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Microbiology > Chapter 9 > Flashcards

Chapter 9 Flashcards

1
Q

definitions of sterilization, inhibition, decontamination, disinfection

A
  • sterilization: the killing or removal of all viable organisms (including endospores)
  • inhibition: effectively limiting microbial growth
  • decontamination: the treatment of an object to make it safe to handle
  • disinfection: directly target the removal of all pathogens, not necessarily all microorganisms
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2
Q

3 physical methods and 2 chemical ones (antimicrobial)

A

physical:
- heat
- radiation
- filtration
Chemicals:
- used on external surfaces: sterilants, disefectants, antiseptics
- used on internally: antibiotics, antivirals, antifungals

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3
Q

what is decimal reduction time (D)

A

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

  • inversely proportional to temperature
  • different microorganisms have different D
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4
Q

what is thermal death time

A
  • time needed to kill cells at a given temperature
    • dependent on the popultaion size of the microorganism tested, so we need to standarize the starting number of cells to be able to compare sensitivity of different microorganisms
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5
Q

what is autoclave + 4 characteristics

A
  • it is a sealed device that uses steam under pressure:
  • allows temperature of water to get above 100degree
  • at 15 psi (pound/square inch), steams reach 121degree, sterilization is achieved in 10-15 min
  • the object being sterilized will reach this temperature. Not suitable for heat- sensitive objetc liquid
  • it’s not the pressure that kills microorganisms but the high temperature
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6
Q

what is pasteurization

A

def: it is the process of using precisely controlled heat to reduce the microbial load in heat-sensitive liquids
* does not kill microorganisms, it is not a method of sterilization
* reduces the microbial load, increases the shelf life of the product
* flash pasteurization: 72degree for 15 sec
* bluck pasteurization: 65 degre, 30 min

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7
Q

pasteurization reduces significantly the population of many pathogens (5)

A 
listeria monocytogenes
salmonella enterica
campylobacter
e.coli 
mycobacterium
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8
Q

what can reduce microbial growth by using radiation

A

UV, X-rays, gamma rays, electrons and microwaves

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9
Q

what causes UV + 3 characteristics

A

it has sufficient energy to cause modifications and breaks in DNA, which inhibit replication, transcription and cause death

  • UV is useful for decontamination of surfaces
  • cannot penetrate solid, opaque or light absorbing surfaces
  • useful for disinfection of drinking water and air
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10
Q

3 characteristics of ionizing radiation

A
  • electromagnetic radiation tha produces ions and other reactive molecules
  • generate electrons and hydroxyl radicals that cause damage to DNA and proteins
  • amount of energy required to reduce viability tenfolds is analogous to D value
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11
Q

3 sources of radiation

A

cathode ray tubes (electrons)
X rays
radioisotopes (emit gamma rays)

** radiation is used for sterelization in the medical field and food industry

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12
Q

why clostridium botulinum are very resistant ro radiation

A

because it can produce spores which are very resistant to radiation

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13
Q

3 characteristics of depth filters

A
  1. fibrous sheet or matmade from an array of fiber (paper or glass)
  2. used to sterilize liquid or air
  3. HEPA filters
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14
Q

3 characteristics of membrane filters

A
  1. function more like a sieve
  2. a type of membrane filter is the nucleation track (nucleopore) filter
  3. filtration speed can be increase by syringe, pump, or vacuum
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15
Q

3 ways to classify antimicrobial agent

A
  1. bacterostatic: inhibit growth of microorganism
  2. bacteriocidal: kill microorganism
  3. bacteriolytic: kill microorganism by inducing lysis
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16
Q

3 terms to measure microbial activity

A
  1. minimum inhibitory concentraion (MIC): it is the smallest amount of an agent to inhibit growth of a microorganism
    - varies with the inoculum size, temp, pH, the organism used..
  2. minimum lethal concentration (MLC): is the lowest concentration of an agent that kills a test organism
  3. minimum bacteriocidal concentration (MBC) is the lowest concentration of an agent that kills a test bacterium
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17
Q

3 roles of chemical antimicrobial agents for external use

A
  1. prevent spreading of a pathogen in the environment
  2. prevent contamination of the host
  3. cure superficial bacterial infections
18
Q

2 types of chemical antimicrobial for external use

A
  1. products use to controle microorganisms in commercial and industrial applications.
    ex: chemicals in air-conditioning, cooling towers, textile and paper products, fuel tanks
  2. products designed to prevent growth of human pathogens in inanimate environment and on external body surfaces: sterilants, disinfectant,sanitizers and antiseptics
19
Q

definition of these terms: sterilants, disinfectant/sanitizers and antimicrobial drugs

A
  • sterilants: destroys all forms of microorganisms, including endospores. called COLD STERILIZATION
  • disinfectant/sanitizers: applied to nonliving objects or surface (can be toxic for animals/humans). don’t kill endospores
  • antispectics: applied to the surface of living tissue or skin (must not be toxic for animals/humans). don’t kill endospores
  • antimicrobial drugs: antibiotics, antifungals, antivirals: applied outside or inside the body of animals/humans (must not be toxic for animals/humans). Don’t kill endospores
20
Q

antimicrobial drugs are classified on the basis of (3)

A
  1. molecular structure
  2. mechanism of action
  3. spectrum of antimicrobial activity

** can be either bacteriostatic or bactericidal

21
Q

5 things a good antimicrobial has

A
  1. NO severe side effects, must be far more toxic for the microorganisms than for the mammalian cells
  2. low risk/benefit ratio
  3. broad spectrum of activity to facilitate rapid medical intervention
  4. appropriate bioavailability and pharmacokinetics (must reach the site of infection)
  5. low cost to develop and manufacture
22
Q

what does antimicrobial targets (attack)

A

A lot of antimicrobial drugs that target proteins synthesis (ribosome) because the subunits in the bacteria and eukaryotes are different so the antimicrobial for bacteria are very specific, it will not attak the one of the host since the ribosomes are different

23
Q

what did Paul Ehrlich in the early 1900s

A

he studied selective toxicity:

def: it is the ability to inhibit or kill a pathogen without affecting the host
- salvarsan: one of the first antimicrobial drugs, used to treat syphilis (Treponema pallidum)

24
Q

5 different synthetic antimicrobial drugs

A
  1. growth factors analogs: they are structurally similar to growth factor but do not function in the cell. Analogs similar to vitamins, amino acids, and other compunds
  2. Sulfa drugs: discovered by Gerhard Domagk in the 1930’s. Sulfanilamide is an analogue of p-aminobenzoic acid. Inhibits folic acid synthesis. bacteriostatic
  3. isoniazid: it is a growth factor analogue effective only against Mycobacterium. Interferes with synthetic of mycolic acid
  4. nucleic acid base analogs: they are formed by the addition of fluorine or bromine. stop DNA replication
  5. quinolones: are antibacterial compunds that interfere with DNA gyrase (control DNA supercoiling) ex:ciprofloxacin
25
Q

definition antibiotics + 2 characteristics

A

def: they are antimicrobial agents naturally produced by a variety of bacteria and fungi to inhibit or kill other microorganisms
- less than 1% of known antibiotics are clinically used
- can be modified to enhance efficiency (semisynthetic antibiotic)
* * Gram + and - have different sensitivity to antibiotics because of their cell wall

26
Q

most important group of antibiotics + 3 exampls

A

B-lactams

  • penicillin
  • cephalosporins
  • cephamycins
27
Q

4 characteristics of Peniciliin

A
  1. discovered by Alexander Fleming (1928), isolated from Penicillium chrysogenum (mold)
    - primarly effective against Gram +
    - some synthetic forms are effective against some Gram -
    - inhibit cell wall synthesis
28
Q

3 characteristics of cephalosporin

A
  • produced by the fungus Cephalosporium
  • same mode of action as the penicillins
  • commonly used to treat gonorrhea (neisseria gonorrhea)
29
Q

sodium hypochlorite is an example of what

A

halogen used as a desinfectant, sterilant, antiseptic

30
Q

what is transpeptidase (TPase)

A

a penicillin binding-protein

** if b-lactams is present, it inhibits (inactivate) TPase so the bacteria can not create their cell wall

31
Q

b-lactams are bacteriostatic/bacteriolytic/bactericidal ?

A
  • bactericidal or bacteriolytic (depending on the species, growth phases..)
  • can be bacteriostatic (in isotonic solutions)
32
Q

many antibiotics are produced by what?

A

bacteria themselves

majority came from streptomyces

33
Q

4 antibiotics from prokaryotes (bacteria themselves)

A
  1. aminoglycosides: kanamycin, neomycin, streptomycin
    - target 30S subunit of the ribosome, cause misreading of mRNA
    - bactericidal
  2. chloramphenicol
    - bind to 23S rRNA and block peptide elongation
    - bacteriostatic
  3. macrolides: erythromycin
    - broad-spectrum antibiotics that target the 50S subunit of the ribosome, block protein synthesis
    - bacteriostatic
  4. tetracylines
    - broad-spectrum, bacteriostatic
    - inhibit 30S ribosomal subunit, block protein synthesis
    * * all come from spectromyces
34
Q

what is antimicrobial drug resistance

A

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

35
Q

mechanisms of antibiotic resistance - antibiotic producers are tolerant : (3)

A
  • lack target sites (no peptidoglycan)
  • modify target sites
  • lack of uptake mechanism
36
Q

some microorganisms are resistant to antibiotics. give 4 antibiotic resistance mechanism

A
  • destruction or mofidication of the antibiotic (B-lactamase)
  • modification of the target site
  • modification of uptake mechanism
  • efflux pump: reduce intracellular concentration
37
Q

5 characteristics of acquisition of resistance

A
  • usually mediated by the acquisition of a new gene (or groups of genes) that provide the cells with a new function (ex: antimicrobial resistance)
  • drug-resistance gene located on the R plasmids
  • evidence indicates that R plasmids predate the antibiotics era (antibiotics came from nature)
  • the uses of antibiotics in medecine, agriculture and vetenary medecine selects for the spread of R plasmids
  • R plasmids can be transferred between bacteria of the same species or related species
38
Q

most antiviral also target ____

A

host structure, resulting in toxicity (viruses use host cell machinery). Risk to the host may not justify the use of antiviral

39
Q

3 examples of antiviral

A
  1. nucleoside analogs (the most popular and commonly used): (e.g. AZT, acyclovir): block reverse transcriptase and production of viral DNA (RNA viruses)
  2. proteases inhibitors: inhibit the large processing of large viral proteins into individual components
  3. fusion inhibitors: prevent viruses from successfull fusing with the host cell
40
Q

antifungal drugs: problem with fungi

A

they are eukaryotes, so they cause special problems to chemotherapy: much of the cellular machinery is the same as that of animals and humans

  • a few drugs target unique metabolic processes not found in mammals:
    1. ergosterol synthesis: (Nystatin, fluconazole)
    2. cell wall synthesis (inhibitor of chitin synthesis)

Microbiology (25 decks)

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