Use of carbohydrate fermentation reactions for differentiating strains of Group D streptococci

Abstract

Thirty-two strains of Lancefield Group D streptococci isolated from fowls gave variable results for acid production from sorbitol and arabinose in media containing 1 per cent. carbohydrate and Andrade's indicator. in tests using inocula derived from cultures kept on agar slopes and in broth. In media containing raffinose, two different brands gave similar results.
Intermediate colour changes gave rise to difficulties in reading results using either bromcresol purple or Andrade's solution as an indicator. Results of electrometric pH determination with 115 strains in arabinose and sorbitol after 7 days' incubation showed that they could be divided into two distinct groups, with few strains producing intermediate results in arabinose and far greater numbers giving intermediate results in sorbitol.