Molecular identification and structural characterization of marine endophytic actinomycetes Nocardiopsis sp. GRG 2 (KT 235641) and its antibacterial efficacy against isolated ESBL producing bacteria

The present study was designed to identify the potential bioactive compound from endophytic actinomycetes (EA) Nocardiopsis sp. GRG 2 (KT 235641) against selected extended spectrum beta lactamase (ESBL) producing Pseudomonas aeruginosa (P. aeruginosa) and Klebsiella pneumoniae (K. pneumoniae). Initially, the multi drug resistance (MDR) effect of selected uropathogens was confirmed by respective UTI panel of Hexa antibiotics disc methods. The zone of inhibition ≤22 mm for ceftazidime, ≤ 27 mm for cefotaxime and ≤8 mm zone of MIC stripe against both the uropathogens of phenotypic methods confirmed, the selected strains were ESBL producer. Among the various EA extracts, GRG 2 extract showed excellent antibacterial activity against both ESBL producing P. aeruginosa and K. pneumonia by agar well diffution method. The molecular identification of selected GRG 2 strain was named as Nocardiopsis sp. GRG 2 (KT235641). The antibacterial metabolites present in the TLC elution was exhibited at 274 nm by UV visible spectrometer. The partial purification of preparative HPLC fraction 3 showed 14, 16 mm against P. aeruginosa and K. pneumoniae, respectively. Based on the antibacterial effect, the FT-IR, GC-MS and LC-MS analysis of fraction 3 was confirmed as 1, 4-diaza-2, 5-dioxo-3-isobutyl bicyclo[4.3.0]nonane (DDIBN). Further, the dose dependent inhibition of DDIBN against both ESBL producing pathogens was observed at 75 μg/mL by minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC). The increased cell death and disrupted cell membrane integrity were observed at MIC of DDIBN by confocal laser scanning electron microscope (CLSM) and scanning electron microscope (SEM). The results were proved that the DDIBN has potential antibacterial metabolites against ESBL producing pathogens and it can be applied for various other biomedical fields.