Streptococcal infection in piglets: the palatine tonsils as portals of entry for Streptococcus suis.

Abstract

Studies of infection with Streptococcus suis (Lancefield’s Group D) were carried out to investigate the role of the palatine tonsils in the pathogenesis of piglet streptococcal meningitis and arthritis caused by this organism. Oral infection with Strep, suis produced clinical disease in 1 of 4 piglets infected at 10 days of age; inapparent infection occurred in the other 3 in which the organism was confined to the tonsils and their drainage lymph nodes. Strep, suis or its antigenic breakdown products, specifically identified by immunofluorescent microscopy, were located in the tonsillar crypt lumina, epithelium, interfollicular tissue and, rarely, in germinal centres of all 4 infected piglets. Histological examination failed to reveal any abnormalities of the tonsils. In a second experiment, phagocytosis of bacteria by epithelial cells of the tonsillar crypts was demonstrated by electron-microscopy. The results revealed the palatine tonsils to be portals of entry for Strep, suis.