Efficacy of edible plant extracts against multi-drug resistant Salmonella serovars in layer flocks

The present study examines the antibacterial effects of edible plants (Neem, Garlic, and Ginger) extracts against Salmonella serovars isolated from layer flocks using phenotypic antimicrobial resistance techniques. The incidence of positive isolates was higher in Dinajpur (13.89%), followed by Thakurgoan (11.91%), Nilphamari (10%), and Panchagarh (8.33%). Organoleptic analysis showed a higher prevalence in the liver (17.86%) compared to the heart (7.14%) and lung (10.72%). Ethanolic extractions were performed from the plants, and the antibacterial activity of these extracts was assessed using the disc diffusion method at concentrations of 80, 100, and 120 mg/mL against multidrug-resistant (MDR) bacteria, which were identified from selected layer flocks using conventional laboratory techniques. These bacteria are resistant to at least two antibiotics. The maximum inhibition zones for Neem, Garlic, and Ginger extracts at 120 mg/mL were 14 mm, 10 mm, and 2 mm, respectively, while the minimum inhibition zones at 80 mg/mL were 10 mm, 3 mm, and none, respectively. Neem leaf extract showed the highest effectiveness against MDR bacteria compared to Garlic and Ginger extracts. Although the organisms were sensitive to ciprofloxacin and colistin, they showed intermediate resistance to levofloxacin and chloramphenicol and resistance to neomycin and kanamycin. When comparing the antibacterial efficacy of resistant antibiotics and plant extracts in vitro, plant extracts showed larger inhibition zones. Therefore, it was concluded that ethanolic Neem leaf extract could serve as an alternative to conventional antibiotics against field isolates of Salmonella spp. in poultry.