In vivo pathogenicity and resistance to phagocytosis of Streptococcus equi strains with different levels of capsule expression.
The glossy non-encapsulated strain of Steptococcus equi, NCTC 9682, was compared with the matt strain Hidaka/95/2 which expresses a medium sized capsule and with the mucoid CF32 which expresses a large sized capsule in phagocytosis assays and for virulence in inoculated horses. The three strains, NCTC 9682, Hidaka /95/2 and CF32 produced 2.0, 3.1, and 5.3 mg/g wet cells respectively after 3 h incubation, but similar amounts of M-like proteins, cytotoxin and mitogen. NCTC 9682 showed no resistance to phagocytosis by equine neutrophils regardless of the presence of opsonin while strains Hidaka /95/2 and CF32 showed almost complete resistance to phagocytosis. Furthermore, NCTC 9682 produced no clinical disease although it infected the guttural pouch and caused seroconversion. Typical strangles with guttural pouch invasion was observed in all horses infected with encapsulated strains.
Anzai
T
T
Epizootic Research Station, Equine Research Institute, Japan Racing Association, Tochigi. anzai@epizoo.equinst.go.jp
Timoney
J F
JF
Kuwamoto
Y
Y
Fujita
Y
Y
Wada
R
R
Inoue
T
T
D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D016667:Bacterial Capsules / Q000235:genetics; D015153:Blotting, Western / Q000662:veterinary; D002227:Carbazoles / Q000737:chemistry; D002244:Carbon; D015169:Colony Count, Microbial / Q000662:veterinary; D004396:Coloring Agents / Q000737:chemistry; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005260:Female; D005562:Formazans / Q000737:chemistry; D015964:Gene Expression Regulation, Bacterial; D006734:Horse Diseases / Q000382:microbiology*; D006736:Horses; D006820:Hyaluronic Acid / Q000032:analysis / Q000235:genetics; D007564:Japan; D008198:Lymph Nodes / Q000382:microbiology; D014066:Palatine Tonsil / Q000382:microbiology; D010587:Phagocytosis / Q000235:genetics*; D013290:Streptococcal Infections / Q000382:microbiology / Q000662:veterinary*; D018502:Streptococcus equi / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity*; D013778:Tetrazolium Salts / Q000737:chemistry; D014481:United States
D000907:Antibodies, Bacterial; D002227:Carbazoles; D004396:Coloring Agents; D005562:Formazans; D013778:Tetrazolium Salts; C028433:chinese ink; C041514:carbazole; C079782:MTT formazan; D002244:Carbon; D006820:Hyaluronic Acid