streptococcus cristatus streptococcus cristatus streptococcus cristatus is a species of viridans streptococcus with tufted fibrils, first isolated from the human oral cavity and throat. the type strain is strain cr311 (= nctc 12479). streptococcus cristatus scientific classification domain: bacteria phylum: bacillota class: bacilli order: lactobacillales family: streptococcaceae genus: streptococcus species: s. cristatus binomial name streptococcus cristatuscorrig. handley et al. 1991