Diversity of capsular polysaccharide gene clusters in Kpc-producing Klebsiella pneumoniae clinical isolates of sequence type 258 involved in the Italian epidemic.

Tommaso Giani,Viola Conte,Luisa Santoriello,Gian Maria Rossolini,Marco Maria D’Andrea,Nagaia Ciacci,Patrice Nordmann,Francesco Amisano,Simone Ambretti

doi:10.1371/journal.pone.0096827

Abstract

Strains of Klebsiella pneumoniae producing KPC-type beta-lactamases (KPC-Kp) are broadly disseminating worldwide and constitute a major healthcare threat given their extensively drug resistant phenotypes and ability to rapidly disseminate in healthcare settings. In this work we report on the characterization of two different capsular polysaccharide (CPS) gene clusters, named cps BO-4 and cps 207-2, from two KPC-Kp clinical strains from Italy belonging in sequence type (ST) 258, which is one of the most successful ST of KPC-Kp spreading worldwide. While cps BO-4 was different from known 78 K-types according to the recently proposed typing schemes based on the wzi or wzc gene sequences, cps 207-2 was classified as K41 by one of these methods. Bioinformatic analysis revealed that they were represented in the genomic sequences of KPC-Kp from strains of ST258 from different countries, and cps BO-4 was also detected in a KPC-Kp strain of ST442 from Brazil. Investigation of a collection of 46 ST258 and ST512 (a single locus variant of ST258) clinical strains representative of the recent Italian epidemic of KPC-Kp by means of a multiplex PCR typing approach revealed that cps BO-4 was the most prevalent type, being detected both in ST258 and ST512 strains with a countrywide distribution, while cps 207-2 was only detected in ST258 strains with a more restricted distribution.

Highlights

The capsular polysaccharide (CPS or K-antigen) is a recognized virulence factor of Klebsiella pneumoniae [1,2]
Among systems that do not require a sequencing step, a PCR-based typing system has been proposed for the detection of isolates of the K1, K2, K5, K20, K54 and K57 capsular types, that are commonly associated with invasive diseases or having a prominent pathogenicity [6]
The two strains had been isolated in 2010 from bloodstream infections of inpatients in two different Italian hospitals and produced either KPC-2 (KK207-2) or KPC-3 (KKBO-4). They were both of ST258, and exhibited a related not identical XbaI PFGE profile [12]

Summary

Introduction

The capsular polysaccharide (CPS or K-antigen) is a recognized virulence factor of Klebsiella pneumoniae [1,2]. This component exhibits a remarkable intra-specific structural diversity which translates into different antigenic properties that may be relevant to bacterial virulence [2,3,4]. Among systems that do not require a sequencing step, a PCR-based typing system has been proposed for the detection of isolates of the K1, K2, K5, K20, K54 and K57 capsular types, that are commonly associated with invasive diseases or having a prominent pathogenicity [6]. Two systems based on amplification and sequencing of the conserved wzi and wzc genes were recently proposed to determine the K-type of K. pneumoniae [9,10]. ST512, ST437 and ST11) have undergone a global dissemination, with epidemic diffusion in some areas of North and South America, Europe and Asia [11,12,13,14,15,16,17,18]

Methods

Results

Conclusion