Study of Serotype Distribution of Streptococcus suis Isolated from Diseased Pigs in Central and Southern Taiwan

• Main Authors: Wei-Ting Chiang, 江偉廷
• Other Authors: Hung-Chih Kuo
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/mxzuuc

碩士 === 國立嘉義大學 === 獸醫學系研究所 === 106 === Streptococcus suis is a gram positive bacterium with capsule that causes economic losses in the swine industry worldwide. Currently 30+ serotypes have been identified and distinguished based on their capsular antigen. Swine infected with S. suis show clinical signs of meningitis, arthritis, pneumonia and sepsis. There has been limited research conducted on serotype distribution and antimicrobial susceptibility of S. suis in Taiwan. This study aims to investigate the relationship amongst serotype, age of onset, location of infection, and drug resistance. Furthermore we aim to establish diagnosis and treatment guidelines for clinical veterinarians by analyzing current trends of S. suis infection in Taiwan. In this study, S. suis isolates were obtained from the brain, lungs, liver, joints, and other diseased organs of infected pigs that were sent to the Animal Disease Diagnostic Center of National Chiayi University in Taiwan from 2013 January to 2017 December. Polymerase chain reaction (PCR) was utilized to identify serotype of the isolates. Minimum inhibitory concentration (MIC) was used to determine antimicrobial susceptibillty and was performed using the microbroth dilution method. In total, 200 strains were isolated from 154 pigs in 128 cases. The majority of the cases were from Yunlin (41.4%) and Chiayi (27.4%). Of the 154 infected pigs, 50.6% were nursery pigs (between 5 to 12 weeks) and 31.1% were suckling pigs (between 0 to 4 weeks). The strains were isolated from the lungs (47.0%), liver (15.5%), joints (14.5%) and brain (13.5%). Serotype1 was the major serotype (15.9%) identified in this study, followed by serotype3 (14.0%), and serotype2 (11.6%). Antimicrobial susceptibility results showed that S. suis isolates were susceptible to amoxicillin, cefazolin, and ceftiofur. However the isolates showed resistance to erythromycin, lincomycin, oxytetracycline, and tylosin. Statistical analysis showed that suckling pigs were more prone to joint infection in comparison to other age groups, and serotype1 tented to be isolated from piglets. There was a significant difference in resistance to doxycycline, enrofloxacin, lincomysin, tylosin, lincospectin, penicillin G, and tiamulintrimethoprim-sulfamethoxazole between different serotypes. In summary, results of this study show that the predominant serotypes in Taiwan are similar to those found in neighboring Asian countries. Furthermore antimicrobial resistance trends identified in this study are similar to those found worldwide. Thus, β-lactam antibiotics should be used, in the treatment of S. suis infections, while the use of tetracyclines and macrolides should be avoided.