Type I infection: This is the most common type of infection, and accounts for 70 to 80% of cases. It is caused by a mixture of bacterial types, usually in abdominal or groin areas. This type of infection is usually caused by various species of Gram-positive cocci, ("Staphylococcus aureus", "Streptococcus pyogenes", and enterococci), Gram-negative rods, ("Escherichia coli", "Pseudomonas aeruginosa"), and anaerobes, ("Bacteroides" and "Clostridium" species). Populations of those affected are typically older with medical comorbidities such as diabetes mellitus, obesity, and immunodeficiency. Usually, trauma is not the cause of such infections. Previous history of abscess infection or gut perforation with bacterial translocation may be elicited. Clostridial infection accounts for 10% of type I infection. "Clostridium" species involved are "Clostridium perfringens", "Clostridium septicum", and "Clostridium sordellii", which typically cause gas gangrene (also known as myonecrosis). "Clostridium perfringens" produces two deadly toxins: alpha-toxin and theta-toxin. Alpha-toxin causes excessive platelet aggregation which blocks blood vessels and deprives the vital organs of oxygen supply. This creates an acidic, oxygen-deficient environment for the proliferation of bacteria. When alpha-toxin is absorbed by soft tissues, it can inhibit the migration of white blood cells from blood vessels into the soft tissue, thus impairing phagocyte function. The two toxins together can cause destruction of red blood cells in blood vessels, damage to the integrity of the blood vessels, and suppression of heart function.