Burkholderia pseudomallei pathogenesis in human skin fibroblasts: A Bsa type III secretion system is involved in the invasion, multinucleated giant cell formation, and cellular damage.

Anek Kaewpan,Niramol Jitprasutwit,Taksaon Duangurai,Passanesh Sukphopetch,Sumate Ampawong,Watcharamat Muangkaew,Amporn Rungruengkitkun,Pornpan Pumirat,Tapanee Kanjanapruthipong,Narisara Chantratita,Roy Martin Roop

doi:10.1371/journal.pone.0261961

Abstract

Burkholderia pseudomallei—a causative agent of melioidosis that is endemic in Southeast Asia and Northern Australia—is a Gram-negative bacterium transmitted to humans via inhalation, inoculation through skin abrasions, and ingestion. Melioidosis causes a range of clinical presentations including skin infection, pneumonia, and septicemia. Despite skin infection being one of the clinical symptoms of melioidosis, the pathogenesis of B. pseudomallei in skin fibroblasts has not yet been elucidated. In this study, we investigated B. pseudomallei pathogenesis in the HFF-1 human skin fibroblasts. On the basis of co-culture assays between different B. pseudomallei clinical strains and the HFF-1 human skin fibroblasts, we found that all B. pseudomallei strains have the ability to mediate invasion, intracellular replication, and multinucleated giant cell (MNGC) formation. Furthermore, all strains showed a significant increase in cytotoxicity in human fibroblasts, which coincides with the augmented expression of matrix metalloproteinase-2. Using B. pseudomallei mutants, we showed that the B. pseudomallei Bsa type III secretion system (T3SS) contributes to skin fibroblast pathogenesis, but O-polysaccharide, capsular polysaccharide, and short-chain dehydrogenase metabolism do not play a role in this process. Taken together, our findings reveal a probable connection for the Bsa T3SS in B. pseudomallei infection of skin fibroblasts, and this may be linked to the pathogenesis of cutaneous melioidosis.

Highlights

Burkholderia pseudomallei is a pathogenic Gram-negative bacterium that causes fatal melioidosis, a disease that is endemic in Southeast Asia and northern Australia
The ability of B. pseudomallei to invade HFF-1 human skin fibroblast cells was examined by infection using a range of multiplicity of infection (MOI) values and the number of intracellular bacteria was determined at 4 h post-infection
The presence of intracellular B. pseudomallei in the HFF-1 skin fibroblast cells was verified by transmission electron microscopy and showed that B. pseudomallei was internalized within the host cells at 4 h post-infection (S2 Fig)

Summary

Introduction

Burkholderia pseudomallei is a pathogenic Gram-negative bacterium that causes fatal melioidosis, a disease that is endemic in Southeast Asia and northern Australia. This bacterium is categorized by the U.S Centers for Disease Control and Prevention (CDC) as a tier 1 threat that could be used as a biological weapon [1]. The incidence of melioidosis in northern Australia during the rainy season was reported to be approximately 50 cases per 100,000 of the population [2]. A high fatality rate of up to 40% is associated with cases of septicemia, and acute pneumonia constitutes around 62% of worldwide melioidosis cases [3, 4]. Melioidosis remains a public health problem worldwide and currently, no effective vaccine or inhibitor to combat this disease is available

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