<P> Necrotizing fasciitis can occur at any part of the body, but it is more commonly seen at the extremities, perineum, and genitals . Only a few of such cases arise from the chest and abdomen . Trauma is the usual cause of the infection such as intravenous drug injection, insulin injection, animals and insect bites, catheter insertion over the skin, or a fistula connecting skin to the internal body organs . Skin infections such as abscess and ulcers can also complicate necrotizing fasciitis . Spreading of infection through blood has been suggested for those with streptococcal pharyngitis . For infection of the perineum and genitals (Fournier gangrene), trauma, surgery, urinary tract infection, stones, and Bartholin gland abscess are the usual causes . </P> <P> Types of soft - tissue necrotizing infection can be divided into four classes according to the types of bacteria infecting the soft tissue . This classification system was first described by Giuliano and his colleagues in 1977 . </P> <P> Type I infection - This is the most common type of infection which accounts for 70 to 80% of the 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 . </P> <P> Clostridium sordellii can also produce two major toxins: all known virulent strains produce the essential virulence factor lethal toxin (TcsL), and a number also produce haemorrhagic toxin (TcsH). TcsL and TcsH are both members of the large clostridial cytotoxin (LCC) family . The key Clostridium septicum virulence factor is a pore - forming toxin called alpha - toxin, though it is unrelated to the Clostridium perfringens alpha - toxin . Myonecrotic infections caused by these clostridial species commonly occur in injecting heroin users . Those with clostridial infections typically have severe pain at the wound site, where the wound typically drains foul - smelling blood mixed with serum (serosanguinous discharge). Shock can progress rapidly after initial injury or infection, and once the state of shock is established, the chance of dying exceeds 50% . Another bacterium associated with similar rapid disease progression is group A streptococcal infection (mostly Streptococcus pyogenes). Meanwhile, other bacterial infections require two or more days to become symptomatic . </P>

Where has the flesh eating bacteria been found