Evaluation of Anti-Salmonella Activity and Acute Toxicity of Azadirachta indica (A. Juss) Seed Oil

Bacterial infections by Salmonella remain a real public health threat causing each year, more than 1.2 million deaths worldwide. The treatment by antibiotics is usually compromised due to the emergence of multi-resistant strains, supply chain problems and the high cost of medicines in developing countries where infectious diseases are usually endemic. Faced to these difficulties, these populations turn to medicinal plants treatment and essential oils, whose uncontrolled use poses effectiveness and safety issues. Using agar diffusion and macrodilution methods, we selected three Salmonella strains to evaluate the antibacterial activity of Azadirachta indica seed oil. Subsequently, an acute toxicity study of the extract was performed on Wistar rats by force feeding of the test groups with 2 ml/100kg of body weight, according to the slightly modified Organisation for Economic Co-operation and Development (OECD) guideline 420. Two of the three bacterial strains were susceptible with diameters of 17mm for Salmonella typhi and 18,5mm for Salmonella paratyphi. Their minimum inhibitory and bactericidal concentrations were 37.5mg/ml and 150mg/ml respectively with a MBC/MIC ratio equals to 4. Acute toxicity analyses showed that the lethal dose 50 (LD 50) of this oil was greater than 2ml/100g. Azadirachta indica seed oil possessed anti-Salmonella bacteriostatic properties on two strains and it was toxicologically safe at the dose of 2 ml/100g of body weight.