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π“œπ‘’π’Ήπ’Ύπ’Έπ’Άπ“ π“œπ’Ύπ’Έπ“‡π‘œπ’·π’Ύπ‘œπ“π‘œπ‘”π“Ž > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

What are antibiotics made from?

A

➝ Natural products of fungi and bacteria
➝ derived from natural products by fermentation
➝ then modified chemically to increase antimicrobial effects

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2
Q

Why are other bacteria and fungi used as a source of antibiotics?

A

➝ Natural antagonism and selective advantage

➝ It allows the organism to live in the soil without other organisms killing them

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3
Q

What is an example of a synthetic antibiotic?

A

➝ Sulphonamides

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4
Q

How did Fleming discover penicillin?

A

➝ He left an agar plate on the windowsill for too long

➝ mold lysed all S. Aureus colonies

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5
Q

What is selective toxicity due to?

A

➝ Differences in structure and metabolic pathways between the host and the pathogen

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6
Q

What is the aim of selective toxicity?

A

➝ target the microbe not the host

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7
Q

Why is selective toxicity difficult to achieve?

A

➝ There is variation between microbes

➝ viruses, fungi and parasites are intracellular

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8
Q

What is the active dose like for toxic drugs?

A

➝ Narrow

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9
Q

What does the dose need to be?

A

➝ high enough to kill the pathogen but low enough to not cause harm to the body

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10
Q

What is it called if the difference between the effective dose and the toxic dose is small?

A

➝ Narrow therapeutic margin

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11
Q

What is the minimum inhibitory concentration?

A

➝ concentration at which the drug needs to be effective

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12
Q

If someone is on vancomycin why do you have to do blood tests?

A

➝ to make sure that the levels of antibiotics have not reached toxic levels

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13
Q

What type of toxicity do aminoglycosides and vancomycin have?

A

➝ ototoxicity and nephrotoxicity

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14
Q

What is microbial antagonism?

A

➝ one organism producing something that inhibits the growth of another due to competition between flora

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15
Q

What does loss of flora lead to?

A

➝ Bacterial or pathogen overgrowth

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16
Q

How can antibiotics cause C.diff?

A

➝ lots of people have C.diff as a commensal in their gut and if they take antibiotics C. diff can outgrow the flora

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17
Q

What is pseudomembranous colitis?

A

➝ swelling or inflammation of the colon due to overgrowth of C.diff

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18
Q

What antibiotics cause antibiotic associated colitis?

A

➝ Clindamycin
➝ Broad spectrum lactams
➝ Fluoroquinolones

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19
Q

Why is it difficult to decontaminate a C.diff infection?

A

➝ The spores are volatile and get everywhere

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20
Q

What does antibiotic + immunity lead to?

A

➝ bacterial clearance

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21
Q

What modifications do you have to do to an antibiotic course to people who are imunosuppressed?

A

➝ more toxic antibiotics

➝ combinations of antibiotics

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22
Q

What are the three ways antibiotics are classified by?

A

➝ Type of activity
➝ Structure
➝ Target site for activity

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23
Q

What do bactericidal antibiotics do and when are they used?

A

➝ Kill bacteria
➝ used when the host defense mechanisms are impaired
➝ required in endocarditis, kidney infection

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24
Q

What do bacteriostatic antibiotics do and when are they used?

A

➝ Inhibit bacteria
➝ used when the host defense mechanisms are intact
➝ used in many infectious diseases

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25
Q

What is the concentration like comparing bactericidal vs bacteriostatic?

A

➝ bacteriostatic is usually lower

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26
Q

What is an example of a bacteriostatic antibiotic?

A

➝ Tetracycline

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27
Q

What is an example of a broad spectrum antibiotic and what are they effective against?

A

➝ Cefotaxime

➝ Effective against many types

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28
Q

What is an example of a narrow spectrum antibiotic and what are they effective against?

A

➝ Penicillin G

➝ effective against very few types

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29
Q

What are first generation cephalosporins effective for?

A

➝ effective for gram + but not gram -

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30
Q

What do you need to do to drugs to make them effective against gram - bacteria?

A

➝ chemically modify them

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31
Q

What are second generation cephalosporins effective for?

A

➝ they were modified to be more effective against gram - but as a result their gram + effectiveness was also reduced

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32
Q

What are third generation cephalosporins useless against?

A

➝ S. aureus

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33
Q

What type of antibiotics are beta lactams?

A

➝ structural mimics of natural substrates for enzymes

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34
Q

What antibiotics have beta lactam rings?

A

➝ penicillins

➝ cephalosporins

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35
Q

What can bacteria have that makes beta lactams ineffective?

A

➝ beta lactamases which degrade the beta lactam structure

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36
Q

Which two antibiotic inhibit folic acid metabolism?

A

➝ Trimethoprim

➝ Sulfonamide

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37
Q

Why is inhibiting folic acid effective?

A

➝ Humans don’t have folic acid enzymes

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38
Q

Which two antibiotics inhibit the cell membrane synthesis?

A

➝ Colistin (cyclic polypeptide)

➝ Daptomycin (lipopeptide)

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39
Q

Which 7 antibiotics inhibit cell wall synthesis?

A 
➝ Cycloserine
➝ Vancomycin, Teichoplanin
➝ Bacitracin
➝ penicillins
➝ Cephalosporins
➝ Monobactams 
➝ carbapenems
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40
Q

Which 3 antibiotics inhibit 50S ribosome subunit and hence protein synthesis?

A

➝ Erythromycin
➝ Chloramphenicol
➝ Clindamycin

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41
Q

Which 8 antibiotics inhibit the 30S ribosome subunits and hence protein synthesis?

A 
➝ Tetracycline
➝ Spectinomycin
➝ Streptomycin
➝ Gentamycin, Tobramycin
➝ Amikacin 
➝ Tigecycline
➝ Doxycycline
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42
Q

Which antibiotic inhibits DNA and RNA processing?

A

➝ Quinolones

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43
Q

How do antibiotics interfere with DNA and RNA processing?

A

➝ inhibit DNA Gyrase

➝ inhibit DNA directed RNA polymerase

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44
Q

How does Rifampicin work?

A

➝ Inhibits bacterial RNA polymerase

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45
Q

What is the function of DNA gyrase?

A

➝ uncoiling DNA during replication

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46
Q

What are anaerobic bacteria treated with?

A

➝ Metronidazole

47
Q

Why is colistin given even though it is toxic?

A

➝ they are effective against UTIs

48
Q

What is the structure of a gram positive cell wall?

A

➝ lipid bilayer plasma membrane with integral proteins
➝ peptidoglycan cell wall
➝ lipoteichoic acids traversing the cell wall and are anchored in the cell membrane

49
Q

What is the structure of a gram negative cell wall?

A

➝ lipid bilayer plasma membrane with integral proteins
➝ periplasmic space
➝ outer membranes with porins

50
Q

How do antibiotics work on gram positive bacteria?

A

➝ they target the enzymes that make peptidoglycan

➝ the enzymes are on the outer side of the lipid bilayer

51
Q

How do antibiotics penetrate gram positive bacteria?

A

➝ they can penetrate the porous structure

52
Q

Why can’t you use antibiotics on gram negative bacteria?

A

➝ the outer membrane is impermeable

➝ the only way things can cross through is through porins

53
Q

What are peptidoglycans made from?

A

➝ cross linked pentapeptides

54
Q

Why does a beta lactam that inhibits S aureus not work on E.coli?

A

➝ The peptidoglycan structure is different

55
Q

Describe how bacterial cell walls get synthesized?

A

➝The synthesis starts off by a precursor monomer of a disaccharide with 5 peptides
➝The last 2 peptides in the monomer are alanines (isomers specific to bacteria D-ala)
➝After this the precursor is linked to a lipid transport molecule which transports it across the membrane
➝5 cross linked amino acids are added to the peptide chain
➝It is polymerised in the cell wall by enzymes
➝The enzyme recognises the terminal D-ala and cleaves it off, it then attaches it to the next pentapeptide
➝The cross linking is done by enzymes called trans and carboxypeptidases
➝They are only found in bacterial cell walls

56
Q

How do antibiotics interfere with the production of the bacterial cell wall?

A

➝block the production of D-ala (cycloserine)
➝ prevent the transport of the D-ala across the membrane
➝Beta lactams inhibit enzymes that do the crosslinking

57
Q

How does vancomycin work to inhibit the production of the bacterial cell wall?

A

➝Vancomycin is not a beta lactam but it affects peptidoglycan synthesis by recognising the D-ala terminal and binds to it
➝This means the carboxypeptidases can’t act on the D-ala substrate because the vancomycin is attached to it

58
Q

What do beta lactams act as?

A

➝ substrate mimics and competitive inhibitors for the trans and carboxypeptidases

59
Q

What happens if you destroy the beta lactam ring?

A

➝ It breaks up the structure and is not a competitive inhibitor

60
Q

What does the periplasmic space in gram negative bacteria contain?

A

➝ peptidoglycan structure

61
Q

What are PBP?

A

➝ penicillin binding proteins

62
Q

What kind of response do bacteria have if they cannot produce peptidoglycan?

A

➝ Autolytic response

63
Q

Why can some bacteria not be treated with beta lactams?

A

➝ Not all bacteria have peptidoglycan cell walls

64
Q

What is an example of bacteria that beta lactams do not work on?

A

➝ mycoplasma pneumoniae

65
Q

How do cell walls get made in gram negative bacterial cell wall?

A

➝PBP (penicillin binding proteins) are cross linking proteins in the cytoplasmic membrane
➝The precursors are made and they are added to the pentapeptide by the PBP then transferred to the periplasmic space

66
Q

What do sulfonamides inhibit and how?

A

➝ dihydropteroate synthetase which is unique to bacteria

➝ the sulfonamide structure is almost identical to PABA and competes against it

67
Q

How is tetrahydrofolic acid synthesized?

A

Dihydropteroate diphosphate + p-aminobenzoic acid (PABA) enz : (dihydropteroate synthase)
↓
dihydropteroic acid
↓
tetrahydrofolic acid enz : (dihydrofolate reductase)

68
Q

Why does trimethoprim not act on host enzymes?

A

➝ It has very low affinity for the host enzyme but high affinity for the bacterial enzyme

69
Q

How does streptomycin work?

A

➝ binds to the 30S ribosome
➝ preventing binding of fmet t-RNA to the A site
➝ preventing initiation complex formation

70
Q

How does gentamicin work?

A

➝ preventing translocation of fmet tRNA to P site

71
Q

How does tetracyline work?

A

➝ competition with new aminoacyl t-RNA at the A site

72
Q

How does chloramphenicol work?

A

➝ Blocks formation of peptide bond peptidyl transferase

➝ binds to 50S subunit

73
Q

How does erythromycin and fusidic acid work?

A

➝ blocks translocation of peptidyl t-RNA

74
Q

What are the 7 reasons that antibiotics are used?

A 
➝  Treatment of bacterial infections
➝  prophylaxis 
➝  decreased carriage rates
➝  prevention of infections
➝  peri-operative cover for gut surgery 
➝  people with higher susceptibility to infection
➝  inappropriate use
75
Q

What are the 3 methods of administration for antibiotics?

A

➝ IV
➝ topical
➝ oral

76
Q

Why would you give IV antibiotics?

A

➝ Vomiting, unconscious, poor gut absorption due to trauma

➝ unable to take oral

77
Q

Why would you give topical antibiotics?

A 
➝  Conjunctivitis
➝  superficial skin infections 
➝ burns
➝  antiseptic creams
➝  heavy metal ointments
78
Q

What does the dose of antibiotic depend on?

A 
➝  age
➝  weight 
➝  renal and liver function 
➝ severity of the infection
➝  susceptibility of the organism
➝  properties of the antibiotic
79
Q

In what 5 situations do you give antibiotic combinations?

A

➝ before an organism identified in life-threatening conditions
➝ polymicrobial infections
➝ less toxic doses of an individual drug possible
➝ synergy
➝ reduce antibiotic resistance

80
Q

What are two life threatening conditions where an antibiotic combination has to be taken?

A

➝ endocarditis

➝ septicaemia

81
Q

What are 2 examples of polymicrobial infections?

A

➝ Abscess

➝ GI perforation

82
Q

What are 4 examples of cephalosporins?

A

➝ Cefalexin
➝ Cefuroxime
➝ Cefotaxime
➝ Ceftazidime

83
Q

What is Cefalexin used to treat?

A

➝ An oral agent primarily used to treat UTIs

84
Q

What is Cefuroxime used for?

A

➝ Parenteral 2nd generation agent with good activity against many gram + and gram - organisms

85
Q

What is Cefotaxime used for?

A

➝ A parenteral 3rd generation agent with greater activity against many gram - and retaining gram + activity

86
Q

What is Ceftazidime used for?

A

➝ A parenteral 3rd generation agent with a spectrum of activity extended to include pseudomonas aeruginosa

87
Q

What are the 3 aminoglycosides?

A

➝ Gentamicin
➝ Amikacin
➝ Streptomycin

88
Q

How must aminoglycosides be given and why?

A

➝ they cannot be absorbed from the gut and must be given parenterally

89
Q

What are aminoglycosides active against?

A

➝ Predominantly against gram - bacteria including pseudomonas aeruginosa

90
Q

Why must serum levels be monitored with aminoglycosides?

A

➝ these agents are nephrotoxic and ototoxic

91
Q

What is an example of a macrolide?

A

➝ Erythromycin

92
Q

What is erythromycin used to treat?

A

➝ gram + infections
➝ especially in those allergic to beta lactams
➝ mycoplasma pneumoniae and legionella pneumophilia

93
Q

What are 2 examples of glycopeptides?

A

➝ Vancomycin and teicoplanin

94
Q

What are glycopeptides used to treat?

A

➝ Active against only gram +

95
Q

How should glycopeptides be given and when?

A

➝ For use when other agents cannot be used e.g MRSA

➝ Parenteral only

96
Q

What are 2 examples of tetracyclines?

A

➝ Oxytetracycline

➝ Doxycycline

97
Q

What kind of spectrum are tetracyclines?

A

➝ broad

98
Q

What are tetracyclines used to treat?

A

➝ Chlamydia
➝ acne
➝ mycoplasma pneumoniae

99
Q

What are two examples of quinolones?

A

➝ Ciprofloxacin

➝ Moxifloxacin

100
Q

What are quinolones used for?

A

➝ complicated UTIs and GI infections

➝ respiratory tract infections

101
Q

What is trimethoprim used for?

A

➝ UTIs

102
Q

What is trimethoprim combined with?

A

➝ Sulfamethoxazole as co-trimoxazole

103
Q

What is metronidazole effective against?

A

➝ anaerobic bacteria (and some parasites)

104
Q

What spectrum is chloramphenicol?

A

➝ broad

105
Q

What is chloramphenicol used for?

A

➝ topically for eye infections

106
Q

Why is chloramphenicol not used systemically?

A

➝ because of side-effects

107
Q

What kind of spectrum is fusidic acid?

A

➝ narrow

108
Q

What is fusidic acid used to treat?

A

➝ staphylococcal infections only

109
Q

What is nitrofurantoin useful for?

A

➝ UTIs

110
Q

What type of drug is linezolid?

A

➝ Oxazolidinone

111
Q

What is linezolid used for?

A

➝ Multi resistant gram + infections only

112
Q

What kind of a drug is daptomycin and what is its spectrum like?

A

➝ lipopetide

➝ similar to vancomycin

113
Q

What is tigecycline used for?

A

➝ used against multiply resistant gram + and -

π“œπ‘’π’Ήπ’Ύπ’Έπ’Άπ“ π“œπ’Ύπ’Έπ“‡π‘œπ’·π’Ύπ‘œπ“π‘œπ‘”π“Ž (17 decks)

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