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Bacteria
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
The LPS which is oriented to the outside of the cell is in contact with the environment. The major surface antigen of all Gram-negative bacteria is the O-antigen, which is a side chain that is attached to the outermost core polysaccharide component of LPS. The core polysaccharide, in turn, is attached to the lipid A component of LPS. The lipid A component is embedded in the phospholipid bilayer of the outer membrane (Figure 15.3). Differences in the O-antigen determine the bacterial serotype.
The Chemistry of O-Polysaccharide Chains in Bacterial Lipopolysaccharides
Published in Helmut Brade, Steven M. Opal, Stefanie N. Vogel, David C. Morrison, Endotoxin in Health and Disease, 2020
Campylobacter bacteria are associated with several diseases such as human enteritis. The LPS of C. jejunii have highly variable structures accounting for the classification into different serotypes (Table 7). C. jejunii serotype 019 (78) is associated with the Guillian-Barré syndrome, a neuropathy, and has an O-antigen with a hyaluronic acid backbone (→4)-β-d-GlcpA-(1→3)-β-d-GlcpNAc-(1→) in which the d-GlcA residues are amidated with 2-amino-1,3-propanediol. This amide is also present in E. coli 0143 and some Shigella and Vibrio LPS. Both serotypes of C. fetus, A (79) and B (80), have been studied. The type A O-antigen is a d-mannan and that of B a d-rhamnan. The B polysaccharide is terminated by a 3-O-methyl-d-Rha residue. If the polysaccharide is elongated from the nonreducing end in the biosynthesis, this sugar then stops further elongation.
Laboratory Diagnostic Tests in the Evaluation of Fever
Published in Benedict Isaac, Serge Kernbaum, Michael Burke, Unexplained Fever, 2019
Acute infection with Salmonella species is characterized by elevation in serum titers toward the H- and O- antigens of these bacteria. High titers toward the O- antigen alone may persist for years and reflect prior infection or immunization.
Phenotypic whole-cell screening identifies a protective carbohydrate epitope on Klebsiella pneumoniae
Published in mAbs, 2022
Sophia K. Berry, Steven Rust, Carolina Caceres, Lorraine Irving, Josefin Bartholdson Scott, David E. Tabor, Gordon Dougan, Graham Christie, Paul Warrener, Ralph Minter, Andrew J. Grant
Several sub-serotypes exist within the O1 and O2 serotypes (Figure S4). Of marked importance are sub-serotypes that harbor the gmlABC locus, which encodes the conversion of D-galactan-I to D-galactan-III,21 and which has been shown to be widely distributed among ST258 isolates,22 leading to the proposal of D-galactan-III as an attractive therapeutic target.22,23 To investigate the potential scope of use of B39, we investigated whether B39 could bind to clinically relevant sub-serotypes within the O1 and O2 serotypes, namely O1 gmlABC− (O1−), O1 gmlABC+ (O1+), O2 gmlABC− (O2−), and O2 gmlABC+ (O2+). The O-antigen structures of these serotypes are shown in Figure 6a.
Classification of Parabacteroides distasonis and other Bacteroidetes using O- antigen virulence gene: RfbA-Typing and hypothesis for pathogenic vs. probiotic strain differentiation
Published in Gut Microbes, 2022
Nicholas C. Bank, Vaidhvi Singh, Alex Rodriguez-Palacios
Extrapolating from prior research on E. coli and Salmonella,18–20 strain dependent mechanisms linked to bacterial surface markers, such as the O-antigen, could be used to help guide research and help propose studies to determine the causes that lead to the varied effects observed for Pdis on human and animal health. The O-antigen is a key virulence molecule of lipopolysaccharides (LPS) constitutively expressed on the cell wall surface of gram-negative bacteria. Lipopolysaccharide is a well understood virulence factor for gram-negative bacteria, consisting of lipid A, an oligosaccharide, and the O-antigen polysaccharide. The O-antigen is the immunogenic component of LPS, and as such can influence the host–bacterium relationship in several ways; potential mechanisms include resisting host complement and phagocytic engulfment, molecular mimicry, and colonization ability.21 Additionally, variation in the amount/type of monosaccharides in O-antigens provide major LPS structural diversity21 and virulence potential across bacteria (e.g. E. coli O157).
Epidemiology of invasive bacterial infections in pneumococcal conjugate vaccine-vaccinated and -unvaccinated children under 5 years of age in Soweto, South Africa: a cohort study from a high-HIV burden setting
Published in Paediatrics and International Child Health, 2020
Siobhan L. Johnstone, David P. Moore, Keith P. Klugman, Shabir A. Madhi, Michelle J. Groome
E. coli was the second leading cause of IBI (after S. pneumoniae) in all the study groups, contributing to 21.3% of all IBI. This indicates that, besides being one of the leading causes of diarrhoea-associated morbidity and mortality in infants and children, the role of E. coli in IBI should not be underestimated [10]. High rates of E. coli IBI in the present setting might highlight the need for improvements in infrastructure in terms of access to clean water and sanitation. E. coli is recognised as a leading cause of acute pyelonephritis in children [11] but this could not be investigated as urine was cultured for very few participants with invasive E. coli infections. The high incidence of E. coli IBI in children <6 months of age is noteworthy, given the identification of E. coli infection as an important contributor to stillbirths and early neonatal deaths [12]. Although there are over 180 O-antigen E. coli serotypes, it is estimated that only 10–12 of them account for the majority of invasive disease [13]. The O-antigen is therefore an important vaccine target and may suggest a route to a maternal vaccine [13]. E. coli was responsible for 39.3% of infections in the <6 months age group (33 events), 73.7% of which were in children under 3 months of age. Prevention of these events would have reduced E. coli infections by 39.3% and total IBI by 8.4% in the study population.