Selective medium for isolation of genus Prevotella from saliva

Objective: Black-pigmented genus Prevotella is an important pathogen in progress and development of gingivitis and periodontitis. Several selective media have been described for the isolation of Prevotella intermediaand Prevotella nigrescens from gingival crevicular fluid sample. The present study is undertaken with the purpose of development of selective medium for isolation of black-pigmented genus Prevotella from saliva sample. Methods: The based medium and the sensitivity of antibiotics were examined using reference strains of P. intermedia ATCC25611 and P. nigrescens ATCC33563 and 25262. The recovery of the new selective medium were calculated and compared with kanamycin-Brucella blood agar (KMB) commonly use for black-pigmented bacteria. Results: We tested tryptic soy, Brucella, and GAM etc. for base medium. However, there are not so big differences among them. Kanamycin and vancomycin are well use for selectivity of black-pigmented bacteria. Our new selective medium is further addition of bestatin and fosfomycin for exclusion of genus Porphyromonas and some Gram-positive and -negative bacteria, respectively. New selective medium did not allow the growth of representative strains of P. gingivalis, Prevotella loescheii and Prevotella denticola. The recovery of P. intermedia and P. nigrescens was 75.7~98.7%. Some white colonies of genus Prevotella grew on the medium. The recovery of black-pigmented genus Prevotella from saliva samples on the selective medium was almost 100% compare with that on KMB medium. The selectivity of the medium for saliva sample was 63.0~85.8%. However, the selectivity of the medium for gingival crevicular fluid sample was similar to that of KMB medium. Conclusion: The new selective medium has a good selectivity for genus Prevotella and eliminates possible false-positive results and is useful for isolation of genus Prevotella from saliva sample. This study was supported in part by a Grant-in-Aid for FRONTIER 2003 from MEXT.