[Dichotomous keys for identifying Staphylococcus isolated from bovine milk]

Area of Science:

• Microbiology
• Food Science
• Epidemiology

Background:

• Raw milk can harbor various Gram-positive, catalase-positive cocci.
• Accurate identification of these bacteria is crucial for food safety and quality control.
• Existing identification methods may require optimization for practical application.

Purpose of the Study:

• To identify different strains of Gram-positive, catalase-positive cocci isolated from raw milk.
• To establish a useful and practical methodology for their correct identification.
• To perform an epidemiological observation of these bacteria in raw milk samples.

Main Methods:

• Isolation and testing of Gram-positive, catalase-positive cocci from raw milk.
• Application of conventional microbiological tests including bacitracin resistance, novobiocin susceptibility, and coagulase tests.
• Utilization of dichotomous keys for Staphylococcus species identification.
• Grouping strains based on coagulase and novobiocin susceptibility.

Main Results:

• Sixty-two strains were analyzed.
• Staphylococcus hyicus was the most frequently isolated species (17.7%).
• Other identified species included Staphylococcus aureus (14.5%), Staphylococcus sciuri (12.9%), and Staphylococcus haemolyticus (11.3%).
• Staphylococcus epidermidis was notably absent in the isolated strains.

Conclusions:

• The study successfully identified key Staphylococcus species in raw milk, highlighting S. hyicus as predominant.
• The proposed identification methodology, utilizing coagulase and novobiocin susceptibility, is effective for differentiating Staphylococcus species.
• This research provides valuable epidemiological data on microbial contaminants in raw milk.