Antimicrobial activity of bacterial strains isolated from cow milk

Cow milk contains various microorganisms which are beneficial and some could be pathogenic. Beneficial bacteria, lactic acid bacteria that are present in the cow milk contribute to the probiotics characteristics whereas other bacteria posseses several probiotics effects. This thesis aims to isolate lactic acid bacteria from cow milk using the selective MRS medium and proves the bacterial strain isolated have probiotic characteristics. Four strains were isolated from 20 colonies, all isolates are Gram positive and catalase positive. The isolate's morphologies are both rod and cocii. Antimicrobial properties characteristics are determined by using disc diffusion method and agar well method. Besides that, the isolates are identified using 16SrRNA universal primers and the fragments are amplified using polymerase chain reaction(PCR). The purified PCR products are sequenced and the isolates are identified using BLAST and Clustal W2 websites. The isolates are closely related to Staphylococci, a rare strains and the strain possess several similarities with lactic acid bacteria. The study reports that there are abundance microorganisms presents in milk and additional method , pasturization of fresh cow milk is important to favour the isolation of beneficial bacteria. There are higher probability to isolate less beneficial bacteria from fresh cow milk as compared to the isolation of lactic acid bacteria although by using the proven methodology and proper selective medium.