Antiseptic effect of natural teat dip containing lactic acid against mastitis-causing Escherichia coli

Aim: This study aimed to estimate the enumeration of total bacteria and coliform on teat skin from dairy cows and evaluate the efficacy of the natural rice gel containing 5% v/v lactic acid (NGL) against Escherichia coli standard and field strains isolated from bovine teat skin. Materials and Methods: A total of 100 bacterial teat skin samples (25 cows) were collected from dairy cows in smallholder farm. The cows were housed in freestall barns. The colonization of total bacteria and E. coli on teat skin was measured by 3M Petrifilm method. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of lactic acid were evaluated for reference strain of E. coli ATCC 25922 and two field strains of E. coli. The natural teat sanitizer was formulated using 5% NGL with modified rice gel. In vitro antiseptic efficacy of 5% NGL was determined by time-kill kinetic assay. E. coli morphology after exposure with 5% NGL was examined under a scanning electron microscope (SEM). Results: The total bacteria and coliform counts from bovine teat skin were 2.11×104 and 1.54×101 colony-forming units/ml, respectively. The MIC and MBC of lactic acid on the tested bacteria were 0.5% v/v. The natural teat dip was successfully prepared with minimum change in consistency after 1 year of storage at 4°C. The reduction rate of 5% NGL on E. coli ATCC 25922 and field strain showed 32.77% and 27.58%, respectively. An appearance under SEM of non-viable E. coli after being incubated with 5% NGL clearly showed atypical form and rough surface cell membrane. Conclusion: The rice gel containing 5% v/v lactic acid is a promising preparation as a natural teat antiseptic for reducing bacteria on teat skin. It was shown to be effective against E. coli causing bovine mastitis in dairy cows.