Antibiotics are substances produced by living organisms that can destroy or inhibit the growth of other

microorganisms. Although most are produced by bacteria a few such as penicillin are made by fungi. Antibiotics can be used to treat relatively mild conditions such as acne as well as potentially life-threatening

conditions such as pneumonia.

What do Macrolides target?

Antibiotic macrolides have a broad spectrum of activity and are used to treat infections caused by

Gram-positive bacteria (e.g., Streptococcus pneumoniae) and Haemophilus influenza

infections such as respiratory tract and soft-tissue infections. The antimicrobial spectrum of

macrolides is slightly wider than that of penicillin, and, therefore, macrolides are a common

substitute for patients with a penicillin allergy or treat penicillin-resistant strains of bacteria.

Streptococcus pneumoniae

Haemophilus influenza infections

How do Macrolides kill the bacteria?

The mechanism of action of macrolides is inhibition of bacterial protein synthesis .Antibiotics in the macrolide group affect ribosomes, the cell’s

protein-building organelles. Ribosomes build proteins in both bacteria and human cells, but there are differences between bacterial and human

ribosomes, for example humans have 80S ribosomes while bacteria have 70S ribosomes. Macrolides block only bacterial ribosomes and prevent them from building proteins. They do this by binding to 23S ribosomal target sites in bacteria. A bacterium that cannot build proteins cannot

survive. Erythromycin, which is commonly used to treat respiratory tract and skin infections, is a macrolide.

Is there any resistance?

Bacteria resist macrolide antibiotics in 3 ways:

(1) Through target-site modification by methylation or mutation that prevents the binding of the antibiotic to its ribosomal target. Mutations affecting the binding site or its tertiary structure can alter the shape and therefore the antibiotic can no longer bind on to it.

(2) Through efflux of the antibiotic caused by the production of active ATP-dependent efflux proteins

that transport the drug outside of the cell

(3) By drug inactivation caused by the production of drug-inactivating enzymes

Sid e effects?

Macrolide can cause serious side effects. One is called pseudomembranous colitis, which can cause severe diarrhoea after you stop using macrolides. This is because the antibiotics may kill some of the

harmless bacteria in your intestines and allow other bacteria to overgrow; leading to a strong

bacterial infection Because macrolides can also be toxic to the liver inflammation and congestion of

bile ducts in the liver may occur.

References: http://en.wikipedia.org/wiki/Macrolide#Uses http://learn.genetics.utah.edu/content/microbiome/antibiotics/ http://www.livestrong.com/article/38199-macrolide-

side-effects/

Macrolide By Agana Gnanakuruparan