SERPINA2 and fasciitis: Taken together, these observations indicate that the twitching motility phenotype of the necrotizing fasciitis strains could be related to the production of a type IV pilin such as PilA, although the production of this protein and the presence of pil orthologs found in the NFAb-1 and NFAb-2 strains as well as the ATCC 17978 isolate (Supplemental Table S6) are not the sole conditions for the expression of twitching motility.