Control of microorganisms Flashcards
1
Q
The killing or removal of all viable organisms including endospores.
A
Sterilization
2
Q
Effectively limiting microbial growth.
A
Inhibition
3
Q
The treatment of an object to make it safe to handle.
A
Decontamination
4
Q
Directly targets the removal of all pathogens, not necessarily all microorganisms.
A
Disinfection
5
Q
What are the physical methods used for antimicrobial control? (3)
A
- heat
- radiation
- filtration
6
Q
What are the chemical methods used on EXTERNAL SURFACES for antimicrobial control? (3)
A
- sterilants
- disinfectants
- antiseptics
7
Q
What are the chemical methods used INTERNALLY for antimicrobial control? (3)
A
- antibiotics
- antivirals
- antifungals
8
Q
How do we call the chemical methods used for antimicrobial control?
A
Antimicrobials
9
Q
What is the most common physical method used for controlling microbial growth?
A
Heat
10
Q
High temperatures _____ macromolecules.
A
denature
11
Q
What do we call the amount of time required to reduce viability tenfold?
A
Decimal reduction time (D) (100, 10, 1, 0.1)
12
Q
What is the relationship between the decimal reduction time and temperature?
A
they are inversely correlated: as heat increases, he time required to achieve desired population decreases (D decreases)
13
Q
The decimal reduction time necessary to kill a defined ______ is ______ of the the initial cell ______.
A
fraction; independent; concentration.
14
Q
Time needed to kill all cells at a given temperature.
A
Thermal death time
15
Q
Thermal death time is ________________ of microorganisms tested. Therefore, you need to ______ the starting number of cells to be able to compare the sensitivity of different microorganisms.
A
dependent on the population size; standardize
16
Q
What is the difference between endospores and vegetative cells regarding thermal resistance?
A
Endospores survive heat that would rapidly kill vegetative cells: a higher temperature is needed to kill endospores.
17
Q
What is the time required to reduce viable endospores by 1D (90% dead)?
A
5min
18
Q
Sealed device that uses steam under pressure.
A
Autoclave
19
Q
Functions of autoclave: (4)
A
- allows temperature of water to get above 100 degrees without boiling
- at 15 psi, steam reaches 121 degrees -> sterilization is achieved in 10-15min
- object sterilized reaches this temperature, not suitable for heat-sensitive object/liquid
- not the pressure that kills the microorganisms but the high temperature
20
Q
Sterilization time:
A
when the temperature of autoclave and object being sterilized are equal (big objects might not be fully sterilized)
21
Q
Autoclave time:
A
form the moment the pressure begins until the end of sterilization time
22
Q
Process of using precisely controlled heat to reduce the microbial-load in heat sensitive liquids
A
Pasteurization (physical method)
23
Q
pasteurization does not kill all organisms, it is not a method of ______.
A
sterilization
24
Q
Reducing microbial load increases _____.
A
shelf-life of product
25
Pasteurization reduces significantly the population of many pathogens: (5)
- Listeria monocytogenes
- salmonella enterica
- campylobacter
- E. coli O157:H7
- mycobacterium
26
Parameters for flash pasteurization:
72 degrees for 15s
27
Parameters for bulk pasteurization:
65 degrees for 30min
28
What are the effects of bulk pasteurization?
there is more protein denaturation therefore it is more used for yoghurt and ice cream production
29
Radiations include: (4) and reduce _____
- UV
- X-Rays
- electrons
- gamma rays
and reduce microbial growth
30
UV has sufficient energy to cause modifications and breaks in ___, which inhibit ____, ____ and cause _____.
DNA; replication, transcription; death
31
Properties of UV: (3)
- useful for decontamination of surfaces
- cannot penetrate solid, opaque or light-absorbing surfaces
- useful for disinfection of drinking water and air
32
Sources of radiation: (3)
- X-rays
- radioisotopes (emits gamma rays: highest radiation)
- cathode ray tubes (electrons)
33
radiation is used for ______ in the medical field and food industry.
sterilization
34
Electromagnetic radiation that produces ions and other reactive molecules.
Ionizing radiation
35
What does an ionizing radiation do?
Generates electrons and hydroxyl radicals that cause damage to DNA and proteins
36
Concerning ionizing radiations, the amount of energy required to reduce viability tenfold is _____ to D value.
analogous
37
Spores are the microorganisms that withstand the ______ ionizing radiation.
highest
38
Why is filtration preferred on sensitive liquids and gases?
it avoids the use of heat
39
How does filtration work?
the pores of filter are small enough to prevent organisms to pass through but big enough to allow gas and liquid to pass through.
40
What are the two types of filters used for filter sterilization?
Depth filters and membrane filters
41
About depth filter: (structure, utilisation)
- made up of fibrous sheet or mat made from an array of finer (paper or glass)
- used to sterilize liquid and air
- HEPA filters
42
About membrane filters:
- function more like a sieve
- example: nucleation tract (nucleopore) filter
- filtration speed can be increased by syringe, pump, vacuum
43
What are the three classifications of antimicrobial agents and what happens?
- bacteriostatic: inhibit growth of microorganisms (total cell count and viable cell count remain equal/stable)
- bacteriocidal: kill microorganism (total cell count remains stable and viable cell count decreases)
- bacteriolytic: kill microorganism by inducing lysis (total cell count and viable cell count both decrease)
44
The smallest amount of an agent needed to inhibit growth of a microorganism.
minimum inhibition concentration (MIC)
| varies with pH, temperature, organism used
45
Lowest concentration of an agent that kills a test ORGANISM.
Minimum lethal concentration (MLC)
46
Lowest concentration of an agent that kills a test BACTERIUM.
Minimum bacteriocidal concentration (MBC)
47
How do you determine MBC?
Take sample from the transparent tubes and plate them on agar plates and see if any organisms grow, the one with no growth is MBC
48
What is the purpose of disc diffusion assay?
Measures antimicrobial activity:
- Antimicrobial agent is added on filter paper
- zone of inhibition will be created around this disc if organism is sensitive to antimicrobial agent -> no growth
- perimeter of this zone of inhibition is the MIC
49
Why are antimicrobial compounds used?
they prevent spreading of a pathogen in the environment, prevent contamination of the host and cure superficial bacterial infections.
50
What are the two categories of antimicrobial agents?
- products used to control microorganisms in industrial and commercial applications (fuel tanks, cooling towers)
- products used to prevent growth of human pathogens in inanimate environments and on external body surfaces (sterilants, disinfectants, sanitizers and antiseptics)
51
Cold sterilization
destroy all forms of microorganisms as well as endospores -> sterilants
52
What are the chemical antimicrobial agents for external use that are applied to non living objects or surfaces (toxic to humans/animals) and that don't kill endospores?
disinfectants/sanitizers
53
What are the chemical antimicrobial agents for external use that are applied on surfaces of living tissues or skin and that don't kill endospores?
antiseptics
54
Example of antimicrobial drugs (3) that are applied inside/outside of human body? (don't kill endospores)
- antifungals
- antivirals
- antibiotics
55
Phenol/phenolics (use/notes)
- disinfectants, antiseptics
| - disrupt cytoplasmic membrane, protein denaturant (high [])
56
Alcohols (use/notes)
- disinfectants, antiseptics
| - lipid solvent and protein denaturants
57
halogens(use/notes)
- disinfectants, antiseptics, sterilants
- Chlorine (Sterilant/disinfectant): oxidizing agent ex: sodium hypochlorite
- Iodine (antiseptic): iodinate tyrosine residues in protein, oxidizing agent
58
Heavy metals (use/notes)
- disinfectant
| - modify proteins, interact with RNA, DNA... several different mechanisms. CuSO4, algaecide
59
Quaternary ammonium (use/notes)
- disinfectant/antiseptic
| - interact with phospholipids of cytoplasmic membrane
60
Alkylating agents (use/notes)
- disinfectant, sterilant
| - formaldehyde, glutaraldehyde. very toxic
61
How do you classify antimicrobial drugs? (3)
- molecular structure
- mechanism of action
- spectrum of antimicrobial activity
62
Antimicrobial drugs can either be ______ or ______. They usually have a ____________
bacteriostatic; bactericidal; specific target
63
A good antimicrobial drug has: (5)
- NO sever side effects, must be far more toxic for microorganism than mammalian cell
- low risk/benefit ratio
- broad spectrum of activity to facilitate rapid medical intervention
- appropriate bioavailability and pharmacokinetics (must reach site of infection)
- low cost to develop and manufacture
64
What are the possible targets? (9)
- DNA-directed RNA polymerase
- protein synthesis (50S or 30S inhibitors)
- protein synthesis (mRNA)
- lipid biosynthesis
- RNA elongation
- DNA gyrase
- cell wall synthesis
- folic acid metabolism
- cytoplasmic membrane structure and function
65
No antibiotics can clear _____ and ____ at the same time -> very specific
bacteria and viruses
66
ability to inhibit or kill a pathogen without affecting the host.
Selective toxicity
67
Who studied selective toxicity?
Paul Ehrlich in early 1900s
68
What was one of the first antimicrobial drugs? (used to treat syphilis)
Salvarsan
69
_________ are structurally similar to growth factors but do not function in the cell. they are similar to vitamins, AA and other compounds.
Growth factor analogs
70
Example of and analogue of p-aminobenzoic acid?and its target? and its group?
SULFANILAMIDE
Group: sulpha drugs (discovered by Gerhard Domagk in 1930s)
Target: inhibits folic acid synthesis
-> bacteriostatic
71
____ is a growth factor analog effective only against Mycobacterium. It interferes with synthesis of ______
Isoniazid; mycolic acid
72
_______ are formed by addition of bromine or fluorine. Stop DNA replication
nucleic acid base analogs
73
_______ are antibacterial compounds that interfere with DNA gyrase (control DNA supercoiling)
Quinolones
74
_____ are antimicrobial agents _________ by a variety of bacteria and fungi to inhibit or kill other microorganisms.
Antibiotics; naturally produced
75
What are semisynthetic antibiotics?
antibiotics that are modified to enhance their efficacy
76
Gram + and gram - bacteria vary in their _____ to antibiotics. The cell wall is a major factor.
sensitivity
77
What is the most important group of antibiotics? and what does it include? (3)
```
Beta-Lactams
it includes:
- penicillins
- cephalosporins
- cephamycins
```
78
About Penicillins:
- who discovered it
- where it comes from
- what is it effective against
- function
- beta-lactam antibiotic
- discovered by Alexander Fleming in 1928
- isolated from Penicillum chrysogenum (mold)
- Primarily effective against Gram + bacteria, some synthetic ae effective against gram -
- inhibit cell wall synthesis
79
About Cephalosporins:
- beta-lactam antibiotic
- produced by fungus Cephalosporium
- same mode of action as penicillins
- used to treat gonorrhea
80
What is a penicillin-binding protein?
Transpeptidase (TPase)
81
Beta-lactams can be _____ or _____ depending on species, growth, etc. They can also be _______ in isotonic solutions.
bactericidal; bacteriolytic; bacteriostatic
82
How does the transpeptidase work?
it covalently binds to beta-lactam ring, breaking the ring -> antibiotic can't work
83
Bacteria also produce the antibiotics that are effective against them. True or False?
True
84
What are 3 types if aminoglycosides? and what are their function?
- kanamycin
- neomycin
- STREPTOMYCIN
- > they are bactericidal and they target 30S ribosomal subunits which cause misreading of mRNA
85
What are chloroamphenicol?
- they bind to 23S rNA causing the inhibition of peptide elongation
- they are bacteriostatic
86
What are macrolides?
- broad spectrum of antibiotics that target the 50S subunit of ribosome, block protein synthesis
- bacteriostatic
87
What are tetracyclines?
- broad spectrum, bacteriostatic
| - inhibit 30S ribosomal subunit, block protein synthesis
88
What are 4 antibiotics from prokaryotes?
- tetracyclines
- macrolides
- chloroamphinicol
- aminoglycosides
89
the acquired ability of a microorganism to resist the effects of a chemotherapeutic agent to which it is normally sensitive.
Antimicrobial drug resistance
90
How does a microorganism become resistant to some antibiotics? (antibiotic resistance mechanism) (4)
- destruction or modification of the antibiotic
- modification of the target site
- modification of the uptake mechanism
- efflux pump: reduce intracellular concentration
91
Antibiotic producers are tolerant because: (3)
- lack target sites (no peptidoglycan)
- modify target sites
- lack of uptake mechanism
92
Acquisition of a new ___ that provide the cells with a new function like _____
gene; antimicrobial resistance
93
Where are the drug-resistant genes located on bacteria?
R plasmid
94
What are the effects of the use of antibiotics in medicine, veterinary medicine, and agriculture on R plasmids?
it selects for the spread of R plasmids
95
R plasmids can't be transferred between bacteria of the same species or related species. True or False?
False
96
How can resistance to antimicrobial drugs be minimized?
by using antibiotics correctly and only when needed -> reduce selection
97
Most antiviral drugs also target _____, resulting in _____
host structures; toxicity
98
Most used antiviral that blocks reverse transcriptase and production of viral DNA.
nuceloside analogs
99
_____ inhibit the processing of large viral proteins into individual components and ______ prevent viruses from successfully fusing with the host cell.
Protease inhibitors; fusion inhibitors
100
Antibiotics are effective against viruses. True or False?
False
101
Why do fungi pose problems for chemotherapy?
because they are eukaryotes
102
what does Fluconazole do?
a drug that targets ergosterol synthesis, a unique metabolic process the isn't found in mammals
