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Selected faecal bacteria and nutrients essential for antagonism of Salmonella typhimurium in anaerobic continuous flow cultures.

Authors
  • Ushijima, T
  • Seto, A
Type
Published Article
Journal
Journal of medical microbiology
Publication Date
Aug 01, 1991
Volume
35
Issue
2
Pages
111–117
Identifiers
PMID: 1875391
Source
Medline
License
Unknown

Abstract

As few as five of the species of bacteria commonly found in human faeces--Escherichia coli, Enterobacter aerogenes, Enterococcus faecalis, Bacteroides ovatus and Fusobacterium varium--when grown together in anaerobic continuous flow cultures exerted antagonistic effects on Salmonella typhimurium as great as those given by mixed bacteria from extracts of human faeces. In a single culture, the population of S. typhimurium was c. 10(8) cfu/ml but in mixed cultures with the five antagonistic bacteria or mixed faecal bacteria it was reduced to c. 10(3) cfu/ml. Antagonism appeared to be the result of competition for the growth limiting amino acids, arginine, serine, threonine and aspartic acid. Optimal manifestation of antagonism required the presence of carbon sources fermentable only by antagonistic bacteria, such as lactose 0.1%, w/v, sucrose 0.1% (w/v) and starch 0.2-0.3% w/v. These carbohydrates promoted the growth of the antagonistic bacteria, particularly E. coli and B. ovatus. However, an increase in concentration by several fold of any one of four growth-limiting amino acids in the medium diminished the antagonistic effects and the population of S. typhimurium rose 10(2)-10(3)-fold.

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