**10.1 Fulminant streptococcal infection (streptococcal myonecrosis)**

Streptococcal myonecrosis, a fulminant form of necrotizing fasciitis, presents a rapidly progressive gangrene of the extremities caused by infection of *Streptococcus pyogenes* (group A β-hemolytic *Streptococcus*), representing a prototype of "flesheating bacteria infection" [89, 90]. The disease affects persons of any age. Groups B and G β-hemolytic *Streptococcus* may also cause an identical fulminant condition [91, 92]. In some cases, protein S deficiency may be responsible for the necrotizing inflammation. It has been reported that vimentin, an intracellular intermediate filament of nonepithelial cells, is upregulated in the injured skeletal muscle cells and functions as the major skeletal-muscle protein binding to streptococci [93]. The lifethreatening gangrene follows the subacute form of necrotizing fasciitis or occurs suddenly without preexisting ulceration. As shown in **Figure 5**, an advanced, deep pocket-forming decubitus in the sacral region may cause the lethal gangrenous lesion categorized in non-clostridial gas gangrene [18].

#### *Pathology of Gangrene DOI: http://dx.doi.org/10.5772/intechopen.93505*

Clinically, high fever, pain at the site of infection, and skin necrosis (gangrene) with hemorrhagic bulla formation are associated. Scarlatiniform rash may be noted. Finally, massive gangrenous necrosis involves the extremity.

Microscopically, pronounced myonecrosis with foci of infection of Grampositive cocci is observed. Gram-positive cocci grow within the lesion of advancing gangrenous necrosis of soft tissue. Cellular reactions are minimal, because of the ischemic (anaerobic) state with poor blood flow. In the cultured blood, short chains of Gram-positive cocci, morphologically typical of *Streptococcus*, are seen (**Figure 33**). Streptococcal septicemia provokes streptococcal toxic shock-like syndrome [94]. The bacterial exotoxins (superantigens) such as streptococcal pyrogenic exotoxins-A, B, C, F, and streptococcal superantigen provoke a severe cytokine storm. Hypercytokinemia activates hemophagocytosis by macrophages. Activation of NLRP3 inflammasome may be an essential event for the cytokine storm in streptococcal toxic shock-like syndrome [95].

The bacteria are commonly sensitive to penicillin and its derivatives, but the intravenous antibiotics administration is clinically ineffective, principally because of the absence of blood flow. The drug can hardly reach the site of infection.
