Biochemical Characteristics of Bacterial Isolates Obtained from Bovine Mastitic Milk Samples

Aim: Bovine mastitis affects the milk production in milking cattle and the milk producer. The major causative organism of mastitis includes the bacteria. The present study is focused on the identification of bacterial isolates obtained from milk samples of bovine mastitis based on their biochemical activities.

Study Design: The bacterial isolates obtained from California mastitis test positive milk samples of in and around Bengaluru district, Karnataka were collected from Department of Veterinary Microbiology, Veterinary College, KVAFSU, Bengaluru, Karnataka and subjected to staining for morphology, Gram’s reaction and other biochemical tests. Identification key for both Gram positive and Gram negative bacterial isolates were prepared and based on the activities they were identified up to species level.

Place and Duration of Study: The work was carried out in the Department of Dairy Microbiology, Dairy Science College, KVAFSU, Hebbal, Bengaluru, Karnataka from Feb.2021 to Feb. 2022.

Methodology: Bacterial isolates obtained were subcultured, purified on plate count agar. The bacterial isolates were coded and subjected to simple staining, spore staining, Gram’s staining, oxidase test, catalase test and other biochemical tests like indole, VP, methyl red, citrate tests by preparing specific sterile media. The results obtained for the tests conducted were compared with the standard identification key and declared the species of bacterial genera.

Result: In the present study, 45 isolates of bovine mastitis obtained were phenotyped through staining techniques and biochemical tests. Among 45 isolates, 40 Gram positive isolates and 5 Gram negative, which were identified as streptococcus agalactiae (12); str. uberis (10); one each of staphylococcus delphini, staph. carnosus and staph. gallanarium while 6 each of staph. equorum; staph. epidermis and 3 staph. aureus. Gram negative (5) isolates were identified as Escherichia coli (3), Salmonella enterica (1) and Alcaligenes sp. (1) based on their biochemical characteristics.

Conclusion: The major mastitis causing bacteria isolated from CMT positive bovine milk samples was Streptococcus agalactiae followed by Str. uberis, Staphylococcus equorum, staph. epidermis, Staph. aureus and Escherichia coli some of which may be harboured in the udder of milch animals while few bacteria may enter through various sources of dairy farm environment. Hence precautions need to be taken about the udder health of the milch animals as well as hygiene of dairy farm to reduce the incidences of mastitis.