Acta Microbiologica 22. (1975)

2. szám - Gadó, I.–Dumbovich, I.: Effect of Some Aminoglycosides Upon a Drug Dependent Escherichia coli Strain

Acta microbiol. Acad. Sei. hung. 22, 95 — 104, 1975 EFFECT OF SOME AMINOGLYCOSIDES UPON A DRUG DEPENDENT ESCHERICHIA COLI STRAIN I. Gadó and I. Dumbovich Section of Microbiology, Research Institute for Pharmaceutical Chemistry, Budapest (Received February 26, 1974) Summary. Escherichia coli Sd-4-73 drug dependent strain was sensitive to kanamycin, gentamicin and neomycin in the absence of drugs stimulating cell multiplication. This sen­sitivity was not considerably influenced by streptomycin, while paromomycin afforded pro­tection against both bacteriostatic and bactericidal effects. The paromomycin concentration optimum for protection was different from its concentration optimum for multiplication. In an earlier paper [1] evidence has been presented that streptomycin (Sm) dependent Escherichia coli strain grew on short-chained alcohols in the absence of Sm. On the basis of this finding, Gorini et al. [2] discovered a phenomenon which they termed “phenotypic masking”, and also the existence of drugn strains, whose drug requirement can be satisfied with Sm, paro­momycin (Pm) or alcohols. These authors studied the colony forming of the drugD strain on agar plates containing kanamycin A (Km) (Table I). Later a partial inhibition was described in the case of a Pm-fKin combination, which was explained by a competition of Pm and Km [3, 4]. In the case of drug0 strain, the bactericidal effect of Km could only be observed when the inoculum had grown on Sm-containing medium, and this bactericidal effect was weaker than the one observed with E. coli В strain [3]. From these results Table I Growth of drugD E. coli mutant on Km containing solid media* Drug in medium Drug in inoculum Nil Km Pm + Km Sm + Km EtOH + Km EtOH— — + — — Sm± — — — — Pm± — + — + * After Goiîini et al. [2]. Acta Microbiologica Academiae Scientiarum Hungaricae 22,1975

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