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Clinical Pathology - > CP1 - Introduction to Antibacterial Agents > Flashcards

CP1 - Introduction to Antibacterial Agents Flashcards

1
Q

what are antibiotics?

A

chemical products of microbes that inhibit or kill other organisms. used interchangeably with antimicrobial agents.

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2
Q

what is an antibiotic spectrum?

A

the spectrum of organisms that the medicine covers

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3
Q

what are the classes of antimicrobial agents?

A
  1. antibiotics
  2. synthetic compounds
  3. semi-synthetic compounds (modified antibiotics)
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4
Q

what are the modes of action of antibiotics?

A
  1. bacteriostatic - inhibit further bacterial growth eg. protein synthesis inhibitors
  2. bactericidal - kill bacteria eg. by preventing the formation of the cell wall
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5
Q

what is the minimum inhibitory concentration

A

the minimum concentration of antibiotic at which visible growth is inhibited

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6
Q

why is the difference between bacteriostatic and bactericidal mode of action only an in vitro concept?

A

this is because some antibiotics are bacteriostatic at a lower temperature and bactericidal at a higher temperature

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7
Q

what are the types of antimicrobial interactions?

A
  1. synergism
  2. antagonism
  3. indifference
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8
Q

why are antimicrobial interactions clinically significant?

A

the synergism between beta-lactam and amino glycoside is used to treat streptococcal endocarditis

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9
Q

why are combined antibiotics given?

A
  1. to increase efficacy
  2. to adequately provide for a broad spectrum
  3. to reduce resistance, since it would be more difficult for bacteria to develop resistance to multiple antibiotics simutaneously
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10
Q

what are the main characteristics of antimicrobials?

A
  1. ability to inhibit critical processes in bacterial cells
  2. it is selectively toxic
  3. the antibacterial needs to be able to get into the microbe
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11
Q

what is selective toxicity?

A

the ability of antimicrobials to target micro-organisms but not human cells

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12
Q

what are the examples of targets of antibiotics?

A
  1. cell wall
  2. protein synthesis
  3. DNA synthesis
  4. RNA synthesis
  5. Plasma Membrane
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13
Q

what is the major component of bacterial cell walls?

A

peptidoglycan (in both gram positive and gram negative bacteria)

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14
Q

what is peptidoglycan composed of?

A

a glycopeptide -
N-acetyl muramic acid (NAM)
N-acetyl glucosamine (NAG)

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15
Q

what are the main classes of antibiotics?

A
  1. B-lactams
  2. Glycopeptides
  3. Aminoglycosides
  4. Macrolides, Lincosamides, Streptogramins (MLS)
  5. Tetracyclines
  6. Oxazolidinones
  7. Sulphonamides
  8. Quinolones and fluoroquinolones
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16
Q

what are the examples of B-lactam antibiotics?

A
  1. amoxicillin
  2. flucoxicillin
  3. Benzylpeneckllin
  4. Cephalosporins (broad spectrum)
  5. Carbapenems (very broad spectrum)
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17
Q

what are thecaracteristics of B-lactams?

A
  1. contain a 4 membered carbon ring called the beta lactic ring
  2. structural analogues of D-alanyl-D-alanine
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18
Q

what is the mode of actions of beta lactam?

A

interferes with the function of penicillin binding proteins (transpeptidase enzymes) involved in cross-linking peptidoglycan to construct the cell wall

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19
Q

what is the mode of administration of beta lactams?

A

orally and IV

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20
Q

why may this not be the chosen class of antibiotics for treatment?

A

1-10% of the population have a general rash and 0.01% of patients have anaphylaxis to beta lactams

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21
Q

which type of beta lactams should be avoided in the elderly?

A

cephalosporins

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22
Q

name some examples of glycopeptides

A

vancomycin

teicoplanin

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23
Q

what are the characteristics of glycopeptides?

A
  1. they are large molecules, which directly bind to the terminal D-alanyl-D-alanine on NAM pentapeptides
  2. they are unable to penetrate the outer membrane porins on gram negative bacteria
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24
Q

what is the mode of action of glycopeptides?

A

they inhibit the binding of transpeptidases and thus prevent peptidoglycan cross-linking

25
Q

what are the examples of aminoglycosides?

A

gentamycin, amikacin

26
Q

what is the mode of action of aminoglycosides?

A

they bind to the 30S ribosomal unit, inhibit protein synthesis
exact mechanism is not fully understood

27
Q

what are the side effects of aminoglycosides?

A
  1. potentially reversible nephrotoxicity
  2. irreversible ototoxicity
    therefore requires therapeutic drug monitoring
28
Q

what is the full form of MLS?

A

macrolides, lincosamides, Streptogramins (MLS)

29
Q

what are the examples of MLS antibiotics?

A

Erythromycin, clarythromycin (macrolides), clindamycin (lincosamide)

30
Q

what is the mode of action of MLS?

A

inhibit protein elongation by binding to the 50S subunit and blocking the exit tunnel

31
Q

which drug has lesser side effects? clarithromycin or erythromycin?

A

clarithromycin

32
Q

which antibiotic is associated with causing c diff infections?

A

clindamycin

33
Q

name some examples of tetracyclines

A

tetracycline, doxytetracycline

34
Q

what is the mode of action of tetracyclines?

A

bind to the 30S subunit and inhibit translation of RNA by inhibiting the binding of tRNA to rRNA

35
Q

examples of oxazolidinones

A

linezolid

36
Q

what is the mode of action of oxazolidinone?

A

inhibits the initiation of protein synthesis by binding to the 50S ribosomal unit and inhibiting the assembly of the initiation complex

37
Q

what is a side effect of linezolid?

A

causes bone marrow suppression

38
Q

what is trimethoprim used for?

A

UTIs

39
Q

what is the mode of action of trimethoprim?

A

inhibits folate synthesis (folic acid is a precursor of purine synthesis) therefore inhibits DNA synthesis

40
Q

what is a characteristic feature of sulphonamides?

A

they can be combined as co-trimoxazole

41
Q

what is the mode of action go sulphonamides?

A

inhibit DNA synthesis

42
Q

examples of quinolones and fluoroquinolones?

A

nalidixic acid
ciprofloxacin
levofloxacin

43
Q

what is the mode of action of quinines and fluoroquinolones?

A

they inhibit either or both DNA gyrase and topoisomerase IV, which are involved in remodelling of DNA during replication

44
Q

what is the mode of action of rifampicin?

A

inhibits DNA polymerase, therefore preventing the synthesis of mRNA

45
Q

how is rifampicin used in clinical practice?

A

always administered in combination with another antibiotic

46
Q

which bacteria do colistin and daptomycin work against?

A

gram negatives

47
Q

what is a structural characteristic of colistin and daptomycin?

A

they are both cyclic lipopeptides

48
Q

what is the mode of action of colistin and daptomycin?

A

destroy PM by targeting a structure*

49
Q

why is this not used as first line treatment?

A

bacteria have colistin resistance

50
Q

which antibiotics are prescribed most commonly?

A

beta lactams

51
Q

what are the stages of beta lactic allergy?

A
  1. intolerance - nausea, diarrhoea, headache
  2. minor allergic reaction - non severe skin rash
  3. severe allergic reaction - anaphylaxis, urticaria, angio-oedema, bronchospasm, severe skin reaction, stevens-johnsons syndrome
52
Q

which antibiotics can be used in patients penicillin allergy?

A

cephalosporins and carbapenems (for non severe)

azetreonam (for all stages)

53
Q

what are the adverse effects of antibiotics on the body?

A 
nausea
vomiting
headache
skin rashes
infusion reactions
allergic reactions
54
Q

how are c diff infections caused?

A

by the destruction of the normal floras resistance to antibiotics, could potentially be a result of antibiotics

55
Q

how does C diff harm the body?

A

by production of enterotoxins A and B and spores

56
Q

what are the common antibiotics used for treatment of c diff?

A 
4 Cs
co-amoxiclav
cephalosporins
ciproflocacin
clindamycin
57
Q

what are the clinical strategies for use of antibiotics?

A

start broad, then focus (once cultures have been obtained)
only start antibiotics if there is a clinical evidence of bacterial infection
stop and re-evaluate the situation at 48 hours

58
Q

which drugs have a good in vevo efficacy in CSF and urine?

A

CSF - Beta lactams

urine - beta lactams and trimethoprim

59
Q

which drugs have a poor in veto efficacy in CSF and urine?

A

CSF - ahminoglycosides and vancomycin

urine - MLS

Clinical Pathology - (15 decks)

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