Molecular basis of extended-spectrum β-lactamase production in nosocomial isolates of Klebsiella pneumoniae from Merida, Venezuela

María Araque, Beatriz Nieves, Laura Lauretti, Gian Maria Rossolini

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Twelve Klebsiella pneumoniae isolates resistant to expanded-spectrum cephalosporins and aztreonam, from patients with nosocomial septicaemia at the intensive care unit of the Andes University Hospital, Merida, Venezuela, were studied for production of extended-spectrum β-lactamase (ESβL) activity. All were also resistant to gentamicin, kanamycin, tetracycline and chloramphenicol but sensitive to cefoxitin, imipenem, amikacin and tobramycin. Production of ESβL activity was confirmed by restoring susceptibility to ceftazidime in the presence of clavulanic acid. All isolates carried an identical plasmid of approximately 87 kb. Resistance to β-lactams, aminoglycosides, tetracycline and chloramphenicol was lost en bloc after plasmid curing by treatment with acridine orange and was transferable en bloc to Escherichia coli by conjugation. Transconjugants always showed the same plasmid profile as that of Klebsiella donors. Isoelectric focusing analysis of the crude extracts of transconjugants showed in all cases, the presence of two β-lactamases of pI 5.4 and 8.2. Analysis of the plasmid carried by one of the transconjugants by means of hybridization assays, revealed the presence of both bla(TEM) and bla(SHV) determinants. Cloning and sequencing of each determinant identified them as bla(TEM-1) and bla(SHV-5), respectively, the latter being responsible for the ESβL activity. Results of this study indicate that ESβL determinants of the SHV-type carried by transferable elements, are spreading among nosocomial isolates of K. pneumoniae in Merida, Venezuela. (C) 2000 Published by Elsevier Science B.V. and International Society of Chemotherapy.

Original languageEnglish
Pages (from-to)37-42
Number of pages6
JournalInternational Journal of Antimicrobial Agents
Issue number1
Publication statusPublished - Jun 2000


  • Extended-spectrum β- lactamases
  • Klebsiella pneumoniae
  • Nosocomial infections
  • SHV-5 β-lactamase
  • TEM-1 β-lactamase
  • Transferable resistance determinants

ASJC Scopus subject areas

  • Applied Microbiology and Biotechnology
  • Microbiology
  • Parasitology
  • Virology
  • Immunology and Allergy
  • Infectious Diseases


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