No abstract

By the combined use of membrane filters and the antibiotic rifampin, intermediate‐size anaerobic spirochetes from periodontal pockets were routinely selected and separated from other oral bacterial contaminants. Electron microscopy of six newly isolated strains showed that they belong to the genus Treponema. The organisms had generation times of about twelve hours; they produced only acetic acid when glucose was used as the carbohydrate in the medium Serum, volatile fatty acids, and thiamine pyrophosphate could be omitted individually as supplements from the growth medium, but sodium bicarbonate was absolutely essential for growth. These treponemes could be maintained by monthly transfers into fresh medium, by freezing in glycerol‐broth medium or by lyophilization.

Six anaerobic oral spirochetes designated strains a, b, c, d, e, and e’ were isolated randomly from periodontal pockets and were maintained in pure culture. The strains were found to belong to the genus Treponema. All strains were similar in cultural, morphological, biochemical, and physiological properties with the exception of the following features: strains c and d were more fastidious nutritionally for sodium bicarbonate as a medium supplement than the other strains; they differed in the number of axial fibrils; and they were also serologically distinct from strains a, b, e, and e’ by agglutination tests and fluorescent immunoassays. However, DNA homology studies indicated that all the isolates were strains of Treponema denticola with divergent phenotypic and serological properties. Serovar a and serovar c, representing two different serogroups, have been deposited in the American Type Culture Collection with the accession numbers ATCC 35405 and ATCC 35404, respectively.

Four hundred strains of oral bacteria were tested for their susceptibility to spiramycin. Actinobacillus actinomycetemcomitans and most species of Lactobacillus were resistant to the antibiotic. All strains of cariogenic Streptococcus mutans and most strains of bacterial species implicated in adult chronic periodontitis (Bacteroides gingivalis, B. intermedius, and Treponema denticola) were susceptible to spiramycin.