Abstract

GUZMAN, Militza  and  ALONSO, Guillermina. Characterization of extended-spectrum ß-lactamases in nosocomial strains of Klebsiella pneumoniae. Invest. clín [online]. 2009, vol.50, n.4, pp.419-431. ISSN 0535-5133.

In this study, 25 strains of K. pneumoniae, isolated from patients with nosocomial infections from August 2002 to December 2003, were examined to determine their antimicrobial susceptibility, plasmid profile, transfer capacity of resistance determinants and bla_TEM, bla_SHV, and bla_CTX-M genes. Nineteen nosocomial strains revealed a weakened susceptibility to third-generation cephalosporins and aztreonam, and were extended-spectrum ß-lactamases (ESBLs) producers. All strains presented conjugable plasmids with a conjugation frequency of 10^-3 to 10^-4 transconjugants/donor cell. The analysis of restriction patterns revealed the presence of three differents plasmids. The Escherichia coli transconjugants were ESBLs producers and expressed resistance for aminoglucosides and chloramphenicol. The bla_TEM gen was found in all transferables plasmids and the bla_SHV and bla_CTX genes were found in transferables and no transferables plasmids. The enzymes identified in the isolates were TEM-1 SHV-5-2a and CTX-M-2. The plasmids present in the K. pneumoniae strains play an important role in the dissemination of the genes encoding resistance to ß-lactams and other antimicrobial agents.

Keywords : Plasmids; extended-spectrum ß-lactamases; antibiotic resistance.

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