Endophytic Bacillus aerophilus from the Leaves of Azadirachta indica as a Potential Biocontrol against Staphylococcus aureus

Aims: The study entailed isolation and identification of Bacillus aerophilus in the leaves of young Azadirachta indica plants, establishing the antimicrobial activity of the endophyte against Staphylococcus aureus, and screening for phytochemicals. The study investigated the potential of the endophytic Bacillus aerophilus in pathogen inhibition and phytochemical screening for bioactive compounds produced by the endophyte that can be used in drug development. The research contributes to the wider scientific goal of curbing rising cases of antibiotic resistance.

Place and Duration of Study: Sample: collected from Kanyonyoo in Kitui County, between August 2022 and June 2023.

Methodology: The bacteria were aseptically isolated and sub-cultured on nutrient agar. For identification, the bacteria underwent biochemical tests and molecular characterization. The 16S rRNA region was amplified and sequenced using universal primers 27F and 1492R. Bacterial isolate K1L003 was identified as Bacillus aerophilus. For antimicrobial testing, the agar disk diffusion method was used against pathogenic Staphylococcus aureus on Mueller Hinton Agar plates (MHA). The controls were doxycycline and vancomycin.

Results: The endophytic isolate only inhibited Staphylococcus aureus (P < .001), with an inhibition mean similar to doxycycline (26 mm), against the pathogen. The endophytic isolate produced terpenoids, saponins, alkaloids, and flavonoids.

Conclusion: Endophytic Bacillus aerophilus has better antimicrobial inhibition potential than vancomycin, against Staphylococcus aureus and produces diverse bioactive secondary metabolites. The endophyte has the potential to produce compounds that are useful in treating drug-resistant Staphylococcal infections.