Prevalence, capsular type and antimicrobial susceptibillity of Streptococcus suis isolated from slaughter pigs in Korea

This study was undertaken to determine the prevalence, capsular serotype, a nd antimicrobial susceptibility of Streptococcus suis isolated from slaught er pigs. Capsular serotype and antimicrobial susceptibility were determined by coagglutination test and agar dilution minimum inhibitory concentration , respectively. Streptococcus suis was isolated from 55 of the 406 palatine tonsillar samples tested (13.8%) and 14 of the 29 sampled herds (48.3%). O f the 55 isolates recovered from slaughter pigs, 26 (47.3%) were untypeable . Of: the remaining 29 isolates, capsular serotypes 9 (9 isolates) and 16 ( 4 isolates) were the most common, followed by capsular serotypes 4 (3 isola tes) and 7 (3 isolates). Every capsulated isolate was typeable and no palat ine tonsillar sample yielded more than one serotype. Most of isolates were susceptible to low concentrations (MIC90) of amoxicillin (2 mug /mL), cefti ofur (1 mug/mL), and penicillin (1 mug/mL). No correlation was found betwee n antimicrobial susceptibility and capsular serotype.