Virulence of Klebsiella pneumoniae Isolates Harboring blaKPC-2 Carbapenemase Gene in a Caenorhabditis elegans Model

Jean-Philippe Lavigne,Gisèle Bourg,Patrice Nordmann,Gaelle Cuzon,Christophe Combescure,Albert Sotto,Stefan Bereswill

doi:10.1371/journal.pone.0067847

Abstract

Klebsiella pneumoniae carbapenemase (KPC) is a carbapenemase increasingly reported worldwide in Enterobacteriaceae. The aim of this study was to analyze the virulence of several KPC-2-producing K. pneumoniae isolates. The studied strains were (i) five KPC-2 clinical strains from different geographical origins, belonging to different ST-types and possessing plasmids of different incompatibility groups; (ii) seven transformants obtained after electroporation of either these natural KPC plasmids or a recombinant plasmid harboring only the bla KPC-2 gene into reference strains K. pneumoniae ATCC10031/CIP53153; and (iii) five clinical strains cured of plasmids. The virulence of K. pneumoniae isolates was evaluated in the Caenorhabditis elegans model. The clinical KPC producers and transformants were significantly less virulent (LT50: 5.5 days) than K. pneumoniae reference strain (LT50: 4.3 days) (p<0.01). However, the worldwide spread KPC-2 positive K. pneumoniae ST258 strains and reference strains containing plasmids extracted from K. pneumoniae ST258 strains had a higher virulence than KPC-2 strains belonging to other ST types (LT50: 5 days vs. 6 days, p<0.01). The increased virulence observed in cured strains confirmed this trend. The bla KPC-2 gene itself was not associated to increased virulence.

Highlights

Klebsiella pneumoniae carbapenemases (KPC) are broad-spectrum b-lactamases, which confer resistance to all b-lactam molecules, including carbapenems
K. pneumoniae KN2303 and K. pneumoniae KN633 were susceptible to all tested aminoglycosides and fluoroquinolones, K. pneumoniae YC was susceptible only to gentamicin, K. pneumoniae A28006 was susceptible to aminoglycosides, and K. pneumoniae 475 was only susceptible to amikacin, levofloxacin and ciprofloxacin
A single plasmid harboring the blaKPC-2 gene was electroporated into the same K. pneumoniae reference strain ATCC10031/CIP 53153

Summary

Introduction

Klebsiella pneumoniae carbapenemases (KPC) are broad-spectrum b-lactamases, which confer resistance to all b-lactam molecules, including carbapenems. Those plasmid-encoded enzymes are identified mostly in K. pneumoniae [1,2,3]. KPC-associated enterobacterial infections do not seem to be specific to sites, organs, or tissues: most are either systemic infections, occurring in patients with multiple invasive devices or urinary tract infections without an indwelling catheter, in immunocompromised patients [4,5]. No specific virulence factors have been identified as being associated to KPC-producing strains [1]. Risk factors associated with the acquisition of KPCproducing bacteria included prolonged hospitalisation, intensive care unit hospitalisation, invasive devices, immunosuppression, and multiple antibiotic agents before initial culture as known for many other multidrug resistance Gram-negative bacilli [4,6]

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