Antibacterial Effect of Bay Leaf (Laurusnabilis) Aqueous Extract and its Nano-Emulsion on Some Pathogenic Bacteria

Abstract

The substantially increasing multiple drug resistance microorganisms, especially dangerous bacteria, created a concern for both humans and animals. Plant components may be utilised to cure or manage infections instead of antibiotics. This study examined the antibacterial effects of Bay leaf (laurusnobilis) aqueous extracts and nano-emulsion against gram-positive (Staphylococcus aureus) and gram-negative (E. coli and Pseudomonas aeruginosa) bacteria and their effects on virulence and antibiotic resistance genes. The MIC) minimum inhibitory concentration (of both was determined using thiazolyl blue tetrazolium bromide (MTT) micro dilution to assess antibacterial activity. Bay leaf (laurusnobilis) extracts and nano-emulsion had antibacterial effects against both gram-positive and gram-negative bacteria, according to MIC values. The nano emulsion showed stronger antibacterial activity against S. aureus and E. coli, with MIC values of 12.5, 50, and 50 μg/ml, respectively, compared to the aqueous extract, which had MIC values of 50 μg/ml for S. aureus and 100μg/ml for E. coli and Pseudomonas aeruginosa. The S. aureus strain has mecA and blaZ resistant genes and coa virulent gene, but no Sea virulent gene. However, E. coli carried Stx2 and iss (Virulent genes) and Mcr1 and floR (resistance genes). The nano-emulsion extract of laurusnobilis Sub-MIC highly reduced the relative expression of Staphylococcus aureus’s coA gene and antibiotic-resistant genes (mecA and blaZ genes) and E.coli’s Stx2 and iss genes and antibiotic-resistant genes (floR and Mcr1 genes) compared to endogenous genes (16s rRNA). As conclusions: The plant extracts and nanoemulsion may prevent pathogenic microorganism-induced deterioration and provide antibacterial agents for gram-positive and gram-negative bacterial infections.