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PHA112 > Microbiology 9 > Flashcards

Microbiology 9 Flashcards

1
Q

when were antibiotics first introduced?

A

1940s

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2
Q

what are the 7 main groups of antibiotics?

A
  • penicillins
  • cephalosporins (ceftriaxone)
  • macrolides (erythromycin)
  • fluoroquinolone (ciprofloxacin)
  • sulfonamides (sulfasalazine)
  • tetracyclines (tetracyclin)
  • aminoglycosides (tobramycin)
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3
Q

what must an antibiotic be?

A

more toxic to microorganism than host

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4
Q

what do all beta-lactams have?

A

beta-lactam ring

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5
Q

what are sulphonamides?

A

synthetic chemicals (first antimicrobial drugs - 1930s)

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6
Q

what do sulphonamides do?

A

competitively inhibits dihydropteroate synthetase (DHPS) - enzyme involved in folate synthesis

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7
Q

where do humans obtain folate from?

A

food

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8
Q

what do sulphonamides have a similar structure to?

A

para-aminobenzoic acid (PABA)

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9
Q

what do bacteriostatic agents do?

A

halt growth (bacteria recover when drug stopped)

  • limit spread of infection
  • growth restarts
  • tetracycline
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10
Q

what do bactericidal agents do?

A

kills bacteria for period of time

  • useful in critically ill patients
  • e.g. meningitis, endocarditis, septicaemia
  • critical cell death events already initiated
  • beta-lactams
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11
Q

describe what is happening in this graph?

A
  • time dependent rate of kill rises to maximum and remains constant
  • conc dependent drug increases rate of kill as [drug] increases
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12
Q

in concentration dependent drugs what does the rate of kill eventually become?

A

constant

(limited by agent diffusion)

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13
Q

bacteriostatic outcomes

A
  • macrolides
  • linezolid
  • clindamycin
  • tetracyclin
  • chloramphenicol
  • trimethoprim-sulfamethoxazole
  • isoniazid (bacteriostatic against lag-phase and dormant TB)
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14
Q

bactericidal outcomes

A
  • fluoroquinolones
  • beta-lactams
  • glycopeptides (e.g. vancomycin)
  • aminoglycosides
  • daptomycin
  • metronidazole
  • nitrofurantoin
  • isoniazid (bacterial against lag phase mycobacteria)
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15
Q

what does the general outcome depend on?

A
  • pathogen
  • bacterial load
  • [drug]
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16
Q

what is the meaning of broad spectrum?

A

effective against a wide range of bacterial species

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17
Q

what is the meaning of narrow spectrum?

A

effective against a limited number of different bacterial species

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18
Q

what do penicillins target?

A
  • gram negative bacteria
  • gram positive bacteria
  • chlamydiae
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19
Q

what do sulphonamides, cephalosporins, quinolones and carbapenems target?

A
  • gram negative bacteria
  • gram positive bacteria
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20
Q

what do streptomycins target?

A
  • mycobacteria
  • gram-negative bacteria
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21
Q

what do tetracyclines target?

A
  • gram negative bacteria
  • gram positive bacteria
  • chlamydiae
  • rickettsiae
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22
Q

what do isoniazids target?

A

mycobacteria

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23
Q

what do polymyxins target?

A

gram negative bacteria

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24
Q

what do vancomycins target?

A

gram positive bacteria

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25
Q

what needs to be considered when choosing antibiotics?

A
  • selectivity (will it treat what you want)
  • toxicity (will it poison)
  • therapeutic index (toxic dose/effective dose)
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26
Q

what does TARGET stand for?

A

T - treat

A - antibiotics

R - responsibly

G - guidance

E - education

T - tools

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27
Q

disinfection?

A

removes microbes from inanimate surfaces

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28
Q

what is disinfection not the same as?

A

sterilisation

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29
Q

what does disinfection do?

A
  • removes infection risk
  • prevents spoilage of perishable goods
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30
Q

what are disinfectants?

A

chemicals with ability to destroy/inhibit microorganisms

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31
Q

what are disinfectants not the same as?

A

antibiotics

32
Q

give examples of disinfectants?

A
  • alcohols (ethanol)
  • aldehydes (formaldehyde)
  • biguanides (chlorhexidine)
  • halogens (hypochlorites)
  • metals (silver)
  • hydrogen peroxide
  • phenols (chlorocresol)
  • surfactants (cationic QACs)
33
Q

what is antisepsis?

A

removal of microbes from living surfaces

(should = non-toxic)

34
Q

what is antisepsis used for?

A

used to reduce microbial populations

(skin before surgery)

(controlling microbial contamination of staff hands)

35
Q

disinfection and antisepsis are NOT the same thing

however what are they both?

A

broad spectrum

36
Q

what can the active ingredient be in both antisepsis and disinfection?

A

can be the same

[active] lower in antiseptics

37
Q

what is a preservative?

A

a substance added to a product (medicinal, food etc) designed to prevent degradation by microbes/unwanted chemical changes

38
Q

what can preservatives also do?

A

preserve products by drying, refrigeration, UV-C irradiation

39
Q

give examples of how preservatives have been used in prehistoric times to prevent food spoilage?

A
  • salt used to preserve meat
  • vegetables preserved in vinegar
40
Q

give examples of how preservatives are used in pharmaceutics?

A
  • increase shelf life by preventing microbial growth and degradation
  • must = non-toxic to humans
    e. g. lactic acid, sodium benzoate, syrup
41
Q

define osmosis?

A

net movement of solvent from high to low conc through membrane

42
Q

what is an isosmotic solution (isotonic)?

A

no net movement of water

43
Q

what is hypoosmotic solution (hyptonic)?

A
  • water moves into cell
  • may cause cell to burst if wall = weak/damaged (LYSIS)
44
Q

what is a hyperosmotic solution (hypertonic)?

A
  • water moves out of cell
  • cytoplasm shrinks (PLASMOLYSIS)
45
Q

how does resistance to spoilage increase?

A

high concentrations of sugars / PEGs

46
Q

what is water activity (Aw)?

A

proportion of uncomplexed water available to support microbial growth

47
Q

as Aw decreases…

A

growth rate decreases until minimal growth-inhibitory Aw reached

48
Q

what are the approximate Aw values?

A
  • bacteria: 0.90-0.95
  • yeasts and moulds: 0.80-0.88
  • no microbial growth expected less than/equal to 0.6
49
Q

what can a lower value of Aw of aqeuous formulations do?

A

increase resistance to microbial attack

  • high conc of sugars/polyethylene glycols
50
Q

what can Aw be reduced by and how?

A
  • desiccation
  • removal of water vapour of products
  • through silica gel/ molecular sieve during manufacturing
  • can = included in blister packs, packagin etc as separate items
51
Q

what can the accumulation of condensation on surface of low Aw products permit?

A

surface yeast and mould spoilage

52
Q

what do paper discs contain?

A

known [antibiotic] which diffuses into inoculated sugar

53
Q

[antibiotic] decreases with log distance until..

A

MIC reached

  • produced clear inhibitory zone after incubation which can be measured to determine sensitivity
54
Q

multiple antibiotics are tested in what?

A

parallel

55
Q

e-test strip diffusion assays

A
  • same principle as disc diffusion
  • [antibiotic] changes along length of strip
56
Q

what can e-test strip diffusion assays be used to test for?

A

antibiotic synergy

  • stack on top of each other
  • layer at side
57
Q

what quantitative result do e-test strip diffusion assays provide?

A

MIC value

58
Q

what is the minimum inhibitory concentration?

A

lowest concentration of chemical which prevents visible growth of a bacterium

59
Q

what is the minimum bactericidal concentration?

A

lowest concentration of an antibacterial agent required to kill particular bacterium

60
Q

where can resistance genes come from?

A
  • bacteria which survived treatment
  • antibiotic producers
  • bacteria that exist alongside antibiotic producers
61
Q

how does antibiotic resistancy happen?

A
  1. lots of germs. few drug resistant
  2. antibiotics kill bacteria causing illness + good bacteria protecting body
  3. drug-resistant bacteria not allowed to grow and take over
  4. some bacteria give drug-resistance to other bacteria, causing problems
62
Q

what is innate resistance?

A

inherent ability of bacteria to resist particular antibiotic

  • lack of cell wall (mycoplasms Vs beta lactams)
  • abnormal antibiotic targets
63
Q

what is acquired resistance?

A

result of changes to normal genome of bacteria

64
Q

what is transformation?

A

direct uptake of DNA through cell membrane

65
Q

what is transduction?

A

intro of genetic material via viral vector

66
Q

what is conjugation?

A

transfer of genetic material between 2 directly connected bacteria

67
Q

how can antibiotic resistance spread?

A
  • drug-resistant bacteria can remain on meat
  • unclean hands
  • drug-resistant bacteria in animal faeces remain on crops
  • fertilizer/water containing animal faeces used on crops
68
Q

ANTIBIOTIC RESISTANCE MECHANISMS

exclusion

A
  • decrease uptake (cell wall modification)
  • increase export (efflux pump production)
69
Q

ANTIBIOTIC RESISTANCE MECHANISMS

inactivation

A
  • modify antibiotic (aminoglycoside acetylation)
  • destroy antibiotic (B lactamase production)
70
Q

ANTIBIOTIC RESISTANCE MECHANISMS

target modification

A
  • target protection
  • enzymatic modification
  • change/bypass of target site
71
Q

what resistance mechanism can work for both antibiotics and disinfectants?

A

efflux pumps

72
Q

what are the disadvantages to developing new antibacterials?

A
  • high development cost (>2.5 billion dollars to get 1 prescription-only med to market)
  • high failure rate (approx 20% success rate in phase I)
  • low return ( acute use only 5-7 days dosing)
  • high risk of resistance
73
Q

FDA and EMA are incentives to what?

A

increase pharma interest

74
Q

most antibacterials in CT are new derivatives of existing classes (e.g. cephalosporins, tetracyclines/aminocyclines, FQs)

give the advantages of these?

A
  • increased activity
  • fewer side effects
  • lower resistance
75
Q

what are the alternatives to traditional antimicrobial agents?

A
  • natural products
  • bacteriophages and derived proteins
76
Q

natural products

A
  • tea + honey have antibacterial compounds
  • black < green < white tea
  • 4 main catechins (polyphenols) in green tea
  • e.g. epigallocatechin gallate, epicatechin, epicatechin 3- gallate, epigallocatechin
  • honey = high sugar content, polyphenols, lysozymes, hydrogen peroxide

POTENTIALLY PRODUCE BROAD SPECTRUM

77
Q

bacteriphages and their derived proteins?

A
  • take advantage of normal phage lytic replication
  • can = highly specific
  • different pharmacology compared to conventional antimicrobials

PHA112 (37 decks)

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