Molecular identification and antimicrobial resistance analysis of a new hypervirulent variant of Klebsiella pneumoniae

Abstract

Objective To investigate the infection case and drug resistance patterns of new hypervirulent (hypermucoviscous) clinical variant of Klebsiella pneumoniae(hvKP)strains, and the virulence and resistance mechanisms. Methods Retrospective study.Two hundred and ten Klebsiella pneumoniae isolates were collected in the First Affiliated Hospital of Nanchang University from January 2011 to December 2013, and 12 hvKP were identified. Multilocus sequence typing (MLST) and enterobacterial repetitive intergenic consensus (ERIC)-PCR were used to type the hvKP isolates. The extended spectrum β-lactamase and carbapenemase producing Klebsiella pneumoniae were screened by the double disc synergy test and the modified Hodge test, respectively. PCR and DNA sequencing were carried out to detect their resistance related genes, serotype and virulence genes. Hypermucoviscosity phenotype (HM) of all strains was determined by string test. Results HvKP were resistant to 15 antibiotics and the extended-spectrum beta-lactamase producing rate was 8/12. In addition, one strain was detected positive by the modified Hodge test. Among the 12 hvKP strains, five ERIC-MLST molecular types were identified, of which A/ST23 and B/ST263 were the most predominant types, accounting for 5/12 and 4/12, respectively. The results of PCR and DNA secquencing showed that 2 were positive for blaKPC-2 (2/12), 9 positive for qnrA1 (9/12), 6 positive for qnrB4 (6/12), 8 positive for qnrS1 (8/12), 6 positive for blaCTX-M-3 (6/12), 7 positive for blaCTX-M-14 (7/12), 10 positive for blaTEM-1 (10/12), and 4 positive for blaSHV-12 (4/12). Eleven hvKP strains were serotype K1, while only one strain was serotype K2. Serotype K3, K5, K20, K54 and K57 were not detected. The positive rate of virulence genes magA, rmpA and aerobactin were 11/12, 9/12 and 9/12, respectively. In addition, the positive rate of kfu, mrkD, wabG and allS were 9/12, 10/12, 4/12 and 2/12, respectively. The positive rate of HM was 8/12. Conclusions The resistance mechanism of hvKP strains was complex and diverse, in which strong toxicity serotype and multiple virulence genes exist, which need attention from clinic. Effective infection control measure should be conducted in order to control the outbreak of resistant hvKP strains. (Chin J Lab Med, 2015, 38: 392-396) Key words: Klebsiella pneumoniae; Virulence; Drug resistance, bacterial; Serotyping