Rising Trend of Colistin Resistance and Shift in Minimum Inhibitory Concentrations Toward the Higher Side Among Enterobacteriaceae Isolated from Clinical Samples

A BSTRACT Background: The emergence of multidrug resistance (MDR) bacteria is a major global health issue that arises a concern for humanity especially when fewer options for antibiotics are available. Colistin used indiscriminately against gram-negative bacteria has led to a rise in Colistin resistance. In our study, we tried to find out the prevalence of Colistin-resistant Enterobacteriaceae isolates from outpatient/Inpatient departments (OPD/IPD) of a Tertiary care hospital. Methodology: 162 clinical samples were collected and processed by using different microbiological techniques gram staining, motility test, and biochemical tests which include catalase test, indole test, oxidase test, vogues-Proskauer test, citrate utilization test, triple sugar iron test, and urease production test. Antimicrobial Sensitivity Testing (AST) was done by Kirby Bauer’s method and minimum inhibitory concentration (MIC) determination by Broth dilution/macro dilution method. Results: Out of 162 Enterobacteriaceae isolates 84 (51.8%) were found to be resistant to Colistin. MIC of 4 mcg/ml was reported in 19.75%, 8 mcg/ml in 17.28%, 16 mcg/ml in 9.25%, and 32 mcg/ml in 5.5% of isolates. Conclusion: In this study, the overall resistance to Colistin was high (51.8%), which highlights an increasing trend of Colistin resistance amongst Enterobacteriaceae isolates, which impacts the clinical outcome and limits the treatment options. This study calls for more research by implementing newer methods to understand the pattern of resistance against Colistin both phenotypically and genotypically.