Streptococcus suis serotype 2 infection in pigs: new diagnostic and pathogenetic aspects.
In a study aimed at improving the diagnosis and elucidating the pathogenesis of Streptococcus suis serotype 2 infection in pigs, a combination of bacterial culture and histopathological and immunohistochemical examination was applied to a range of tissues from 42 naturally infected pigs with typical macroscopical lesions. By culture, 21 pigs (50%) were shown to be systemically infected with S. suis serotype 2; seven (17%) were infected with S. suis serotype 7, two with other bacteria, and 12 yielded no bacterial pathogens. The highest isolation rate for S. suis serotype 2 was obtained from the lateral cerebral ventricles and other regions of the brain, whereas the bacterium was only rarely isolated from the liver or spleen. Immunohistochemically, a diagnosis of S. suis serotype 2 infection was obtained in two of 12 (17%) animals from which no pathogens had been cultured. Moreover, immunohistochemistry differed from culture in revealing a greater number of positive tissue specimens. The microanatomical distribution of bacteria pointed toward the pharyngeal and palatine tonsils as principal portals of entry. Furthermore, S. suis serotype 2 bacteria were frequently identified immunohistochemically in the regional lymph nodes of the upper respiratory tract, possibly reflecting primary lymphogenous spread from the tonsils.
Madsen
L W
LW
Laboratory of Veterinary Pathology, Royal Veterinary and Agricultural University, Bülowsvej 17, Copenhagen, DK-1870, Denmark.
Svensmark
B
B
Elvestad
K
K
Aalbaek
B
B
Jensen
H E
HE
D000818:Animals; D000942:Antigens, Bacterial / Q000032:analysis; D001431:Bacteriological Techniques / Q000662:veterinary; D001921:Brain / Q000276:immunology / Q000473:pathology; D007150:Immunohistochemistry / Q000662:veterinary; D014066:Palatine Tonsil / Q000382:microbiology / Q000473:pathology; D013290:Streptococcal Infections / Q000382:microbiology / Q000473:pathology / Q000662:veterinary*; D017011:Streptococcus suis / Q000145:classification / Q000302:isolation & purification / Q000502:physiology*; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology* / Q000473:pathology
D000942:Antigens, Bacterial