plenary 3 antibacterials Flashcards
1
Q
antibiotics definition
A
microbial metabolites which can kill or inhibit the growth of susceptible bacteria
2
Q
what does the therapeutic use of ABs depend on
A
their selective toxicity
3
Q
at therapeutic levels ABs have either
A
bacteriostatic or bacteriocidial effect
4
Q
what does bacteriostatic mean
A
inhibits the growth of bacteria, allowing the host immune defenses to eliminate the infection
5
Q
what does bacteriocidal mean
A
cause irreperable damage and bacterial cell death
6
Q
name some bacteriostatic antimicrobials
A
- tetracyclines
- chloramphenicol
- macrolides
- sulfonamides
- trimetoprim
- nitrofurans
- lincosamides
- rifampicins
- novobiocin
7
Q
name some bacteriocidal antimicrobials
A
- beta lactam ABs
- polypeptides
- aminoglycosides
- quinolines
- bacitracin
- vancomycin
- nitroimidazoles
8
Q
modes and sites of action for antibacterial drugs
A
- inhibition of cell wall synthesis
- inhibition of cell membrane function
- inhib. protein synthesis
- inhib DNA dependant RNA polymerase
- inhib DNA gyrase
- disrupt DNA structure
- Inhibit DNA synthesis
9
Q
which inhibit cell wall synthesis
A
- beta lactam abs
- bacitracin
- vancomycin
10
Q
which inhibit cell wall funct
A
polypeptides
11
Q
which inhibit protein synthesis at 30S
A
- aminoglycosides
- tetracyclines
12
Q
which inhibit protein synthesis at 50S
A
- chloramphenicol
- macrolides
- lincosamides
- nitrofurans
13
Q
which inhibit DNA dependant RNA polymerase
A
rifampicins
14
Q
which inhibit DNA gyrase
A
- quinolones
- novobiocin
15
Q
which disrupt DNA structure
A
nitroimidazoles
16
Q
which inhibit DNA synthesis
A
- sulfonamides
- trimethoprim
17
Q
cell wall inhibitors
A
- penicillins
- cephalosporins
- vancomycin
18
Q
penicillins mechanism of action
A
block polypeptide synthesis
19
Q
what are penicillins active against
A
only against actively growing cells
20
Q
are penicillins active against Gr-
A
mainly Gr+ but some Gr-
21
Q
are penicillins sensitive to acids
A
yes
22
Q
how are penicillins eliminated
A
by renal excretion
23
Q
penicillins half life
A
short
24
Q
penicllins solubility in lipids
A
low
25
penicillins IC conc
low
26
how are bact becoming resistant to penicillins
- beta-lactamase enzymes
| - lack of penicillin binding protein receptors
27
which microbacteria do cephalosporins come from
cephalosporin acremonium
28
are cephalosporins Gr-
mainly
29
resistance to cephalosporins
- structural
- modification of binding site
- beta-lactamase enzyme
30
as we incr generations what happens to the spectrum of cephalosporins
it increases
31
generation one cephalosporins
Gr+ rods, Gr- cocci
32
2nd generation cephalosporins
wider spectrum, lactamase stability
33
3rd generation cephalosporins
more wider spectrum
34
4th generation cephalosporins
very broad spectrum
35
against which type is vancomycin
only against Gr+ bacteria
36
polymyxins mechanism of action
they do damage to the cell membrane funct
37
two parts of polymyxins
hydrophobic and hydrophilic parts
38
what do polymyxins do when they bind to the cell membrane phospholipids
they cause structural disorganisation, permeability damage and cell lysis
39
polymyxins are selectively toxic to which type of gram bact
gr-
40
do polymyxins act on multiplying cells
yes, both resting and multiplying
41
resistance to polymyxins
rare
42
aminoglycosides mechanism of action
inhibition of protein synthesis
43
aminoglycosides are active against which types of bacteria
Gr- bact, mycobacteria
44
adverse effects aminoglycosides
ototoxic and nephrotoxic
45
aminoglycosides resistance
- binding site
- anaerobic bact
- inactivating enzymes
- pH - active in alkaline enviro
46
tetracyclines mechanism of action
inhibition of binding of tRNA
47
spectrum tetracyclines
wide
48
resistance tetracyclines
- inhibition of transport
| - efflux
49
where do we see a cross resistance in the tetracyclines group
between tetracyclines
50
chloramphenicol mechanism of action
inhibition of protein synthesis
51
which enzymes do the chloramphenicol group inhibit
peptidyl-transferase - inhibit transpeptidation
52
spectrum chloramphenicols
wide
53
are chloramphenicols lipid soluble
yes
54
resistance chloramphenicols
chloramphenicol-acetylase
55
macrolides mechanism of action
inhibition of binding of tRNA to ribosomes
56
are macrolids lipid soluble
yes
57
macrolides act on which type of bacteria
mainly Gr+ and some Gr-
58
macrolids resistance
structural, modification of binding site, cross resistance
59
lincosamides mechanism of action
inhibition of peptidyl transferase
60
which bact do lincosamides act on
mainly Gr- aerobic and anaerobic, mycoplasma
61
quinolines mechanism of action
inhibition of superhelix of DNA
62
which enzyme in particular do quinolines inhibit
DNA-gyrase
63
which types of bact do quinolines act on
both Gr+ and Gr-
64
quinolines resistance
- transport
- obligate anaerobes
- modification of gyrase
65
rifampins mechanism of action
inhibition of RNA replication
66
rifampins inhibit which enzyme in particular
DNA dependant RNA polymerase
67
rifampins spectrum
wide
68
rifampins resistance
mutation results in alteration of enzyme
69
bc resistance is common how is rifampin usually used
in combo therapy
70
sulfonamides mechanism of action
interfere with biosynthesis of folic acid and prevent synthesis of purine nucleotides
71
what do sulfonamides produce to stop folic acid production
functional analogues of PABA to compete for enzyme-> forming non funct folic acid analogues
72
which type of bact do sulfonamides act on
mainly Gr+
73
sulfonamides resistance
- metabolic changes
- inactivating enzymes
- exogenous folic acid
74
at which enzyme do sulfonamides stop folic acid synthesis
pteridine synthetase
75
at which enzyme do trimethoprims stop folic acid synthesis
dihydrofolate reductase
76
under what conditions are nitrofurans most active
anaerobic conditions
77
what are the unstable reduction products that nitrofurans produce able to cause
strand breakage in bacterial DNA
78
when are nitrofurans usually used
in local treatment and treatment of UTIs
79
ntiroimidazoles' reactive metabolites can do what
damage bacterial DNA
80
nitroimidazoles act on what types of bact
- anaerobes and microaerophiles
| - Gr- and Gr+
81
why shouldnt nitroimidazoles be used in lab animals
theyre carcinogenic
82
resistance to antibacterials can occur as a result of
- enzymatic drug inactivation
- modification of binding sites
- decr IC accumulation
- alteration in metabolism
83
types of resistance
- innate
- acquired
- cross resistance
- multiresistant bact strains
84
whats innate resistance
chromosonally encoded, relates to general physio of bacterial cell
85
whats acquired resistance
can arise from a mutation or transfer of genetic material encoding, resistance genes
86
whats cross resistance
a single mechanism confers resistance to multiple antimicrobial agents, commonly seen with closely related antimicrobial agents
87
methods of antimicrobial susceptibility testing
- disc diffusion method
- broth-dilution method
- E-test
88
factors affecting the zone of inhibition
- the size of the inoculum
- the test medium
- the antimicrobial agent and its conc
- incubation conditions
89
susceptible diameter
>20mm
90
moderately susceptible diameter
15
91
resistant
<15mm
92
principles of antibiotic therapy
- targeted Ab treatment necessary
- most effective ab
- correct dosage
- correct treatment time
- tissue conc must exceed effective conc at site of infection
