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Infectious Disease and Microbiology > Microbial Growth Control > Flashcards

Microbial Growth Control Flashcards

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1
Q

_______ are routinely used to control microbial growth

A

chemicals

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2
Q

antimicrobial agent

A

natural or synthetic chemical that kills or inhibits the growth of microorganisms

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3
Q

Agents that kill organisms are called_____

A

cidal agents

-prefix indicates type of organism killed

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4
Q

agents that dont kill but only inhibt growth are called____

A

static

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5
Q

antimicrobial agents can differ in their

A

selective toxicity

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6
Q

_______ agents are _____ toxic for _____ than for _____ tissues

A

selective, more, microorganisms, animal

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7
Q

antimicrobial agents with selective toxicity are especially useful for treating infectious diseases because

A

they kill selected microorganims in vivo without harming the host

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8
Q

antibacterial agents can be classified as

A

bacteriostatic, bactericidal and bacteriolytic

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9
Q

viable cells are measured by

A

plate counts

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10
Q

bacteriostatic agents are frequently

A

inhibitors of protein synthesis

-act by binding to ribosomes

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11
Q

Bacteriocidal agents

A

bind tightly to their cellular targets, arent removed by dilution, and kill cells

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12
Q

some cidal agents are also

A

lytic agents

-kills by cell lysis and release of cytoplasmic contents

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13
Q

lysis_____ the_____ _____ _______ and the _____ _____ _____ shown by a ________ in _______ ______

A

lysis decreases the viable cell number and also the total cell number shown by a decrease in culture turbidity

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14
Q

bacteriolytic agents include

A

ATB that inhibit cell wall synthesis

-such as Penicillin

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15
Q

How many phases is the typical growth curve for population of cells grown in a closed system characterized by?

A

Four

-lag phase, exponential phase, stationary phase, death phase

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16
Q

lag phase

A

interval between when a culture is inoculated and when growth begins

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17
Q

exponential phase

A

cells in this phase are typically in the healthiest state

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18
Q

stationary phase

A

either an essential nutrient is used up or waste product of the organism accumulates in the medium

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19
Q

death phase

A

if incubation continues after cells reach stationary phase the cells will eventually die

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20
Q

What establishes the relationship between viable and total cell counts?

A

The turbidity of each culture coupled with viable plate counts

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21
Q

antimicrobial activity

A

measured by determining the smallest amount of an agent needed to inhibit the growth of a microorganism (MIC)

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22
Q

Minimum Inhibitory Concentration (MIC)

A

lowest concentration of agent that completely inhibits the growth of the test organism (Tube dilution technique)

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23
Q

To determine the MIC for a given agent against a given organism

A

a series of culture tubes is prepared and inoculated with the same number of microorganisms
-each tube contains medium with increasing concentration of the agent

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24
Q

turbidity

A

visible growth

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25
Q

MIC varies with

A

organism used, inoculum size, composition of culture medium, incubation time and condition of incubation (temp, pH and aeration)

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26
Q

disc diffusion technique

A

common assay for antimicrobial activity

  • petri dish containing an agar medium inoculated with a culture test organism
  • known amount of antimicrobial agent added to filter paper discs
  • agent diffuses from disc into agar establishing gradient
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27
Q

The_________ the chemical diffuses away from the filter paper the ______ the concentration of the gradient

A

farther, lower

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28
Q

zone of inhibiton

A

created with a diameter proportional to the amount of antimicrobial agent added to the disc, the solubility of the agent the diffusion coefficient and the overall effectiveness of the agent

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29
Q

What technique is routinely used to test pathogens for ATB susceptibility?

A

disc diffusion technique

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30
Q

Two categories chemical antimicrobial agents for external use divided into

A
  • Products used to control microorganisms in commercial and industrial applications
  • Products designed to prevent growth of human pathogens in inanimate environments and on external body surfaces
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31
Q

Sterilants, disinfectants, sanitizers

A

decontaminate nonliving materials

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32
Q

antiseptics and germicides

A

to reduce microbial growth on living tissues

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33
Q

sterilants

A

destroy all forms of microbial life including endospores

-chemical sterilants (sterilizers or sporocides)

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34
Q

Sterilants are used in situations where

A

it is impractical to use heat or radiation for decontamination or sterilization

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35
Q

Cold sterilization

A

performed in enclosed devices which employ a gaseous chemical agent such as Ethylene Oxide (EO)
-alkylating agent that disrupts DNA

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36
Q

Liquid sterilants are used for

A

instruments that cant withstand high temperatures or gas

-Sodium hypochlorite (bleach)

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37
Q

disinfectants

A

chemicals that fill microorganisms but not necessarily endospores and are used on inanimate objects

  • disinfectants such as ethanol and cationic detergents used to disinfect
  • alcohol (EtOh or isopropanol 70% in water), NaClO 5-8% (bleach)
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38
Q

sanitizers

A

agents that reduce but may not eliminate microbial numbers to levels considered safe without adversely affecting quality of product or its safety

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39
Q

antiseptics and germicides

A

chemical agents that kill or inhibit growth of microorganisms and are nontoxic enough to be applied to living tissues, components used for hand washing or for treating surface wounds

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40
Q

antimicrobial efficacy

A

several factors affect the efficacy of chemical antimicrobial
-many disinfectants are neutralized by organic material

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41
Q

Only _____ are effective against _______ endospores

A

sterilants, bacterial

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42
Q

Mycobacterium tuberculosis is resistant to

A

action of common disinfectant because of the waxy nature of the cell wall

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43
Q

antimicrobial drugs are classified based on their

A

molecular structure, mechanism of action, spectrum of antimicrobial activity

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44
Q

What are the two broad categories antimicrobial agents fall into?

A

Synthetic agents and antibiotics

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45
Q

Synthetic antimicrobial drugs

A

growth factor analogs:salvarsan, isoniazid
nucleic acid base analogs: fluorouracil, bromouracil
quinolones: ciprofloxacin

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46
Q

naturally occuring antimicrobial drugs: antibiotics

A

beta-lactam antibiotics: penicillin and cephalosporins

antibiotics from prokaryotes : amynoglicocides, macrolides, tetracyclins, daptomycins, platensimycin

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47
Q

Cell wall synthesis

A

cycloserine, vancomycin, bacitracin, penicllins, cephalosporins, monobactams, carbapenems, amoxicillin

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48
Q

DNA gyrase

A

nalidixic acid, ciprofloxacin, novobiocin

49
Q

RNA elongation

A

Actinomycin

50
Q

DNA directed RNA polymerase

A

Rifampin, streptovaricins

51
Q

Protein synthesis

50S inhibitors

A

Erythromycin (macrolides)
Chloramphenicol
Clindamycin
Lincomycin

52
Q

Folic acid metabolism

A

Trimethoprim

Sulfonamides

53
Q

Cytoplasmic membrane

structure and function

A

Polymyxins

Daptomycin`

54
Q

Protein synthesis

30S inhibitors

A 
Tetracyclines
Spectinomycin
Streptomycin
Gentamicin
Kanamycin
Amikacin
Nitrofurans
55
Q

lipid biosynthesis

A

platensimycin

56
Q

Protein synthesis

tRNA

A

mupirocin, puromycin

57
Q

each antimicrobial agent

A

affects a limited and well-defined group of microorganism

58
Q

Systematic work on Antimicrobial Drugs was first initiated by

A

paul ehrlich
-Nobel prize wining,
German, physician, scientist)
-selective toxicity

59
Q

selective toxicity

A

ability of a chemical agent to inhibit or kill a pathogen microorganisms
without adversely affecting the host

60
Q

salvarsan

A

one of the first antimicrobial drugs, an Arsenic-containing compound
used for the treatment of syphilis (T. pallidum), was the most successful
-adminstered intramuscularly

61
Q

growth factor analogs (GFA)

A

specific chemical substances
required in the medium because the organism can
not synthesize them
-structurally similar to growth factors but do
not function in the cell
-GFA disrupts cell
metabolism
-used in the treatment of viral and fungal
infections and as mutagens

62
Q

sulfa drugs

A

discovered by Gerhard Domagk in the 1930s

-selectively toxic in bacteria because they synthesize their own folic acid

63
Q

Sulfanilamide blocks the synthesis of _____ thereby inhibit __________ synthesis

A

folic acid, nucleic acid

64
Q

isoniazid

A 
Growth Factor Analog
effective only against Mycobacterium
-Interferes with synthesis of Mycolic acid,
a mycobacterial cell wall component
-most effective single
drug used for control and treatment
of TBC
65
Q

Nucleic acid base analogs have been formed by

A

the addition of Bromine or Fluorine atoms

66
Q

fluorine

A 
relatively small atom and
does not alter the overall shape of the
nucleic acid base
-changes the
chemical properties so compound does not function in cell
metabolism
-blocks nucleic acid
synthesis
67
Q

quinolones

A

antibacterial compounds that interfere with bacterial DNA gyrase (Ciprofloxacin), prevents the supercoiling of DNA, a required step for packing DNA in the
bacterial cell.

68
Q

DNA ______ is found in ____ bacteria

A

gyrase, ALL

69
Q

________ are effective for treating

both _______ and ________, bacterial infections.

A

Fluoroquinolones, Gram-positive, Gram-negative

70
Q

Fluoroquinolones such as Ciprofloxacin (Cipro) are used to treat

A

uncomplicated UTI
(Urinary Tract Infections), acute bacterial sinusitis, acute bacterial exacerbation of chronic
bronchitis when no other treatments options are available
-drug of choice for treating anthrax

71
Q

Moxifloxacin has been approved for treatment of

A

resistance strains of TBC, Mycobacterium

tuberculosis

72
Q

_______ are naturally produced _______agents produced by microorganisms

A

Antibiotics, antimicrobial

73
Q

natural ATB can often be modified to enhance

A

efficacy (semisynthetic)

74
Q

Who invented penicillin?

A

Alexander Fleming discovered it

75
Q

b-Lactam antibiotics

A

one of the most important
groups of antibiotics of all time.
– Include Penicillins, Cephalosporins, and Cephamycins,
-share a characteristic structural component,
the b-lactam ring

76
Q

penicillin

A

Discovered by Alexander Fleming, 1928
– Primarily effective against Gram-positive bacteria
against Staphylococcal and Pneumococcal infection
– Some synthetic forms are effective against some Gram-
Negative bacteria (Ampicillin, Carbenicillin),
– The structural differences in the N-acyl group allow
them to be transported inside the Gram-negative outer
membrane, where they inhibit cell wall synthesis.
– b-Lactam ATB are inhibitors of cell wall synthesis
– Penicillin binds to transpeptidase enzymes inhibiting the
transpeptidation process (cross-linking of two glycanlinked
peptide chains).
– Some individuals develop allergies to b-Lactam ATB

77
Q

Cephalosporins

A
  • beta-lactam ATB
  • produced by fungus cephalosporium
  • same mode of action as penicillins
  • clinically semisynthetic ATB with broader spectrum of ATB
  • typically more resistant to beta-lactamases
78
Q

What are cephalosporins commonly used to treat?

A

gonorrhea infections

79
Q

For the treatment of Gonorrhea CDC recommends

A

dual therapy

-single dose of 250 mg intramuscular ceftriaxone and 1g of oral Azithromycin (bacterial protein inhibitor)

80
Q

ATB affecting

A

protein synthesis
-Many ATB inhibit protein synthesis by
interacting with the ribosome and
disrupting translation

81
Q

streptomycin inhibits

A

protein chain initiation

82
Q

Puromycin, Chloramphenicol,
Cycloheximide and Tetracycline
inhibit

A

protein chain elongation

83
Q

some ATB specifically inhibit

A

Transcription by inhibiting RNA synthesis

84
Q

Rifampin inhibit RNA synthesis by

A

binding to the β-subunit of

RNA polymerase, also used for the treatment of Tuberculosis

85
Q

aminoglycosides are

A

ATB that contain amino sugars bonded by glycosidic linkage

  • streptomycin: Kanamycin, Netilmicin, Neomycin, Gentamacin, Amikacin
  • target the 30S subunit of the ribosome: inhibits protein synthesis
  • clinically useful against gram-negative bacteria
86
Q

What was the first effective ATB used for the treatment of Tuberculosis (TB)?

A

Streptomycin

87
Q

Both Kanamycin and Streptomycin are synthesized by

A

Streptomyces species

88
Q

macrolides

A

contain lactone rings bonded to sugars

  • large number of macrolide ATB
  • erythromycin best known
89
Q

erythromycin

A

broad spectrum antibiotic
-targets 50S subunit of bacteria ribosome
-inhibits protein synthe
-used in place of penicillin
-only antibiotic ophthalmic ointment recommended for use in
neonates for prophylaxis of Gonococcal

90
Q

Erythromycin is particularly useful for treatment of

A

Legionellosis

91
Q

tetracyclines

A

produced by several species of Streptomyces, are an important group
of ATB
-inhibits almost all Gram-positive and Gram-negative
Bacteria
-basic structure consist of a Naphthacene ring system
-protein synthesis inhibitor , interferes with bacterial 30S ribosome subunit function

92
Q

tetracyclines and b-lactam ATB comprise

A

two most important

groups of ATB in the medical field

93
Q

daptomycin

A
  • produced by streptomyces
  • cyclic lipopeptide ATB
  • used mainly to treat gram + bacteria
94
Q

platensimycin

A 
first member of a new structural class of ATB
-produced by streptomyces platensis
95
Q

antiviral drugs

A

viruses use their eukaryotic host to reproduce and perform metabolic functions, most
antiviral drugs also target host structures, resulting in host toxicity

96
Q

Nucleoside Reverse Transcriptase Inhibitors (NRTI)

A

antiviral agents

97
Q

protease inhibitors (PI)

A

drugs prevents viral replication by
binding the active site of HIV protease
-prevents virus maturation

98
Q

enfuvirtide

A

fusion inhibitor

  • composed of 36-amino acid synthetic peptide
  • binds to gp41 membrane protein
99
Q

What are the two categories of drugs that successfully limit influenza infection?

A

adamantanes: amantadine and rimantadine, synthetic amines that interfere with an influenza A ion transport protein
neuraminidase inhibitors: block the active site of neuraminidase in
Influenza A and B viruses, inhibiting virus release form infected cells.

100
Q

________ are ______ useful than the ______ inhibitors

because resistance to Adamantanes develops rapidly in strains of influenza virus

A

Adamantes, less, Neuraminidase

101
Q

interferons

A

small proteins in the cytokine family that prevent viral multiplication by
stimulating antiviral proteins in uninfected cells

102
Q

Interferons are produce in 3 molecular forms:

A

IF-α (leukocytes), IF-β (fibroblasts), IF-γ (activated lymphocytes)

103
Q

antifungal drugs

A

Fungi pose special problems in terms of treatment because Fungi and Humans are Eukaryotic organisms

104
Q

membrane functions

A

Polyenes bind to
Ergosterol and disrupt
membrane integrity

105
Q

Cell wall synthesis:

A

Polyoxins inhibit Chitin (a long-chain polymer of a N-acetylglucosamine) synthesis
Echinocandins inhibit Glucan (a polysaccharide of D-glucose monomers) synthesis

106
Q

Ergosterol synthesis:

A

Azoles and Allylamines

inhibit synthesis

107
Q

Nucleic acid synthesis:

A

5-Fluorocytosine is a nucleotide
analog that inhibits nucleic
acid synthesis

108
Q

Microtubule formation:

A

Griseofulvin disrupts
microtubule aggregation
during mitosis

109
Q

Ergosterol

A

sterol found in fungi.

It is not present in plant or animal cells

110
Q

Ergosterol inhibitors

A

target the unique fungal plasma membrane component Ergosterol

111
Q

polyenes

A

a group of ATB produce by Streptomyces

-Bind to ergosterol, disrupting membrane function

112
Q

azoles and alylamines

A

synthetic agents that selectively inhibit Ergosterol biosynthesis and therefore have broad antifungal activity.

113
Q

Echinocandins:

A

for systemic fungal infections in immunocompromised patients.
– Inhibit 1,3 b-D glucan synthase (not present in mammals)
-Used to treat Candida albicans and C. auris infections

114
Q

Antimicrobial drug resistance:

A

acquired ability of a microorganism to resist the effects of a chemotherapeutic
agent to which it is normally susceptible

115
Q

Most drug-resistant bacteria isolated from patients contain

A

drug-resistance genes located on R plasmids

116
Q

Resistance is typically due to

A

Genes on the R-factor plasmid that encode enzymes that modify and
inactivate the drug or genes that encode enzymes the prevent the uptake of the drug or actively
pump it out.

117
Q

r plasmid

A

genes encode enzymes that
modify and inactivate the drug or genes that encode enzymes that prevent
uptake of the drug or actively pump it out

118
Q

saquinavir

A

Binds to active site of HIV protease enzyme

119
Q

Bacteriophage therapy

A

the therapeutic use of bacteriophages to treat pathogenic bacterial
infections

Infectious Disease and Microbiology (9 decks)

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