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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

(113 cards)

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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
What is the concentration like comparing bactericidal vs bacteriostatic?
➝ bacteriostatic is usually lower
26
What is an example of a bacteriostatic antibiotic?
➝ Tetracycline
27
What is an example of a broad spectrum antibiotic and what are they effective against?
➝ Cefotaxime | ➝ Effective against many types
28
What is an example of a narrow spectrum antibiotic and what are they effective against?
➝ Penicillin G | ➝ effective against very few types
29
What are first generation cephalosporins effective for?
➝ effective for gram + but not gram -
30
What do you need to do to drugs to make them effective against gram - bacteria?
➝ chemically modify them
31
What are second generation cephalosporins effective for?
➝ they were modified to be more effective against gram - but as a result their gram + effectiveness was also reduced
32
What are third generation cephalosporins useless against?
➝ S. aureus
33
What type of antibiotics are beta lactams?
➝ structural mimics of natural substrates for enzymes
34
What antibiotics have beta lactam rings?
➝ penicillins | ➝ cephalosporins
35
What can bacteria have that makes beta lactams ineffective?
➝ beta lactamases which degrade the beta lactam structure
36
Which two antibiotic inhibit folic acid metabolism?
➝ Trimethoprim | ➝ Sulfonamide
37
Why is inhibiting folic acid effective?
➝ Humans don't have folic acid enzymes
38
Which two antibiotics inhibit the cell membrane synthesis?
➝ Colistin (cyclic polypeptide) | ➝ Daptomycin (lipopeptide)
39
Which 7 antibiotics inhibit cell wall synthesis?
``` ➝ Cycloserine ➝ Vancomycin, Teichoplanin ➝ Bacitracin ➝ penicillins ➝ Cephalosporins ➝ Monobactams ➝ carbapenems ```
40
Which 3 antibiotics inhibit 50S ribosome subunit and hence protein synthesis?
➝ Erythromycin ➝ Chloramphenicol ➝ Clindamycin
41
Which 8 antibiotics inhibit the 30S ribosome subunits and hence protein synthesis?
``` ➝ Tetracycline ➝ Spectinomycin ➝ Streptomycin ➝ Gentamycin, Tobramycin ➝ Amikacin ➝ Tigecycline ➝ Doxycycline ```
42
Which antibiotic inhibits DNA and RNA processing?
➝ Quinolones
43
How do antibiotics interfere with DNA and RNA processing?
➝ inhibit DNA Gyrase | ➝ inhibit DNA directed RNA polymerase
44
How does Rifampicin work?
➝ Inhibits bacterial RNA polymerase
45
What is the function of DNA gyrase?
➝ uncoiling DNA during replication
46
What are anaerobic bacteria treated with?
➝ Metronidazole
47
Why is colistin given even though it is toxic?
➝ they are effective against UTIs
48
What is the structure of a gram positive cell wall?
➝ lipid bilayer plasma membrane with integral proteins ➝ peptidoglycan cell wall ➝ lipoteichoic acids traversing the cell wall and are anchored in the cell membrane
49
What is the structure of a gram negative cell wall?
➝ lipid bilayer plasma membrane with integral proteins ➝ periplasmic space ➝ outer membranes with porins
50
How do antibiotics work on gram positive bacteria?
➝ they target the enzymes that make peptidoglycan | ➝ the enzymes are on the outer side of the lipid bilayer
51
How do antibiotics penetrate gram positive bacteria?
➝ they can penetrate the porous structure
52
Why can't you use antibiotics on gram negative bacteria?
➝ the outer membrane is impermeable | ➝ the only way things can cross through is through porins
53
What are peptidoglycans made from?
➝ cross linked pentapeptides
54
Why does a beta lactam that inhibits S aureus not work on E.coli?
➝ The peptidoglycan structure is different
55
Describe how bacterial cell walls get synthesized?
➝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
How do antibiotics interfere with the production of the bacterial cell wall?
➝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
How does vancomycin work to inhibit the production of the bacterial cell wall?
➝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
What do beta lactams act as?
➝ substrate mimics and competitive inhibitors for the trans and carboxypeptidases
59
What happens if you destroy the beta lactam ring?
➝ It breaks up the structure and is not a competitive inhibitor
60
What does the periplasmic space in gram negative bacteria contain?
➝ peptidoglycan structure
61
What are PBP?
➝ penicillin binding proteins
62
What kind of response do bacteria have if they cannot produce peptidoglycan?
➝ Autolytic response
63
Why can some bacteria not be treated with beta lactams?
➝ Not all bacteria have peptidoglycan cell walls
64
What is an example of bacteria that beta lactams do not work on?
➝ mycoplasma pneumoniae
65
How do cell walls get made in gram negative bacterial cell wall?
➝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
What do sulfonamides inhibit and how?
➝ dihydropteroate synthetase which is unique to bacteria | ➝ the sulfonamide structure is almost identical to PABA and competes against it
67
How is tetrahydrofolic acid synthesized?
Dihydropteroate diphosphate + p-aminobenzoic acid (PABA) enz : (dihydropteroate synthase) ↓ dihydropteroic acid ↓ tetrahydrofolic acid enz : (dihydrofolate reductase)
68
Why does trimethoprim not act on host enzymes?
➝ It has very low affinity for the host enzyme but high affinity for the bacterial enzyme
69
How does streptomycin work?
➝ binds to the 30S ribosome ➝ preventing binding of fmet t-RNA to the A site ➝ preventing initiation complex formation
70
How does gentamicin work?
➝ preventing translocation of fmet tRNA to P site
71
How does tetracyline work?
➝ competition with new aminoacyl t-RNA at the A site
72
How does chloramphenicol work?
➝ Blocks formation of peptide bond peptidyl transferase | ➝ binds to 50S subunit
73
How does erythromycin and fusidic acid work?
➝ blocks translocation of peptidyl t-RNA
74
What are the 7 reasons that antibiotics are used?
``` ➝ 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
What are the 3 methods of administration for antibiotics?
➝ IV ➝ topical ➝ oral
76
Why would you give IV antibiotics?
➝ Vomiting, unconscious, poor gut absorption due to trauma | ➝ unable to take oral
77
Why would you give topical antibiotics?
``` ➝ Conjunctivitis ➝ superficial skin infections ➝ burns ➝ antiseptic creams ➝ heavy metal ointments ```
78
What does the dose of antibiotic depend on?
``` ➝ age ➝ weight ➝ renal and liver function ➝ severity of the infection ➝ susceptibility of the organism ➝ properties of the antibiotic ```
79
In what 5 situations do you give antibiotic combinations?
➝ before an organism identified in life-threatening conditions ➝ polymicrobial infections ➝ less toxic doses of an individual drug possible ➝ synergy ➝ reduce antibiotic resistance
80
What are two life threatening conditions where an antibiotic combination has to be taken?
➝ endocarditis | ➝ septicaemia
81
What are 2 examples of polymicrobial infections?
➝ Abscess | ➝ GI perforation
82
What are 4 examples of cephalosporins?
➝ Cefalexin ➝ Cefuroxime ➝ Cefotaxime ➝ Ceftazidime
83
What is Cefalexin used to treat?
➝ An oral agent primarily used to treat UTIs
84
What is Cefuroxime used for?
➝ Parenteral 2nd generation agent with good activity against many gram + and gram - organisms
85
What is Cefotaxime used for?
➝ A parenteral 3rd generation agent with greater activity against many gram - and retaining gram + activity
86
What is Ceftazidime used for?
➝ A parenteral 3rd generation agent with a spectrum of activity extended to include pseudomonas aeruginosa
87
What are the 3 aminoglycosides?
➝ Gentamicin ➝ Amikacin ➝ Streptomycin
88
How must aminoglycosides be given and why?
➝ they cannot be absorbed from the gut and must be given parenterally
89
What are aminoglycosides active against?
➝ Predominantly against gram - bacteria including pseudomonas aeruginosa
90
Why must serum levels be monitored with aminoglycosides?
➝ these agents are nephrotoxic and ototoxic
91
What is an example of a macrolide?
➝ Erythromycin
92
What is erythromycin used to treat?
➝ gram + infections ➝ especially in those allergic to beta lactams ➝ mycoplasma pneumoniae and legionella pneumophilia
93
What are 2 examples of glycopeptides?
➝ Vancomycin and teicoplanin
94
What are glycopeptides used to treat?
➝ Active against only gram +
95
How should glycopeptides be given and when?
➝ For use when other agents cannot be used e.g MRSA | ➝ Parenteral only
96
What are 2 examples of tetracyclines?
➝ Oxytetracycline | ➝ Doxycycline
97
What kind of spectrum are tetracyclines?
➝ broad
98
What are tetracyclines used to treat?
➝ Chlamydia ➝ acne ➝ mycoplasma pneumoniae
99
What are two examples of quinolones?
➝ Ciprofloxacin | ➝ Moxifloxacin
100
What are quinolones used for?
➝ complicated UTIs and GI infections | ➝ respiratory tract infections
101
What is trimethoprim used for?
➝ UTIs
102
What is trimethoprim combined with?
➝ Sulfamethoxazole as co-trimoxazole
103
What is metronidazole effective against?
➝ anaerobic bacteria (and some parasites)
104
What spectrum is chloramphenicol?
➝ broad
105
What is chloramphenicol used for?
➝ topically for eye infections
106
Why is chloramphenicol not used systemically?
➝ because of side-effects
107
What kind of spectrum is fusidic acid?
➝ narrow
108
What is fusidic acid used to treat?
➝ staphylococcal infections only
109
What is nitrofurantoin useful for?
➝ UTIs
110
What type of drug is linezolid?
➝ Oxazolidinone
111
What is linezolid used for?
➝ Multi resistant gram + infections only
112
What kind of a drug is daptomycin and what is its spectrum like?
➝ lipopetide | ➝ similar to vancomycin
113
What is tigecycline used for?
➝ 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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