title: Characterization of imipenem-resistant Serratia marcescens producing IMP-type and TEM-type beta-lactamases encoded on a single plasmid.
abstract: To evaluate the roles of blaIMP and blaTEM genes in the resistance of Serratia marcescens against beta-lactams and to find the spreading ways of these genes, 19 clinical isolates of imipenem-resistant Serratia marcescens were analyzed. Six strains bore blaIMP and blaTEM genes on a single plasmid, as confirmed by transferring resistance determinants via conjugation and transformation, and by detecting bla genes with PCR analysis. The six strains showed two different genomic patterns on pulsed-field gel electrophoresis. All the transconjugants and transformants gained high-level resistance to ampicillin, cephalexin, cefoxitin and cefotaxime, and showed a reduced susceptibility to imipenem, but maintained full susceptibility to aztreonam. In addition, the expressions of blaIMP and blaTEM genes were constitutive, either in Serratia marcescens clinical isolates or in their transconjugants and transformants. These findings may explain the rapid spread of the above resistance determinants among Enterobacteriaceae via transmissible plasmids in the clinical setting.
authors.affiliation: Department of Medical Biology, Showa University School of Medicine, Tokyo, Japan. whzhao@med.showa-u.ac.jp
authors.forename: Wei-Hua
authors.initials: WH
authors.lastname: Zhao
authors.forename: Zhi-Qing
authors.initials: ZQ
authors.lastname: Hu
authors.forename: Gelin
authors.initials: G
authors.lastname: Chen
authors.forename: Kouichiro
authors.initials: K
authors.lastname: Matsushita
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Fukuchi
authors.forename: Tadakatsu
authors.initials: T
authors.lastname: Shimamura
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003227:Conjugation, Genetic; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D022761:Gene Transfer, Horizontal; D005838:Genotype; D006801:Humans; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000235:genetics*; D016133:Polymerase Chain Reaction; D016868:Serratia Infections / Q000382:microbiology; D012706:Serratia marcescens / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics; D014169:Transformation, Bacterial; D018440:beta-Lactam Resistance / Q000235:genetics*; D001618:beta-Lactamases / Q000096:biosynthesis* / Q000145:classification / Q000235:genetics; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D047090:beta-Lactams; D001618:beta-Lactamases