Colistin Resistant Gram-Negative Bacteria Isolated from Various Clinical Samples in North Indian Tertiary Care Center

>Background: Antibiotic resistance and their mischaracterization often lead to treatment failure. In the present scenario, resistance to colistin is emerging. Poor testing methods for colistin resistance detection can increase the risk of treatment failures and even mortality. In this study, we analyzed the burden of multidrug-resistant (MDR), Extensively drug-resistant (XDR), pandrug resistant (PDR), and colistin resistant Gram-negative bacteria and also evaluated Vitek-2 compact and Broth Microdilution (BMD) for the detection of colistin resistance at North Indian Tertiary-Care Hospital. Methods: A total of 11237 samples were processed in which 1822 (16.21%) were gram-negative bacilli (GNB). All GNB after identification by Vitek-2 compact, were subjected to antibiotic sensitivity testing by Vitek-2 and characterized as MDR, XDR, and PDR as per guidelines of Centers for Disease Control and Prevention US (CDC) and European Centre for Disease Prevention and Control (ECDC). Identification of colistin resistance in Enterobacteriaceae family, Pseudomonas aeruginosa, Acinetobacter baumannii was made by broth microdilution (BMD) method. BMD was used as a standard gold method for colistin resistance. Results: A total of 43.57% MDR, 9.49% XDR, and 3.5% PDR gram-negative bacteria was isolated from various departments and from various sites. Vitek-2 compact detected 47 (2.75%) and MBD method detected 38 (2.23%) colistin-resistant gram-negative bacilli. Vitek-2 compact failed to detect nine colistin-resistant organisms. The highest resistance towards colistin was seen in A. baumannii (6%), followed by P. aeruginosa (5%), Escherichia coli (1.07%), Klebsiella pneumonia (1%). Conclusions: There is a need for quick and efficient antibiotic resistance management efforts against colistin resistance. Vitek-2 compact gives unsatisfactory and inaccurate results in the detection of colistin susceptibility