Original Articles

Evaluation of Colistin Susceptibility among Multidrug-Resistant Gram-Negative Pathogens isolated from Blood Culture: Evidence from a Tertiary Care Setting in Delhi, India

Abstract

Background:   Antibiotic resistance is a grave threat to managing bloodstream infections, with MDR gram-negative pathogens like carbapenem-resistant Klebsiella pneumoniae and Escherichia coli escalating globally. This study sought to assess the colistin susceptibility profiles of MDR gram-negative clinical isolates obtained from blood cultures within a high-burden tertiary care facility in Delhi.

Methods:   This cross-sectional study was conducted in the Department of Microbiology at UCMS & GTB Hospital, Delhi, from January 2023 to June 2024. A total of 80 multidrug-resistant gram-negative clinical isolates from blood cultures were included. Carbapenem resistance was confirmed using the Modified Carbapenem Inactivation Method (mCIM), while colistin resistance was determined through Broth Microdilution Testing (BMD).

Results:   A study conducted over one year tested 80 Enterobacterales isolates, with 74 (92.5%) identified as CRE using the Kirby Bauer disc diffusion method and confirmed by mCIM testing. The majority of isolates (44%) were from NICU, with a male predominance (60%). Enterobacter species (40%) was the most prevalent, followed by Klebsiella pneumoniae (26.6%), Citrobacter species (20%), and Escherichia coli (13.4%). The study found high multidrug resistance, with 100% resistance to most antibiotics in Enterobacter and Klebsiella species. All 74 isolates showed intermediate colistin susceptibility, with 43.2% exhibiting an MIC of 0.031 µg/mL.

Conclusion:   This study highlights the urgent need for colistin stewardship programs to address the rise of CRE. The emergence of colistin resistance, especially in NICUs and ICUs, requires enhanced monitoring and rapid diagnostics. Focusing on vulnerable populations like neonates and critically ill patients is crucial to combat multidrug-resistant infections.

1. Magiorakos AP, Srinivasan A, Carey RB, et al. Multidrug-resistant, extensively drug-resistant and pandrug-resistant bacteria: an international expert proposal for interim standard definitions for acquired resistance. Clin Microbiol Infect 2012; 18(3):268-81.
2. Kontopidou F, Plachouras D, Papadomichelakis E, et al. Colonization and infection by colistin-resistant Gram-negative bacteria in a cohort of critically ill patients. Clin Microbiol Infect 2011; 17(11): E9-E11.
3. Marchaim D, Chopra T, Pogue JM, et al. Outbreak of colistin-resistant, carbapenem-resistant Klebsiella pneumoniae in metropolitan Detroit, Michigan. Antimicrob Agents Chemother 2011; 55(2):593-9.
4. Arjun R, Gopalakrishnan R, Nambi PS, et al. A study of 24 patients with colistin-resistant Gram-negative isolates in a tertiary care hospital in South India. Indian J Crit Care Med 2017; 21(5): 317-21
5. Mammina C, Bonura C, Di Bernardo F, et al. Ongoing spread of colistin-resistant Klebsiella pneumoniae in different wards of an acute general hospital, Italy, June to December 2011. Euro Surveill 2012; 17(33):20248.
6. Pawar SK, Mohite ST, Datkhile KD, et al. Closing the gap between phenotypic and genotypic detection of carbapenem resistant Enterobacteriaceae. J Clin Diagn Res 2018; 12:1-4.
7. CLSI: CLSI M100 Performance for antimicrobial susceptibility testing, 32rd edition. Clinical and laboratory standard institute. (2022). Accessed: 13/09/2024: https://clsi.org/media/wi0pmpke/m100ed32_sample.pdf.
8. Nordmann P, Naas T, Poirel L. Global spread of carbapenemase-producing Enterobacteriaceae. Emerg Infect Dis 2011; 17(10):1791-8.
9. van Duin D, Doi Y. The global epidemiology of carbapenemase-producing Enterobacteriaceae. Virulence 2017; 8(4):460-9.
10. Logan LK, Renschler JP, Gandra S, et al. Carbapenem-resistant Enterobacteriaceae in children, United States, 1999–2012. Emerg Infect Dis 2015; 21(11):2014-21.
11. Klein SL, Flanagan KL. Sex differences in immune responses. Nat Rev Immunol 2016; 16(10):626-38.
12. Pitout JD, Nordmann P, Poirel L. Carbapenemase-producing Enterobacteriaceae: a global epidemic. Clin Microbiol Rev 2015; 28(2):337-76.
13. Nordmann P, Poirel L. Epidemiology and diagnostics of carbapenem resistance in Gram-negative bacteria. Clin Infect Dis 2019; 69(Suppl 7): S521-S528.
14. Humphries RM, Abbott AN, Hindler JA. Understanding and addressing CLSI breakpoint revisions: a primer for clinical laboratories. J Clin Microbiol 2019; 57(6):e00203-19.
15. Kumar M, Rubens M, Fair R, et al. Distribution of carbapenem-resistant Enterobacteriaceae (CRE) in India. Microorganisms 2020; 8(10):1412.
16. Kaye KS, Pogue JM. Infections caused by resistant Gram-negative bacteria: epidemiology and management. Pharmacotherapy 2015; 35(10):949-62.
17. Gashaw Y, Asmare Z, Tigabie M, et al. Prevalence of colistin-resistant Enterobacteriaceae isolated from clinical samples in Africa: a systematic review and meta-analysis. BMC Infect Dis 2025; 25:437.
IssueVol 13 No 3 (2025) QRcode
SectionOriginal Articles
Keywords
Broth Microdilution method Carbapenem-Resistant Enterobacterales (CRE) Modified Carbapenem Inactivation Method (mCIM).

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How to Cite
1.
Nirmal S, Nirmal K, Jayaraj H, Singh P, Das S. Evaluation of Colistin Susceptibility among Multidrug-Resistant Gram-Negative Pathogens isolated from Blood Culture: Evidence from a Tertiary Care Setting in Delhi, India. J Med Bacteriol. 2025;13(3):37-44.