PEDIATRICS Vol. 4 No. 2 August 1949, pp. 214-221
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MECHANISM OF EMERGENCE OF RESISTANCE TO STREPTOMYCIN IN FIVE SPECIES OF GRAM NEGATIVE BACILLI

HATTIE E. ALEXANDER M.D.1 and GRACE LEIDY A.B.1

1 The Babies Hospital and the Department of Pediatrics, Columbia University, College of Physicians and Surgeons, New York, N.Y.

The following evidence has been presented as proof of the mutational origin of streptomycin resistant variants of five different species—E. coli, Salmonellae, Shigellae, S. typhosa and Ps. aeruginosa:

1. Demonstration of their independence of the action of streptomycin by showing their continuous irregular occurrence with different prevalence in independent cultures of same population size and strain.

2. Transmission of resistance unchanged in degree through many subcultures in the absence of streptomycin.

3. A low rate of occurrence of the resistant variants, not varying significantly among different strains of the same species.

A fraction of the resistant mutants of each of these five organisms grows poorly or not at all in the absence of high concentrations of streptomycin.

The therapeutic implications of these facts are discussed.

Submitted on November 13, 1948