ABSTRACT
We isolated two plasmids, pS51A and pS51B which were 5782 bp and 4854 bp in size, respectively, from the third generation cephalosporin-resistant E. cloacae suspected to express metallo-beta-lactamase, and analyzed their structures. These two plasmids encode RNA I/RNA II genes for replication origin, relaxase genes of mobABCD for plasmid transfer, and several open reading frames. According to the classification of mobilizable plasmids by gene organization of the relaxases, pS51A and pS51B belong to the ColE1 superfamily of mobilizable plasmids, commonly detected in Enterobacteriaceae. The metallo-beta-lactamase gene was not identified in either pS51A or pS51B by homology search of the putative open reading frames. Open reading frames encoded in pS51A include E. coli protein L-like, E. coli heat shock protein-like, and E. coli plasmid replication initiation protein-like, and those encoded in pS51B include helix-turn-helix protein-like, E. coli plasmid replication initiation protein-like, and Salmonella replication initiation protein-like. These plasmids are stably maintained in one strain of E. cloacae, thus, the encoded gene functions may confer growth advantage to the host cell.
Subject(s)
Enterobacter cloacae/genetics , Plasmids , Amino Acid Sequence , Bacterial Proteins/genetics , Base Sequence , Cephalosporin Resistance , Endodeoxyribonucleases/genetics , Enterobacter cloacae/enzymology , Enterobacter cloacae/growth & development , Escherichia coli/genetics , Heat-Shock Proteins , Molecular Sequence Data , Open Reading Frames/genetics , Plasmids/chemistry , Plasmids/genetics , RNA/genetics , RNA, Bacterial/genetics , Replication Origin/genetics , Transcription Factors , beta-Lactamases/geneticsABSTRACT
In antimicrobial susceptibility test for enterobacteriaceae, the efficacies of carpapenems are predicted by the minimum inhibitory concentration (MIC) of imipenem, and that of fluoroquinolones are predicted by the MIC of levofloxacin. To assess its judgement, we compared the MICs of imipenem, meropenem, panipenem, and doripenem for carbapenems, and ciprofloxacin, levofloxacin, tosufloxacin and pazufloxacin for fluoroquinolones of clinically isolated enterobacteria, Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Serratia marcescens, Enterobacter cloacae and Citrobacterfreundii, those resistant to the third generation cephalosporin. MIC distributions in low concentration range are estranged in some strains, conspicuously S. marcescens, E. cloacae and C. freundii: meropenem and doripenem displayed low MIC value than imipenem and panipenem. Since the estrangements are appeared MIC value of less than 8 microg/ml, the interpretive results (susceptible, intermediate, resistant) are not affected. In fluoroquinolones, all 4 agents showed almost identical MIC distributions, thus the MIC of levofloxacin is accepted to use the reference for other fluoroquinolones. The existence of the strains harboring carbapenem-resistant gene displaying low MIC value of carbapenems was reported. For the sensitive detection of the candidate of carbapenem-resistant strains, cut-off value of each carbapenem should be reconsidered, and also other phonotype analysis should be applied. Genomic analysis also would be required to detect the carbapenem-resistant gene.
