Paper Title
STREPTOCOCCUS AGALACTIAE CAUSING MASTITIS IN DAIRY COWS FROM WARITCHAPHUM DAIRY COOPERATIVE, SAKON NAKHON PROVINCE, THAILAND

Abstract
Abstract - Background and rational: Streptococcus agalactiae is a Gram-positive, spherical bacterium that causes infections in dairy cattle and is also the main cause of subclinical mastitis in dairy cattle. The objective of this study was to determine the prevalence and antimicrobial susceptibility test of S. agalactiae, a cause of mastitis in dairy cows From Waritchaphum Dairy Cooperative Sakon Nakhon Province. Methods: The study was carried out as a survey of S. agalactiae causing mastitis in dairy cows The milk quality was examined using the California Mastitis Test (CMT) technique. Raw milk samples were collected from 10 dairy cows with mastitis from 9 farms.Streptococcus strains that cause bovine mastitis were identified species and the antimicrobial resistance genes by the Polymerase Chain Reaction (PCR) method. The antimicrobial susceptibility test of bacteria was determined by the broth microdilution method. Results: The study found that S. agalactiae was identified in 100% milk samples on all farms. The antimicrobial resistance genes to tetracycline and macrolide were identified in 64.71% (11/17) of S. agalactiae. Among these isolates were identified 35.3% (6/17) tetM gene followed by 17.6% (3/17) tetM + ermB, 5.9% (1/17) tetE + tetM + tetW + ermB and 5.9% (1/17) ermB Among 11 isolates that present of antimicrobial resistance genes were resistance to tetracycline 100% (11/11) with an MIC value of256 µg/ml, followed by clindamycin 9.1% (1/11) with an MIC value of 64 µg/ml. Conclusion: This study can suggest that it could be beneficial to farmers, livestock, and veterinarians in selecting appropriate antibiotics to treat mastitis and can be used as preliminary information to find guidelines for prevention and control standards development for bovine mastitis. Keyword: S. agalactiae, Mastitis, Daily cows, Thailand