Contamination rate of Brucella in raw sheep milk and the effects of cell-free supernatant of Lactobacillus acidophilus on its biofilm production

Brucellosis is one of the most important zoonotic bacterial diseases in humans and vertebrate animals. Lactic acid bacteria (LAB) and their production compounds have been proposed as potential biocontrol agents in biofilm formation. The present research aimed to determine the effects of cell-free supernatant (CFS) from Lactobacillus acidophilus on the biofilm production of Brucella isolates from raw sheep milk of Mahabad city (Iran). In this study, 100 sheep milk samples were randomly collected from different urban and rural areas of Mahabad. To isolate Brucella, the samples were cultured in Brucella broth and then streaked on Brucella agar with the selective supplement, and to identify the species of Brucella, related metabolic tests were performed. The biofilm production capability of the isolates, as well as the antibiofilm activity of the CFS, were evaluated by the microplate assay method. The results showed that out of 100 milk samples, 3 samples (3%) are contaminated with Brucella melitensis. Also, all three isolates were biofilm-formers. Two isolates were recognized as moderate and one isolate as a strong biofilm-former. Different concentrations of CFS reduced the biofilm production of isolates significantly (P˂ 0.01). Also, the concentration of 10% of CSF showed the highest antibiofilm activity. From the findings, it can be concluded that Brucella contamination in raw sheep milk in the Mahabad region is relatively high. There is a need for a full performance of Brucellosis screening and vaccination programs in livestock herds of the region. It can also be concluded that the CFS of L. acidophilus can remove Brucella biofilm. Therefore, L. acidophilus CFS as an antibiofilm compound can be proposed to control the growth of Brucella.