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Year 5 path SW COPY > Microbiology 20: Antimicrobials 1 > Flashcards

Microbiology 20: Antimicrobials 1 Flashcards

1
Q

What coverage do Glycopeptides antibiotics have ?

A

Gram +ve

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2
Q

When would Glycopeptide antibiotics be indicated ?

A

Gram +ve bacteria resistant to Beta lactams

E.g MRSA

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3
Q

Why are beta lactams considered bactericidal ?

A

They dont kill existing bacteria, they inhibit cell wall synthesis so stop new bacteria from forming their cell walls and hence causing lysis.

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4
Q

Give 3 examples of classes of beta lactams ?

A

Penicillins
Cephalosporins
Carbapenems

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5
Q

Give an example of a drug that is a beta lactamase inhibitor ?

A

Clavulanic acid

tazobactam

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6
Q

As you go up the generations of cephalosporins what happens to their activity against gram +ve and -ve bacteria ?

A

As you go up the generations the activity against gram -ve goes up and +ve goes down.

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7
Q

What complications can glycopeptides cause ?

A

Nephrotoxicity

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8
Q

Give 2 examples of Glycopeptides ?

A

Vancomycin

Teicoplanin

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9
Q

Which Glycopeptide is often used to treat C.difficile infection ?

A

Vancomycin

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10
Q

Which antibiotic is commonly used to treat meningitis ?

A

Ceftriaxone (cephalosporin)

Can’t normally penetrate blood brain barrier but does so when there is inflammation ie in meningitis

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11
Q

List 5 classes of Protein synthase inhibitors ?

A 
Aminoglycosides
Tetracyclines
Macrolides
Chloramphenicol
Oxazolidinones (Linezolid)
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12
Q

Why are Proteinase inhibitors selective for bacteria and not hum an cells ?

A

They bind to the ribosomal subunit which is a different size in bacteria (30S) compared to human cells

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13
Q

What antibiotic coverage do Aminoglycosides (gentamicin) have ?

A

Good gram -ve activity

Poor gram +ve and anaerobe activity

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14
Q

what antibiotic coverage do Tetracyclines (doxycycline) have ?

A

Mostly gram +ve

Very good for intracellular pathogens e.g chlamydia and mycoplasma

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15
Q

Which class of Protein synthesis inhibitors are contraindicated in children and pregnant women ?

A

Tetracyclines

Deposit in bone and also cause discolouration of teeth

Chloramphenicol is contraindicated in the 3rd trimester as it can cause “grey baby syndrome”

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16
Q

What is a dangerous complication of giving babies chloramphenicol ?

A

Grey baby syndrome

Aplastic anaemia

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17
Q

What is the antibiotic coverage of Linezolid ?

A

Very active against gram +ve bacteria

Poor activity against gram -ve bacteria

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18
Q

In which infection is Linezolid particularly useful ?

A

MRSA

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19
Q

Give 2 side complications you can get with Linezolid ?

A

Optic neuritis

Thrombocytopenia

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20
Q

Give 2 classes of DNA synthesis inhibitors ?

A

Quinolones

Nitroimidazoles

21
Q

What antibiotic coverage do quinolones (ciprofloxacin) have ?

A

very active against gram -ves

New quinolones: moxifloxicin and levofloxacin have more gram +ve cover than gram -ve

22
Q

Give one example of a Nitroimidazole ?

A

Metronidazole

23
Q

Which bacteria is Metronidazole particularly effective against ?

A

Anaerobes (C.Difficile)

24
Q

Give one example of a class of RNA synthesis inhibitors ?

A

Rifampicins

25
Q

Which antibiotic turns your secretions (urine, tears etc) an Orange colour ?

A

Rifampicin

26
Q

What is the antibiotic treatment for Pneumocystis jirovecii pneumonia ?

A

Septrin (Sulphonamides + Trimethoprim) (co-trimoxazole)

27
Q

Which antibiotic is commonly used to treat skin infections such as cellulitis or impetigo ?

A

Flucloxacillin

28
Q

List 2 serious side effects of gentamicin ?

A
  • Ototoxic

- Nephrotoxic

29
Q

Which antibiotic is often given in the case of penicillin allergy ?

A

Erythromycin (macrolide)

30
Q

List 2 mechanisms of resistance that MRSA uses against Beta lactams ?

A
  • Beta lactamses (inactivation)
  • PBP2a (altered target) - Normally beta lactams bind to penicillin binding proteins in the cell wall to cause their effect. Binding To PBP2a means the cell wall is not affected.
31
Q

list 3 examples of selective targets

A

peptidoglycan layer of cell wall
inhibition of bacterial protein synthesis
DNA gyrase and other prokaryote-specific enzymes

32
Q

difference between gram -ve and + ve cell walls

A

gram -ve = outer membrane - peptidoglycan - cytoplasmic membrane
gram +ve - thick peptidoglycan cell wall - cytoplasmic membrane

33
Q

features of beta lactam antibiotics

A

inactivate enzymes used in terminal stages of cell wall synthesis
cells will have a weak cell wall
active against rapidly-dividing bacteria
ineffective against bacteria without a cell wall
penicillins, cefalosporins, carbapenems, monobactams

34
Q

features of penicillins

A

active against gram-positives
eg streptococci
broken down by beta-lactamase produced by S aureus and many gram -ves

35
Q

what are beta lactamase inhibitors

A

clavulanic acid and tazobactam
protect penicillins from breakdown by beta lactamase
increases coverage of antibiotics to include S. Aureus , gram -ves and anaerobes

36
Q

features of glycopeptides

A

large molecules
active against gram +ves
inhibit cell wall synthesis
used to treat serious MRSA infections

inc vancomycin and teicoplanin

binds amino acid chains and prevents glycosidic bonds and peptide cross-links from forming

37
Q

which antibiotics inhibit protein synthesis

A 
aminoglycosides (gentamicin, amikacin, tobramycin)
tetracyclines 
Macrolides (erythromycin)
licosamides (clindamycin)
chloramphenicol 
oxazolidinones (linezolid)
38
Q

features of aminoglycosides

A

binds to amino-acyl site of the 30s ribosomal subunit
ototoxic and nephrotoxic
no activity against anaerobes
prevents elongation of peptide chain

39
Q

features of tetracyclines

A

broad spectum Ab with activity against IC pathogens (chlamydia, mycoplasma)
do not give to children and pregnant women
light-sensitive rash
binds to ribosomal 30S subunit, inhibits protein synthesis

40
Q

features of macrolides

A

bacteriostatic
minimal activity against gram -ves
mild staph/strep infections in penicillin allergic
active against: campylobacter spp, legionella, pneumophila
bind to 50S subunit of the ribosome

41
Q

features of chloramphenicol

A

bacteriostatic
broad antibacterial activity
rarely used

42
Q

list antibiotics which inhibit DNA synthesis

A

quinolones (cipro, levofloxacin, moxifloxacin)

nitroimidazoles (metronidazole, tinidazole)

43
Q

features of fluoroquinolones

A

act on the alpha subunit of DNA gyrase
broad antibacterial activity esp against gram negative organisms inc pseudomaonas aeruginosa
uses: UTIs, pneumonia, atypical pneumonia, bacterial gastroenteritis

44
Q

list antibiotics which are cell membrane toxins

A

daptomycin - gram positive only, MRSA and VRE infections

colistin - gram -ves inc Pseudomonas aeruginosa, acinetobacter baumanii
klebsiella pneumoniae

45
Q

features of sulfonamides and diaminopyrimidines

A

interfere with folic acid metabolism

trimethoprim - community acquired UTIs

46
Q

what are mechanisms of antibiotic resistance?

A

1 - inactivation (B lactams, aminoglycosides, chloramphenicol)
2 - altered target (B lactams, macrolides, quinolones)
3 - reduced accumulation (tetracyclines, B lactams)
4 - bypass antibiotic-sensitive step in cell division (trimethoprim, sulphonamides)

47
Q

how can antibiotic resistance develop via inactivation

A

beta lactamases

S Aureus and gram negative bacilli

48
Q

how can antibiotic resistance develop via altered targets

A

MRSA - mecA gene encoded PBP2a - low affinity for binding beta lactams
Strep pneumoniae - penicillin resistance via stepwise mutations in PBP genes

Macrolides - modified 23S NRA, reducing binding of macrolides

Year 5 path SW COPY (106 decks)

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