Introduction: Non-fermenters have gained significance as etiological agents of mild to potentially life threatening healthcare associated infections in recent years. Pseudomonas and Acinetobacter are amongst the commonest non fermenters causing infections in a hospital setting. The aim of this study was to find the prevalence of colistin resistance in Pseudomonas and Acinetobacter isolates from inpatients. Methodology: This retrospective study was done in our hospital which is a tertiary care centre, from April 2016 to March 2017. Identification and antibiotic susceptibility testing was done by VITEK®2 system (BioMerieux, North Carolina/USA). Antibiotic susceptibility results were interpreted according to the criteria of Clinical Laboratory Standards Institute M100S (26th edition). Patient information and microbiological profile of the organism isolated was recorded. For statistical analysis, data was described in terms of fractions and percentages and percentages were used to compare the data in two sets. Results: The most common isolates amongst non fermenters were Acinetobacter sp.(45.93%), and Pseudomonas sp. (41.62%). 92.13% of the Acinetobacter baumannii isolates were MDR and 88.76% were resistant to carbapenems. Sixtyfour percent of Acinetobacter baumannii isolates were susceptible to colistin and tigecycline only and 7.86% were resistant to colistin. In case of Pseudomonas aeruginosa, 74.67% isolates were MDR and 56% were resistant to carbapenems. Nearly 77.33% isolates were susceptible, 5.33% were intermediate 17.34% were resistant to colistin. The colistin resistant isolates of Acinetobacter baumannii and Pseudomonas aeruginosa were predominantly isolated from endotracheal aspirate (57.14%) and pus (61.53%) samples respectively. Overall 5 out of 23 (21.74%) colistin resistant isolates were resistant only to colistin and were susceptible to all other antibiotics tested. Conclusion: Increasing role of non fermenters as pathogens in the hospital settings is worrying. Judicious use of antibiotics is needed to curb the high antibiotic resistance amongst non-fermenters. 

Keywords: Colistin Resistance; Acinetobacter; Pseudomonas; Non Fermenters.