Phenotypic and Molecular Characterization of Carbapenem Resistance Among Gram-Negative Bloodstream Isolates: Emergence of blaNDM and blaOXA-48 Co-production in a Tertiary Care Hospital in South Kerala, India
R. Jayadeep, Ashna Ajimsha, O. R. ReshmaAbstract
Background:
Carbapenem-resistant Gram-negative bacilli can cause difficult to treat bloodstream infections contributing to morbidity and mortality worldwide. Rapid detection of carbapenemase production and knowledge of responsible genes have a major role in infection management. However, regional variations in carbapenemase distribution remain insufficiently characterized, particularly among bloodstream isolates from South Kerala. The aim of our study was to characterize carbapenem resistance among Gram-negative isolates by phenotypic and genotypic methods.
Methods:
A descriptive, laboratory-based cross-sectional study was conducted at a tertiary care hospital in South Kerala over 18 months. Blood culture isolates were identified; antimicrobial susceptibility testing was done by Kirby Bauer disc-diffusion method, with VITEK 2 (bioMérieux, France) confirmation. Carbapenem resistance was assessed phenotypically by Carba-NP (Carbapenemase Nordmann-Poirel) test, mCIM and eCIM (Modified and EDTA modified carbapenem inactivation methods), and genotypically by polymerase chain reaction (PCR).
Results:
Of 203 blood culture isolates, Gram-negative bacilli accounted for 158 (77.8%), in which
Conclusions:
Carbapenem resistance among Gram-negative bloodstream isolates in this study is heterogeneous. The emergence of dual carbapenemase producers underscores the need for integrated phenotypic and molecular surveillance to support early detection, targeted treatment, and effective antimicrobial stewardship.