Molecular epidemiology and antimicrobial susceptibility of extended- and broad-spectrum β-lactamase-producing Klebsiella pneumoniae isolated in Portugal

All 187 Klebsiella pneumoniae isolated over six consecutive months of 1999 in 17 Portuguese health institutions were studied: 89% were resistant to ampicillin, 31% to trimethoprim/sulfamethoxazole, 17% to aminoglycosides and 3% to fluoroquinolones; 16% were multidrug-resistant and 14% expressed an extended-spectrum β-lactamase (ESBL) phenotype confirmed by genotyping. Molecular methods identified: 11 isolates possessing blaESBL-SHV genes (blaSHV-2A, blaSHV-5, blaSHV-12 and blaSHV-55), 9 isolates with blaESBL-TEM (blaTEM-3, blaTEM-10 and blaTEM-24) and 7 isolates with blaGES-1, encoding ESBL enzymes; and 160 isolates with blaSHV-1 and blaSHV-type encoding non-ESBL enzymes. Overall, 15 new β-lactamases were detected: SHV-60 to SHV-62, SHV-71 and SHV-73 to SHV-83. The genetic relatedness of 108 isolates was studied by pulsed-field gel electrophoresis (PFGE) analysis. The isolates were diverse and 18 clusters were defined, the largest including 12 isolates of different specimens, 6 of which expressed GES-1 enzymes. Twenty additional strains isolated during a second period (March–November 2006) in three of the participating hospitals contained ESBL-encoding genes, whereas none of the isolates in the same hospitals in 1999 carried such genes: blaSHV-5, blaSHV-12, blaTEM-10, blaTEM-52, blaCTX-M-15, blaCTX-M-32 and blaCTX-M-61 (first described in the country). In this period, three new enzymes were detected: SHV-106 to SHV-108. We provide evidence that the genotypes of K. pneumoniae isolates is changing towards the emergence of ESBL enzymes.