Continued Study of Oral Nocardia

¹ University of Kansas City, School of Dentistry, Kansas City, Missouri

A definitive study was carried out on 28 strains of Nocardia dentocariosus isolated from carious human teeth. All the strains studied constantly demonstrated variability in both colonial and cellular morphology. Colony form varied from smooth to rough; colony size varied from microscopic to macroscopic punctiform colonies. The cells varied from cocci to filaments with subsequent fragmentation during growth. Media routinely recommended for the isolation of nocardia did not support growth of oral nocardia, and no selective medium for the isolation of oral nocardia was found to be effective in this study. The growth requirements of oral nocardia appear to be quite similar to those of many other oral micro-organisms. Standard tests routinely used for identification procedures have proved to be unreliable. Gelatinase activity was constant only in buffered solutions, and catalase has proved to be an adaptive enzyme. Although the oral nocardia have individual distinguishable characteristics, they bear a close resemblance to actinomyces, streptococci, streptomyces, arthrobacters, and corynebacteria.