PubMed · 13550574
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G BABAEV. 1958. [Brucellar endocarditis].. https://pubmed.ncbi.nlm.nih.gov/13550574/
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The genus Brucella comprises important human and animal pathogens, as well as numerous environmental and symbiotic species. Lipopolysaccharide (LPS), a major component of the outer membrane of Gram-negative bacteria, plays a crucial role in bacterial physiology and host interactions. In this study, the structures of lipid A, the hydrophobic anchor of lipopolysaccharide, isolated from two plant-associated strains, Brucella cytisi ESC1ᵀ and Brucella lupini LUP21ᵀ, were presented. Lipid A preparations were structurally characterized using chemical methods, MALDI-TOF mass spectrometry, and nuclear magnetic resonance spectroscopy. The obtained results indicated that both lipid A molecules have almost identical structures. Their sugar backbones consist exclusively of 2,3-diamino-2,3-dideoxy-d-glucose (d-GlcpN3N). Phosphate residues were connected to distal and proximal GlcpN3N in approximately half of the lipid A molecules. Fatty acid analysis revealed the presence of C14:0 (3-OH), C16:0 (3-OH), and traces of C18:0 (3-OH). All of these were primary fatty substituents of the sugar backbone and were amide-linked residues. Lactobacillic acid C19:0cyc and 27-hydroxyoctacosanoic acid (C28:0 (27-OH)) were found as ester-linked secondary acyl residues. In turn, C28:0 (27-OH) was partly esterified by a 3-hydroxybutyroyl residue. Two unsubstituted 3-hydroxyfatty acids were linked exclusively to the proximal d-GlcpN3N residue. It was pointed out that sequences of putative genes encoding enzymes required for lipid A biosynthesis and genes encoding specific enzymes involved in structural modifications of lipid A occurring in the genomes of both bacterial species are almost identical. The high sequence similarity of these proteins reflects the observed similarities in the lipid A structures in both investigated Brucella species.
In mice, nitric oxide (NO) production by inducible NO synthase (iNOS), is a component of the control of Brucella infection. In humans, the involvement of iNOS in infection is still a matter of debate. Based on in vitro experiments, it was recently postulated that in humans, Brucella infection tends to become chronic because NO cannot exert its deleterious effect. In fact, conditions allowing NO production by human macrophages in culture are poorly defined, rendering the in vitro study of NO function difficult. Using DFGiNOS U937 macrophagic cells engineered to produce NO and U937 cells activated by ligation of IgE receptors, we showed that the intracellular development of Brucella was impaired in human macrophages, which produced NO. Although Brucella-infected human macrophagic phagocytes did not release NO in commonly used models of infection, the machinery required to produce NO was expressed in these cells and could be triggered by cell membrane receptors present on the infected cells. Therefore, the lack of NO production in isolated human macrophages infected by Brucella under in vitro conditions did not exclude a possible involvement of NO in the control of human brucellosis.
Brucellosis is a worldwide 're-emerging' zoonosis causing high economic losses and severe human disease. Consequently, rapid and reliable, sensitive and specific, easy to perform and automated detection systems for Brucella spp. are urgently needed to allow early diagnosis and adequate antibiotic therapy in time. Real-time PCR assays using hybridization probes meet all these requirements. In 2003 various assays have been developed and evaluated for use in human and animal brucellosis. Genus-specific real-time PCR assays e.g. based on the bcsp31 gene will lead to an early diagnosis but for the purpose of epidemiological surveillance a species-specific real-time PCR deriving from the conventional AMOS (AbortusMelitensisOvisSuis)-PCR is necessary. Advantages and disadvantages of the different methods for real-time detection of Brucella spp. and a newly developed PCR-ELISA system for the high throughput of clinical samples will be discussed.