Antibiotics Flashcards by Caitlin R

What are the inhibitors of cell wall?

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

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What are the antibiotics classes active against ribosomes?

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

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What are the antibiotics choices for MRSA

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

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What is the main side effect limiting chloramphenicols systemic use?

Aplastic anaemia in 1 in 30000

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What antibiotics block folic acid synthesis?

Trimethoprim

Sulphonamides

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What is the mechanism of action of fluroquinolones?

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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What are the mechanisms bacteria use to develop resistance?

Chromosomal mutation
Plasmids
Tansposons (free DNA)
Bacteriophange

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What are the ESCAPPM organism and what are their significance?

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

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

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What are the mechanisms of resistance?

Antibiotic inactivation
Alteration of target site
Decreased antibiotic permeability
Active efflux

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

Benzylpenicillin 
Benzathine 
Procaine 
Phenoxymethyl 
Gram pos cocci

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

Wider gram neg - E.coli, haemophilus and enteroccoci

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What penicillins cover pseudomonas?

The very broad spectrum - piptaz and timentin

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Which generations of cephalosporins have more gram negative cover?

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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What are the 1st generation cephalosporins?

Cephalexin
Caphazolin
Cephalothin

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What bacteria do cephalosporins have no effect against?

MRSA
Listeria
Enterococci

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

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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What antibiotics are active against ESBL producting bacteria?

Meropenem
cotrimoxazole
Ertapenem

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What are carbepenems not active against?

MRSA 
Stenotrophomonas 
VRE 
Burkholderia 
Atypical bugs - legionella myooplasma

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What is the problematic side effect of imipenem?

Seizures especially with decreased renal function

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

Glycopeptide along with teicoplanin

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

What is spectrum of activity of glycopeptides?

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

What is the mechanism of resistance in VRE?

Transferred via plasmids

There is an alteration in the binding site

What are the treatment options for enterococcus?

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

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

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

What is the effect of low oxygen environments on aminoglycosides?

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.

What is the aminmoglycoside with the least side effects?

Tobamycin

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

``` Azithromycin Clarithromycin Erythromycin Roxithromycin Bacteriostatic, reversibly bind to 50S ribosome preventing protein synthesis ```

What is the spectrum of macrolides?

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

What are the adverse effects of macrolides

GI upset esp erythromycin Ototoxicity Hepatotoxicity Prolong QTc

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

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

What is the spectrum of tetracyclines?

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

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

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

What is the spectrum of fluroquinlones?

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

What is the main role for moxifloxacin?

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

What are the side effects of fluroquinolones

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

What is clindamycin and what is its mechanism of action?

It is a lincosamide along with lincomycin. | It is bacteriostatic and binds to the 50S subunit of the ribosome inhibiting protein synthesis

What is the spectrum of lincosamides?

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

What is the primary role for monobactams?

Aztreonam Only gram neg coverage Good for ESCAPPM, pseudomonas

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

Rifampicin and rifabutin | Inhibits RNA polymerase

What is the main mechanism of resistance to rifampicin?

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

What is the spectrum of rifamycins?

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

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

A pink/red colour

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

A Nitroimidazole along with tinidazole. | It binds to bacterial DNA disrupting its structure and preventing neucleic acid synthesis

What is the spectrum of action of nitroimidazoles?

Anaerobes - gram +, - and protozoa | Notably good for c.diff

What is in bactrim?

Trimethoprim and sulfamethoxazole

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

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

What is the role of linezolid?

Vancomycin resistant MRSA | VRE

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

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

What are the side effects of bactrim?

``` Hyperkalaemia Hypersensitivity GI upset Skin sensitivity Bone marrow suppression ```

What clinical infection can daptomycin not be used for?

Pneumonia - no penetrance