Computational and Experimental Evaluation of Azadirachta indica Leaf Extract against Multidrug-Resistant Citrobacter koseri

Azadirachta indica has long been recognized for its antibacterial properties, whereas Staphylococcus saprophyticus and Citrobacter koseri represent important public health concerns because of their ability to cause skin infections. The present study was designed to identify bioactive phytocompounds from the methanolic leaf extract of A. indica and to assess their inhibitory activity against these pathogens using both in vitro and computational methods. The bacterial isolates were obtained from human pus samples collected from boils. For enrichment, the samples were cultured in diluted tryptic soy broth for four hours, followed by streaking onto tryptic soy agar plates and incubation at 37 C for 24 hours. Species identification of the selected colonies was confirmed by amplification of the 16S rDNA gene using polymerase chain reaction based on a previously reported protocol. The amplified products were purified using a QIAquick PCR purification kit according to the manufacturer protocol. Purified amplicons were sequenced by Macrogen Inc., South Korea, using the Sanger sequencing approach. The resulting nucleotide sequences were analyzed using the basic local alignment search tool to confirm bacterial identity. Sequence alignment and dendrogram construction were performed using MEGA software to compare the isolates with closely related organisms. After confirmation of the isolates, the antibacterial effectiveness of the plant extract and selected antibiotics was evaluated.