Major Mammary Pathogens as Contributors to Total Bacterial Counts in Raw Milk

Abstract

The purpose of this study was to assess the contribution of major mammary pathogens, as well as of coliform and Gram-negative non-coliform bacteria to standard plate counts (SPCs) of bulk tank milk samples (BTMSs). Randomly selected anonymous BTMSs were collected from 268 dairy herds (with approximately 29,000 cows) in the Czech Republic during 2007. The most frequently detected pathogens were found to be E. faecalis (16.1%; geometric mean 9.8 × 102 CFU/ml) and S. uberis (13.6%; 9.0 × 102 CFU/ml). Highly significant positive correlations (P < 0.01) between the bacterial counts of the dominant pathogens and the relevant SPC were found for E. faecalis and S. dysgalactiae, as were significant correlations (P < 0.05) for S. uberis, E. faecium, and S. aureus. Highly significant positive correlations (P < 0.01) were found between SPC and coliform count and between SPC and Gram-negative non-coliform bacteria count. The results suggest, therefore, a recent dominance of environmental pathogens especially streptococci and enterococci, over contagious mammary pathogens in BTMSs. The geometric means of SPC in BTMSs with mammary pathogen (7.7 × 104 CFU/ml for environmental; 7.4 × 104 CFU/ml for contagious pathogens) exceed significantly (P < 0.05) the geometric means of SPC of pathogen free BTMSs (4.4 × 104 CFU/ml). This study revealed that the major mammary pathogens contribute significantly to SPCs of BTMSs.