Action of Sulfanilamide on Hemolytic Enterococcus (Streptococcus fecalis hemolyticus)

Abstract

It is generally agreed that sulfanilamide, sulfapyridine, and related compounds are effective in the treatment of infections due to a limited number of microorganisms only. In vitro, these chemo-therapeutic substances may be bacteriostatic or bactericidal toward susceptible strains. There is, however, no absolute parallelism between the effectiveness of sulfanilamide in vivo and in vitro; nor between susceptibility or resistance of certain species or groups of microörganisms and their respective position in the system of bacteria. The susceptibility toward the action of sulfanilamide may be quite different even among relatively closely related groups. Thus, sulfanilamide may inhibit the growth of Lancefield Group A hemolytic streptococci in broth, while strains of hemolytic streptococci Group D (hemolytic enterococci) are quite resistant toward this drug (Bliss and Long). Recently, it was reported, that sulfanilamide in a concentration of 800 mg per 100 ml may continuously inhibit the growth of fibrinolytic hemolytic streptococci even when relatively large numbers were used for inoculation; in contrast, strains of hemolytic enterococci, characterized by their growth on 40% bile agar, by their capacity to reduce methylene blue and litmus in skimmed milk, by their production of a pH below 4.8 in 1 % glucose broth, and by their ability to ferment mannitol, were only slightly or not at all inhibited in 0.8% sulfanilamide broth. The culture medium used in these experiments was phenol-red broth (Difco), to which 1% soluble starch, 0.2% agar, and 1% maltose or dextrose, respectively, were added. Subsequently, it was found that essentially the same results were obtained when starch and agar were omitted from this medium. These observations are in agreement with the findings of Long and Bliss, who showed that streptococci of Group D are resistant toward the bacteriostatic action of sulfanilamide in concentrations up to 0.8%, while in higher concentrations this drug slightly retarded the growth of a few strains.