Susceptibility of chicken embryos to group A streptococci: Correlation with fibrinogen binding

• Published in: FEMS immunology and medical microbiology 1993-10, Vol.7 (3), p.231-240
• Main Authors: Schmidt, Karl‐Hermann, Wiesner, Joachim, Gerlach, Dieter, Reichardt, Werner, Ozegowski, Jörg‐Hermann, Köhler, Werner
• Format: Article
• Language: English
• Subjects: Animals; Antigens, Bacterial; Bacterial Outer Membrane Proteins; Bacterial Proteins - metabolism; Bacteriology; Biological and medical sciences; Blood Proteins - metabolism; Carrier Proteins; Chick Embryo; Chicken embryo model; Exotoxins - toxicity; Fibrinogen - metabolism; Fibrinogen binding; Fundamental and applied biological sciences. Psychology; Group A streptococci; Hyaluronic Acid - toxicity; Immune Sera; Immunoblotting; Lethal Dose 50; Lipopolysaccharides - toxicity; Membrane Proteins; Microbiology; M‐protein; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; Plasma protein binding; Protein Binding - physiology; Rabbits; Streptococcal Infections - microbiology; Streptococcus; Streptococcus pyogenes - immunology; Streptococcus pyogenes - metabolism; Streptococcus pyogenes - pathogenicity; Virulence
• ISSN: 0928-8244; 1574-695X
• DOI: 10.1111/j.1574-695X.1993.tb00403.x

One problem in investigating group A streptococcal infections and virulence is the lack of appropriate in vivo models. In this study we introduce the chicken embryo model for determining virulence of Streptococcus pyogenes. We found that M protein positive strains, if administered intravenously, were highly virulent for 12‐day‐old chicken embryos. The LD50 of the strains tested could be correlated directly with the amount of cell wall exposed M protein, which has been determined by the capacity of streptococci to bind fibrinogen and by the ability of streptococci to survive in fresh normal human blood. The number of colony forming units (cfu) of M+ strains necessary to kill 50% of embryonated eggs was significantly lower (104 cfu). Albumin and/or IgG binding to streptococcal cells, which can also take place in proteins of the M protein family which do not bind to fibrinogen, did not show that clear correlation to the virulence in chicken embryos that did fibrinogen binding. Application of anti‐streptococcal M protein antisera from chicken and rabbit reduced the lethality of the chicken embryos. In contrast, no correlation was found between lethality of chicken embryos and the in vitro production of erythrogenic toxins by the administered strains. Thus the results indicate that the presence of M‐protein with its fibrinogen binding activity on the streptococcal cell surface is necessary for virulence of group A streptococci in the chicken embryo model.