Phytochemical Evaluation of Ocimum gratissimum as a Potential Therapeutic Agent Against characterized Multidrug-Resistant and Extended Spectrum Beta Lactamase Producing Salmonella Isolated from Swine

This study investigated the phenotypic resistance patterns, molecular determinants of extended-spectrum β-lactamase production, phytochemical composition, and antibacterial potential of Ocimum gratissimum leaf extracts against extended-spectrum β-lactamase producing multidrug resistance Salmonella isolates recovered from swine. A total of 81 Salmonella isolates were recovered from porcine samples and identified using standard microbiological techniques. Antimicrobial susceptibility profiling was performed using the Kirby–Bauer disc diffusion method against ten commonly prescribed antibiotics. Extended-spectrum β-lactamase production was phenotypically confirmed using the double-disc synergy test, while multiplex polymerase chain reaction was employed to detect clinically relevant β-lactamase resistance genes. Crude aqueous and ethanolic leaf extracts of Ocimum gratissimum were prepared and evaluated for antibacterial activity against confirmed extended-spectrum β-lactamase producing isolates using the agar well diffusion assay. Minimum inhibitory concentrations were determined by standard broth dilution techniques, and qualitative phytochemical analysis was conducted by gas chromatography-mass spectrometry to identify the major bioactive constituents responsible for antimicrobial activity. The findings revealed a high prevalence of multidrug resistance among the Salmonella isolates, characterized by extensive resistance to β-lactam antibiotics and molecular confirmation of extended-spectrum β-lactamase associated resistance genes. Both aqueous and ethanolic extracts of Ocimum gratissimum exhibited pronounced inhibitory activity against all tested multidrug resistance extended-spectrum β-lactamase producing isolates, with an average Minimum inhibitory concentration of 1.78 mg/mL, demonstrating broad-spectrum antibacterial efficacy. Phytochemical analysis confirmed the presence of biologically active secondary metabolites, including flavonoids, alkaloids, tannins, and saponins, whose synergistic interactions are likely responsible for the observed antimicrobial effects. The combined phenotypic, molecular, and phytochemical evidence highlights the remarkable therapeutic potential of Ocimum gratissimum as a natural antimicrobial agent against drug-resistant Salmonella. This study provides compelling evidence supporting the development of Ocimum gratissimum which has some antimicrobial potential against multidrug resistance and extended-spectrum β-lactamase producing Salmonella isolates. Ocimum gratissimum can to an extent serve as a phytotherapeutic compounds for managing infections caused by multidrug resistance and extended spectrum β-latamase producing Salmonella within veterinary and public health settings. Further studies involving bioactive compound isolation, toxicity assessment, pharmacokinetic evaluation, and in vivo efficacy are recommended to facilitate its translation into clinically relevant antimicrobial therapeutics.

Keywords: Antimicrobial resistance, Extended-spectrum β-lactamase, Multidrug-resistant Salmonella, Ocimum gratissimum, Phytotherapy, Swine.