Nutritional Requirements for Synthesis of Heat-Labile Enterotoxin by Enterotoxigenic Strains of Escherichia coli

Abstract

Optimal growth conditions have been established for production of heat-labile enterotoxin (LT) by both porcine and human strains of enterotoxigenic (ENT') Escherichia coli. There were no unusual growth factor requirements, and some strains produced fairly high levels of LT in a basal salts medium containing 0.5% glucose if the pH was carefully controlled. Several amino acids markedly stimulated LT synthesis when added to the basal salts-glucose medium. Methionine and lysine were the most stimulatory for both human and porcine strains. Either aspartic acid or glutamic acid further enhanced LT synthesis in the presence of methionine and lysine, with aspartic acid being more stimulatory for porcine strains and glutamic acid more stimulatory for human strains. There were no apparent vitamin requirements and no unusual cations needed for toxin synthesis except that Fe3" was slightly stimulatory for porcine strains. The stimulation by Fe3" was observed only in the presence of the three amino acids, suggesting that

Culture conditions affect cytotoxin production by Serratia marcescens

“…It has been demonstrated that the production of some cytotoxins can be affected by several factors such as the composition of the growth medium (Gilligan and Robertson, 1979;Haslam et al, 1986;Yamakawa et al, 19941, conditions of culture such as pH, aeration or incubation temperature (MacLeod and Gyles, 1989;Maurelli et al, 1984;Serafim et al, 19941, and concentration of iron in the environment (Bjorn et al, 1978;Weinstein et al, 1988).…”

Effects of Cultural Conditions on the Synthesis of Salmonella Toxin

“…Various workers have demonstrated that the critical range of temperature between 25 and 40°C is necessary for bacterial enterotoxin production (Craig 1966;Evans and Richardson 1968;Richardson 1969;Gilligan and Robertson 1979). Craig (1966) revealed that the yield of cholera toxin was inversely proportional to incubation temperature within the range of 30 to 41°C; however, Richardson (1969) indicated that the optimal range for enterotoxin production appeared to fall between 25 and 30°C for V. chokrae.…”

“…Craig (1966) revealed that the yield of cholera toxin was inversely proportional to incubation temperature within the range of 30 to 41°C; however, Richardson (1969) indicated that the optimal range for enterotoxin production appeared to fall between 25 and 30°C for V. chokrae. Gilligan and Robertson (1979) studied the effect of temperature on the release of LT (heat-labile enterotoxin) in several strains of E. coli. They concluded that the release of cell-associated LT was stimulated at 26°C and reached a maximum value at 37°C.…”

“…The production of several bacterial enterotoxins was demonstrated to be greatly influenced by the nutritional composition of growth media as well as by the conditions under which the cultures were maintained (Evans and Richardson 1968;Richardson 1969;Richardson and Noftle 1970;Callahan et al 1971;Callahan et al 1973;Evans et al 1973;Mundell et al 1976;Sagar et al 1979;Gilligan and Robertson 1979). The development of defined nutritional and cultural conditions for maximum production of enterotoxins of Vihw eholerae (Evans and Richardson 1968;Richardson 1969;Richardson and Noftle 1970;Callahan et al 1971;Callahan et al 1973;Sagar et al 1979) and Escizerichiu coli (Evans et al 1973;Mundell et al 1976;Gilligan and Robertson 1979) has contributed to the study and subsequently the understanding of the pathogenic mechanisms of these diarrheal diseases. We have previously examined the influence of nutritional factors on the synthesis of Salmonella toxin in small flask cultures .…”

Cyclic nucleotides, gut physiology and inflammation

“…One potential scenario is that cAMP released by the host cells into the intestinal lumen is sensed by ETEC to promote adherence to host cells . Of note, microaerophilic conditions and media rich in glucose and salt induce LT expression . Thus, glucose‐regulated enhancement of ETEC adhesion might be mediated, in part, by LT production and increase in cAMP release by IECs .…”