Streptococcus pyogenes is a microorganism of the bacterial kingdom considered a unique and extremely complex opportunistic pathogen. The bacterium is particularly unique because it has the ability to cause various diseases, with mild to severe outcomes. Streptococcus pyogenes is named so because strepto means chains, coccus is used to describe a spherical shape, and pyogenes is used to describe a pus-forming organism. "S. pyogenes is considered one of the most frequent pathogens in humans and can be found on the skin or in the respiratory tracts of 5-15% of the population, without causing disease” (Todar, 2002). Although the bacterium is often transported in asymptomatic by many people, it can potentially cause life-threatening invasive disease in cases where it reaches deep tissues, such as streptococcal toxic shock syndrome and necrotizing fasciitis type II, also known as necrotizing fasciitis of the flesh Invasive infections streptococcal infections also include joint or bone infections, destructive wound infections, myositis, meningitis and endocarditis (Todar, 2002). Non-invasive forms include pharyngitis (sore throat), scarlet fever, cellulitis and impetigo (superficial skin infection also known as pyoderma).Because the noninvasive forms are common, predictable, and fairly easy to treat, this article will discuss the rare, invasive, and often fatal forms caused by S. pyogenes, particularly necrotizing fasciitis. Causal agents. pyogenes is a gram-positive, non-motile, non-spore-forming coccus that exists in chains or pairs of cells (Todar, 2002) and is negative for oxidase and catalase (Khan, 2013). Individual cells have a round to ovoid shape and a diameter of 0.6-1.0 micrometers. S. pyones is an aerotolerant anaer...... middle of paper ......erica, 12(2), 181-186.Sharkawy A, Low DE, Saginur R, et al. Severe group A streptococcal soft tissue infections in Ontario: 1992-1996. CID 2002;34:454-60.Steer AC, Lamagni T, Curtis N, Carapetis JR. (2012) Invasive cluster of streptococcal disease: epidemiology, pathogenesis and management. Drugs. 2012;72(9):1213-27. http://dx.doi.org/10.2165/11634180-000000000-00000. PMid:22686614.Todar, Ken. 2002. “Streptococcus pyogenes” Tortora G, Funke B, Case C. 2007. Microbiology: An Introduction, 9th edition. Pearson Education, Inc. Trent, J. Kirsner, R. (2002). Wounds from necrotizing fasciitis. http://www.medscape.com/viewarticle/444061_4Wong CH, Chang HC, Pasupathy S, Khin LW, Tan JL, Low CO. Necrotizing fasciitis; clinical presentation, microbiology and determinants of mortality. J Bone Joint Am 2003; 85 –A:1454