ABSTRACTClinical microorganisms isolated during a 5-year study in our hospital that could not be identified by conventional criteria were studied by 16S rRNA gene sequence analysis. Each isolate yielded a ≥1,400-bp sequence containing <5 ambiguities which was compared with the GenBank 16S rRNA gene library; 1,404 such isolates were tested, and 120 were considered unique (27 isolates) or rare (≤10 cases reported in the literature) human pathogens. Eleven new species, “Actinobaculum massiliae,” “CandidatusActinobaculum timonae,”Paenibacillus sanguinis, “CandidatusBacteroides massiliae,”Chryseobacterium massiliae, “CandidatusChryseobacterium timonae,”Paenibacillus massiliensis, “CandidatusPeptostreptococcus massiliae,” “CandidatusPrevotella massiliensis,”Rhodobacter massiliensis, and “CandidatusVeillonella atypica” were identified. Sixteen species were obtained from humans for the first time. Our results show the important role that 16S rRNA gene sequence-based bacterial identification currently plays in recognizing unusual and emerging bacterial diseases.