Some immunological properties of lipopolysaccharide from Acinetobacter baumannii

Abstract

Acinetobacter baumannii, mainly biotype 9, is an important nosocomial opportunist pathogen in Chile and other countries. The biological basis of its virulence and prevalence is still unknown. As lipopolysaccharide (LPS) is often associated with virulence, some biological properties of purified LPS from seven nosocomial isolates, comprising four isolates of A. baumannii biotype 9, two isolates of biotype 8 and one isolate of biotype 1, were investigated. LPS was extracted and purified from each isolate by the hot phenol-water method, and its ability to elicit a mitogenic response and to induce the synthesis of a tumour necrosis factor (TNF-a) in mouse spleen cells was determined. Activity was evaluated in vivo by determining the splenic index in comparison with LPS from Salmonella Typhimurium. All seven LPS samples were mitogenic on the basis of cellular proliferation experiments and six induced synthesis of TNF-a. Similar results were obtained in in-vivo experiments in which LPS induced spleen cell growth, as shown by determination of the splenic index. These results suggest that the LPS of A. baumannii might contribute to the pathogenic properties of this species.

Clinical and Pathophysiological Overview of Acinetobacter Infections: a Century of Challenges

“…LPS from A. baumannii induces inflammatory cytokines, such as IL-8 and tumor necrosis factor (TNF), from mouse splenocytes and human macrophages at levels equivalent to those stimulated by LPS from Escherichia coli (122,123). The LPS activates cytokine production in a manner requiring TLR4, whereas whole A. baumannii is able to activate cytokines via both TLR4 and, for unclear reasons, TLR2 (123).…”

Effect of EDTA on the resistance of clinical isolates of Acinetobacter baumannii to the bactericidal activity of normal human serum

“…Prevalence of certain biotypes suggests that those micro-organisms have special properties or factors. Work in this laboratory has demonstrated that nosocomial isolates of A. baumannii produce a smooth-type LPS (S-LPS), and this macromolecule might contribute to pathogenicity [3]. Furthermore, many strains of Acinetobacter are capsulate and the capsular polysaccharide (CPS) might be associated with protection of bacteria from phagocytosis and complement [2].…”

Increased in-vitro and in-vivo biological activity of lipopolysaccharide extracted from clinical low virulence vacA genotype Helicobacter pylori strains

“…Spleen cell suspensions were obtained and challenged with 10 ìg of LPS as described above, but for a period of 24 h. The stimulated cells were concentrated by low speed centrifugation as described previously [24] and TNF-AE was determined in the supernates of cell cultures by a Mouse TNF-AE ELISA kit (BioSource International, Camarillo, USA), according to the manufacturer's instructions. Positive and negative controls were the same as those used for B-cell proliferation assays.…”

“…Blastogenic response was evaluated by the ability of LPS to induce spleen growth, expressed as a splenic index ¼ [spleen weight (g)=mouse weight (g)] 3 1000 [24]. Briefly, groups of four female mice were inoculated intraperitoneally with 10 ìg of LPS and killed after 4 days by cervical dislocation to allow extraction of the spleen.…”