The platelet interactivity phenotype of Streptococcus sanguis influences the course of experimental endocarditis

Abstract

A strain of Streptococcus sanguis that induced rabbit platelets to aggregate in vitro (Agg+ phenotype) was hypothesized to be a more virulent pathogen than an Aggstrain in experimental endocarditis in rabbits. A left ventricular catheter was implanted, and then an Agg+ or Aggstrain was inoculated intravenously. Vegetations formed on the aortic semilunar valves but were unaffected by the duration of implantation of the catheter. Vegetations enlarged by accumulating platelets and their mass increased directly with the duration of endocarditis. Inoculation of the Agg+ strain consistently caused endocarditis with significantly larger vegetations, a more severe clinical course (including febrile episodes, hematological changes, and signs of myocardial ischemia), more gross lesions in major organs, and greater mortality than inoculation with the Agg-strain, saline, or the Agg+ strain pretreated with monospecific rabbit immunoglobulin G or Fab fragments against its platelet aggregation-associated protein (PAAP; class II). In experimental endocarditis, PAAP expressed by Agg+ S. sanguis appeared to be an important virulence factor.INFECT. IMMUN. M.on July 10, 2020 by guest http://iai.asm.org/ Downloaded from

Anti‐Fibrin Antibody Binding in Valvular Vegetations and Kidney Lesions during Experimental Endocarditis

“…General protocol. Experimental endocarditis was induced in New Zealand white (NZW) rabbits as described previously (17,25). On day 0, the rabbits were anesthetized and aortic valves were injured by only a 30-min placement of an in-dwelling catheter as modified previously (25).…”

“…Protocol for farm-bred rabbits. To initiate endocarditis in adult farm-bred NZW rabbits (3.4 to 4.2 kg), 1 ml of sterile pyrogen-free saline containing 10 8 colonyforming units (CFUs; 10 100 ) of S. sanguinis 133-79 was infused intravenously (17,25) in 15 of 19 rabbits. After 3 days of experimental endocarditis, 6 rabbits received 99rnTc-labeled anti-fibrin antibody, and 2 were infused with 99rnTc-labeled IgG (n = 2).…”

“…Radioscintigraphy. Rabbits were imaged by radioscintigraphic techniques, as reported previously (17). To evaluate changes quantitatively, 99mTc was infused and imaged for lO-min intervals beginning 10 and 60 min later in most rabbits.…”

“…The radioscintigraphic imaging of the aortic valvular vegetations was obscured by radioactivity within the heart chambers. Making quantitative comparisons required that radioactivity in the vegetations and the blood be determined by gamma counting as accomplished previously (17). To estimate clearance from the circulation during each experiment, radioactivity was also determined in the blood by gamma counting.…”

Experimental infective endocarditis induced by human supragingival dental plaque in rats

“…Studies show that increased bacteraemia results from poor oral health (17,18). Using animal models, the contribution of the haematogeneous spread of single cultured oral bacteria to IE has been examined in detail (19)(20)(21)(22)(23). However, there have been no previous studies in which human dental plaque samples were used to induce IE in animals.…”