Differences in virulence between two strains of Streptococcus suis type II after experimentally induced infection of newborn germ-free pigs.
Fifteen newborn germ-free pigs were inoculated with 2 strains, D-282 and T-15, of Streptococcus suis type II. Some pigs also were preinoculated with Bordetella bronchiseptica, which successfully predisposed them to S suis infection. The 2 streptococcal strains were differentiated by muramidase treatment, which released certain high molecular-weight proteins, termed muramidase-released proteins (MRP), from the cell wall of strain D-282, but not from the cell wall of strain T-15. Only strain D-282 (MRP-positive) induced clinical signs of disease and markedly increased neutrophil numbers in pigs. Streptococci were more frequently isolated from fecal swab specimens obtained from pigs inoculated with strain D-282 (MRP-positive) than from specimens obtained from pigs inoculated with strain T-15 (MRP-negative). Both strains were isolated from nasal swab specimens obtained from all infected pigs. Postmortem examination revealed fibrinopurulent meningitis, polyserositis, and polyarthritis in pigs inoculated with strain D-282; this strain was isolated from the CNS, serosae, visceral organs, heart, and joints. Whereas strains D-282 caused several pathologic changes, strain T-15, isolated from the lungs, caused only pneumonia. Both strains were isolated from the tonsils of all pigs. Virulence differed distinctly between the MRP-positive and the MRP-negative strains.
Department of Bacteriology, Central Veterinary Institute, Lelystad, The Netherlands.
U
U
Vecht
J P
JP
Arends
E J
EJ
van der Molen
L A
LA
van Leengoed
D000818:Animals; D000831:Animals, Newborn / Q000382:microbiology; D001426:Bacterial Proteins / Q000032:analysis*; D001885:Bordetella Infections / Q000150:complications / Q000662:veterinary; D002531:Cerebellum / Q000382:microbiology / Q000473:pathology; D005260:Female; D005856:Germ-Free Life; D009113:Muramidase / Q000378:metabolism; D009504:Neutrophils; D013045:Species Specificity; D013290:Streptococcal Infections / Q000150:complications / Q000382:microbiology / Q000662:veterinary*; D013291:Streptococcus / Q000032:analysis / Q000302:isolation & purification / Q000472:pathogenicity*; D013552:Swine / Q000382:microbiology; D013553:Swine Diseases / Q000382:microbiology*; D014774:Virulence
D001426:Bacterial Proteins; D009113:Muramidase