The M protein is a cell-surface protein and virulence factor found on Group A streptococci (*Streptococcus pyogenes*) that helps the bacteria evade the host immune system. Variations in M proteins allow differentiation of more than 80 strains of Group A strep, and changes in this protein can alter the infectivity of a strain.

M Protein

Lancefield classification is a method for serotyping various $$\beta$$-hemolytic strains of *Streptococcus* species based on their cell-surface antigens using an agglutination assay.

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An agglutination assay is a diagnostic technique that uses the clumping of bacteria to detect specific cell-surface antigens.

Agglutination Assay

https://openstax.org/details/books/microbiology/

Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

Microbiology is produced through a collaborative publishing agreement between OpenStax and the American Society for Microbiology Press. The book aligns with the curriculum guidelines of the American Society for Microbiology.

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