizers

A

Applied to nonliving objects or surface( can be toxic for animals/humans). Do not kill endospores

51
Q

What is antiseptic

A

Applied tot the surface of living tissues or skin. Do not kill endospores

52
Q

What is antimicrobial drugs

A

Antibiotics, antifungals: applied outside or inside the body of animals/humans. DO not kill endospores

53
Q

Phenol/phenolics are (D/A/S) and how they work

A

D, A

Disrupt cytoplasmic membrane, protein denaturant( in high concentration)

54
Q

Alcohols are (D/A/S) and how they work

A

D,A

Lipid solvent and protein denaturants

55
Q

Halogens are (D/A/S) and how they work

A

Chloride (S,D): oxidizing agent

Iodine(A): iodinate tyrosine residues in protein, oxidizing agent

56
Q

Heavy metals are (D/A/S) and how they work

A

D

Modify proteins, interact with RNA,DNA.

57
Q

Quaternanry ammonium is (D/A/S) and how they work

A

D,A

Interact with phospholipids of cytoplasmic membrane

58
Q

Alkylating agents are (D/A/S) and how they work

A

D,S
Formaldehyde
Very toxic

59
Q

Antimicrobial drugs are classified on the basis of

A
  • Molecular structure
  • Mechanism of action
  • Spectrum of antimicrobial activity
60
Q

Antimicrobial drugs should have what action in microorganisms

A

Batceriostatic or batceriocidal

Usually have a specific target

61
Q

A good antimicrobial drug has

A
  • No severe side effects, must be far more toxic for the microorganism than mammalian cells
  • Low risk/benefit ration
  • Broad stectrum of activity to facilitate rapid medical intervention
  • Appropriate bioavaialbility and pharmacokinetics ( must reach the site of infection)
  • Low cost to develop and manufacture
62
Q

What are the targets for antimicrobial drugs

A
  • Cell wall synthesis
  • DNA gyrase (topoisomerase)
  • RNA elongation
  • DNA-directed RNA polymerase
  • Protein synthesis (50 S inhibition or 30 S)
  • Protein synthesis (tRNA)
  • Lipid biosynthesis
  • Cytoplasmic membrane structure and function
  • Folic acid metabolism
63
Q

Fungi, bacteria and viruses have different ___

A

Antimicrobial drugs

64
Q

The drug with the broadest spectrum of action on bacteria

A

Tetracycline (obligatory parasytic and normal bacteria)

65
Q

What is synthetic antimicrobial drugs

A

Invented in the lab

66
Q

Selective toxicity is

A

The ability to inhibit or kill a pathogen without affecting the host

67
Q

Who studied selective toxicity and the first antimicrobial drug made

A

Paul Ehrlich in early 1900s

Salvarsan- used to treat syphilus

68
Q

What are growth factor analogs

A

Structurally similar to growth factors but not function in the cell

69
Q

What is used a growth factor analog for folic acid

A

Sulfanilamide. It is analogous for p-aminobenzoic acid, Inhibits folic acid synthesis. Bacteriostatic

70
Q

Sulfa drugs were discovered by and when

A

Gerhard Domagk

1930s

71
Q

What are isoniaxid

A

A grwoth factor analog effective only against Mycobacterium. Interferes with synthesis of mycolic acid

72
Q

What are nucleic acid base analogs

A

Formed by the addition of bromide or fluorine. Stop DNA replication

73
Q

What are quinolones

A

They interfere with DNA gyrase (control DNA supercoiling). EX. ciprofloxacin

74
Q

What are antibiotics

A

Antimicrobial agents naturally produced by a variety of bacteria and fungi to inhibit or kill other microorganisms

75
Q

How can you modify antibiotics

A

To make them semisynthetic to increase efficiency

76
Q

Why gram positive and gram negative bacteria vary in their sensitivity to antibiotics

A

Because of the cell wall

77
Q

What are beta-lactams

A

One of the most important groups of antibiotics of all time. Include penicillins, cephalosporins, and cephamycins

78
Q

Who discovered penicillin and when

A

Alexander Fleming in 1928

Isolated from mold

79
Q

Penicillin is primarily effective against

A

Gram-positive bacteria. Some synthetic forms are effective against gram-negative bacteria

80
Q

How does penicillins work

A

It inhibits cell wall synthesis

81
Q

What is the important structure in penicillin

A

beta-lactam ring

82
Q

Methicillins are

A

Cnanged R griup from penicilin G to Methicillin.

It is acid stable and beta-lactamase resistant- the enzymes that destroy penicillin

83
Q

What other form of penicillin is resistant to beta-lactamase

A

Oxacillin

84
Q

What is special about Ampicillin

A

Broadened spectrum of activity ( especially against gram-positive bacteria), acid-stable, sensitive to beta-lactamase

85
Q

What is special about carbenicillin

A

Broadened spectrum of activity ( especially against Pseudomonas aeruginosa), acid-stable but ineffective orally, sensitive to beta-lactamase

86
Q

What are cephalosporins

A

Produced by the fungus
same mode of action as penicillins
Common to treat gonorrhea

87
Q

Explain in detail how penicillin works

A

transpeptidase is bound to b-lactam ring, which is broken, but it dissactivates transpeptidase

88
Q

Beta lactams are ( bacteristatic/lytic, etc.)

A

Bacteriocidal or bacteriolytic ( depends on species,etc.)

Can be bacteristatic ( in isotonic solution)

89
Q

The majority of antimicrobial drugs that are used clinically are coming from

A

Streptomyces

90
Q

Example of streptomyces: aminoglycosides

A
  • Target 30s subunit of the ribosome, cause misreading of mRNA
  • Batcericidal
91
Q

Example of streptomyces:Chloramphenical

A
  • Bind to 23S rRNA and block peptide elongation

- Bacteriostatic

92
Q

Example of streptomyces: Macrolides

A
  • Broad spectrum antibiotics that target 50s subunit of the ribosome, block protein synthesis
  • Bacteriostatic
93
Q

Example of streptomyces: tetracyclines

A
  • Broad-spectrum, bacteriostatic.

- Inhibit 30S ribosomal subunit, block protein synthesis

94
Q

What is antimicrobial resistance

A

-The acquired ability of microorganism to resist the effects of a chemotherapeutic agent to which it is normally sensitive

95
Q

Antibiotic producers are tolerant to ( how they are tolerant)

A
  • Lack target sites (no peptidoglycan)
  • Modify target sites
  • Lack of uptake mechanism
96
Q

Antibiotic resistant mechanism

A
  • Destruction or modification of the antibiotic ( beta-lactamase)
  • Modification of the target site
  • Modification of uptake mechanism
  • Efflux pumps: reduce intracelluar concentration
97
Q

how do we know that the bacteria acquired antibiotic resistant

A

By the acquisition of a new gene that provides the cell with a new function

98
Q

Where do most bacteria have antimicrobial gene

A

R plasmid

99
Q

R plasmids can be transferred between

A

The same species or related species

100
Q

Resistance can be minimized by

A

Using antibiotics correctly and only when needed ( reduce selection)

101
Q

What is the issue with antiviral drugs

A

They target host structures as well. Risk to the host may not justify the use of antiviral

102
Q

Most successful and commonly used antivirals are

A

The nucleoside analogs: block reverse transcriptase and production of viral DNA (RNA viruses)

103
Q

What do protease inhibitors do

A

Inhibit the processing of large viral proteins into individual components

104
Q

What are fusion inhibitors

A

Prevent viruses from successfully fusing with the host cell

105
Q

Why fungi pose a special problem for chemotherapy

A

Because they have cellular machinery as that of human and animals

106
Q

What drugs target fungi?

A
  • Ergosterol synthesis( Fluconazole)

- Cell wall synthesis( inhibitor if chitin synthesis)

Introductory Microbiology (21 decks)

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