Comparative Analysis of Colistin Resistance in Pseudomonas aeruginosa: VITEK® 2 Compact Versus Broth Microdilution Method

Background Colistin, a last-resort antibiotic, has witnessed a surge in resistance, posing a significant threat to public health. Accurate and timely detection of colistin resistance is crucial for effective clinical management. This study aims to compare two commonly used methods, the VITEK® 2 Compact (bioMerieux, Marcy-l'Étoile, France) system and broth microdilution (BMD), for identifying colistin resistance in clinical isolates. Materials and methods The study was carried out in the Microbiology Department at Krishna Institute of Medical Sciences, Karad. The laboratory processed the specimens for identification, followed by antimicrobial susceptibility testing using the automated VITEK® 2 Compact system and the gold-standard BMD method. Results A total of 92 <i>Pseudomonas aeruginosa</i> isolates were examined using automation (VITEK® 2 Compact) and the BMD methods, and the findings were analyzed. A gender-based analysis of the study population showed that 67% were males and 33% were females. Among the various specimens received, the highest number of colistin-resistant isolates was found in urine (38 isolates, 41.30%), then pus (25 isolates, 25.17%), endotracheal tube (13 isolates, 14.13%), sterile fluid (7 isolates, 7.60%), blood (3 isolates, 3.26%), sputum (3 isolates, 3.26%), vaginal swab (2 isolates, 2.17%), and catheter (1 isolate, 1.08%). Of the 92 <i>P. aeruginosa</i> isolates, 59 (64.1%) were resistant to colistin by the BMD, while 41 (44.56%) were resistant by the VITEK® 2 Compact. Conclusion Colistin is increasingly used for multidrug-resistant Gram-negative infections. In this study, some isolates showed differing results between VITEK® 2 Compact and BMD. The statistical analysis showed moderate kappa agreement, confirming the consistent reliability of the VITEK® 2 Compact system for testing colistin minimum inhibitory concentrations. Consequently, we can employ the VITEK® 2 Compact automated system as an alternative.