Acquired immunity against mouse typhoid: genetic restriction and comparative efficacy of ribosomal and conventional vaccines

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Abstract
Summary. The effects of ethyleneglycoltetra-acetic acid (EGTA) and EGTA+magnesium (MgEGTA) on the viable counts of 10 strains of Escherichia coli 06 have been studied in normal human serum (NHS), heat-inactivated serum (HIS) and in culture media with and without the addition of a β-lactam antibiotic. The addition of EGTA to NHS largely prevented bactericidal activity against serum-sensitive strains while, in contrast, it reduced the growth of a serum-resistant strain. These apparently paradoxical effects are due to the lower growth rate permitted by the reduced amount of available magnesium in the presence of EGTA.