Harnessing the antibacterial activity of Quercus infectoria and Phyllanthus emblica against antibiotic-resistant Salmonella Typhi and Salmonella Enteritidis of poultry origin

Background and aim: In a scenario of the ineffectiveness of the current drugs against antibiotic-resistant pathogens, the herbal extracts can serve as an alternative remedy. This study appraises the antibacterial potency of Quercus infectoria (gall), Phyllanthus emblica (fruit) individually and synergistically against antimicrobial-resistant (AMR) Salmonella Typhi and Salmonella Enteritidis in a time and dose-dependent manner. Further, the antibacterial phytocompounds were identified employing gas chromatography-mass spectrometry (GC-MS).

Materials and methods: Preliminary antibacterial activity of the plant extracts was assessed using the agar disk diffusion method. In vitro evaluations of Q. infectoria methanolic extract (QIME) and P. emblica methanolic extract (PEME) against S. Typhi and S. Enteritidis were carried out using plate count method.

Results: QIME and PEME at a dose rate of 50 mg/ml and 25 mg/ml, respectively, had a complete bactericidal effect on AMR S. Typhi and S. Enteritidis whereas 10 log₁₀ CFU/ml of exponential growth was seen in untreated control groups. At the lower concentrations, QIME and PEME had a significant bacteriostatic effect (3-6 log₁₀ reduction of the test isolates). The synergistic antibacterial effect obtained from the combination of these two plant extracts at 12.5 mg/ml was superior (p<0.001) than the individual treatments. Phytochemical profiling indicated the presence of tannins, flavonoids, saponins, and terpenoids in both the plant extracts. GC-MS analysis of QIME and PEME revealed the presence of 16 and 15 antibacterial phytocompounds, respectively. Further 1, 2, 3 Benzenetriol was found as the prominent active principle.

Conclusion: The findings validate that QIME and PEME are potential antibacterial agents against AMR S. Typhi, S. Enteritidis and can play a promising role in antimicrobial packaging, poultry feed additives and can also serve as a platform for formulating effective phytotherapeutics.

Keywords: Phyllanthusemblica; Quercusinfectoria; Salmonella; antimicrobial-resistant; gas chromatography-mass spectrometry; phytochemicals.