Chloramphenicol is an antibiotic that was derived from the bacterium Streptomyces venezuelae and is now produced synthetically. Chloramphenicol is effective against a wide variety of microorganisms, but due to serious side-effects (e.g., damage to the bone marrow, including aplastic anemia) in humans, it is usually reserved for the treatment of serious and life-threatening infections (e.g., typhoid fever). It is used in treatment of cholera, as it destroys the vibrios and decreases the diarrhoea. It is effective against tetracycline-resistant vibrios. It is also used in eye drops or ointment to treat bacterial conjunctivitis.

C₁₁H₁₂C_l2N₂O₅ Chloramphenicol M_W=323.13

(2,2-Dichlor-N-[(aR,bR)-b-hydroxy-a-hydroxymethyl-4-nitrophenethyl]acetamid)
Image in the PD.

Mechanism and Resistance

Chloramphenicol stops bacterial growth by binding to the bacterial ribosome (blocking peptidyl transferase) and inhibiting protein synthesis.

Resistance to chloramphenicol is conferred by the cat-gene. This gene codes for an enzyme called "chloramphenicol acetyltransferase" which inactivates chloramphenicol by covalently linking one or two acetyl groups, derived from acetyl-S-coenzyme A, to the hydroxyl groups on the chloramphenicol. The acetylation prevents chloramphenicol from binding to the ribosome.