Necrotizing soft tissue infections (NSTIs) are life-threatening infections leading to destruction of fascia, ie, necrotizing fasciitis (NF), and sometimes fat or muscles. NF incidence is estimated to 2-4 cases per 100 000 inhabitants per year. NF has a 20-30% mortality (28% in our 1996-2012 retrospective database) and heavy burden - 15% amputation and long-term disability in 30% of survivors -. Although GAS is the main agent involved, most of NF are considered polymicrobial (70-80% according to a 2010 classification). We performed a NGS prospective study of bacterial flora comparing culture, targeted metagenomic (TM) and Shotgun metagenomic (SM) in 34 patients who underwent surgical procedures: type I (digestive) NSTIs was proeminent but types II and III were represented too. Combination of SM and culture seems the most valuable. We also found that « healthy areas » were colonized with the same bacteria than necrotic areas. Management is based on IDSA guidelines including prompt surgical debridement and broad spectrum antibiotics. The results of our still in revision Cochrane systematic review should not change those conclusions. Clindamycin is widely used in an attempt to better control toxinic manifestations and the value of IVIG is still controversial with a negative RCT just published. Delay to surgery is a key factor of survival and surgery should be performed in centers experiencing NSTIs management (at least 3 NSTIs per year in our nationwide multilevel study). Since 2013, we organized a NF referal center in Paris area with a decreased mortality in our preliminary results.