Microbial Growth Control Flashcards
1
Q
_______ are routinely used to control microbial growth
A
chemicals
2
Q
antimicrobial agent
A
natural or synthetic chemical that kills or inhibits the growth of microorganisms
3
Q
Agents that kill organisms are called_____
A
cidal agents
-prefix indicates type of organism killed
4
Q
agents that dont kill but only inhibt growth are called____
A
static
5
Q
antimicrobial agents can differ in their
A
selective toxicity
6
Q
_______ agents are _____ toxic for _____ than for _____ tissues
A
selective, more, microorganisms, animal
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
8
Q
antibacterial agents can be classified as
A
bacteriostatic, bactericidal and bacteriolytic
9
Q
viable cells are measured by
A
plate counts
10
Q
bacteriostatic agents are frequently
A
inhibitors of protein synthesis
-act by binding to ribosomes
11
Q
Bacteriocidal agents
A
bind tightly to their cellular targets, arent removed by dilution, and kill cells
12
Q
some cidal agents are also
A
lytic agents
-kills by cell lysis and release of cytoplasmic contents
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
14
Q
bacteriolytic agents include
A
ATB that inhibit cell wall synthesis
-such as Penicillin
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
16
Q
lag phase
A
interval between when a culture is inoculated and when growth begins
17
Q
exponential phase
A
cells in this phase are typically in the healthiest state
18
Q
stationary phase
A
either an essential nutrient is used up or waste product of the organism accumulates in the medium
19
Q
death phase
A
if incubation continues after cells reach stationary phase the cells will eventually die
20
Q
What establishes the relationship between viable and total cell counts?
A
The turbidity of each culture coupled with viable plate counts
21
Q
antimicrobial activity
A
measured by determining the smallest amount of an agent needed to inhibit the growth of a microorganism (MIC)
22
Q
Minimum Inhibitory Concentration (MIC)
A
lowest concentration of agent that completely inhibits the growth of the test organism (Tube dilution technique)
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
24
Q
turbidity
A
visible growth
25
MIC varies with
organism used, inoculum size, composition of culture medium, incubation time and condition of incubation (temp, pH and aeration)
26
disc diffusion technique
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
27
The_________ the chemical diffuses away from the filter paper the ______ the concentration of the gradient
farther, lower
28
zone of inhibiton
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
29
What technique is routinely used to test pathogens for ATB susceptibility?
disc diffusion technique
30
Two categories chemical antimicrobial agents for external use divided into
- 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
31
Sterilants, disinfectants, sanitizers
decontaminate nonliving materials
32
antiseptics and germicides
to reduce microbial growth on living tissues
33
sterilants
destroy all forms of microbial life including endospores
| -chemical sterilants (sterilizers or sporocides)
34
Sterilants are used in situations where
it is impractical to use heat or radiation for decontamination or sterilization
35
Cold sterilization
performed in enclosed devices which employ a gaseous chemical agent such as Ethylene Oxide (EO)
-alkylating agent that disrupts DNA
36
Liquid sterilants are used for
instruments that cant withstand high temperatures or gas
| -Sodium hypochlorite (bleach)
37
disinfectants
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)
38
sanitizers
agents that reduce but may not eliminate microbial numbers to levels considered safe without adversely affecting quality of product or its safety
39
antiseptics and germicides
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
40
antimicrobial efficacy
several factors affect the efficacy of chemical antimicrobial
-many disinfectants are neutralized by organic material
41
Only _____ are effective against _______ endospores
sterilants, bacterial
42
Mycobacterium tuberculosis is resistant to
action of common disinfectant because of the waxy nature of the cell wall
43
antimicrobial drugs are classified based on their
molecular structure, mechanism of action, spectrum of antimicrobial activity
44
What are the two broad categories antimicrobial agents fall into?
Synthetic agents and antibiotics
45
Synthetic antimicrobial drugs
growth factor analogs:salvarsan, isoniazid
nucleic acid base analogs: fluorouracil, bromouracil
quinolones: ciprofloxacin
46
naturally occuring antimicrobial drugs: antibiotics
beta-lactam antibiotics: penicillin and cephalosporins
| antibiotics from prokaryotes : amynoglicocides, macrolides, tetracyclins, daptomycins, platensimycin
47
Cell wall synthesis
cycloserine, vancomycin, bacitracin, penicllins, cephalosporins, monobactams, carbapenems, amoxicillin
48
DNA gyrase
nalidixic acid, ciprofloxacin, novobiocin
49
RNA elongation
Actinomycin
50
DNA directed RNA polymerase
Rifampin, streptovaricins
51
Protein synthesis
| 50S inhibitors
Erythromycin (macrolides)
Chloramphenicol
Clindamycin
Lincomycin
52
Folic acid metabolism
Trimethoprim
| Sulfonamides
53
Cytoplasmic membrane
| structure and function
Polymyxins
| Daptomycin`
54
Protein synthesis
| 30S inhibitors
```
Tetracyclines
Spectinomycin
Streptomycin
Gentamicin
Kanamycin
Amikacin
Nitrofurans
```
55
lipid biosynthesis
platensimycin
56
Protein synthesis
| tRNA
mupirocin, puromycin
57
each antimicrobial agent
affects a limited and well-defined group of microorganism
58
Systematic work on Antimicrobial Drugs was first initiated by
paul ehrlich
-Nobel prize wining,
German, physician, scientist)
-selective toxicity
59
selective toxicity
ability of a chemical agent to inhibit or kill a pathogen microorganisms
without adversely affecting the host
60
salvarsan
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
growth factor analogs (GFA)
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
sulfa drugs
discovered by Gerhard Domagk in the 1930s
| -selectively toxic in bacteria because they synthesize their own folic acid
63
Sulfanilamide blocks the synthesis of _____ thereby inhibit __________ synthesis
folic acid, nucleic acid
64
isoniazid
```
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
Nucleic acid base analogs have been formed by
the addition of Bromine or Fluorine atoms
66
fluorine
```
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
quinolones
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
DNA ______ is found in ____ bacteria
gyrase, ALL
69
________ are effective for treating
| both _______ and ________, bacterial infections.
Fluoroquinolones, Gram-positive, Gram-negative
70
Fluoroquinolones such as Ciprofloxacin (Cipro) are used to treat
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
Moxifloxacin has been approved for treatment of
resistance strains of TBC, Mycobacterium
| tuberculosis
72
_______ are naturally produced _______agents produced by microorganisms
Antibiotics, antimicrobial
73
natural ATB can often be modified to enhance
efficacy (semisynthetic)
74
Who invented penicillin?
Alexander Fleming discovered it
75
b-Lactam antibiotics
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
penicillin
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
Cephalosporins
- 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
What are cephalosporins commonly used to treat?
gonorrhea infections
79
For the treatment of Gonorrhea CDC recommends
dual therapy
| -single dose of 250 mg intramuscular ceftriaxone and 1g of oral Azithromycin (bacterial protein inhibitor)
80
ATB affecting
protein synthesis
-Many ATB inhibit protein synthesis by
interacting with the ribosome and
disrupting translation
81
streptomycin inhibits
protein chain initiation
82
Puromycin, Chloramphenicol,
Cycloheximide and Tetracycline
inhibit
protein chain elongation
83
some ATB specifically inhibit
Transcription by inhibiting RNA synthesis
84
Rifampin inhibit RNA synthesis by
binding to the β-subunit of
| RNA polymerase, also used for the treatment of Tuberculosis
85
aminoglycosides are
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
What was the first effective ATB used for the treatment of Tuberculosis (TB)?
Streptomycin
87
Both Kanamycin and Streptomycin are synthesized by
Streptomyces species
88
macrolides
contain lactone rings bonded to sugars
- large number of macrolide ATB
- erythromycin best known
89
erythromycin
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
Erythromycin is particularly useful for treatment of
Legionellosis
91
tetracyclines
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
tetracyclines and b-lactam ATB comprise
two most important
| groups of ATB in the medical field
93
daptomycin
- produced by streptomyces
- cyclic lipopeptide ATB
- used mainly to treat gram + bacteria
94
platensimycin
```
first member of a new structural class of ATB
-produced by streptomyces platensis
```
95
antiviral drugs
viruses use their eukaryotic host to reproduce and perform metabolic functions, most
antiviral drugs also target host structures, resulting in host toxicity
96
Nucleoside Reverse Transcriptase Inhibitors (NRTI)
antiviral agents
97
protease inhibitors (PI)
drugs prevents viral replication by
binding the active site of HIV protease
-prevents virus maturation
98
enfuvirtide
fusion inhibitor
- composed of 36-amino acid synthetic peptide
- binds to gp41 membrane protein
99
What are the two categories of drugs that successfully limit influenza infection?
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
________ are ______ useful than the ______ inhibitors
| because resistance to Adamantanes develops rapidly in strains of influenza virus
Adamantes, less, Neuraminidase
101
interferons
small proteins in the cytokine family that prevent viral multiplication by
stimulating antiviral proteins in uninfected cells
102
Interferons are produce in 3 molecular forms:
IF-α (leukocytes), IF-β (fibroblasts), IF-γ (activated lymphocytes)
103
antifungal drugs
Fungi pose special problems in terms of treatment because Fungi and Humans are Eukaryotic organisms
104
membrane functions
Polyenes bind to
Ergosterol and disrupt
membrane integrity
105
Cell wall synthesis:
Polyoxins inhibit Chitin (a long-chain polymer of a N-acetylglucosamine) synthesis
Echinocandins inhibit Glucan (a polysaccharide of D-glucose monomers) synthesis
106
Ergosterol synthesis:
Azoles and Allylamines
| inhibit synthesis
107
Nucleic acid synthesis:
5-Fluorocytosine is a nucleotide
analog that inhibits nucleic
acid synthesis
108
Microtubule formation:
Griseofulvin disrupts
microtubule aggregation
during mitosis
109
Ergosterol
sterol found in fungi.
| It is not present in plant or animal cells
110
Ergosterol inhibitors
target the unique fungal plasma membrane component Ergosterol
111
polyenes
a group of ATB produce by Streptomyces
| -Bind to ergosterol, disrupting membrane function
112
azoles and alylamines
synthetic agents that selectively inhibit Ergosterol biosynthesis and therefore have broad antifungal activity.
113
Echinocandins:
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
Antimicrobial drug resistance:
acquired ability of a microorganism to resist the effects of a chemotherapeutic
agent to which it is normally susceptible
115
Most drug-resistant bacteria isolated from patients contain
drug-resistance genes located on R plasmids
116
Resistance is typically due to
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
r plasmid
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
saquinavir
Binds to active site of HIV protease enzyme
119
Bacteriophage therapy
the therapeutic use of bacteriophages to treat pathogenic bacterial
infections
