Specificity of Phenotypic Adaptation of Bacillus Cereus to Tetracycline

Abstract

SUMMARYBacillus cereus strain 5 6 9~ became resistant to tetracyclines, arsenite and cyanide. The degree of resistance acquired was independent of the inducing concentration up to 2 x I r 5 M. Recovery from tetracycline and arsenite inhibition involved a change in the bacteria themselves ; cyanide resistance involved also the destruction of this inhibitory agent. Although there were many similarities between the tetracycline and arsenite recoveries, two distinct mechanisms were involved. Adaptation to tetracycline was not observed with B. megaterium, Pseudomonas aeruginosa or Escherichia coli. Bacillus megaterium and E. coli did adapt to cyanide. Although polymyxin B was inactive by itself against B. cereus, lytic activity due to the antibiotic was seen when a tetracycline was also present in the medium. The lytic activity ceased when the bacilli recovered from tetracycline. Bacillus cereus did not adapt to other inhibitors of protein synthesis, RNA synthesis or oxidative phosphorylation.

Oxytetracycline‐Glucose‐Yeast Extract Agar for Selective Enumeration of Moulds and Yeasts in Foods and Clinical Material

“…This, in all probability, is the reason why, although Put et al (1968) encountered such variants in their ecological studies on soil, we failed to isolate them at any level of significance from foods, and correspondingly never found them to interfere with the enumeration of moulds and yeasts in foods, when using oxytetracycline agar. This assumption finds further support in observations of Connamacher (1969) who were not successful in increasing the oxytetracycline resistance in bacilli to levels > 5 pg/ml. When examining patients' stools, containing 106-109 Enterobacteriaceaelg, sparse bacterial growth was observed in OGY used in this instance for the enumeration of yeasts.…”