Molecular characterization of multidrug-resistant <italic>Klebsiella pneumoniae</italic> isolates

Hou, Xiang-huaSong, Xiu-yuMa, Xiao-boZhang, Shi-yangZhang, Jia-qin

<p><italic>Klebsiella pneumoniae</italic> is an important cause of healthcare-associated infections worldwide. Selective pressure, the extensive use of antibiotics, and the conjugational transmission of antibiotic resistance genes across bacterial species and genera facilitate the emergence of multidrug-resistant (MDR) <italic>K. pneumoniae</italic>. Here, we examined the occurrence, phenotypes and genetic features of MDR <italic>K. pneumoniae</italic> isolated from patients in intensive care units (ICUs) at the First Affiliated Hospital of Xiamen University in Xiamen, China, from January to December 2011. Thirty-eight MDR <italic>K. pneumoniae</italic> strains were collected. These MDR <italic>K. pneumoniae</italic> isolates possessed at least seven antibiotic resistance determinants, which contribute to the high-level resistance of these bacteria to aminoglycosides, macrolides, quinolones and β-lactams. Among these isolates, 24 strains were extended-spectrum β-lactamase (ESBL) producers, 2 strains were AmpC producers, and 12 strains were both ESBL and AmpC producers. The 38 MDR isolates also contained class I (28/38) and class II integrons (10/38). All 28 class I-positive isolates contained <italic>aacC1</italic>, <italic>aacC4</italic>, <italic>orfX</italic>, <italic>orfX’ and aadA1</italic> genes. β-lactam resistance was conferred through <italic>bla</italic>_SHV (22/38), <italic>bla</italic>_TEM (10/38), and <italic>bla</italic>_CTX-M (7/38). The highly conserved <italic>bla</italic>_KPC-2 (37/38) and <italic>bla</italic>_OXA-23(1/38) alleles were responsible for carbapenem resistance, and a <italic>gyrA</italic>site mutation (27/38) and the plasmid-mediated <italic>qnrB</italic> gene (13/38) were responsible for quinolone resistance. Repetitive-sequence-based PCR (REP-PCR) fingerprinting of these MDR strains revealed the presence of five groups and sixteen patterns. ...(AU)

1. Molecular characterization
2. <italic>Klebsiella pneumoniae</italic>
3. Multidrug resistance