Abstract:
The objectives of this study were to isolate lactic acid bacteria which were capable of inhibiting the growth of Mastitis pathogens in dairy cows; Staphylococcus aureus and Escherichia coli as well as study the characteristics of inhibiting agents, produced from isolated lactic acid bacteria. There were 250 isolates with anti-Mastitis pathogen properties, isolated from raw cow milk samples. Five isolates, showing dominant anti-Mastitis pathogen properties (inhibition zone ranged from 9.80±0.21-10.70±0.36 millimeter and 9.27±0.11-10.92±0.04 millimeter for Staphylococcus aureus and Escherichia coli, respectively) were chosen for the biochemical tests. It was found that all five isolates were gram-positive bacteria and could not produce catalase. Their antimicrobial activities were also studied in various conditions such as pH change, proteinase K treatment and high temperature treatment. It was found that proteinase K treatment and high temperature treatment at 50 and 100C did not effect on their antimicrobial activity. On the other hand, the antimicrobial activity of these five isolates could not be found under the condition of pH adjustment to 7.0. This data implied that the antimicrobial activity might come from the organic acid condition, produced by lactic acid bacteria. In addition, the nucleotide sequence of 16S rDNA indicated that these five lactic acid bacteria were in Lactobacillus sp.