Iranian journal of microbiology · 2026
Detection and prevalence of the bla NDM-1 gene in carbapenem-resistant Klebsiella pneumoniae bloodstream isolates from a tertiary care institute.
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Ramakrishnan Susheem, Bashir Gulnaz, Bali Nargis Kaur, Rashid Sabah, Mathew Dona, Nisar Qounser, Mir Mohd Iqbal
Аннотация
BACKGROUND AND OBJECTIVES: Carbapenem resistance mediated by bla NDM-1 in Klebsiella pneumoniae has emerged as a major challenge, particularly in intensive care settings with high antibiotic pressure. This compromises therapeutic options and contributes to poor clinical outcomes. The present study aimed to determine the prevalence of bla NDM-1 among isolates of K. pneumoniae from a tertiary care hospital, evaluate the performance of phenotypic tests against PCR-based detection, assess antimicrobial susceptibility profiles, and analyze clinical outcomes.
MATERIALS AND METHODS: In this study, over 18 months, 130 non-duplicate K. pneumoniae isolates were identified, and antimicrobial susceptibility testing was performed by VITEK-2 Compact and broth microdilution for colistin. Imipenem-resistant isolates were subjected to the Combined disc diffusion test (CDDT) and Double disc synergy test (DDST) for metallo-beta-lactamase (MBL), and conventional PCR targeting bla NDM-1. Demographic data and outcomes were recorded.
RESULTS: Of the 130 isolates, 111 were imipenem-resistant, of which CDDT detected MBLs in 94.6%, and DDST detected MBLs in 76.6%. PCR confirmed bla NDM-1 in 77.5% and was more commonly associated with cases of sepsis. bla NDM-1 -positive isolates were resistant to β-lactams, fluoroquinolones and aminoglycosides. No isolate was found to be colistin-resistant. 26.7% of the patients with bla NDM-1-positive bacteremia died.
CONCLUSION: This study highlights the high prevalence of bla NDM-1 in K. pneumoniae isolates. Among the phenotypic tests, CDDT outperformed DDST and showed the best agreement with PCR, supporting its use as a screening method for MBL, but confirmatory PCR remains essential. The restricted treatment options underscore the need for stringent infection control and robust antimicrobial stewardship to curb transmission and preserve last-line agents.
MATERIALS AND METHODS: In this study, over 18 months, 130 non-duplicate K. pneumoniae isolates were identified, and antimicrobial susceptibility testing was performed by VITEK-2 Compact and broth microdilution for colistin. Imipenem-resistant isolates were subjected to the Combined disc diffusion test (CDDT) and Double disc synergy test (DDST) for metallo-beta-lactamase (MBL), and conventional PCR targeting bla NDM-1. Demographic data and outcomes were recorded.
RESULTS: Of the 130 isolates, 111 were imipenem-resistant, of which CDDT detected MBLs in 94.6%, and DDST detected MBLs in 76.6%. PCR confirmed bla NDM-1 in 77.5% and was more commonly associated with cases of sepsis. bla NDM-1 -positive isolates were resistant to β-lactams, fluoroquinolones and aminoglycosides. No isolate was found to be colistin-resistant. 26.7% of the patients with bla NDM-1-positive bacteremia died.
CONCLUSION: This study highlights the high prevalence of bla NDM-1 in K. pneumoniae isolates. Among the phenotypic tests, CDDT outperformed DDST and showed the best agreement with PCR, supporting its use as a screening method for MBL, but confirmatory PCR remains essential. The restricted treatment options underscore the need for stringent infection control and robust antimicrobial stewardship to curb transmission and preserve last-line agents.