Unstable L-form of Proteus mirabilis induced by fosfomycin

An unstable L-form of Proteus mirabilis was induced on solid medium by sensitivity test discs (200 micrograms of fosfomycin + 20 micrograms of glucose-6-phosphate). The L-colonies were subcultured on agar containing the antibiotic at a concentration of 60 micrograms/ml. On antibiotic-free medium, all the cells reverted to the bacterial phase. On antibiotic-containing agar, the reversion took place as well although at a much lower frequency. Parents and revertants differed in glucose metabolism while they reacted identically in H2S, indole, and urea tests.