Molecular detection of Streptococcus agalactiae in bovine raw milk samples obtained directly from bulk tanks

Microbiological identification of Streptococcus agalactiae in milk samples from bulk tanks is an auxiliary method to control contagious mastitis. Still, there are some limitations for time-consuming cultures or identification methods and additional concerns about the preservation and transport of samples. In the present study, bulk tank milk samples from 247 dairy farms were cultured and compared through polymerase chain reaction (PCR), directed to 16S rRNA genes of Streptococcus agalactiae, followed by determination of the bulk tank bacterial counts and Streptococcus agalactiae isolation. The mean value of bulk tank milk bacterial counts was 1.08 x 106 colony forming units per ml and the bacterium was identified through the microbiological method in 39.7% and through PCR in 44.5% of the samples. Results indicated a sensitivity of 0.86 and a specificity of 0.83. The lack of significant differences between the results obtained by the standard microbiological culturing and PCR indicated a substantial agreement between the methods. The data suggest that PCR can be used for bulk tank milk samples to detect contagious mastitis caused by Streptococcus agalactiae.

Source: Elias et al. – Research in Veterinary Science, 93, 34-38, 2012

Complete abstract: www.m²-magazine/org > 031-25.02.2013