Dynamics of a nosocomial outbreak of multidrug-resistant Pseudomonas aeruginosa producing the PER-1 extended-spectrum β-lactamase

F. Luzzaro, E. Mantengoli, M. Perilli, G. Lombardi, V. Orlandi, A. Orsatti, G. Amicosante, G. M. Rossolini, A. Toniolo

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From November 1998 to August 1999, a large outbreak occurred in the general intensive care unit of the Ospedale di Circolo in Varese (Italy), caused by Pseudomonas aeruginosa producing the PER-1 extended-spectrum β-lactamase. A total of 108 clinical isolates of P. aeruginosa resistant to broad-spectrum cephalosporins were recovered from 18 patients. Epidemic isolates were characterized by synergy between clavulanic acid and ceftazidime, cefepime, and aztreonam. Isoelectric focusing of crude bacterial extracts detected two nitrocefin-positive bands with pI values of 8.0 and 5.3. PCR amplification and characterization of the amplicons by restriction analysis and direct sequencing indicated that the epidemic isolates carried a blaPER-1 determinant. The outbreak was of clonal origin as shown by pulsed-field gel electrophoresis analysis. This technique also indicated that the epidemic strain was not related to three other PER-1-positive isolates obtained at the same hospital in 1997. Typing by enterobacterial repetitive intergenic consensus-PCR showed that minor genetic variations occurred during the outbreak. The epidemic strain was characterized by a multiple-drug-resistance phenotype that remained unchanged over the outbreak, including extended-spectrum cephalosporins, monobactams, aminoglycosides, and fluoroquinolones. Isolation of infected patients and appropriate carbapenem therapy were successful in ending the outbreak. Our report indicates that the blaPER-1 resistance determinant may become an emerging therapeutic problem in Europe.

Original languageEnglish
Pages (from-to)1865-1870
Number of pages6
JournalJournal of Clinical Microbiology
Issue number5
Publication statusPublished - 2001

ASJC Scopus subject areas

  • Microbiology (medical)
  • Microbiology


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