Antibiotics Flashcards
1
Q
What are the 4 main sites of antimicrobial action?
A
- Cell wall
- Protein synthesis
- Cell membranes
- Nucleic acid synthesis
2
Q
How do B-lactams function? What are some examples?
A
Penicillin is one.
B-lactams bind Penicillin Binding Proteins (PBPs), a type of transpeptidase.
This prevents the crosslinking of the peptidoglycan wall.
B-lactams mimic d-ala-d-ala residues on peptide side chains.
This stimulate autolysins to break down the cell wall.
3
Q
What do B-lactams mimic?
A
The d-ala-d-ala residues on peptide side chains.
This stimulates autolysins –> break down the cell wall.
4
Q
What type of antibiotic are glycopeptides?
A
- Inhibitors of cell wall synthesis, vancomycin, teicoplanin are examples.
- Bind terminal d-ala-d-ala on the peptide chain which prevents crosslinking.
5
Q
How do glycopeptides function as antibiotics?
A
Bind terminal d-ala-d-ala residues on the peptide chain and prevent cross linking.
6
Q
What are some common glycopeptides?
A
Vancomycin
Teicoplanin
7
Q
What is the mechanism of action of polymyxins?
A
Inhibit/disrupt the cell membrane. They cause leakage of cytoplasmic contents.
8
Q
How do nitroimidazoles function?
A
Act on nucleic acid synthesis, affecting DNA.
9
Q
How does rifampicin function?
A
Act on RNA polymerase.
Rifampicin is used for the treatment of tuberculosis in combination with other antibiotics, such as pyrazinamide, isoniazid, and ethambutol
10
Q
Vancomycin
A
Glycopeptide
11
Q
Fluoroquinolones function how?
A
Inhibit DNA synthesis.
12
Q
What drugs inhibit the metabolic synthesis of nucleic acid?
A
Sulphonamides, trimethoprim.
13
Q
Colistin
A
Polymyxin
14
Q
How do ciprofloxacin and levofloxacin function?
A
inhibit nucleic acid synthesis, via inhibiting metabolism.
15
Q
Teicoplanin
A
Glycopeptide
16
Q
What is the function of DNA gyrase? what inhibits this?
A
DNA gyrase removes DNA supercoils ahead of the replication fork. It is inhibited by both ciprofloxacin and levofloxacin.
17
Q
What is topoisomerase IV? what inhibits it?
A
It separates DNA strands after replication.
Inhibited by ciprofloxacin and levofloxacin.
18
Q
Macrolides, streptogramins and lincosamides all have what in common?
A
They bind to the 50s subunit of DNA and interfere with protein synthesis. They have overlapping binding sites.
19
Q
Inhibitors of Type II DNA gyrase and/or type IV topoisomerases.
A
Ciprofloxacin and levofloxacin.
20
Q
Sulphonamide
A
Inhibits nucleic acid synthesis, via inhibiting metabolism
21
Q
How does fusidic action function as an antibiotic?
A
Fusidic acid works by interfering with bacterial protein synthesis, specifically by preventing the translocation of the elongation factor G (EF-G) from the ribosome. It also can inhibit chloramphenicol acetyltransferase enzymes.
22
Q
What do aminoglycosides and tetracyclines have in common?
A
Both inhibit 30s subunit of ribosomes.
23
Q
What three antibiotics share the same mechanism of action and have overlapping binding sites?
A
Macrolides, streptogramins and lincosamides all function by inhibiting the 50s subunit of the ribosome. Prevent protein synthesis.
24
Q
Trimethoprim
A
Inhibits nucleic acid synthesis, via inhibiting metabolism
25
Which antibiotic works via preventing the translocation of the elongation factor G (EF-G) from the ribosome?
Fusidic acid works by interfering with bacterial protein synthesis, specifically by preventing the translocation of the elongation factor G (EF-G) from the ribosome. It also can inhibit chloramphenicol acetyltransferase enzymes.
26
These two antibiotics inhibit the 30S subunit of ribosomes.
Tetracyclines + aminoglycosides.
27
Oxazolidinones function how?
Oxazolidinones inhibit protein synthesis by binding to the P site at the ribosomal 50S subunit.
28
Linezolid works by:
Inhibiting protein synthesis by binding to the P site at the ribosomal 50S subunit. Member of the Oxazolidinone class of antibiotics.
29
Which antibiotic can inhibit chloramphenicol acetyltransferase enzymes?
Fusidic acid works by interfering with bacterial protein synthesis, specifically by preventing the translocation of the elongation factor G (EF-G) from the ribosome. It also can inhibit chloramphenicol acetyltransferase enzymes.
30
Macrolides
Macrolides, streptogramins and lincosamides all function by inhibiting the 50s subunit of the ribosome. Prevent protein synthesis.
31
Most aminoglycosides bind to what?
The 30S subunit, decreasing initiation and assembly of the ribosome and decreasing binding of tRNA in the A site and translocation/
32
Some aminoglycosides bind to what? (same as oxazolidinones)
The 50S subunit, decreasing the assembly of the initiation complex.
33
Doxycycline and minocycline are examples of what?
Tetracyclines. 30S subunit binders, decreasing binding of tRNA in the A site.
34
What is the mechanism of action of chloramphenicol?
Disrupts the formation of peptide bonds by binding to the 50s subunit of ribosomes.
35
Streptogramins
Macrolides, streptogramins and lincosamides all function by inhibiting the 50s subunit of the ribosome. Prevent protein synthesis.
36
Which antibiotics inhibit protein synthesis by binding to the P site at the ribosomal 50S subunit?
Oxazolidinones inhibit protein synthesis by binding to the P site at the ribosomal 50S subunit.
37
Macrolides such as..... function by....
Erythromycin, clarithromycin bind to 50S subunit, decreasing the translocation of tRNA from A to P site.
38
Cycloserine and bacitracin are similar how?
Both affect bacterial cell wall synthesis.
39
Lincosamides
Macrolides, streptogramins and lincosamides all function by inhibiting the 50s subunit of the ribosome. Prevent protein synthesis.
40
Penicillin, cephalosporin, monobactam and carbapenem all have what in common?
B-lactam ring.
41
What does the R group of a penicillin determine?
```
Solubility,
Stability,
Selectivity,
BA,
B-lactamase resistance.
```
42
What are the 4 main classes of penicillin's?
1. BL sensitive.
2. BL resistant
3. Broad spectrum
4. Anti-pseudomonal.
43
Which penicillin's are broad spectrum in activity? [4]
1. Ampicillin
2. Amoxicillin
3. Co-amoxiclav
4. Augmentin
44
Which penicillin's are B-lactamase resistant? [3]
1. Flucloxacillin
2. Co-fluampicil
3. Temocillin (from G-ve)
45
Which penicillin's are B-lactamase sensitive? [3]
1. Benzylpenicillin (PEN G)
2. Benzathine benzylpenicillin
3. Phenoxymethylpenicillin (PEN V)
46
What are the anti-psuedomonal penicillin's? [3]
1. Piperacillin
2. Piperacllin + tazobactam: Tazocin
3. Ticarcillin + Clavulonic acid: Timentin.
47
Benzathine benzylpenicillin
B-lactamase sensitive penicillin
48
Amoxicillin
Broad spectrum penicillin
49
Temocillin
B-lactamase resistant penicillin.
50
Benzylpenicillin (PEN G)
B-lactamase sensitive penicillin
51
Co-fluampicil
B-lactamase resistant penicillin.
52
Ampicillin
Broad spectrum penicillin
53
Phenoxymethylpenicillin (PEN V)
B-lactamase sensitive penicillin
54
Timentin
Ticarcillin + Clavulonic acid: anti-psuedomonal penicillin
55
Flucloxacillin
B-lactamase resistant penicillin.
56
Augmentin
Broad spectrum penicillin
57
Tazocin
Piperacillin + tazobactam: anti-psuedomonal penicillin
58
Piperacillin
anti-psuedomonal penicillin
59
Co-Amoxiclav
Broad spectrum penicillin
60
What are the typical uses of Pen G?
```
Throat infections
Endocarditis
Meningitis
Pneumonia
Cellulitis
Osteomyelitis
```
61
How do we maintain adequate and safe levels of Pen G?
Administer large doses, frequently and combine with benzathine benzylpenicillin which has slow release from the IM site.
62
What are the clinical uses of Amoxicillin?
Broad spectrum
Throat infections, otits media, sinusitis, oral infections.
Resp tract infections, UTIs, GIT.
63
What are the shared side effects of the penicillins?
```
Hypersensitivity
Neurotoxicity
Renal failure
Diarrhoea and pseudomembranous colitis.
C.diff
```
64
What are the properties of Cephalosporins?
1. Resistant to BLs but not ESBLs.
2. Active against G+ve due to affinity for PBPs, resistance to BLs.
3. Active against G-ve due to penetration through outer membrane.
65
How do polymyxins function?
Act at cell membrane.
Disrupts membrane leading to leakage of cytoplasmic contents.
Binds tightly to lipid A component of LPS in the outer membrane of gram negative bacteria.
66
Cefazolin and cefradine are examples of:
1st gen cephalosporins.
67
How did 2nd gen cephalosporins improve upon on 1st generation?
Improved gram-ve activity and increased resistance to betalactamases:
Cefuroxime
Cefaclor
68
Cefuroxime and Cefaclor are examples of:
2nd gen cephalosporins.
69
How were the 3rd gen cephalosporins an improvement on 2nd generation ones?
Improved activity and increased resistance to BLs.
| Cefotaxime, Ceftriaxone.
70
4th generation cephalosporins are commonly used against:
Psuedomonas.
Many can cross BBB.
Cefepime
Cefpirome
71
Cefepime and Cefpirome are:
4th gen cephalosporins.
72
Carbapenems function how?
```
Inhibition of cell wall synthesis.
Beta lactam ring containing.
Meropenem
Doripenem
Imipenem.
Highly resistant to limited and ESBL.
Broad spectrum of activity.
Active against P. aeruginosa.
```
73
Are carbapenems active against P. aeruginosa?
Yes.
74
What are carbapenems commonly used to treat?
```
Sept.
HAP.
Intraabdominal infections.
Skin and soft tissue infections.
Complicated UTI.
```
75
What issues are there with carbapenem use?
NDM-1, emerging resistance due to BLs.
76
What is aztreonam?
A beta-lactam antibiotic.
Inhibitor of cell wall synthesis.
Less likely to cause hypersensitivity.
77
Meropenem, doripenem and imipenem are what?
```
Carbapenems.
Inhibition of cell wall synthesis.
Beta lactam ring containing.
Highly resistant to limited and ESBL.
Broad spectrum of activity.
Active against P. aeruginosa.
```
78
Polymyxins bind tightly to what?
Lipid A compenent of LPS in the outer membrane of gram negative bacteria.
79
What is the MOA of bacitracin?
The CSS lipid molecule carrier transports PG monomers across the cytoplasmic membrane.
Bacitracin binds tightly to CSS-PP.
Blocks CSS-P recycling, decreasing the amount of carrier molecules.
80
How does bacitracin resistance occur?
Increased activity of phosphokinase leading to increased carrier molecules.
81
How does resistance to macrolides occur?
Altered target site.
Plasmid-mediated methylation of 23S rRNA by erm gene.
Inducible or constitutive.
82
The erm gene contributes to resistance to which antibiotic class?
Macrolides
83
How do glycopeptides function as antibiotics?
Inhibit cell wall synthesis.
Not active against Gram -ve.
Bind to terminal D-ala.
84
How do the uses of teicoplanin and vancomycin differ?
Vanc: systemic infections when given via an IV infusions and for C. diff infections when given orally.
Teicioplanin: IM/IV injection or infusion for systemic infections.
B-lactam resistant MRSA etc.
85
What is cycloserine?
Broad spectrum antibiotic effective against TB.
Can cause CNS side effects, rashes, liver damage.
As a cyclic analogue of D-alanine, cycloserine acts against two crucial enzymes important in the cytosolic stages of peptidoglycan synthesis.
86
Bacitracin
Used alongside poymyxin B in Polyfax. Used topically for skin and eye infections and the prevention of wound infections.
87
How do polymyxins function as antibiotics?
Lipid A compenent of LPS in the outer membrane of gram negative bacteria.
Cause membrane disruption and leakage of cytoplasm.
88
Polymyxin B
Topical.
89
Antibiotic with the side effect of contact allergic dermatitis:
Bacitracin.
Used alongside poymyxin B in Polyfax. Used topically for skin and eye infections and the prevention of wound infections.
Side effect of contact allergic dermatitis.
90
A cyclic analogue of D-alanine:
As a cyclic analogue of D-alanine, cycloserine acts against two crucial enzymes important in the cytosolic stages of peptidoglycan synthesis.
91
Antibiotic used alongside poymyxin B in Polyfax. Used topically for skin and eye infections and the prevention of wound infections.
Bacitracin.
| Side effect of contact allergic dermatitis.
92
Daptomycin
(Cubicin) is a lipopeptide that causes rapid depolarisation of cytoplasmic membrane leading to loss of function.
93
How are sulphonamides and trimethroprim similar? How do they differ?
Both inhibitors of the metabolism needed for NA synthesis.
S inhibits dihydropterate synthetase.
T inhibits dihydrofolate reductase.
Prevent synthesis of purines/pyrimidines.
94
How are sulphonamides and trimethoprim used?
S: limited clinical use.
T: orally for G-ve UTI (Not Ps), in combination as Co-trimoxale for pneumocytis pneumonia (PCP).
95
Inhibitor of nucleic acid metabolism found in combination as: Co-trimoxale:
Trimethoprim.
| Severe side effects: liver damage, bone marrow suppression etc.
96
Which antibiotic is a lipopeptide that causes rapid depolarisation of cytoplasmic membrane leading to loss of function?
Daptomycin/cubicin
97
Examples of fluoroquinolone antibiotics:
Ciprofloxacin
Levofloxacin
Moxifloxacin
Travafloxacin
98
MOA of fluoroquinolones:
Inhibit effective DNA replication.
| DNA gyrase + type IV topoisomerase.
99
Which antibiotic has side effects involving tendon damage which can appear months after effective treatment?
Ciprofloxacin.
100
Nitroimidazoles:
Metronidazole etc:
Fragment DNA.
Can lead to candida superinfection.
101
How are aminoglycosides used in practice?
IV for serious infections from aerobic bacteria.
102
Aminoglycosides block what?
Block assembly of the initiation complex and binding of tRNA to the A site.
Act at 30s subunit.
103
What are the side effects of Doxycycline?
Tetracycline:
| causes staining in teeth and a phototoxic reaction.
104
What is clindamycin?
Lincosamide.
105
Linezolid is what type of antibiotic?
Oxazolidinones.
| Binds 23S rRNA in 50s subunit, decreasing assembly of the initiation complex.
106
What spectrum is fusidic acid?
Narrow.
107
True or False:
| Chloramphenicol is used topically to treat eye infections
True
108
True or False:
| Fusidic acid is a narrow spectrum antibiotic used to treat skin infections
True
109
True or False:
| Aminoglycosides are a first line drug for community acquired pneumonia
FALSE.
110
True or False:
| Macrolides are used as an alternative to penicillins
True
111
True or False:
| Tetracyclines are broad spectrum antibiotics sometimes used to treat respiratory tract infections
True
112
True or False:
| Bacitracin inhibits cell wall synthesis by preventing assembly of the di-peptide D-ala-D-ala.
FALSE
| CSS Carrier molecules.
113
True or False:
| Acetylated chloramphenicol binds to the 50S ribosomal subunit and prevents protein synthesis.
FALSE:
Acetylation is how chloramphenicol is deactivated.
Fusidic acid can inhibit chloramphenicol acetyltransferases.
114
True or False:
| Polymyxins act primarily by binding to lipopolysaccharide in the outer membrane.
True. Lipid A.
115
True or False:
| Ciprofloxacin and clindamycin both inhibit bacterial protein synthesis
FALSE.
Ciprofloxacin: DNA gyrase/topoisomerase.
Clindamycin = lincosamide = 50s subunit?
116
True or False:
| Trimethoprim and the sulphonamides both inhibit synthesis of tetrahydrofolic acid
True
117
True or False:
| Resistance to b-lactams is often through enzymic inactivation
True
118
True or False:
| Resistance to tetracyclines can occur from efflux pumps
True, esp tetracyclines and quinolones.
119
True or False:
| Resistance to erythromycin usually results from methylation of 16S rRNA
False.
| Methylation of 23s caused by erm gene results in macrolide resistance.
120
True or False:
| Resistance to vancomycin can result from an altered target site
True.
| D-ala --> D-lactate = 5Hbonds --> 4Hbonds = unstable.
121
True or False:
| Resistance to rifampicin results from mutations in DNA gyrase
FALSE.
| Results from RNA polymerase mutations.
122
True or False:
| Fusidic acid can cause super infections
FALSE
| Fusidic acid is narrow spectrum.
123
True or False:
| Aminoglycosides can cause nephrotoxicity and ototoxicity
True.
124
True or False:
| Rifampicin can affect metabolism of the hormonal birth control pill
True. Also Isoniazid.
125
True or False:
| Chloramphenicol can cause 'Grey baby syndrome'
True
126
True or False:
| Erythromicin binds motilin receptor and can cause disturbances of the gastro-intestinal tract
True
127
True or False:
| Streptococcus mutans can cause meningitis.
```
FALSE.
These can cause it:
S. Aureus.
L. Monocytogenes.
S. Pneumoniae
N. Meningitidis
```
128
True or False:
| Penicillin G is given orally to treat tonsilitis
False.
| Pen G is IV only.
129
True or False:
| Tetracycline can be given topically to treat acne vulgaris
True.
130
True or False:
| Gentamicin is given orally to treat complicated urinary tract infections
False. IV/ antibiotics of last resort.
131
True or False:
| Erythromicin is a narrow spectrum antibiotic used to treat ear infections
FALSE: broad spectrum.
132
True or False:
| Vancomycin is given i.v. to treat serious infections caused by Gram negative bacteria
False.
| Gram -ve bacteria are intrinsically resistant to large drugs like glycopeptides.
133
True or False:
| eicoplanin and bacitracin are inhibtors of cell wall synthesis
True.
134
True or False:
| Rifampicin and trimethoprim are inhibitors of nucleic acid synthesis
True
135
True or False:
| Gentamicin and tetracycline bind to the 30S ribosomal subunit and inhibit protein synthesis
True
136
True or False:
| Polymyxin E distorts the outer membrane of Gram positive cocci
FALSE
| Only Gram -ve have an outer membrane.
137
True or False:
| Tetracyclines act on mammalian and microbial ribosomes
True
138
True or False:
| Pulmonary TB is caused by Mycobacterium tuberculosis
True
139
True or False:
| Meningitis can be caused by Streptococcus pneumoniae
True
140
True or False:
| Cellulitis is often caused by Streptococcus bovis
False. Staph. Aureus.
141
True or False:
| Urinary tract infections can be caused by E. coli
True
142
True or False:
| Community acquired pneumonia can be caused by Haemophilus influenzae
True
143
Zileuton is to _____ as celecoxib is to _____
5-lipoxygenase, COX-2
144
For Gentamicin, what values should be monitored to ensure efficacy and what values should be monitored to avoid toxicity?
Peak values should be monitored to ensure efficacy.
| Trough values should be monitored to avoid toxicity.
