EFS and periodontitis: In that study, upregulation of all CRISPR-associated genes and, in particular, of cas3 in the systems present in P. gingivalis as well as in Tannerella forsythia, another organism associated with periodontitis, was observed (21); however, matching site comparisons from the patients that did not progress during this period showed no upregulation of CRISPR-associated genes (20).