ISOLATION AND CHARACTERIZATION OF ISOGENIC TRANSDUCTANTS RELATED WITH THE RESISTANCE FROM IN VITRO FOSFOMYCIN RESISTANT STRAINS

Abstract

The mutation sites in FR182 and FR190, which were selected as fosfomycin (FOM) resistant mutants in vitro from an Escherichia coli (E. coli) K-12 derivative, were found to be close to the 52min. and the 85min., respectively, on linkage map of E. coli K-12. Therefore, the site of mutatio nin FR182 appears to be ptsl and that in FR190 to be cyaA based on the physiological and biochemical characteristics. We isolated isogenic transductants from the FOM resistant strains (from FR182, resistant strain AMG3 and sensitive strain AMG4, and from FR190, resistant strain AMI5 and sensitive strain AMI6) by transducing the genes of the resistant strains into recipients that were deficient in alkaline phosphatase. Under anaerobic conditions, MICs in the isogenic transductants were all decreased and the resistant transductants showed similar FOM sensitivities to the respective sensitive transductants. The FOM resistant strains were clearly lysed by much lower concentrations of FOM in the presence of cyclic adenosine-3',5'-monophosphate (cAMP) or glucose 6-phosphate (G6P) than in their absence, but the extent of lysis was more pronounced when both cAMP and G6P were present together, resembling the lysis of sensitive strains in same condition.