Detection of csgA gene in carbapenem-resistant Acinetobacter baumannii strains and targeting with Ocimum sanctum biocompounds

Carbapenem-resistant Acinetobacter baumannii (CRAB) is considered highly virulent due to csgA gene-mediated biofilm formation. The present study aimed to target the same gene, employing the antibiofilm effect of Ocimum sanctum (O. sanctum) essential oil compounds among CRAB strains.

A semi-quantitative adherent bioassay was performed to detect the biofilm formation in 73 CRAB strains. This was followed by molecular characterization, Polymerase Chain Reaction (PCR) amplification, and csgA gene sequencing. An antibiofilm assay under in vitro conditions, with essential oils of O. sanctum was performed. This was followed with further docking analysis of csgA protein with the selected compounds from the O. sanctum essential oils. A Molinspiration assessment was also done to elicit the drug likeliness of the biocompounds.

The biofilm assay showed 58.9% as high-grade and 31.5% as low-grade biofilm formers, while 9.58% were non-biofilm formers. Molecular characterization of the csgA gene showed 20.54% (15/73) positivity. The strains that were imipenem resistant also showed the csgA gene to be present (100%; 15/15), with 60% (9/15) and 20% (3/15) for meropenem and doripenem resistance respectively. A crystal violet assay for determining cell viability was done in vitro, which gave Minimum biofilm inhibition concentrations of 50% (MBEC50) at 25 µl and 90% (MBEC90) at 50 µl. The docking analysis done in silico showed benzofuran to possess the lowest binding energy and highest hydrogen bond interactions.

The results indicate benzofuran, from the O. sanctum essential oils, to be effective in targeting the csgA gene among CRAB strains. Additionally, validation of these findings through in vivo studies is required.