Nutritionally variant streptococci from patients with endocarditis: growth parameters in a semisynthetic medium and demonstration of a chromophore

Abstract

Nutritionally variant streptococci were previously characterized by their growth as satellite colonies and by their nutrient requirements of cysteine or vitamin B6 for growth in complex media. To further understand the growth characteristics of these strains, fresh isolates from patients with endocarditis were studied using chemically defined enriched with 2% Todd-Hewitt dialysate. Under anaerobic conditions, growth yields of the strains in this medium were comparable to those obtained from a complex medium supplemented with vitamin B6; under aerobic conditions, most strains had higher growth yields in the semisynthetic medium. The requirement for cysteine and vitamin B6 in semisynthetic medium was no greater than that of other Streptococcus spp. EM studies demonstrated normal cell wall structures in organisms grown in the semisynthetic medium as compared with abnormal and irregular cell wall thickening in organisms grown in supplemented complex medium. These strains appeared to contain a common component when growth in the semisynthetic medium as demonstrated by the appearance of a chromophore after boiling the bacteria at pH 2. The demonstration of a medium with permits adequate growth with a normal ultrastructure of nutritionally variant streptococci will permit the further study of these streptococci.