Isolation, identification and characterization of Streptococcus agalactiae of bovine origin in North China

Abstract:

[Objective] In order to characterize Streptococcus agalactiae isolates of bovine origin from North China. [Methods] Five hundred and fifty-seven milk samples were collected in 2012?2015 from dairy cows with subclinical mastitis in Inner Mongolia Autonomous Region, Hebei Province and Beijing, and S. agalactiae isolates were identified by biochemical analysis and molecular biological methods. Their drug sensitivities were detected using standard disk difusion method, and the genes for capsular type, surface protein and virulence factors were amplified by PCR. [Results] Twenty-eight streptococcal isolates were ientified as S. agalactiae with a isolation rate of 5.03% and similar drug sensitivities. All of 28 S. agalactiae isolates belonged to capsular type Ia with similar virulence gene patterns and undefined surface protein types. [Conclusion] These data indicate that the S. agalactiae isolates of bovine origin in different regions of North China had similar drug sensitivities and virulence gene patterns, which provided the rationale for development of therapeutic strategy and vaccines against bovine mastitis S. agalactiae.

Key words:Dairy cow mastitis, Streptococcus agalactiae, Serotype, Surface protein gene, Virulence factor