Open Access Highly Accessed Research article

Phenotypic, genomic, and transcriptional characterization of Streptococcus pneumoniae interacting with human pharyngeal cells

Sheila Z Kimaro Mlacha127, Sandra Romero-Steiner3, Julie C Dunning Hotopp2, Nikhil Kumar2, Nadeeza Ishmael2, David R Riley2, Umar Farooq2, Todd H Creasy2, Luke J Tallon2, Xinyue Liu2, Cynthia S Goldsmith4, Jacquelyn Sampson3, George M Carlone3, Susan K Hollingshead5, J Anthony G Scott16 and Hervé Tettelin2*

Author Affiliations

1 Kenya Medical Research Institute, Wellcome Trust Research Programme, Kilifi, Kenya

2 Department of Microbiology and Immunology, Institute for Genome Sciences, University of Maryland School of Medicine, 801 W. Baltimore Street, Baltimore, MD 21201, USA

3 Division of Bacterial Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA

4 Division of High-Consequence Pathogens and Pathology, Centers for Disease Control and Prevention, Atlanta, GA, USA

5 Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL, USA

6 Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK

7 Present address: Respiratory & Meningeal Pathogens Research Unit, University of the Witwatersrand/Medical Research Council, Johannesburg, South Africa

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BMC Genomics 2013, 14:383  doi:10.1186/1471-2164-14-383

Published: 9 June 2013

Abstract

Background

Streptococcus pneumoniae is a leading cause of childhood morbidity and mortality worldwide, despite the availability of effective pneumococcal vaccines. Understanding the molecular interactions between the bacterium and the host will contribute to the control and prevention of pneumococcal disease.

Results

We used a combination of adherence assays, mutagenesis and functional genomics to identify novel factors involved in adherence. By contrasting these processes in two pneumococcal strains, TIGR4 and G54, we showed that adherence and invasion capacities vary markedly by strain. Electron microscopy showed more adherent bacteria in association with membranous pseudopodia in the TIGR4 strain. Operons for cell wall phosphorylcholine incorporation (lic), manganese transport (psa) and phosphate utilization (phn) were up-regulated in both strains on exposure to epithelial cells. Pneumolysin, pili, stress protection genes (adhC-czcD) and genes of the type II fatty acid synthesis pathway were highly expressed in the naturally more invasive strain, TIGR4. Deletion mutagenesis of five gene regions identified as regulated in this study revealed attenuation in adherence. Most strikingly, ∆SP_1922 which was predicted to contain a B-cell epitope and revealed significant attenuation in adherence, appeared to be expressed as a part of an operon that includes the gene encoding the cytoplasmic pore-forming toxin and vaccine candidate, pneumolysin.

Conclusion

This work identifies a list of novel potential pneumococcal adherence determinants.

Keywords:
Streptococcus pneumoniae; Gene expression; Microarray; Adherence; Invasion; Genome; Mutagenesis; SP_1922; Ply operon