Evaluation ofin vitrosensitivity of Colistin to carbapenemase producing gram-negative bacilli

Abstract

Context: Increasing resistance in gram-negative bacteria presents a critical problem. Limited therapeutic option has forced infectious disease clinicians and microbiologists to reappraise the clinical application of Colistin. Aims: Emergency of resistance to multiple drugs leaves behind very few therapeutic options to fight out carbapenemase resistant gram-negative bacilli (GNB). Our objective was to study the in vitro sensitivity of Colistin to carbapenemase GNB. Settings and Design: This is the 6 months retrospective study. Materials and Methods: Present study was carried out in the Microbiology department in a tertiary care hospital and teaching institute, during the study period (June-November 2013). A total of 782 GNB were isolated. Out of 782, 172 were carbapenemase producer which were taken for present study. The entire testing was done under strict internal quality control using American type culture collection (ATCC) strains. Results: During the study period, 782 were examined. Out of 782 strains, 172 were found to produce carbapenemase activity. Out of 172 GNB strains, 164 (95.34%) were sensitive Colistin. Out of 164, 57 (34.75%) isolates sensitive to Colistin were found to be positive for extended spectrum beta-lactamase (ESBL) and carbapenemase production and 107 (65.24%) produced only carbapenemase. Among the resistant strains (08), 3 (37.5%) showed both carbapenemase and ESBL production and 5 (62.5%) were found to be positive only for carbapenemase production. Conclusions: Use of Colistin as therapeutic option can be increased by better understanding of the pharmacokinetics and pharmacodynamics of Colistin and its methanesulphate will allow the design of appropriate dosing regimens for maximizing efficacy while minimizing toxicity and the development of resistance.