Macrolides and Ketolides – Bacterial Protein Synthesis Inhibitors (Antibiotics)

00:00 Let's move on to the macrolides antibiotics.

00:03 These macrolides antibiotics are very important group of medications because we use them all the time.

00:08 Specially in respiratory infections.

00:11 Now these agents are blocking the 50S unit from translation.

00:15 Important agents include erythromycin and clarithromycin.

00:19 They're rapidly eliminated from the body.

00:22 They're considered broad spectrum antibiotics.

00:25 And as I said before they're most commonly used in respiratory infections.

00:29 Azithromycin concentrates into macrophages and other tissues and it is actually eliminated quite slowly.

00:37 It is active against many gram-positive organisms and has more activity against susceptible gram-negative organisms.

00:45 It's also active against several atypical organisms including Mycoplasma pneumoniae, Legionella pneumophila and Chlamydophila pneumoniae.

00:55 The nice thing about azithromycin is that you can actually give it as a three day set of medications but it will last for ten days.

01:03 So the killing activity actually lasts much longer than the drug is actually in the body.

01:10 Other medications are more narrow spectrum within this drug group.

01:14 The selectivity targets are generally gram positive anaerobes and aerobes.

01:19 And these are used often in clostridioides difficile infections.

01:22 Let's talk about the resistance to macrolides antibiotics.

01:26 It's actually quite an interesting topic because of the mechanism and the resistance patterns.

01:32 Now you actually will develop ejector pump mechanisms in some bacteria that literally pump out the drug, the active drug out of the cell.

01:41 It's quite an interesting phenomenon.

01:43 The other thing that may happen in resistance patterns is changing the binding site of the macrolide by perhaps adding a methyl group.

01:50 Now the problem here is that there is a 100% cross resistance pattern between one macrolide and another.

01:57 So if for example you give a patient clarithromycin for a respiratory infection on week 1, they come back with resistance and you decide to try a different medication, there's going to be cross resistance between those two, say between clarithromycin and azithromycin.

02:13 There's partial cross resistance with drugs like clindamycin and the streptogramins as well.

02:20 And the resistance in the enterobactriaceae species and that is due to the production of drug destroying esterases.

02:29 Not because of the ejector pump.

02:31 So it's a slightly different mechanism but still 100% cross resistant pattern.