Structural and serological studies on the O-antigen of Proteus mirabilis O14, a new polysaccharide containing 2-[(R)-1-carboxyethylamino]ethyl phosphate.
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An O-specific polysaccharide was obtained by mild acid degradation of Proteus mirabilis O14 lipopolysaccharide (LPS) and found to contain D-galactose, 2-acetamido-2-deoxy-D-glalactose, phosphate, N-(2-hydroxyethyl)-D-alanine (D-AlaEtn), and O-acetyl groups. Studies of the initial and O-deacetylated polysaccharides using one- and two-dimensional 1H- and 13C-NMR spectroscopy, including COSY, TOCSY, NOESY, H-detected 1H,13C heteronuclear multiple-quantum coherence, and heteronuclear multiple-bond correlation experiments, demonstrated the following structure of the repeating unit: [equation: see text] This is the second bacterial polysaccharide reported to contain alpha-D-Galp6PAlaEtn, whereas the first one was the O-antigen of P. mirabilis EU313 taken erroneously as strain PrK 6/57 from the O3 serogroup [Vinogradov, E. V., Kaca, W., Shashkov, A.S., Krajewska-Pietrasik, D., Rozalski, A., Knirel, Y.A. & Kochetkov, N.K. (1990) Eur. J. Biochem., 188, 645-651]. Anti-(P. mirabilis O14) serum cross-reacted with LPS of P. mirabilis EU313 and vice versa in passive hemolysis and ELISA. Absorption of both O-antisera with the heterologous LPS decreased markedly but did not abolish the reaction with the homologous LPS. These and chemical data indicated that both strains have similar but not identical O-antigens. Therefore, we propose that P. mirabilis EU313 should belong to a new subgroup of the O14 serogroup. (+info)
Structure of the O-specific polysaccharide of a serologically separate strain Proteus penneri 2 from a new proposed serogroup O66.
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O-specific polysaccharide chain of Proteus penneri strain 2 lipopolysaccharide was studied by full and partial acid hydrolysis, Smith degradation, methylation analysis, and NMR spectroscopy, including two-dimensional rotating-frame NOE spectroscopy (ROESY) and 1H,13C heteronuclear multiple-quantum coherence (HMQC) experiments. Together with D-glucose and 2-acetamido-2-deoxy-D-glucose, the polysaccharide was found to contain two rarely occurring sugars, 6-deoxy-L-talose (L-6dTal) and 2,3-diacetamido-2,3,6-trideoxy-L-mannose (L-RhaNAc3NAc), and the following structure of a non-stoichiometrically O-acetylated tetrasaccharide repeating unit was established: [equation: see text] The O-specific polysaccharide studied has a unique composition and structure and, accordingly, P. penneri 2 is serologically separate among Proteus strains. Therefore, we propose for P. penneri 2 a new Proteus O-serogroup O66 where this strain is at present the single representative. (+info)
Hypermutation in pathogenic bacteria: frequent phase variation in meningococci is a phenotypic trait of a specialized mutator biotype.
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Expression of serogroup B meningococcal capsular polysaccharide undergoes frequent phase variation involving reversible frameshift mutations within a homopolymeric repeat in the siaD gene. A high rate of phase variation is the consequence of a biochemical defect in methyl-directed mismatch repair. The mutator phenotype is associated to the absence of DNA adenine methyltransferase (Dam) activity in all pathogenic isolates and in 50% of commensal strains. Analysis of the meningococcal dam gene region revealed that in all Dam- strains a gene encoding a putative restriction endonuclease (drg) that cleaves only the methylated DNA sequence 5'-GmeATC-3' replaced the dam gene. Insertional inactivation of the dam and/or drg genes indicated that high rates of phase variation and hypermutator phenotype are caused by absence of a functional dam gene. (+info)
Protein GRAB of streptococcus pyogenes regulates proteolysis at the bacterial surface by binding alpha2-macroglobulin.
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In the molecular interplay between pathogenic microorganisms and their host, proteolytic mechanisms are believed to play a crucial role. Here we find that the important human pathogen Streptococcus pyogenes (group A Streptococcus) expresses a surface protein with high affinity (Ka = 2.0 x 10(8) M-1) for alpha2-macroglobulin (alpha2M), the dominating proteinase inhibitor of human plasma. The immunoglobulin-binding protein G of group C and G streptococci also contains an alpha2M-binding domain and a gene encoding protein GRAB (protein G-related alpha2M-binding protein) was identified in the S. pyogenes Genome Sequencing data base. The grab gene is present in most S. pyogenes strains and is well conserved. Protein GRAB has typical features of a surface-attached protein of Gram-positive bacteria. It also contains a region homologous to parts of the alpha2M-binding domain of protein G and a variable number of a unique 28-amino acid-long repeat. Using Escherichia coli-produced protein GRAB and synthetic GRAB peptides, the alpha2M-binding region was mapped to the NH2-terminal part of protein GRAB, which is the region with homology to protein G. An isogenic S. pyogenes mutant lacking surface-associated protein GRAB showed no alpha2M binding activity and was attenuated in virulence when injected intraperitoneally in mice. Finally, alpha2M bound to the bacterial surface via protein GRAB was found to entrap and inhibit the activity of both S. pyogenes and host proteinases, thereby protecting important virulence determinants from proteolytic degradation. This regulation of proteolytic activity at the bacterial surface should affect the host-microbe relation during S. pyogenes infections. (+info)
A low rate of nucleotide changes in Escherichia coli K-12 estimated from a comparison of the genome sequences between two different substrains.
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Two genome sequences of Escherichia coli K-12 substrains, one partial W3110 and one complete MG1655, have been determined by Japanese and American genome projects, respectively. In order to estimate the rate of nucleotide changes, we directly compared 2 Mb of the nucleotide sequences from these closely-related E. coli substrains. Given that the two substrains separated about 40 years ago, the rate of nucleotide changes was estimated to be less than 10(-7) per site per year. This rate was supported by a further comparison between partial genome sequences of E. coli and Shigella flexneri. (+info)
The routine serological investigation of cases and contacts of rubella.
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The results of testing sera from 111 patients with rubella-like illnesses and 283 contacts of patients with rubella-like illnesses are described. A sensitive haemagglutination-inhibition test was used in conjunction with fractionation of serum proteins when this was indicated. It was concluded that the testing of serum protein fractions for IgM and IgG rubella antibody greatly increased the effectiveness of laboratory diagnosis. Evidence is presented that during the study period subclinical rubella was relatively uncommon in adults and that the accuracy of clinical diagnosis was high. (+info)
First episodes of genital herpes in a Swedish STD population: a study of epidemiology and transmission by the use of herpes simplex virus (HSV) typing and specific serology.
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OBJECTIVES: To determine the proportion of herpes simplex virus type 1 (HSV-1) and HSV type 2 (HSV-2) in first episodes of genital herpes. To evaluate the use of HSV specific serology for classifying first episodes of genital herpes and for defining HSV serostatus in the patients' sexual partners. METHODS: 108 consecutive patients with first episodes of genital herpes seen at three STD clinics in Sweden from 1995 to 1999 were included in the study. HSV culture and typing were performed and serum was tested for antibodies against a type common HSV antigen and a type specific HSV-2 antigen, glycoprotein G2 (gG2). A structured interview including questions about sexual behaviour and sexual partners was taken. "Steady" partners were offered a blood test for HSV serology and counselling. RESULTS: Of 108 patients, 11 had a negative HSV culture. Of the 97 who were HSV culture positive, 44% (43/97) were typed as HSV-1 and 56% (54/97) as HSV-2. For 86 of these 97 patients, HSV serology from the initial visit was available. Of 52 primary infections, thus initially seronegative, 64% were HSV-1 infections and of 19 female primary infections 16 (84%) were HSV-1. In 17% the first episode of genital herpes corresponded to the first clinical recurrence of an infection acquired earlier in life. There was a significant correlation between having orogenital sex and being infected with HSV-1 and also a history of labial herpes in the partner. Only 20% of partners of patients with an HSV-2 infection had a history of genital herpes. CONCLUSIONS: Almost half of first episodes of genital herpes are caused by HSV-1. In young women with a primary genital infection, HSV-1 is much more frequent than HSV-2. Besides HSV typing, we found specific HSV serology of value for classifying first episodes and for diagnosing a subclinical HSV-2 infection in partners. Anamnestic data supported the suggestion that the orogenital route of transmission was common in genital HSV-1 infections. (+info)
Autoantibodies in childhood connective tissue diseases and in normal children.
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The prevalence of nine serum autoantibodies has been studied in 117 children with various connective tissue disorders and in 134 normal controls. In juvenile rheumatoid arthritis rheumatoid factor was present in 5%, and antinuclear factor in 4%, compared with an incidence of 4% and 0% respectively in controls. In Henoch-Schonlein purpura there was little evidence of associated autoimmune disorder. Gastric parietal cell and thyroid microsomal antibodies were found in 9% and 10% of our control population, but the significance of this is not clear. It is concluded that in children the presence or absence of autoantibodies as diagnostic criteria should be interpreted with the greatest caution. (+info)