Antimicrobials Flashcards
1
Q
What can antimicrobials be classified into?
A
Antibacterials
Antifungals
Antivirals
Antiprotozoals
2
Q
How can antibacterials be classified?
A
Bactericidal or bacteriostatic
Broad or narrow
Target site
Chemical structure
3
Q
What do bactericidal antibacterials do?
A
Kill bacteria
4
Q
What do bacteriostatic antibacterials do?
A
Mainly inhibit
5
Q
What does the target site of an antibacterial depend on?
A
The mechanism of action
6
Q
What are the ideal features of an antimicrobial agent?
A
Selectively toxic Few adverse effects Reach site of infection Oral and IV formulation Long-half life No interference with other drugs
7
Q
Why should an antimicrobial be selectively toxic?
A
So it is minimally toxic
8
Q
Why should an antimicrobial have a long half life?
A
Allows for infrequent dosing
9
Q
What are the classes of mechanism of action of antibacterials?
A
Affect cell wall synthesis
Affect protein synthesis
Affect cell membrane function
Affect nucleic acid synthesis
10
Q
Give two examples of classes of antimicrobials that affect cell wall synthesis
A
Beta-lactams
Glycopeptides
11
Q
Give three examples of classes of antimicrobials that affect protein synthesis
A
Tetracyclines
Aminoglycosides
Macrolides
12
Q
Give an example of a class of antimicrobial that affects cell membrane function?
A
Polymixins
13
Q
Give an example of a polymixin
A
Colistin
14
Q
Give an example of a class of antimicrobial that affects nucleic acid synthesis
A
Quinolones
15
Q
Give two examples of quinolones
A
Trimethoprim
Rifampicin
16
Q
What are the most important classes of antibacterials?
A
Those that affect cell wall synthesis and those that interfere with protein synthesis
17
Q
What class of antibacterial is penicillin?
A
Beta-lactam
18
Q
What is penicillin binding protein?
A
A bacterial protein that physiologically cross-links the cell walls in bacteria
19
Q
What is the mechanism of action of penicillin?
A
It binds to penicillin binding protein and inhibits it from cross-link the cell wall
20
Q
What class of antimicrobial is vancomycin?
A
Glycopeptide
21
Q
What is the mechanism of action of vancomycin?
A
It sits on the cross-links of the forming cell wall and stops penicillin binding protein from attaching, preventing cross-links from being attached to each other by the cell wall cross-linking enzyme
22
Q
What class of antimicrobial are fluoroquinolones?
A
Quinolone
23
Q
What is the mechanism of action of fluoroquinolones?
A
Interferes with the action of DNA gyrase during bacterial growth
24
Q
What does DNA gyrase do?
A
Physiologically catalyses the supercoiling of DNA
25
How do fluoroquinolones interfere with the action of DNA gyrase?
Binds to both the enzyme and DNA to form a ternary (three molecule) complex, inhibiting the rejoining step and thus causes cell death
26
What are the mechanisms of antimicrobial resistance?
Drug inactivating enzymes
Altered target
Altered uptake
27
Give two examples of antimicrobials affected by drug inactivating enzymes
Beta-lactamases
| Aminoglycosides
28
What happens in the altered target mechanism of antimicrobial resistance?
Target enzyme has a lowered affinity for antibacterial
29
Give three examples of antimicrobials affected by the altered target mechanism of resistance
Methicillin
Macrolides
Trimethoprim
30
What is caused by antibiotic resistance to methicillin?
MRSA
31
How can altered uptake be achieved in antibiotic resistance?
Decreased permeability
| Increased efflux
32
Give an example of an antimicrobial affected by the decreased permeability mechanism of resistance
Beta-lactams
33
Give an example of an antimicrobial affected by the increased efflux mechanism of resistance
Tetracyclines
34
How can antibiotic resistance be genetically obtained?
Chromosomal gene mutation
| Horizontal gene transfer
35
How does a chromosomal gene mutation result in antimicrobial resistance?
A chromosome mutates to contain a gene that confers resistance.
An antibiotic is then applied and the resistant gene is selected for, as only the resistant bacteria will survive.
The surviving bacteria can then replicate to produce large numbers of bacteria the now carry the mutated resistance gene
36
What can antibiotic resistance genes be carried on?
Chromosomes
Plasmids
Transposons
37
How can antibiotic resistance genes be transferred?
Conjugation
Transduction
Transformation
38
How does antimicrobial resistance transfer by conjugation?
Resistant cell carries the gene on a plasmid or transposon that passes it on to another cell via pili
39
How does antimicrobial resistance transfer by transduction?
Resistant cell is infected by bacteriophage virus.
During replication of bacteriophages within resistant cell, bacterial DNA containing resistant gene is packaged into one of the phages
The bacteriophage then goes on to transfer the resistant gene to a non-resistant cell that incorporates it into its genes via recombination
40
How does antimicrobial resistance transfer by transformation?
Resistant cell carries the gene on a chromosome of plasmid
The resistant cell dies, and releases its DNA
The free DNA is picked up by the competent non-resistant cell, that has now acquired resistance
41
What happens once antimicrobial resistant is acquired by another cell?
It can go on to replicate so that it's off-spring now possess the resistance gene
42
How can antibiotic activity be measured?
Disc sensitivity tests
| Minimum inhibitory concentration
43
What happens in disc sensitivity tests?
Discs of antimicrobials are placed in a petri-dish containing clear agar, where a culture of bacteria is to be grown
44
How are the results of a disc sensitivity test interpreted?
The size of the clear agar around each disc correlates with its effectiveness
45
What happens in a minimum inhibitory concentration test?
There are two control test tubes, one with no antibacterials and bacteria, and one with no antibacterials and no bacteria.
The concentration of antibacterial is halved each test tube, and observe to see when no bacterial growth is observed- when the broth is not turbid
46
What are the types of beta-lactams?
Penicillins
Cephalosporins
Carbapenums
Monobactams
47
Give 5 examples of penicillins
```
Benzylpenicillin
Amoxicillin
Flucloxacillin
Co-amoxiclav
Tazocin
```
48
What is co-amoxiclav?
Amox and clavulanate
49
What is tazocin?
Piperacillin + tazobactam
50
Give an example of a cephalosporin?
Ceftriaxone
51
Give an example of a carbapenum
Meropenum
52
Give an example of a monobactam
Aztreonam
53
What is penicillin mainly active against?
Streptococci
54
What is amoxicillin active against?
Gram +ve, some gram -ve
55
What is flucloxacillin active against?
Staphylococci and streptococci
56
Give two beta-lactamase inhibitor combinations
Co-amoxiclav
| Tazocin
57
What is co-amoxiclav active against?
Gram +ve
Anaerobes
More gram -ve than other penicillins
58
What is Tazocin active against?
Same as co-amoxiclav, and even more gram negative, including pseudomonas
59
How are cephalosporins organised?
Into generations
60
How do each generation of cephalosporin differ?
Each generation has increased activity against gram -ve and decreased activity against gram +ve
61
What is the advantage of cephalosporins over penicillin?
More broad spectrum drug
62
What is the disadvantage of cephalosporins over penicillins?
No anaerobes activity
63
Where does ceftriaxone have good activity?
In the CSF
64
What are there concerns over regarding cephalosporins?
Association with C. Difficile
65
What are the advantages of meropenum?
Very broad spectrum, including anaerobes
Active against most Gram -ve
Generally safe in penicillin allergy
66
When are meropenum not safe in penicillin allergy?
Anaphylaxis
67
What is vancomycin active against?
Most gram +ve
68
What is the resistance situation regarding vancomycin?
Some enterococci are resistant
| Resistance in staphs is rare
69
What is the problem with vancomycin?
Not absorbed
| Therapeutic drug monitoring
70
When is vancomycin given orally?
C. Difficle only
71
Why is therapeutic drug monitoring required for vancomycin?
Narrow therapeutic window
72
What is the activity of teicoplanin similar to?
Vancomycin
73
What is the advantage of teicoplanin over vancomycin?
Easier to administer
74
What are the similarities between tetracyclines and doxycycline?
Similar spectrum
| Oral only
75
Where are tetracycline and doxycycline used?
Broad-spectrum, but specific use in penicillin allergy, usually from gram +ve
Atypical pathogens in pneumonia
Chlamydia and some protozoa
76
Who shouldn't tetracycline and doxycycline be given to?
Children under 12 years
77
Why shouldn't tetracycline and doxycycline be given to children under 12 years?
Stains teeth and bones
78
What is the most common aminoglycoside?
Gentamicin
79
What is gentamicin active against?
Profound activity against gram negatives
80
Where does gentamycin have good activity?
In the blood and urine
81
What is the problem with gentamicin?
Potentially nephrotoxic/ototoxic
82
What is required with gentamicin?
Therapeutic drug monitoring
83
What is gentamicin generally reserved for?
Severe gram -ve sepsi
84
Give two macrolides
Erythromycin
| Clarithromycin
85
What is good about erythromycin?
Well distributed, including intracellular penetration
86
Where is erythromycin used?
Alternative to penicillin for mild gram +ve infections
| Active against atypical respiratory pathogens
87
What is the most common example of quinolone?
Ciprofloxacin
88
What is the mechanism of action of ciprofloxacin?
Inhibit DNA gyrase
89
What is ciprofloxacin active against?
Very active against atypical pathogens
90
What is the problem with ciprofloxacin?
Increasing resistance
| Risk of C. Difficile
91
What is the mechanism of action of trimethoprim and sulphonamides?
Inhibitors of folic acid synthesis
92
When is trimethoprim used alone in the UK?
UTI
93
What is co-trimoxazole?
Sulphamethoxazole and trimethoprim
94
What is co-trimoxazole used for?
Treat PCP
| Has activity against malaria
95
What are the classes of antifungals?
Azoles
| Polyenes
96
What are azoles active against?
Yeasts, and sometimes molds
97
What is the mechanism of action of azoles?
Inhibits cell membrane synthesis
98
Give an example of an azole?
Fluconazole
99
What is fluconzole used for?
Treat Candida
100
What is itra/vori/posaconazole active against?
Aspergillus
101
Give two polyenes
Nystatin
| Amphotericin
102
What is the mechanism of action polyenes?
Inhibit cell membrane function
103
What is nystatin used for?
Topical treatment of Candida
104
What is amphotericin used for?
IV treatment of systemic fungal infection, e.g. Aspergillus
105
Give two antivirals
Aciclovir
| Oseltamivir
106
What is the mechanism of action of aciclovir?
When phosphorylated, it inhibits viral DNA polymerase
107
What is aciclovir active against?
Herpes simplex
| Varicella zoster
108
Give two things caused by herpes simplex
Genital herpes
| Encephalitis
109
Give two things caused by varicella zoster
Chickenpox
| Shingles
110
What is the commercial name for oseltamivir?
Tamiflu
111
What is the mechanism of action of tamiflu?
Inhibits viral neuraminidase
112
What does tamiflu treat?
Influenza A and B
113
What conditions require specialist antivirals for treatment?
HIV
HBV
HCV
CMV
114
What kind of antimicrobial is metronidazole?
Antibacterial and antiprotozotal
115
What bacteria is metronidazole active against?
Anaerobic
116
What protozoa is metronidazole active against?
Amoebae
Giardia
Trichomonas
117
What does amoebae cause?
Dysentry
118
What does giardia cause?
Diarrhoea
119
What does trichomonas cause?
Vaginitis
120
What is the purpose of antimicrobial stewardship?
Aims to guide practitioners on how to use antimicrobials in children, young people, and adults, with the outcome of slowing the progress of antimicrobial resistance. This will hopefully ensure that antimicrobials remain an effective treatment for infection
