Streptococcus pyogenes disease and molecular pathogenesis

Published on October 29, 2009   49 min

A selection of talks on Oral Health

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Welcome to another lecture in the series on bacterial pathogenesis. I'm Patrick Cleary. I'm a Professor of Microbiology at the University of Minnesota Medical School. The focus of my lecture is Streptococcus pyogenes, a review of the diseases and the molecular pathogenesis associated with this organism.
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I'd like to start out by giving you a brief overview of the genus Streptococcus. In the 1940s and 50s, Rebecca Lancefield sub-classified streptococci using polysaccharide antigens produced by different strains of streptococci as the antigenic marker of different species. She grouped streptococci into groups. Group A through N. Since her work, however, microbiologists have given these streptococci genus and species names. For example, streptococcus pyogenes is also called group A streptococcus. Many of these streptococci have two names. They have a genus and species name, but they also are referred to by their group name. Streptococcus agalactiae or group B streptococcus is the cause of neonatal infections and I'll talk about them in a little more detail in the next slide. Streptococcus dysgalactiae is a complicated collection of different strains of streptococci. Human isolates have been termed group C and G streptococcus and resemble Streptococcus pyogenes both as far as the kinds of infections they cause and the virulence factors that they produce. Their classification is a little bit murky, so I prefer to continue to use the Lancefield designation of group C and G streptococci. The dysgalactiae species or group also contain animal pathogens, Streptococcus equi is an example. It causes sore throats or strangles in horses. The oral streptococci are also a complicated collection of species and subspecies. One which has been studied in some detail is Streptococcus mutans. It's the cause of dental caries. Other species in the oral cavity which seldom cause infections, however, can cause serious infections if they get into the bloodstream. The streptococcus most often associated with invasive and serious infections is Streptococcus pneumoniae. Once again, this is a member of the normal flora and many of us carry this organism in our mouth. I'll say a little more about this organism in an upcoming slide.

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Streptococcus pyogenes disease and molecular pathogenesis

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