Distribution of Enterococcal Species in Commercial Frozen Foods

Abstract

Enumeration and isolation of enterococci in 72 samples of commercial frozen foods were carried out by using AE (Azide Esculin) agar plates. Among 561 strains which isolated from 61 samples, 447 strains from 58 samples were identified with enterococci by the completed test: gram positive cocci, negative catalase test, growth in 6.5% Sodium chloride glucose broth, and final pH in glucose broth between 4.0 and 4.4. These enterococcal isolates were divided into the species according to the “MSAG” tests, fermentation of mannitol, sorbitol and arabinose, and liquefaction of gelatine. Ninty five strains (21.3%) of Streptococcus faecalis were recovered from 32 samples, 102 (22.8%) of S. faecalis subsp, liquefaciens from 32 samples, 212 (47.4%) of S. faecium from 40 samples, 15 (3.4%) of S. durans from 7 samples, 23 (5.1%) of atypical forms were isolated from 14 samples. In order to investigate the result of identification tests mentioned above, 133 of the enterococcal isolates were examined by the 6 additional tests: fermentation of glycerol, melezitose and melibiose, nutritional requirement of folic acid, reduction of triphenyltetrazolium chloride, and resistance to 0.04% potassium tellurite. The results showed that most of the enterococcal species which had been primarily determined by the “MSAG” tests were approved after the additional 6 tests.