Assessment of Colistin Treatment in Multidrug-Resistant Gram-Negative Bacterial Infections

Objective: Colistin is a concentration-dependent antibiotic which belongs to the polymyxin group of cyclic cationic polypeptide antibiotics. Clinical use of colistin varies due to its complex pharmacokinetic and pharmacodynamic features. In this study, we aimed to evaluate the use of colistin in multidrug-resistant Gram-negative bacterial infections. Methods: 193 patients aged >= 18 years who were hospitalized from May 2014 to January 2015 and who received colistin were included in the study. Patient's data were retrospectively evaluated. Pathogens, their resistance rates, dose of colistin, its duration and route of administration, its side effects, and clinical and microbiological responses were recorded. Results: Colistin was administered to the patients with confirmed or suspected infections due to multidrug-resistant Gram-negative organisms approximately on the 20th day of hospital admission. Another antimicrobial was used in combination with colistin administered by IV or intrathecal route in all patients and a carbapenem was the drug most used for combination therapy. IV colistin doses varied widely among patients and a loading dose was not administered in 98% of patients. Inhaled and intrathecal treatment doses were administered in accordance with the literature. Intrathecal colistin administration was always with IV colistin, however inhaled colistin was occasionally administered without IV form. When inhaled colistin alone and combined with IV form were compared, no difference was found in cure rates. The most common side effect of colistin was nephrotoxicity in 33 (25.4%) patients and neurotoxicity in 7 (3.6%) patients. Analyses revealed that advanced age was the only factor which affected the development of nephrotoxicity (p<0.001). Colistin treatment was terminated in 19 patients out of 193 due to side effects. Rate of colistin resistance among infectious agents was 4.3%. Colistin resistance developed on the 19.9 +/- 9.4 days of treatment. Cure rate in colistin receiving patients was 56% and the most crucial factor determining the mortality was advanced age (63.9 +/- 2) (p=0.001). Conclusions: Nephrotoxicity is the most common side effect of colistin which is one of the treatment options for multidrug-resistant Gram-negative bacterial infections. It has been observed that there were different modes of administration in the same hospital regarding the application of colistin, and the loading dose recommended in the drug package and in the literature was not applied in almost all patients.