Susceptibility of faecal Streptococcus group to some surface-active agents.

Tests for susceptibility of three repesentative surface-active agents, incorporated in solid and liquid medium, were carried through with 75 strains of the Streptococcus group. Hyamine 2389 was the most active compound against the tested strains, followed by Teepol 610. Nearly all the tested strains were highly resistant to Nonidit P 42 "nonionic", whether incorporated in solid or liquid medium. The strains may be arbitrarily divided into those sensitive to Hyamine at the level of 60 ppm in nutrient agar (Str. faecium, most of the atypical strains and the unclassified isolates) and those resistant to Hyamine (Str. faecalis, Str. faecalis var. liquefaciens, Str. faecalis var. zymogenes). In liquid medium, Hyamine at a level of 24 ppm showed detrimental effects on the majority of the test organisms (96%). The different species differed slightly in their susceptibility to Teepol, and 360 ppm was the critical concentration.