Characterization of Lactococcus lactis isolates from bovine mastitis

Area of Science:

• Microbiology
• Food Science
• Veterinary Medicine

Background:

• Lactococcus lactis is a common dairy starter with Qualified Presumption of Safety (QPS) status.
• Increasing reports link L. lactis to human and animal infections, like bovine mastitis.
• Distinguishing between pathogenic and safe L. lactis strains is crucial.

Purpose of the Study:

• To investigate genotypic and phenotypic differences between L. lactis mastitis isolates and dairy starter strains.
• To assess if phenotypic traits associated with pathogenicity can be identified.

Main Methods:

• Genotypic characterization using 16S rRNA gene sequencing and RAPD-PCR.
• Phenotypic characterization including stress tolerance (temperature, lysozyme, bile salts, pH), carbohydrate fermentation, antibiotic resistance, and in vitro adhesion to udder epithelial cells.

Main Results:

• Genotypic analysis revealed no significant differences between mastitis isolates and starter strains.
• Phenotypic analysis showed mastitis isolates possess increased tolerance to stress conditions and enhanced adhesion capacity.
• Mastitis isolates also exhibited improved carbohydrate fermentation compared to starter strains.

Conclusions:

• Phenotypic variations, not genotypic ones, differentiate L. lactis mastitis isolates from dairy starters.
• These traits enhance survival in homeothermic animals and resemble properties of probiotic strains.
• Further research is needed to understand the implications of these phenotypic differences for pathogenicity and potential probiotic use.