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Open Access Highly Accessed Research article

Pyrosequencing-based analysis reveals a novel capsular gene cluster in a KPC-producing Klebsiella pneumoniae clinical isolate identified in Brazil

Pablo Ivan Pereira Ramos1, Renata Cristina Picão24, Eliana Carolina Vespero3, Marsileni Pelisson3, Luiz Fernando Goda Zuleta1, Luiz Gonzaga P Almeida1, Alexandra L Gerber1, Ana Tereza R Vasconcelos1, Ana Cristina Gales4 and Marisa Fabiana Nicolás1*

Author Affiliations

1 Laboratório Nacional de Computação Científica (LNCC), Petrópolis, Rio de Janeiro, Brazil

2 Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil

3 Departamento de Patologia Clínica, Análises Clínicas e Toxicologia, Universidade Estadual de Londrina, Londrina, Brazil

4 Laboratório ALERTA, Divisão de Doenças Infecciosas, Universidade Federal de São Paulo, São Paulo, Brazil

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BMC Microbiology 2012, 12:173  doi:10.1186/1471-2180-12-173

Published: 11 August 2012

Abstract

Background

An important virulence factor of Klebsiella pneumoniae is the production of capsular polysaccharide (CPS), a thick mucus layer that allows for evasion of the host's defense and creates a barrier against antibacterial peptides. CPS production is driven mostly by the expression of genes located in a locus called cps, and the resulting structure is used to distinguish between different serotypes (K types). In this study, we report the unique genetic organization of the cps cluster from K. pneumoniae Kp13, a clinical isolate recovered during a large outbreak of nosocomial infections that occurred in a Brazilian teaching hospital.

Results

A pyrosequencing-based approach showed that the cps region of Kp13 (cpsKp13) is 26.4 kbp in length and contains genes common, although not universal, to other strains, such as the rmlBADC operon that codes for L-rhamnose synthesis. cpsKp13 also presents some unique features, like the inversion of the wzy gene and a unique repertoire of glycosyltransferases. In silico comparison of cpsKp13 RFLP pattern with 102 previously published cps PCR-RFLP patterns showed that cpsKp13 is distinct from the C patterns of all other K serotypes. Furthermore, in vitro serotyping showed only a weak reaction with capsular types K9 and K34. We confirm that K9 cps shares common genes with cpsKp13 such as the rmlBADC operon, but lacks features like uge and Kp13-specific glycosyltransferases, while K34 capsules contain three of the five sugars that potentially form the Kp13 CPS.

Conclusions

We report the first description of a cps cluster from a Brazilian clinical isolate of a KPC-producing K. pneumoniae. The gathered data including K-serotyping support that Kp13’s K-antigen belongs to a novel capsular serotype. The CPS of Kp13 probably includes L-rhamnose and D-galacturonate in its structure, among other residues. Because genes involved in L-rhamnose biosynthesis are absent in humans, this pathway may represent potential targets for the development of antimicrobial agents. Studying the capsular serotypes of clinical isolates is of great importance for further development of vaccines and/or novel therapeutic agents. The distribution of K-types among multidrug-resistant isolates is unknown, but our findings may encourage scientists to perform K-antigen typing of KPC-producing strains worldwide.

Keywords:
Capsular gene cluster; Capsular polysaccharide; K-antigen; KPC-producing K. pneumoniae; Molecular serotyping; Monosaccharide biosynthesis pathways