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B Adler

Publications and source records attributed to B Adler.

At least 37 records · Page 2Linked to original sources
PubMed2000

Pasteurella multocida capsule: composition, function and genetics.

Pasteurella multocida is an important animal pathogen and many strains express a polysaccharide capsule. The antigenicity of the capsule can be used to identify five serogroups A, B, D, E and F. Disease predilection is generally related to serogroup, with haemorrhagic septicaemia strains belonging to serogroups B or E and fowl cholera strains to serogroup A. The importance of the capsule in virulence has been implicated in a number of studies but these studies have been hampered by a lack of isogenic strains and an understanding of capsule biosynthesis at the molecular level. Recently, the nucleotide sequences and genetic organisation of the capsule biosynthetic loci have been determined for strains of P. multocida serogroups A and B.

Bacterial Capsules↗
PubMed2000

The incidence of lymphoma in first-degree relatives of patients with Hodgkin disease and non-Hodgkin lymphoma: results and limitations of a registry-linked study.

BACKGROUND: The precise incidence of familial Hodgkin disease (HD) and non-Hodgkin lymphoma (NHL) in first-degree relatives is unknown. Through record linkage using two population-based sources, the authors estimated the risk of HD and NHL in family members of lymphoma probands. METHODS: The authors identified 8,037 first-degree relatives of 2,606 lymphoma cases (28.5% HD, 71.5% NHL) treated between 1970 and 1993 in 3 hospitals in Israel via the family file of the Population Registry. The authors linked this file with the Israel Cancer Registry, then calculated the standardized incidence ratio (SIR) by dividing the observed number of cases with the expected, adjusting for age, gender, calendar year, and continent of origin. RESULTS: The family file yielded incomplete ascertainment of relatives (for 771 probands, no relatives were identified). Twenty cases of lymphoma--6 HD and 14 NHL--were identified among relatives of lymphoma patients. The SIR for HD was 1.15 (95% confidence interval [CI]: 0.42-2.51) and for NHL 1.71 (95% CI: 0.93-2.87), considering the entire population of first-degree relatives. SIRs among siblings of lymphoma probands were 3.12 (95% CI: 1.01-7.29) for HD, 2.16 (95% CI: 0.45-6.31) for NHL, and 2.68 (95% CI: 1.15-5.27) for all lymphomas. There were 4 HD/HD, 1 NHL/NHL, and 3 NHL/HD sibling pairs. For HD/HD and NHL/NHL sibling pairs, the interval between lymphoma occurrence in proband and sibling was 1-4 years, whereas for HD/NHL pairs this ranged from 16 to 21 years. CONCLUSIONS: The risk of lymphoma among siblings of lymphoma probands was over 2.5-fold that of the general population and lower among other family members. The temporal proximity of HD/HD and NHL/NHL sibling pairs argues for environmental as well as genetic etiology. This method was hampered by incomplete data.

Adolescent↗
PubMed2000

The molecular biology of pasteurella multocida.

Pasteurella multocida is an important veterinary and opportunistic human pathogen. The species is diverse and complex with respect to antigenic variation, host predeliction and pathogenesis. Certain serological types are the aetiologic agents of severe pasteurellosis, such as fowl cholera in domestic and wild birds, bovine haemorrhagic septicaemia and porcine atrophic rhinitis. The recent application of molecular methods such as the polymerase chain reaction, restriction endonuclease analysis, ribotyping, pulsed-field gel electrophoresis, gene cloning, characterisation and recombinant protein expression, mutagenesis, plasmid and bacteriophage analysis and genomic mapping, have greatly increased our understanding of P. multocida and has provided researchers with a number of molecular tools to study pathogenesis and epidemiology at a molecular level.

Animals↗
PubMed2000

The type 4 fimbrial subunit gene of pasteurella multocida.

Colonisation of host tissue by Gram- negative bacteria is facilitated by various adhesins, one of which is type 4 fimbriae (pili). These structures have been associated with pathogenesis in several bacterial species, and have been shown to mediate colonisation of epithelial surfaces. Recently, type 4 fimbriae were identified and characterised from P. multocida strains A, B and D. The type 4 fimbrial subunit protein (PtfA) was identified as an 18-kDa protein which was isolated from whole membrane fractions. We report here the isolation and characterisation of the gene (ptfA) encoding the PtfA protein from P. multocida VP161 (serotype A:1). Part of the gene was cloned on a 2-kb genomic DNA fragment. The complete ptfA gene was obtained using inverse PCR. The gene and its flanking regions were characterised, and the deduced PtfA amino acid sequence was compared to type 4 subunit protein sequences from other bacterial species. The ptfA gene was amplified and sequenced from several P. multocida strains. Comparison of these sequences revealed variation within the type 4 subunit gene of P. multocida.

Amino Acid Sequence↗
PubMed2000

Overexpression and immunogenicity of the Oma87 outer membrane protein of Pasteurella multocida.

The outer membrane protein of Oma87 from Pasteurella multocida A:1 has significant similarity to the D15 protective antigen of Haemophilus influenzae (Ruffolo and Adler, 1996). Four fragments of Oma87 from a P. multocida serotype D strain were cloned into a pGEX expression vector and transformed into E. coli JM105. Western blot analysis revealed that convalescent chicken sera reacted with only GST-F1 fusion protein which contained amino acids 18 through to 130 of Oma87 fused to the GST protein. Vaccination with the GST-F1 protein failed to protect chickens against challenge with a virulent P. multocida serotype A.

Animals↗
PubMed2000

Genetic organisation of the capsule biosynthetic locus of Pasteurella multocida M1404 (B:2).

Capsules from a range of bacterial species have been shown to be major virulence determinants and capsule has been implicated in virulence in Pasteurella multocida. Moreover, capsular serogroup appears to be related to disease predilection. Haemorrhagic septicaemia strains belong to serogroup B and E, fowl cholera strains to serogroup A and atrophic rhinitis strains to serogroup D. The entire capsule biosynthetic locus of P. multocida A:1 has been cloned and its nucleotide sequence determined (Chung et al., 1998. FEMS Microbiol. Lett. 166, 289-296); however, nothing is known of the P. multocida B:2 capsule locus. In this work we have determined the nucleotide sequence and genetic organisation of the P. multocida M1404 (B:2) capsule locus. By analogy with the cap loci of other bacteria, the nucleotide sequence can be divided into three functional regions. Regions 1 and 3 comprise six genes involved in transport of the polysaccharide capsule to the cell surface. The deduced products of these genes show high similarity to proteins involved in capsule export in other bacteria. Region 2 comprises nine genes which are likely involved in biosynthesis of the polysaccharide capsule. The deduced products of three of these genes (bcbA, bcbB and bcbC) show significant similarity to proteins known to be involved in polysaccharide biosynthesis while the other six show no similarity to known proteins. However, their organisation indicates they are co-transcribed with bcbA, bcbB, bcbC and the Region 1 capsule export genes, suggesting strongly that they are also involved in capsule biosynthesis.

Amino Acid Sequence↗
PubMed2000

Cloning and characterisation of the Pasteurella multocida ahpA gene responsible for a haemolytic phenotype in Escherichia coli.

Haemolysins are membrane-damaging agents which have been described as bacterial virulence factors due to their ability to lyse erythrocytes and other host cells, and therefore inducing a greater inflammatory response (Elliott et al., 1998). Pasteurella multocida was found to be haemolytic under anaerobic conditions. In this study, we cloned and characterised a P. multocida gene, designated ahpA, which conferred a haemolytic phenotype on Escherichia coli when incubated under anaerobic conditions. A deletion was introduced into the ahpA open reading frame which abolished the haemolytic phenotype. The clone containing ahpA showed erythrocyte specificity, causing haemolysis of bovine and equine erythrocytes, and demonstrated weak haemolysis on ovine erythrocytes. Upon further investigation, AhpA was found to affect the expression of the E. coli K-12 latent haemolysin, SheA, under anaerobic conditions.

Amino Acid Sequence↗
PubMed2000

The sigA gene which is borne on the she pathogenicity island of Shigella flexneri 2a encodes an exported cytopathic protease involved in intestinal fluid accumulation.

In this study, the sigA gene situated on the she pathogenicity island of Shigella flexneri 2a was cloned and characterized. Sequence analysis showed that sigA encodes a 139.6-kDa protein which belongs to the SPATE (serine protease autotransporters of Enterobacteriaceae) subfamily of autotransporter proteins. The demonstration that SigA is autonomously secreted from the cell to yield a 103-kDa processed form and possesses a conserved C-terminal domain for export from the cell were consistent with the autotransporter pathway of secretion. Functional analysis showed that SigA is a secreted temperature-regulated serine protease capable of degrading casein. SigA was cytopathic for HEp-2 cells, suggesting that it may be a cell-altering toxin with a role in the pathogenesis of Shigella infections. SigA was at least partly responsible for the ability of S. flexneri to stimulate fluid accumulation in ligated rabbit ileal loops.

Animals↗
PubMed2000

The capsule is a virulence determinant in the pathogenesis of Pasteurella multocida M1404 (B:2).

Capsules from a range of pathogenic bacteria are key virulence determinants, and the capsule has been implicated in virulence in Pasteurella multocida. We have previously identified and determined the nucleotide sequence of the P. multocida M1404 (B:2) capsule biosynthetic locus (J. D. Boyce, J. Y. Chung, and B. Adler, Vet. Microbiol. 72:121-134, 2000). The cap locus consists of 15 genes, which can be grouped into three functional regions. Regions 1 and 3 contain genes proposed to encode proteins involved in capsule export, and region 2 contains genes proposed to encode proteins involved in polysaccharide biosynthesis. In order to construct a mutant impaired in capsule export, the final gene of region 1, cexA, was disrupted by insertion of a tetracycline resistance cassette by allelic replacement. The genotype of the tet(M) OmegacexA mutant was confirmed by Southern hybridization and PCR. The acapsular phenotype was confirmed by immunofluorescence, and the strain could be complemented and returned to capsule production by the presence of a cloned uninterrupted copy of cexA. Wild-type, mutant, and complemented strains were tested for virulence by intraperitoneal challenge of mice; the presence of the capsule was shown to be a crucial virulence determinant. Following intraperitoneal challenge of mice, the acapsular bacteria were removed efficiently from the blood, spleen, and liver, while wild-type bacteria multiplied rapidly. Acapsular bacteria were readily taken up by murine peritoneal macrophages, but wild-type bacteria were significantly resistant to phagocytosis. Both wild-type and acapsular bacteria were resistant to complement in bovine and murine serum.

Animals↗
PubMed2000

Curli loci of Shigella spp.

An unstable chromosomal element encoding multiple antibiotic resistance in Shigella flexneri serotype 2a was found to include sequences homologous to the csg genes encoding curli in Escherichia coli and Salmonella enterica serovar Typhimurium. As curli have been implicated in the virulence of serovar Typhimurium, we investigated the csg loci in all four species of Shigella. DNA sequencing and PCR analysis showed that the csg loci of a wide range of Shigella strains, of diverse serotypes and different geographical distributions, were almost universally disrupted by deletions or insertions, indicating the existence of a strong selective pressure against the expression of curli. Strains of enteroinvasive E. coli (EIEC), which share virulence traits with Shigella spp. and cause similar diseases in humans, also possessed insertions or deletions in the csg locus or were otherwise unable to produce curli. Since the production of curli is a widespread trait in environmental isolates of E. coli, our results suggest that genetic lesions that abolish curli production in the closely related genus Shigella and in EIEC are pathoadaptive mutations.

Bacterial Proteins↗
PubMed2000

Functional analysis of genes in the rfb locus of Leptospira borgpetersenii serovar Hardjo subtype Hardjobovis.

Lipopolysaccharide (LPS) is a key antigen in immunity to leptospirosis. Its biosynthesis requires enzymes for the biosynthesis and polymerization of nucleotide sugars and the transport through and attachment to the bacterial membrane. The genes encoding these functions are commonly clustered into loci; for Leptospira borgpetersenii serovar Hardjo subtype Hardjobovis, this locus, named rfb, spans 36.7 kb and contains 31 open reading frames, of which 28 have been assigned putative functions on the basis of sequence similarity. Characterization of the function of these genes is hindered by the fact that it is not possible to construct isogenic mutant strains in Leptospira. We used two approaches to circumvent this problem. The first was to clone the entire locus into a heterologous host system and determine if a "recombinant" LPS or polysaccharide was synthesized in the new host. The second approach used putative functions to identify mutants in other bacterial species whose mutations might be complemented by genes on the leptospiral rfb locus. This approach was used to investigate the function of three genes in the leptospiral rfb locus and demonstrated function for orfH10, which complemented a wbpM strain of Pseudomonas aeruginosa, and orfH13, which complemented an rfbW strain of Vibrio cholerae. However, despite the similarity of OrfH11 to WecC, a wecC strain of E. coli was not complemented by orfH11. The predicted protein encoded by orfH8 is similar to GalE from a number of organisms. A Salmonella enterica serovar Typhimurium strain producing no GalE was used as a background in which orfH8 produced detectable GalE enzyme activity.

Animals↗
PubMed2000

HIV testing in gay sex clubs.

The purpose of this study was to evaluate a programme of human immunodeficiency virus (HIV) antibody testing at gay sex clubs. Conducting secondary analyses with 2 datasets, we evaluated HIV-testing preferences of patrons at 2 sex clubs and compared their risks to testers at a standard testing clinic. Sex club testers had significantly more partners and were significantly older than their clinic peers. Sixteen per cent of sex club testers reported that they would not test if testing were not available at the sex club. Gay sex clubs offer an opportunity to reach men at high risk for HIV, some who otherwise may not test.

Adult↗
PubMed2000

Birthweight recall by mothers of Israeli children.

The objective of this study was to examine the reliability and validity of maternally recalled birthweight (BW) in a population of 6-y-old children in Jerusalem. The study population consisted of 259 children entering the first grade in two schools in the city. We compare the recalled BW at entrance to school and the BW values as recorded in the Mother and Child Health Clinic of the Hadassah Community Health Center. The mean recalled BW was 11.7 g lower than the mean recorded BW (P>0.05). There were no statistical differences in mean BW values between the two data sources (according to socio-demographic characteristics) except for mother's age and origin, where no trends could be detected. Fifty-eight percent of the mothers accurately recalled the BW of their children to within 100 g and 80% recalled the BW to within 500 g. Seventy-three percent of mothers of low-birthweight children recalled a BW value of less than 2500 g and 99% of mothers of normal BW children recalled a BW of 2500 g or more. Correlation coefficients between the two sources ranged from 0.89 to 0.96. Given the high degree of accuracy, maternally recalled birthweight is a reliable and valid measure of birthweight 6 y post-partum and its use is justified when no records of birthweight are available. Public Health (2000) 114, 161-163

Birth Weight↗
PubMed2000

Lipopolysaccharide biosynthesis in Leptospira.

Lipopolysaccharide is the major surface antigen of Leptospira. Variation in LPS structure is the basis for the more than 200 serovars that have been identified. Despite the importance of this antigen in immunity and diagnostics, there is relatively little known about the genetics and chemistry of leptospiral LPS, as compared to some members of the Enterobacteriaceae. The nucleotide sequence of the locus encoding enzymes for the biosynthesis of the O-antigen component of leptospiral LPS (rfb locus) has been determined for three serovars namely, L. interrogans serovar Pomona, L. interrogans serovar Hardjo subtype Hardjoprajitno and L. borgpetersenii serovar Hardjo subtype Hardjobovis. In the absence of data relating to the chemical structure or genetic tools to construct isogenic mutants in Leptospira, similarity analysis has been used to provide insight into the mechanisms by which the leptospiral O-antigen is assembled by comparison with characterized systems from other bacteria. In addition, comparison of the gene layout in each of the serovars provides an indication of the genetic basis for serovar diversity.

Enterobacteriaceae↗
PubMed2000

Technological advances in the molecular biology of Leptospira.

Pathogenic members of the genus Leptospira have been refractory to genetic study due to lack of known mechanisms of genetic exchange. To bypass this limitation, several techniques have been useful for Leptospira gene discovery, including heterologous complementation of Escherichia coli mutants, screening of DNA libraries with probes, and random sequence analysis. Construction of combined physical and genetic maps revealed the presence of two circular chromosomal replicons. The organization of the L. interrogans genome is quite variable, with genetically similar strains differentiated by many rearrangements. These rearrangements likely occur through recombination between repetitive DNA elements found scattered throughout the genome. Analysis of intervening sequences and genes encoding LPS biosynthetic enzymes provide evidence of lateral transfer of DNA between Leptospira spp. We have also gained insight into the biology of these bacteria by analyzing genes encoding LPS and outer membrane proteins (OMPs). Some of these OMPs are differentially expressed. Characterization of mechanisms governing the expression of the OMP genes should provide insight into host-parasite interactions. Furthermore, recent advances in heterologous expression of leptospiral OMP genes are opening new avenues of vaccine development.

Animals↗
PubMed1999

Nonfasting plasma total homocysteine level and mortality in middle-aged and elderly men and women in Jerusalem.

BACKGROUND: Elevated plasma total homocysteine level has been associated with cardiovascular disease in many studies, mostly in Europe and North America. Data on persons from other areas and on associations with overall mortality are sparse. OBJECTIVE: To determine the relation of plasma homocysteine level to all-cause and cause-specific mortality. DESIGN: Prospective observational study with 9- to 11-year follow-up. SETTING: A free-living, multiethnic Jewish population in western Jerusalem, Israel. PARTICIPANTS: 1788 residents of Jerusalem (808 men and 980 women) who were at least 50 years of age and were examined between 1985 and 1987 as part of the Kiryat Yovel Community Health Study. MEASUREMENTS: Nonfasting plasma homocysteine level was determined in frozen stored samples. Deaths during follow-up were identified by linkage with the national population registry. RESULTS: Plasma homocysteine levels exceeded 14 micromol/L in 28% of men and 20% of women. During the study period, 405 deaths occurred. In multivariate Cox models that controlled for possible confounders, a nonmonotonic increase in mortality hazard ratios was associated with ascending quintile of homocysteine level: 1.0, 1.4, 1.3, 1.5, and 2.0 (P < 0.001 for trend). The relation was similar for cardiovascular and noncardiovascular causes of death (excluding cancer). The association was weaker when deaths that occurred during the first 5 years of follow-up were excluded; corresponding hazard ratios for ascending quintile of homocysteine level were 1.0, 1.0, 1.2, 1.1, and 1.6 (P = 0.063 for trend). Age- and sex-adjusted percentages of deaths "attributable" to elevated plasma homocysteine level (> or = 14 micromol/L) were 12.5% (95% CI, 6.7% to 18.8%) for all deaths, 16.0% (CI, 7.2% to 25.6%) for deaths during the first 5 years of follow-up, and 8.3% (CI, 1.5% to 16.1%) for later deaths. CONCLUSIONS: A mildly to moderately elevated nonfasting plasma homocysteine level is a substantial risk marker for death from all causes. The association seems to be stronger during the first 5 years of follow-up.

Aged↗
PubMed1999

Candidate vaccine antigens and genes in Pasteurella multocida.

Pasteurella multocida is the causative agent of fowl cholera and other diseases of production animals. Isolates are classified into five groups based on capsular antigens and into 16 serotypes based on LPS antigens. Strains causing fowl cholera are most frequently designated A:1, A:3 or A:4. Whole cell bacterins can provide some degree of protection, but only against the homologous LPS serotype. There is good evidence that cross-protective antigens are expressed only under in vivo conditions. Empirically derived, live, attenuated vaccines can protect against heterologous serotypes, but because the basis for attenuation is undefined, reversion to virulence is not uncommon. Work in our laboratory is aimed at using a variety of approaches to identify potential protective antigens or virulence genes to be used as candidates for attenuating mutations or as the basis for vaccine antigen delivery systems. The gene encoding an outer membrane protein, Oma87, which is a homologue of the D15 protective antigen of Haemophilus influenzae, was cloned and sequenced. Rabbit antiserum prepared against recombinant Oma87 could passively protect mice against infection. Type 4 fimbriae form the basis of vaccines against ovine footrot and bovine keratoconjunctivitis. We have identified type 4 fimbriae on the surface of P. multocida, purified the fimbrial subunit protein, PtfA, and determined its N-terminal amino acid sequence. Subsequent cloning of the ptfA gene and its inactivation will now be used to assess the importance of type 4 fimbriae in virulence. There has long been anecdotal evidence for the importance of capsule in virulence, but unequivocal genetic evidence for such a role is lacking. We have cloned and characterised the capsule biosynthetic locus in P. multocida A:1 and identified four bex genes involved in capsule transport and genes encoding enzymes involved in the biosynthesis and transfer of the N-acetyl glucosamine and glucuronic acid components of the capsule. It has been suggested that the low concentration of available iron in vivo acts as an environmental cue for expression of cross-protective antigens. Accordingly, we have cloned and characterised the gene encoding transferrin binding protein, Tbpl, so that its role in immunity and virulence can be investigated. Although P. multocida is not normally considered haemolytic, we have observed haemolysis under anaerobic conditions. Standard library construction and screening resulted in the identification of the mesA gene which encodes an esterase enzyme resulting in a haemolytic phenotype under anaerobic conditions. Virulence studies with mesA- mutants were performed to assess its role in pathogenesis. Using a promoterless phoA gene vector system, the cloning of proteins homologous to known surface proteins of other species as well as proteins unique to P. multocida, allowing their potential as vaccine components to be assessed.

Amino Acid Sequence↗