Objective: This study was conducted to screen the antibacterial activity of Acacia nilotica plant extract and four disinfectants(TH₄, Tek-trol, Virkon S and peracetic acid)against pathogens causing mastitis (E.coli, Staphylococcus aureus and Streptococcus agalactiae).
 Design:  Descriptive study
Animals: Three hundred eighty-two dairy cows 
Procedures: Three thousands and seventy seven samples were collected from three dairy farms at Dakahlia province. Samples include animal samples (1528 of both quarter milk and teat skin swabs) and 221 environmental samples include 60  bedding, 60 Milk linear, 36 feed, 36 water, 11 bulk tank milk and 18 workers' hand swabs. All samples were examined bacteriologically for isolation and identification of mastitis causing pathogens (S. aureus, E. coli and St. agalactiae). Furtherly, minimum inhibitory concentration (MIC) and minimum bacterial concentration (MBC) tests were used to investigate the antimicrobial activities of selected disinfectants and Acacia nilotica extract toward isolated strains.
Results: TH₄ and aqueous Acacia nilotica extract were effective against S. aureus and St. agalactiae, with MIC values as low as 3.13 μg/ml of the original concentrations. Meanwhile, the antimicrobial actions of Tek-trol and Acacia nilotica extract toward E. coli isolates only reached 12.5 μg/ml. The in-vitro bactericidal effect showed that, MBC values of Acacia nilotica plant extract achieved the highest inhibitory concentration up to 25 μg/ml among the tested disinfectants.
Conclusion and clinical relevance: In conclusion, Acacia nilotica plant extract have antibacterial activity comparable to commercialdisinfectants for the control of mastitogenic pathogens in dairy farms, providing a promising tool for mastitis control in dairy farms.