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Infectious diseases > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

What are the inhibitors of cell wall?

A

Beta lactams which are penicillins, cephalosporins, carbepenems and monobactams
Glycopeptides

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2
Q

What are the antibiotics classes active against ribosomes?

A 
30S 
- Tetracyclines 
- Aminoglycosides 
50S 
- Macrolides 
- Lincosamides 
- Chloramphenicol 
- Fusidic acid 
- Lineozlid
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3
Q

What are the antibiotics choices for MRSA

A

Vancomycin
Linezolid
Fusidic acid and rifampicin
Pristinomycin (a macrolide and a depsipeptin)

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4
Q

What is the main side effect limiting chloramphenicols systemic use?

A

Aplastic anaemia in 1 in 30000

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5
Q

What antibiotics block folic acid synthesis?

A

Trimethoprim

Sulphonamides

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6
Q

What is the mechanism of action of fluroquinolones?

A

DNA gyrase inhibitor. Gyrase in gram negatives and topoisomerase 4 in gram positives are required to maintain the DNA in the double helix structure.

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7
Q

What are the mechanisms bacteria use to develop resistance?

A

Chromosomal mutation
Plasmids
Tansposons (free DNA)
Bacteriophange

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8
Q

What are the ESCAPPM organism and what are their significance?

A 
Enterobacter 
Serratia 
Citrobacter 
Acinetobacter 
Providentia 
Proteus vulgaris 
Morganella morganii 
These bacteria have chromosomally encoded beta lactamse which is inducible with treatment with a cephalosporin
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9
Q

What is ESBL? Which bacteria most commonly carry this resistance?

A

Extended spectrum b-lactamase
This inactivates all cephalosporins and penicillins
Usually seen in E.Coli and Klebsiella - aka UTIs

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10
Q

What are the mechanisms of resistance?

A

Antibiotic inactivation
Alteration of target site
Decreased antibiotic permeability
Active efflux

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11
Q

What are the narrow spectrum pencillins? And what do they cover?

A 
Benzylpenicillin 
Benzathine 
Procaine 
Phenoxymethyl 
Gram pos cocci
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12
Q

What do the moderate spectrum penicillins cover than the narrow do not?

A

Wider gram neg - E.coli, haemophilus and enteroccoci

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13
Q

What penicillins cover pseudomonas?

A

The very broad spectrum - piptaz and timentin

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14
Q

Which generations of cephalosporins have more gram negative cover?

A

The later generations mostly from 3rd gen (ceftriaxone and cefotaxime) onwards
Pseudomonas is only covered by ceftazidine (3rd gen) and cefepime (4th gen)

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15
Q

What are the 1st generation cephalosporins?

A

Cephalexin
Caphazolin
Cephalothin

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16
Q

What bacteria do cephalosporins have no effect against?

A

MRSA
Listeria
Enterococci

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17
Q

What are the carbapenems and what are their mechanisms of action?

A

Meropenem
Imipenem
Ertapenem
A beta lactam they bind to penicillin binding sites and disrupt cell wall synthesis. They are resistant to most beta lactamases.

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18
Q

What antibiotics are active against ESBL producting bacteria?

A

Meropenem
cotrimoxazole
Ertapenem

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19
Q

What are carbepenems not active against?

A 
MRSA 
Stenotrophomonas 
VRE 
Burkholderia 
Atypical bugs - legionella myooplasma
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20
Q

What is the problematic side effect of imipenem?

A

Seizures especially with decreased renal function

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21
Q

What class is vancomycin and what is its mechanism of action?

A

Glycopeptide along with teicoplanin

Inhibits cell wall synthesis by binding to precurser units - no beta lactam ring

22
Q

What is spectrum of activity of glycopeptides?

A 
MRSA 
MSSA 
Enterococci (not VRE) 
Pneumococcus 
Does not have any significant gram neg cover
23
Q

What is the mechanism of resistance in VRE?

A

Transferred via plasmids

There is an alteration in the binding site

24
Q

What are the treatment options for enterococcus?

A

Naturally resistant to all cephalosporins
Amoxicillin or ampicillin
Vancomycin
*for serious infections often paired with an aminoglycoside for synergy

25
Q

What is the mechanism of action and the types of aminoglycosides?

A

They bind with the 30S ribosomal subunit in the cell which inhibits protein synthesis

26
Q

What is the effect of low oxygen environments on aminoglycosides?

A

Aminoglycosides act on the intracellular ribosomal subunit. It takes 2 steps to gain intracellular access - a porin then electron transport. This last step is dependant on a number of factors including O2. Anaerobic bacteria are intrinsically resistant and low O2 environments like an abscess also prevent adequate uptake.

27
Q

What is the aminmoglycoside with the least side effects?

A

Tobamycin

28
Q

What are the macrolides and what is their mechanism of action?

A 
Azithromycin 
Clarithromycin 
Erythromycin 
Roxithromycin 
Bacteriostatic, reversibly bind to 50S ribosome preventing protein synthesis
29
Q

What is the spectrum of macrolides?

A 
Atypicals (legionella, mycoplasma, chlamydia) 
Gram + cocci 
Some gram - cocci and anaerobes 
Nontuberculous mycobacteria eg MAC 
Pertussis 
Haemophilus
30
Q

What are the adverse effects of macrolides

A

GI upset esp erythromycin
Ototoxicity
Hepatotoxicity
Prolong QTc

31
Q

What are the tetracyclines and what is their mechanism of action?

A

Doxycycline
Minocycline
Tigecycline
Bind to 30S ribosome, prevent protein formation

32
Q

What is the spectrum of tetracyclines?

A

Gram + and - coverage
Atypicals
Rickettsia and spirochates
Some protozoa eg malaria
Some nontuberculous mycobaceria
Minocycline can be active against bacteria that are resistant to other tetracyclines
Tigecycline is very broad including MRSA, VRE, anaerobes but not psuedomonas

33
Q

What is the oral anti-pseudomonal drug, what class is it and what is its mechanism of action?

A

Ciprofloxacin a fluroquinolone. Other drugs in this class are moxifloxacin, norfloxicin. It is a DNA gyrase inhibitor which destabilises the DNA helix structure. In gram + it acts on topoisomerase 4 which has the same action

34
Q

What is the spectrum of fluroquinlones?

A

Very broad spectrum.
Ciprofloxicin - Gram - including pseudomonas, haemophilus, legionella and some mycobacteria
Norfloxacin - same as cipro but only for mucosal infections
Moxifloxacin - Gram + and -, anaerobes, atypicals, some mycobacterium. Not good for pseudomonas

35
Q

What is the main role for moxifloxacin?

A

Very broad spectrum esp gram +. Used for severe penicillin allergies

36
Q

What are the side effects of fluroquinolones

A 
GI upset 
C. Diff 
Photosensitivty 
CNS effects 
Cartilage effects - Achilles tendon rupture or tendonitis 
QTc prolongation 
Drug interactions
37
Q

What is clindamycin and what is its mechanism of action?

A

It is a lincosamide along with lincomycin.

It is bacteriostatic and binds to the 50S subunit of the ribosome inhibiting protein synthesis

38
Q

What is the spectrum of lincosamides?

A

Gram positive cocci including MRSA
Anaerobes
Toxoplasma
No useful gram neg coverage

39
Q

What is the primary role for monobactams?

A

Aztreonam
Only gram neg coverage
Good for ESCAPPM, pseudomonas

40
Q

What are the rifamycins and what are their mechanism of action?

A

Rifampicin and rifabutin

Inhibits RNA polymerase

41
Q

What is the main mechanism of resistance to rifampicin?

A

Only a single gene mutation is required to alter the binding site leading to resistance.

42
Q

What is the spectrum of rifamycins?

A

Gram +
Mycobacterial species
Can be used in combination with fusidic acid for MRSA

43
Q

What colour does the urine change to if treated with rifamycins?

A

A pink/red colour

44
Q

What class does metronidazole belong to and what is its mechanism of action?

A

A Nitroimidazole along with tinidazole.

It binds to bacterial DNA disrupting its structure and preventing neucleic acid synthesis

45
Q

What is the spectrum of action of nitroimidazoles?

A

Anaerobes - gram +, - and protozoa

Notably good for c.diff

46
Q

What is in bactrim?

A

Trimethoprim and sulfamethoxazole

47
Q

What is the mechanism of action of chloramphenicol and what is it active against?

A

Binds to and inhibits 50S subunit of the ribosome inhibiting bacterial protein synthesis
It is a broad spectrum with activity against gram pos and neg as well as rickettsia and chlamydia

48
Q

What is the role of linezolid?

A

Vancomycin resistant MRSA

VRE

49
Q

What is the mechanism of action of daptomycin? What is its role?

A

Binds to cell membranes causing depolarisation. This inhibits protein, DNA and RNA synthesis leading to cell death.
It is primarily used for antibiotic resistant gram positive bacteria including VRE

50
Q

What are the side effects of bactrim?

A 
Hyperkalaemia 
Hypersensitivity 
GI upset 
Skin sensitivity 
Bone marrow suppression
51
Q

What clinical infection can daptomycin not be used for?

A

Pneumonia - no penetrance

Infectious diseases (5 decks)

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