RAG1 and periodontitis: Besides, we found rag-1 was detected from 14 cases, mostly with higher GI and PD/PI/SBI, and often combined with rag-3 and/or rag-4, suggesting the P.gingivalis carrying rag-1 is the strong virulent genotype and can be closely associated with severe periodontitis, which is consistent with Hanley et al[44].