Streptococcus pyogenes is a microorganism from the kingdom of bacteria that is considered to be a unique and extremely complex opportunistic pathogen. The bacterium is especially unique because it has the ability to cause several diseases, ranging from 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 tract of 5-15% of the population, without causing disease” (Todar, 2002). Although the bacteria is often carried non-symptomatically by many people, it has potential to cause life-threatening invasive diseases in cases where it reaches the deep tissue, such as streptococcal toxic shock syndrome and type II necrotizing fasciitis, also known as the flesh-eating disease. Invasive streptococci infections also include joint or bone infections, destructive wound infections, myositis, meningitis, and endocarditis (Todar, 2002). Noninvasive forms include pharyngitis (strept throat), scarlet fever, cellulitis and impetigo (superficial skin infection also known as pyoderma). Since the noninvasive forms are common, predictable, and fairly easy to treat, this paper will discuss the rare invasive and often, fatal forms disease caused by S. pyogenes, specifically necrotizing fasciitis.
S. pyogenes is a gram-positive, non-motile, non-sporeforming coccus that exist in chains or pairs of cells (Todar, 2002) and are negative for oxidase and catalase (Khan, 2013). Individual cells are round-to-ovoid n shape, and 0.6-1.0 micrometer in diameter. S. pyones is an aerotolerant anaerobe that metabolizes by fermentation and requires enriched medium containing blood in order to grow. S. pyogenes display antigen A on its cell wall, and has been subsequently classified using Lancefield stereotyping as Group A Streptococci, often referred to as GAS. Group A Streptococci typically have capsules composed of hyaluronic acid and are beta hemolytic species, meaning they are capable of completely rupturing red blood cells (Todar, 2002). These hemolytic capabilities significantly attribute to the virulence of necrotizing fasciilitis, as well as specific super-antigens interfering with host immunity. In addition, the cell wall of S. pyogenes is remarkably complex and chemically diverse, containing many antigenic factors that further contribute to its overall ability to cause disease, including the M and F proteins, hyaluronic capsule, exotoxins, and nucleases.
Cases for both noninvasive and invasive infections caused by S. pyogenes can be found worldwide. “More than 10 million noninvasive GAS infections (primarily throat and superficial skin infections) occur annually in the United States” (Khan, 2013). On the other hand, invasive GAS diseases including necrotizing fasciitis and streptococcal toxic...