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

Kimaro Mlacha SZ, Romero-Steiner S, Hotopp JC, Kumar N, Ishmael N, Riley DR, Farooq U, Creasy TH, Tallon LJ, Liu X, Goldsmith CS, Sampson J, Carlone GM, Hollingshead SK, Scott JA, Tettelin H.

Source

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

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.