A Quantitative Analysis of the Resistance of Mycobacteria to Streptomycin

Studies on Streptomycin‐resistant Strains of the Tubercle Bacillus. I*

“…In the following experiments a larger inbculum was employed, as this increases the chance of finding primarily streptomycin-resistant variant$. Furthermore, the incubation period was prolonged, because in previous determinations of the resistance the writer had observed that sometimes growth would appear in higher streptomycin concentrations when the incubatioii period was prolongedin conformity with observations reported by Youmans & Willi~ton*~ (1948) and Yegian & Vanderlinde= (1948). With two of the strains, moreover, old cultures were employed for inoculum, as it has been established that old cultures, with their cells in their terminal phase, are more resistant to chemicals (Thjetta16, 1946).…”

Probability Distribution of Drug-Resistant Mutants in Unselected Populations of Mycobacterium tuberculosis

“…Various investigators have tested populations from large cultures. Although the size of the mutant clones in replicates of each culture was approximately the same (3,5,9,19), the sizes of the clones between strains varied considerably (1-3, 5,8,9,13,19). The reason for the wide fluctuation in the proportion of mutants between strains is clearly indicated by the results of the fluctuation analysis: the size of the mutant clone depends upon the time when the first mutation occurred and, therefore, the proportion of mutants in a growing culture should increase with time (6, 11, 15).…”

Spontaneous Mutation to Streptomycin Resistance and Dependence in Escherichia Coli

“…All colonies surviving 32 units, or more, per ml were of the latter type (table 1). This absence of intermediate forms possessing higher degrees of resistance has also been found in Hemwphilus influenzae (Alexander and Leidy, 1947), and in Mycobacterium tuberculosis and Mycobacterium ranae (Yegian and Vanderlinde, 1948). The Meningococcus data (Miller and Bohnhoff, 1947) appear at first sight to constitute an exception, but the apparent difference could be due to the use of surface platings, a condition that greatly reduces the selective action of the drug.…”