Attachment of Burkholderia pseudomallei to pharyngeal epithelial cells: a highly pathogenic bacteria with low attachment ability.

Abstract

Abstract. Respiratory infections are initiated by the attachment of bacteria to pharyngeal epithelial cells. We studied the attachment of Burkholderia pseudomallei to pharyngeal epithelial cells. After one, two, three, and four washes, there were 22.6 Ϯ 8.9, 15.7 Ϯ 7.0, 6.8 Ϯ 3.1, and 4.6 Ϯ 1.1 (mean Ϯ SD) attached bacteria/cell, respectively. If the bacterial concentration was maintained at 1 ϫ 10 8 colony-forming units (cfu)/ml and three washes were done, at concentrations of 2.5 ϫ 10 4 , 5 ϫ 10 4 , and 1 ϫ 10 5 cells/ml there were 9.9 Ϯ 3.6, 3.3 Ϯ 0.8, and 2.5 Ϯ 1.1 attached bacteria/cell, respectively. If the cell concentration was kept at 2.5 ϫ 10 4 cells/ml and three washes were done, at bacterial concentrations of 1 ϫ 10 5 , 1 ϫ10 6 , 1 ϫ 10 7 , 1 ϫ 10 8 , and 1 ϫ 10 9 cfu/ml, there were 0.3 Ϯ 0.3, 0.6 Ϯ 0.6, 1.0 Ϯ 0.2, 5.1 Ϯ 2.3, and 9.6 Ϯ 1.9 attached bacteria/cell, respectively. There were 4.8 Ϯ 1.9, 5.5 Ϯ 2.5, 5.6 Ϯ 1.9, and 6.4 Ϯ 2.6 attached bacteria/cell at 0, 30, 120, and 240 min of incubation, respectively. Pharyngeal cells from 10 persons (seven men and three women, mean Ϯ SD age ϭ 30.7 Ϯ 8.1 years, 12 experiments with a single isolate) showed that there were 7.8 Ϯ 4.3 attached bacteria/cell. It was found that the efficiency of attachment of this bacteria was very low (7.0 Ϯ 3.3 bacteria/cell). Electron microscopy revealed that there were no fimbriae but a thin capsular polysaccharide layer on the surface of B. pseudomallei. Attachment to pharyngeal epithelial cells appeared to be mediated by this structure.Burkholderia pseudomallei, a gram-negative bacilli, is a natural saprophyte that can be isolated from soil, stagnant streams, ponds, and rice paddies in areas endemic for melioidosis. This bacteria is usually transmitted by cutaneous and respiratory routes; however cutaneous transmission is significantly more prevalent than the respiratory route. 1-3 The most common form of this disease is a pulmonary infections that ranges from acute bronchitis to overwhelming necrotizing pneumonia. Burkholderia pseudomallei is one of the lifethreatening causes of pneumonia in Southeast Asia and northern Australia. The initial step in the pathogenesis of respiratory infection is the attachment of the bacteria to the pharyngeal epithelial cells. Until now no studies have been done on the adherence of this bacteria to respiratory cells. A recent study has shown that B. pseudomallei was present in the pharynx of approximately half of the patients with pulmonary melioidosis, but absent in the controls. 4 This indicates that colonization of the pharynx by B. pseudomallei might be associated with the pathogenesis of this infection. Therefore, this study was conducted to describe the basic aspects of attachment of B. pseudomallei to pharyngeal epithelial cells. This will lay the groundwork for exploring the pathogenic mechanisms of melioidosis. MATERIALS AND METHODSBacteria. All eight strains of B. pseudomallei used were obtained from Chiang Mai University (Chiang Mai, Thailand) and their identification was confirm...

Melioidosis: Epidemiology, Pathophysiology, and Management

“…4th World Melioidosis Congr., abstr. 3,2004). The case-fatality rate for patients with severe melioidosis otherwise appears in line with those in more developed countries (69).…”

Mediation of attachment of Burkholderia pseudomallei to human pharyngeal epithelial cells by the asialoganglioside GM1-GM2 receptor complex.

“…The attachment assay was done as previously described. 10 Bacteria at a concentration of 1 ϫ 10 8 cfu/ml suspended in phosphate-buffered saline (PBS), pH 7.2, and pharyngeal epithelial cells at a concentration of 2.5 ϫ 10 4 cells/ml, were mixed at a ratio of 1:1 (i.e., 4,000 bacteria per pharyngeal epithelial cell). The mixture was incubated in a shaking water bath at 37ЊC for 30 min.…”

“…In a recent report, we have shown that B. pseudomallei has the capacity to attach to pharyngeal epithelial cells, and have developed a method for the in vitro study of the attachment of this bacteria to these cells. 10 Bacteria express adhesin, which mediates attachment to a specific receptor present on the host cell. It has been suggested that the receptor of B. pseudomallei on the pharyngeal epithelial cells is a polysaccharide.…”

“…It has been suggested that the receptor of B. pseudomallei on the pharyngeal epithelial cells is a polysaccharide. 10 Unraveling the mechanism of attachment will help in understanding the pathogenesis of this infection and aid in the development of prevention or treatment strategies based on the anti-attachment mechanism. Therefore, the present study was undertaken to identify the receptor for B. pseudomallei on human pharyngeal epithelial cells.…”

Passive protection against Burkholderia pseudomallei infection in mice by monoclonal antibodies against capsular polysaccharide, lipopolysaccharide or proteins

“…It has been suggested that the polysaccharide capsule of B. pseudomallei plays a role in environmental protection [12], immune system evasion [13,14] and attachment to epithelial cells [15]. Capsular polysac-charide may also allow the bacteria to resist the bactericidal effects of the phagolysosome, enabling the organism to survive within the host [16,17].…”