Survival and growth of yogurt culture in MRS broth in the presence of selected rodenticides

The objective of this study was to measure the survival and growth of yogurt culture (Y1 885) in MRS broth in the presence of rodenticides and to determine whether yogurt culture could eventually be used as a biomarker to detect rodenticides in milk. Serially diluted rodenticides were added to tubes containing MRS broth. Commercial yogurt culture was then inoculated in MRS broth sample and incubated at 42 °C for 6 hours. The Optical Density (OD 610 nm) and pH of the broth were recorded at 2, 4, and 6 hour intervals. The bacterial counts, a-galactosidase and β-galactosidase activity were also measured at the end of incubation. The yogurt cultures showed detectable sensitivity (significant change (p<0.05) in OD in the medium) to diphacinone at 0.005mg/ml, to brodifacoum at 0.02 mg/ml, and to bromadiolone at 0.06 mg/ml. There were significant differences (p<.05) in the bacterial count, pH, α-galactosidase and β-galactosidase activity in the presence of toxins in the medium. The results indicate that yogurt culture could be used as a biomarker for the early detection of rodenticides in milk. With some adjustments, this process could be utilized as a fast and accurate test for the presence of pesticides in dairy food products.