The presence and serological types of streptococcus suis strains isolated from pigs originating from some farms in Serbia

Streptococcus suis is a normal inhabitant of the respiratory system of pigs. Clinically healthy pigs are a major reservoir of the pathogen, but, as well, the most important link in the epidemiology of infection in humans. Hence, the aim of this study was to establish the presence of S. suis on some pig farms in Serbia and to determine their serotype affiliation. For this research, we tested 226 samples: nasopharyngeal tonsil swabs, nasal cavities swabs, parts of or all nasopharyngeal tonsils, swabs from dead animals, swabs from pig carcasses, and swabs from the butchers knives. Identification of S. suis strains was performed with antisera specific for capsular antigens. S. suis serotype 2 was established in 67.7% cases, and serotypes 7, 9 and 1 were isolated in a much smaller percentage (17.6, 8.8 and 5.9%, respectively). Serotype 2 is the only serotype isolated from all the collected samples. Serotype 9 was isolated from healthy pig tonsil swab and from 2 nasal swabs, and was not found in the samples taken from diseased pigs. The serotype 1 was isolated only from nasopharyngeal tonsil swabs of piglets, while serotype 7 was isolated from nasopharyngeal tonsil swabs, nasopharyngeal tonsil sections, but also from nasal swabs of healthy pigs. It can be concluded that the infections caused by different serotypes of S. suis are present in the herd of pigs in Serbia; hence, it is very important to identify what serotypes of S. suis are involved in pathogenesis of infections in pigs