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[Production of thermolabile exotoxin by strains of Escherichia coli isolated in Argentina].

Authors
  • Rivas, M
  • Binsztein, N
  • López Moral, L
  • Cinto, R
Type
Published Article
Journal
Revista Argentina de microbiología
Publication Date
Jan 01, 1987
Volume
19
Issue
3
Pages
91–100
Identifiers
PMID: 3332383
Source
Medline
License
Unknown

Abstract

The production of heat-labile enterotoxin (LT) by E. coli strains was studied. Four strains isolated from acute infant diarrhea cases in Argentina and one reference strain, all of them producers of different levels of LT, were employed. GM1-ELISA was used as titration method. The production was assayed in two culture media; Evans (Ev) and Trypticase Soy Broth (CTS) with or without glucose and with different concentrations of lincomycin (0; 30; 45 y 90/micrograms/ml). The effects of pH and inoculum concentration were also examined. Higher levels of LT were found to be produced in Ev (mean production value X = 233.1 ng/ml) than in CTS (X = 133.8 ng/ml), although the difference was statistically not significant (P = 0.22). Lincomycin addition stimulated toxin synthesis and release in both media, and these effects were found to increase with the concentration of the antibiotic (P less than 0.01). Glucose increased the LT levels of low-producing strains and also the growth rate, cellular yield and LT levels of 40T and CC2e strains. Levels of LT released were found to be independent of inoculum concentration. In CTS without pH control, the LT production was one half the levels attained with regulated pH. This was not an effect on the release of the toxin as the determination included both the extracellular LT and the intracellular toxin accumulated in the periplasmic space, which is released by polymyxin B treatment. A pH-dependent inactivation of the synthetized and release toxin was demonstrated.

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