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Year 5 Pathology > Microbiology > Flashcards

Microbiology Flashcards

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1
Q

What are the potential targets for antibiotics?

A 
Inhibit cell wall synthesis
Inhibit protein synthesis
Inhibit folate synthesis 
Inhibit DNA synthesis
Inhibit RNA synthesis
Cell membrane toxin
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2
Q

Which classes of antibiotics inhibit cell wall synthesis?

A

Beta-lactams

Glycopeptiides

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3
Q

What are the diffreent types of beta-lactam?

A

Penicillins e.g. benzylpenicillin, penicillin V
Cephalosporins e.g. ceftriaxone
Carbapenems e.g. meropenem

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4
Q

What are the indications for beta-lactams?

A

Gram positive

3rd generation cephalosporin - gram negative

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5
Q

Give 2 examples of glycopeptides

A

Vancomycin, Teicoplanin

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6
Q

What are the indications for glycopeptides?

A

MRSA

C. difficile

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7
Q

Examples 1st generation cephalosporin

A

cephalexin

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8
Q

Examples 2nd generation cephalosporin

A

cefuroxime

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9
Q

Examples 3rd generation cephalosporin

A

ceftriaxone (has led to more C diff infections)
Ceftazidime (anti-pseudomonas)
cefotaxime

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10
Q

Which classes of antibiotics inhibit protein synthesis?

A 
Aminoglycoside - 30s
Tetracycline - 30s 
Macrolides - 50s
Chloramphenicol - 50s
Oxazolidines - 23s of 50s
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11
Q

Examples of aminoglycosides

A

gentamicin
amikacin
tobramycin

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12
Q

Example of tetracycline

A

Doxycycline

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13
Q

Examples of macrolide

A

Erythromycin
Clarithromycin
Clindamycin

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14
Q

Example of chloramphenicol

A

eye drops

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15
Q

Example of oxazolidinone

A

Linezolid

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16
Q

Indications for aminoglycoside

A

e.g. gentamycin for Gram -ve sepsis

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17
Q

Indications for tetracycline

A

e.g. doxycycline for intracellular pathogens e.g. mycobacteria, chlamydia, rickettsiae

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18
Q

Indications for macrolides

A

e.g. erythromycin for gram +ve infection in penicillin-allergic patients

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19
Q

Indications for chloramphenicol

A

Bacterial conjunctivitis

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20
Q

Indications for oxazolidinones

A

Gram +ve, MRSA +ve, VRE

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21
Q

Tx for Gram +ve, VRE +ve

A

Linezolid

Daptomycin

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22
Q

Which classes of antibiotics inhibit DNA synthesis?

A

Quinolones (inhibit DNA gyrase)

Nitroimidazoles

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23
Q

Give examples of quinolones

A

ciprofloxacin

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24
Q

Give an example of a nitroimidazole

A

Metronidazole

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25
Indications for quinolones
Gram -ve
26
Indications for nitroimidazole
Anarobes and protozoa
27
What classes of antibiotics inhibit RNA synthesis?
Rifamycin (inhibits RNA polymerase)
28
Give an example of a rifamycin
Rifampicin
29
Indications for rifampicin
TB, chlamydia
30
Tx for anaerobes and protozoa
Metronidazole
31
1st and 2nd line Tx for UTI
1st line: Trimethoprim (DHF redutase/folate inhibitor) | 2nd line: Nitrofurantoin (DNA synthesis inhibitor)
32
What classes of antibiotics act as cell membrane toxins?
Polymyxin | Cyclic lipopeptide
33
Give an example of a polymyxin
Colistin
34
Give an example of a cyclic glycopeptide
Daptomycin
35
Indication for Polymyxins
Gram -ve 9pseudomonas, Klebsiella, Acinetobacter)
36
Indication for cyclic lipopeptide
Gram +ve, MRSA +ve, VRE +ve
37
What classes of antibiotics inhibit folate metabolism?
Sulfonamides (DHOp synthase inhibitor) | Diaminopyrimidines (DHF reductase inhibitor)
38
Give an example of a sulfonamide
Sulphamethoxazole
39
Indication for sulfonamides
PCP (With trimethoprim: co-trimoxazole)
40
Indications for diaminoprimidines
UTI (e.g. Trimethoprim)
41
What are some broad-spectrum antibiotics?
Co-amoxiclav (B lactam penicillin) Tazocin (B lactam penicillin) Ciprofloxacin (quinolone) Meropenem (B lactam Carbapenem)
42
What is Tazocin?
Piperacillin (penicillin) + Tazobactam (B lactamase inhibitor)
43
What is Co-amoxiclav
Amoxicillin (penicilli) + Clavulonic acid (B lactamase inhibitor)
44
Examples of narrow spectrum ABx
Flucloxacillin, Metronidazole, gentamicin
45
MOA of B lactams Activity Ineffective against
Inactivate transpeptidase enzymes/PBP, stop terminal stages of cell wall synthesis Bactericidal, active against rapidly dividing bacteria Ineffective against bacteria with no PtG cell wall e.g. Chlamydia, Mycoplasma
46
Penicillin uses Broken down by
Gram +ve organisms e.g. Strep, Clostridia | B lactamase -produing S. Aureus
47
Amoxicillin uses Broken down by
Broad spectrum, extends coverage to enterococci and Gram -ves B lactamase producing S Aureus and many Gram -ves
48
Flucloxacillin uses Broken down by
similar to penicillin, less active STABLE to B lactamase produced by S Aureus
49
Use piperacillin
Similar to amoxicillin, extends to pseudomonas coverage and other non-enteric Gram -ves Broken down by Gram -ve and B-lactamase producing S Aureus
50
Clavulonic acid + tazobactam
B lactamase inhibitors, extend coverage to S Aureus , Gram -es and anaerobes
51
What changes within generations of cephalosporins?
More activity against Gram -ve bacilli
52
Example 1st generation cephalosporin
cephalexin
53
Example 2nd generation cephalosporin
cefuroxime
54
Example 3rd generation cephalosporin
Cefotaxime Ceftriaxon Ceftazidime
55
What are ESBL organissm resistant to?
penicillins + cephalosporins
56
Use of cefuroxime
Stable to B lactamases produced by Gram -ves. Similar cover to Co-amoxiclav but less active against anaerobes
57
Ceftriaxone associated with
C. Diff infections
58
Use of ceftazidime
anti-pseudomonas
59
Use of carbapenems What is an issue?
stable to ESBL enzymes Cabapenemase enzymes more widespread, and now MDR Acinetobacter and Klebsiella species
60
Key points for B lactams
Relatively non-toxic renally excreted (dec dose if renal impairment) Short half life dont cross intact BBB cross -allergenic (penicillins approx 10% cross-reactivity with cephalosporins)
61
Why are glycopeptides effective against Gram +ves?
Glycopeptides inhibit cell wall synthesis, bactericidal Large molecules, unable to penetrate Gram -ve outer cell wall active against Gram +ve organisms
62
Tx for MRSA
Vancomycin (glycopeptide) | IV only
63
What is used to treat C diff?
oral Vancomycin
64
Issue with glycopeptides? Consequence?
Nephrotoxic Monitor drug levels to prevent accumulation
65
Examples glycopeptides
Vancomycin, Teicoplanin
66
Adverse effects Teicoplanin
leucopaenia, neutropaenia
67
Features of aminoglycosides What is significant
Bind amino-acyl site of 30s ribosomal subunit Rapid, conc dependent bactericidal Ototoxic, nephrotoxic
68
Combination of B-lactams and aminoglycosides?
Synergistic
69
Aminoglycosides no activity against
anaerobes and low pH (abscess)
70
Examples of tetracyclines
Doxycycline
71
Features of tetracyclines What is significant
Broad spectrum, activity against intracellular pathogens (chlamydia, rickettsiae, mycoplasmas) bacteriostatic Widespread resistance limits usefullness
72
MOA tetracyclines
bind 30s subunit, stop binding of aminoacyl-tRNA to ribosomal acceptor site, inhibit protein synthesis
73
Contra-indications tetracyclines (Doxycycline)
children, pregnant women also cuases light-sensitive rash
74
Examples macrolides
Erythromycin Clarithromycin Clindamycin
75
MOA macrolides
bind 50s ribosome subunit, interfering with protein translocation and stimulate dissociation of peptidyl-tRNA
76
Macrolide effective against Features of macrolides
Gram +ve ONLY, Campylobacter and Legionella given to penicillin-allergic pts for Staph/Strep infections
77
Treatment for Campylobacter and L. pneumophilia
Macrolide
78
MOA aminoglycoside
bind 30s ribosomal subunit prevent elongation polypeptide chain cause misreading f codons along mRNA
79
MOA chloramphenicol
bind to peptidyl-transferase of 50s ribosomal subunit bacteriostatic
80
Significant adverse effects of chloramphenicol
Aplastic anaemia | Grey baby syndrome in neonates (inability to metabolise drug)
81
MOA Oxazolidinones
binds 23s of 50s subunit, stops 70s complex
82
Examples of Oxazolidinones
Linezolid
83
Linezolid used as Tx for
MRSA and VRE Gram +ves
84
Cautions with Linezolid
Very expensive thrombocytopenia optic neuritis use with Micro/ID input
85
Antibiotics: Inhibitors of DNA synthesis
Quinolones | Nitroimidazoles
86
Examples of Quinolones
Ciprofloxacin, Moxifloxacin, Levofloxacin
87
MOA Quinolones Used for
inhibit DNA gyrase and topoisomerase IV Gram +ve, intracellulars e.g. Chlamydia
88
Uses of Ciprofloxacin
UTIs atypical pneumonias gastroenteritis
89
MOA Nitroimidazoles
under anaerobic conditions, active intermediate produced that causes DNA strand breakage
90
Examples Nitroimidazoles
Metronidazole, Tinidazole
91
What are nitrofurans?
Compounds related to nitroimidazoles e.g. nitrofurantoin used for UTIs
92
Antibiotics: inhibit RNA synthesis
Rifampicin
93
Rifampicin MOA
RNA polymerase inhibitor
94
Rifampicin used for
TB | Chlamydia
95
Consider when treating with Rifampicin
Monitor LFTs beware with other drugs metabolised in live Orange secretions
96
Why should you never use rifampicin as a single agent?
develops rapid resistance (due to chromosomal mutation)
97
Antibiotics: cell membrane toxins
Glycolipids e.g. Daptomycin | Polymyxins e.g. Colistin
98
Tx for MRSA and VRE +ve organisms
Daptomycins and Linezolid (Oxazolidinones)
99
Features of colistin
Active against Gram -ves (Pseudomonas, Acinetobacter, Klebsiella pneumoniae) Not absorbed by mouth Nephrotoxic Used for MDR organisms
100
Antimicrobials: Folate synthesis inhibitors (which then indirectly act on DNA)
Sulhonamides | Trimethoprim
101
Why is sulphonamide and trimethoprim combined treatment useful?
synergistic action as they act on sequential stages of same pathway
102
Co trimoxazole components
Trimethoprim + sulphonamide | used for Pneumocystis jirovecii pneumonia
103
Trimethoprim uses
community acquires UTIs
104
What are the mechanisms of antibiotic resistance? AIR-B
Altered target Inactivation Reduced accumulation (impaired uptake, enhanced efflux) Bypass Abx sensitive step
105
How does resistance to B lactams occur? NB
Inactivation Beta lactamases Not in the mechanism of resistance in penicillin resistant pneumococci and MRSA
106
How does B lactam resistance develop in MRSA?
ALTERED TARGET | mecA encodes new PBP (2a) which has low affinitiy for B lactams
107
How does Strep pneumonia resist Beta lactams?
ALTERED TARGET penicillin resistance is the result of acquisition of step-wise mutations in PBP genes, lower level resistance can be overcome by increasing the dose
108
What are ESBLs? What can they do? NB
Extended spectrum beta lactamases Able to break down cephalosporins, becoming more common (in E Coli and Klebsiella) Resistant to cephalosporins regardless of in vitro finding
109
What are carbapenemases?
Break down all B lactams Emerging CRO Klebsiella strains
110
What leads to macrolide resistance?
ALTERED TARGET Adenine-N6 methyltransferase modifies 23s rRNA modification reduced binding of MLS ABx and leads to resistance encoded by ERM genes (erythromycin ribosome methylation)
111
Mechanism flucloxacillin resistance
Alteration of target
112
Mechanism of ESBL E Coli resistance
Due to enzymatic inactivation of antibiotic | can use carbapenems

Year 5 Pathology (13 decks)

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