Colistin: re-emergence of the 'forgotten' antimicrobial agent.

The treatment of the emerging multidrug resistant (MDR) gram-negative organisms is a challenge. The development of newer antibiotics has recently slowed down. This has led to the re-emergence of the 'old forgotten' antibiotic "Colistin", whose use had almost stopped (after 1970's) due to the high incidence of nephrotoxicity and neurotoxicity. Colistin (polymyxin E) is a polypeptide antibiotic belonging to polymyxin group of antibiotics with activity mainly against the gram-negative organisms. Use of colistin has been increasing in the recent past and newer studies have shown lesser toxicity and good efficacy. Colistin acts on the bacterial cell membrane resulting in increased cell permeability and cell lysis. Colistin can be administered orally, topically, by inhalational route, intramuscularly, intrathecally, and also intravenously. Parenteral Colistin (in the form of colistimethate sodium) has been used to treat ventilator-associated pneumonia (VAP) and bacteremia caused by MDR bacteria such as Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii. Inhaled Colistin is used for treating pneumonia/VAP due to MDR gram-negative organisms and also used prophylactically in patients with cystic fibrosis. This manuscript is a brief review of Colistin and its clinical applications in the pediatric population.