Antibacterial effects of Psidium guajava leaf extracts on diarrhea caused by Salmonella typhimurium and Escherichia coli in sheep

Diarrhea in neonatal ruminants, especially sheep, poses a serious challenge in livestock management, often leading to high mortality rates. The primary pathogens responsible are Salmonella typhimurium and Escherichia coli. This study explores the antibacterial potential of Psidium guajava (guava) leaf extracts as an alternative to conventional treatments. Guava leaves, collected from Tubah subdivision, Mezam, were processed into aqueous and ethanolic extracts. Phytochemical analysis revealed the presence of bioactive compounds including resins, alkaloids, saponins, glycosides, tannins, and flavonoids. Antibacterial activity was assessed using agar well diffusion and Minimum Inhibitory Concentration (MIC) methods. The aqueous extract displayed dose-dependent antibacterial effects, with inhibition zones of 16.0 mm against E. coli and 15.2 mm against S. typhimurium at 100 mg/ml, which were less effective compared to Gentamycin (19 mm). The MIC values for the aqueous extract were 6.25–3.13 mg/ml for E. coli and 12.5–6.25 mg/ml for S. Typhimurium. In contrast, the ethanolic extract showed slightly superior efficacy with inhibition zones of 16.2 mm for E. coli and 17.6 mm for S. Typhimurium at 100 mg/ml. The MIC values for the ethanolic extract were 3.13–1.56 mg/ml for E. coli and 6.25–3.13 mg/ml for S. typhimurium, indicating higher potency than the aqueous extract. Conclusively, both guava leaf extracts exhibit significant antibacterial properties, with the ethanolic extract being more potent. These results validate the traditional use of Psidium guajava and suggest its potential as a natural antimicrobial agent, though further research is needed to optimize its therapeutic applications.