Carbapenemase-encoding genes among enterobacterales isolated from blood culture in oncology care

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Objectives: Carbapenemase-producing carbapenem-resistant enterobacterales (CP-CRE) pose a significant clinical challenge, especially in oncological patients, representing a substantial therapeutic hazard. The study aims to assess the prevalence and profile of carbapenemase genes among CP-CRE isolates from bloodstream infections (BSIs) in a tertiary care cancer institute in Eastern India. Materials and Methods: An 18-month prospective, observational, single-center study was conducted. Blood culture isolates from suspected BSIs were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Antimicrobial susceptibility testing was performed using automated broth microdilution (VITEK-2). Carbapenemase gene detection was carried out using the RESIST-5 O.K.N.V.I. lateral flow immunoassay targeting New Delhi metallo-β-lactamase (NDM), oxacillinase-48-like carbapenemase (OXA-48), Klebsiella pneumoniae carbapenemase (KPC), Verona integron-encoded metallo-β-lactamase (VIM), and imipenemase (metallo-β-lactamase) (IMP). Statistical analysis: Descriptive statistics summarized prevalence and distribution patterns. Results: Of 1674 blood cultures processed, 532 (31.7%) were positive. Enterobacterales were isolated in 259 cases (48.7% of positive cultures). Among these, 94 isolates (36.3% of Enterobacterales; 17.6% of culture-positive samples) were carbapenem-resistant. K. pneumoniae (56.4%) and Escherichia coli (36.2%) were the predominant species. Gene profiling revealed NDM alone (44.6%) as the most common, followed by NDM + OXA-48 (31.9%) and OXA-48 alone (17%). No isolates carried KPC, VIM , or IMP genes. 6 (6.3% of the carbapenem-resistant enterobacterial isolates) showed no detectable genes by the RESIST-5 panel. Mortality was 28.7% ( n = 94). For most CP-CRE, colistin and tigecycline remained the principal in vitro therapeutic options following further clinical and laboratory evaluations. Conclusions: The predominance of NDM and OXA-48 genes in bloodstream isolates highlights the critical need for stewardship practices involving resistance gene profiling. Routine carbapenemase gene profiling using simple immunochromatographic tests may facilitate earlier clinical decision-making in similar clinical settings, particularly in oncology settings, while interpretation should be integrated with antimicrobial susceptibility testing and clinical context.

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