Clinical and Microbiological Aspects of Colistin Resistance in Klebsiella pneumoniae Isolates From Tertiary-Care Hospital

Klebsiella pneumoniae is a major opportunistic pathogen responsible for a wide range of hospital-acquired infections such as pneumonia, urinary tract infections, bloodstream infections, and septicemia. The increasing occurrence of multidrug-resistant (MDR) and carbapenem-resistant strains has led to the reintroduction of colistin as an antibiotic of last resort used to treat severe infections caused by Gram-negative bacteria. However, the emergence of colistin resistance has emerged as a significant global public health concern, particularly in tertiary-care hospital settings, as it restricts available treatment options and complicates infection control measures. This review emphasizes the phenotypic patterns, underlying mechanisms, risk factors, and clinical importance regarding colistin resistance in K. pneumoniae isolates. Phenotypically resistant strains generally show minimum inhibitory concentration (MIC) values of ≥4 µg/mL. Resistance mechanisms include lipopolysaccharide modification, plasmid-mediated mcr genes, biofilm formation, and efflux pump activity. Risk factors such as extended hospital stays, admission to intensive care units, previous antibiotic use, and the utilization of invasive medical devices contribute to the development and dissemination of resistant strains. Ongoing surveillance, precise antimicrobial sensitivity testing using the broth microdilution method, and effective infection control practices are crucial to minimizing the burden of colistin-resistant infections in tertiary-care hospitals.