Streptococci in Dried and Frozen Foods

Abstract

Streptococci were obtained on KF and bile-esculin agars from 209 (57%) samples of a variety of dried foods and from 299 (87%) samples of frozen vegetables. They were not obtained from dried tea, coffee, flavored drinks, or fruits. Numbers per gram were greater in frozen vegetables than in dried foods. Nearly 60% of the 2334 strains isolated were identified as follows: Streptococcus faecalis (8.9%), Streptococcus faecium (21.1%), S. faecium biotype casseliflavus (18.9%), Streptococcus lactis (2.2%), Streptococcus bovis (0.04%), Aerococcus (2.7%), and Leuconostoc (4.5%). The 1173 strains of unidentified streptococci formed 32 groups when characterized for growth at 10 and 45 C, in broth containing 6.5% NaCl, and in broth adjusted to pH 9.6; and the deamination of arginine. The isolated strains were classified into seven plant streptococcal (PS) types. Unidentified streptococci obtained from foods were as variable in their charcteristics as those obtained from plants. The variety of species obtained indicated that neither KF nor bile-esculin agars were reliable in the selection of S. faecalis from foods.