抄録
A multidrug-resistant strain of Serratia marcescens (S. marcescens), SM19, was isolated from a urine specimen of a patient who suffered from multiple infections of Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Pseudomonas spp., Non-Fermenter spp. and Corynebacterium spp. SM19 showed high resistance to all of the β-lactams including carbapenems, and also to various inhibitors of protein synthesis, such as aminoglycosides (amikacin, streptomycin), tetracycline and chloramphenicol, and inhibitors of nucleic acid synthesis, such as ofloxacin. The production of the carbapenem-hydrolyzing IMP-type β-lactamase by SM19 is responsible for its resistance to carbapenems. The IMP-type β-lactamase possessed some characteristics of metallo-β-lactamase, in that the enzyme activity could be enhanced by ZnCl2 and inhibited by the metal chelator EDTA. PCR analysis confirmed the presence of the blaIMP gene which encodes the IMP-type β-lactamase in SM19. The expression of the blaIMP gene was highly constitutive, with lower induction rates of 2.5-4.5 fold in the presence of the inducers cefotaxime or imipenem at half their minimum inhibition concentrations. Unlike other resistant strains of S. marcescens, however, the blaIMP gene could not be transferred into E. coli by either conjugation or transformation via electroporation, suggesting the possibility of multiple locations of the blaIMP gene on both the plasmid and the chromosome in various strains of S. marcescens.
