Bernard Van der Zeijst

Leiden University Medical Centre | LUMC · Department of Medical Microbiology

Objective To develop an algorithm (sCOVID) to predict the risk of severe complications of COVID-19 in a community-dwelling population to optimise vaccination scenarios. Design Population-based cohort study. Setting 264 Dutch general practices contributing to the NL-COVID database. Participants 6074 people aged 0–99 diagnosed with COVID-19. Main...

Not all physicians advocate for large-scale vaccination programmes against COVID-19. In this article, we respond on some of their reflections. Moreover, we explain that there are strong arguments for these large-scale vaccination programmes, aimed to prevent COVID-19 associated morbidity, mortality and overwhelmed health care systems, and to hinder...

Objective: To develop an algorithm (sCOVID) to predict the risk of severe complications of COVID-19 in a community-dwelling population to optimise vaccination scenarios. Design: Population based cohort study Setting: 264 Dutch general practices contributing to the NL-COVID database Participants: 6074 people aged 0-99 diagnosed with COVID-19 Main ou...

Per 1 juni 2020 zijn de testmogelijkheden op SARS-CoV-2 verruimd. Iedereen met klachten, die wijzen op een infectie met het coronavirus kan zich via de GGD laten testen op dragerschap voor het virus. Na een positieve test voert de GGD contactonderzoek uit. Dit ruimere testbeleid zal zeker helpen om de covid-19-uitbraak in te perken. Maar er zijn om...

Vaccination was a key factor in reducing viral diseases after the transition of a nomadic lifestyle to a sedentary society. Without vaccination, our highly urbanized society would not be sustainable. Vaccine development is an, increasingly, long and expensive process. This poses severe problems for the development of vaccines against new emerging v...

Aim: Exon 18 expression of NCAM has been recognized as a biomarker for small cell lung cancer (SCLC). To use this finding for an improved diagnosis of SCLC and personalized treatment of patients, techniques to identify and quantitate E18, the exon 18 encoded protein moiety of NCAM, are needed. We developed three monoclonal antibodies for this purpo...

Background: The Neural Cell Adhesion Molecule (NCAM) is a glycoprotein expressed as 120, 140 and/or 180 kDa isoforms, all derived through alternative splicing of a single gene. NCAM 120 contains no intracellular domain, whereas NCAM 140 and 180 have different intracellular domains determined by alternative splicing of exon 18. NCAM has been descri...

An improved whole cell pertussis vaccine, designated as Plow, which is low in endotoxicity due to a chemical extraction of lipo-oligosaccharide (LOS) from the outer membrane, was evaluated for safety, immunogenicity and potency, comparatively to a traditional whole cell pertussis vaccine. Current whole cell pertussis vaccines are effective but cont...

Seasonal influenza causes more morbidity and mortality in older adults than in young adults, apparently because of a decline in immune function with increasing age, known as immunosenescence. In this study, we compared the capacity of dendritic cells (DCs) from healthy older adults (≥65 years) with DCs from healthy young adults (20-40 years) to ini...

Each year rotavirus gastroenteritis results in thousands of paediatric hospitalisations and primary care visits in the Netherlands. While two vaccines against rotavirus are registered, routine immunisation of infants has not yet been implemented. Existing cost-effectiveness studies showed inconsistent results for these vaccines because of lack of c...

Congenital cytomegalovirus (CMV) infection is an important public health problem with approximately 7 in 1,000 newborns infected and consequently at risk for hearing impairment. Newborn hearing screening will fail to detect this hearing impairment in approximately half of the cases because late onset hearing loss is frequent. Hearing impairment has...

Influenza infections are responsible for significant morbidity and mortality each year, with the highest infection rates found in the elderly population. The main strategy to reduce the impact of influenza infections in the elderly population is vaccination. However, the efficacy of influenza vaccines that are licensed for use in the elderly is rel...

Hepatitis B is a serious public health problem. Worldwide three different levels of hepatitis B endemicity (high, intermediate and low) can be distinguished. Areas with different levels of endemicity require tailored vaccination strategies to fit the needs for individuals at risk and/or countries, depending on the infection risk per age group, vacc...

The effect of in vivo and in vitro passage on C. jejuni flagellins and flagellin genes have been studied in clinical and environmental isolates associated with a milk-borne outbreak of campylobacteriosis. The milk isolate initially expressed a flagellin with apparent molecular mass of 62 kDa, while the human faecal isolate expressed a 58 kDa flagel...

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As reported in a recent issue of Eurosurveillance, a mumps outbreak is ongoing in the Netherlands despite high vaccination coverage of 90-95% [1]. The reported mumps cases are restricted to geographic regions with a high percentage of residents who are members of a religious community that rejects vaccination. Consequently, two thirds of the mumps...

The decision to include a vaccine in a national vaccination programme (or not) is usually evidence-based. Thereby, it is essential that the target disease causes a high burden of disease and that vaccination reduces this burden considerably. Furthermore, vaccination should be considered to be cost-effective by a government. Vaccines are usually adm...

There is concern that variola virus, the aetiological agent of smallpox, may be used as a biological weapon. For this reason several countries are now stockpiling (vaccinia virus-based) smallpox vaccine. Although the preventive use of smallpox vaccination has been well documented, little is known about its efficacy when used after exposure to the v...

The use of classical smallpox vaccines based on vaccinia virus (VV) is associated with severe complications in both naïve and immune individuals. Modified vaccinia virus Ankara (MVA), a highly attenuated replication-deficient strain of VV, has been proven to be safe in humans and immunocompromised animals, and its efficacy against smallpox is curre...

In a search for the genetic basis for the structural difference between the related Streptococcus pneumoniae capsular serotypes 15B and 15C and for the reported reversible switching between these serotypes, the corresponding capsular polysaccharide synthesis (cps) loci were investigated by keeping in mind that at the structural level, the capsules...

Screening of 7,680 Salmonella enterica serovar Enteritidis mutants for attenuation in a chicken macrophage infection model yielded a series of mutants including several with defects in previously unrecognized Salmonella virulence genes. One of the newly identified genes was the pbpA2 gene, belonging to the penicillin binding protein gene family.

The capsular polysaccharide (CPS) synthesis locus of Streptococcus pneumoniae serotype 9V was amplified by long-range PCR and sequenced. The locus was 17368 bp in size and contained 15 ORFs. The genetic organization of the cluster shared many features with other S. pneumoniae capsule loci, including the presence of four putative regulatory genes at...

Campylobacter jejuni is an enteropathogen for humans but commensal for chickens. In both hosts, the flagella and motility are important colonization factors. The flagellin gene is duplicated inCampylobacter, but only one flagellin gene,flaA, is sufficient for motility. We found that, during colonization of the chicken intestine, a nonmotile flaAmut...

The direct repeat region in Mycobacterium tuberculosiscomplex strains is composed of multiple direct variant repeats (DVRs), each of which is composed of a 36-bp direct repeat (DR) plus a nonrepetitive spacer sequence of similar size. It has been shown previously that clinical isolates show extensive polymorphism in the DR region by the variable pr...

A nonflagellated mutant of Salmonella enterica serotype Enteritidis was constructed by disrupting the flagellin gene (fliC). Northern blot analysis indicated that the mutation did not affect expression of the downstream fliU gene. Infection experiments with differentiated Caco-2 cells revealed that the mutant was about 50-fold less invasive than th...

Campylobacter jejuni is a Gram-negative bacterium and is a commensal of many animal species (Skirrow and Blaser, 1992). In humans it is the major cause of human bacterial enteritis both in developed and developing countries (Tauxe, 1992; Taylor, 1992). Many cases of Campylobacter enteritis in humans have been associated with the consumption of or c...

A view is presented on the future vaccination policy in the Netherlands. The report addresses the following four subjects. (i) Improvement of the current national vaccination programme (RVP). Maintaining and improving the quality of the RVP requires efforts related to efficacy, safety and adverse effects, vaccination schemes, (re)vaccination of eld...

Given the lack of functional transposons for use in Campylobacter spp., an alternative method of insertional mutagenesis using natural transformation was developed. High efficiencies of transformation were only obtained with species-specific DNA. This feature was a key element in the construction of mutant libraries of this bacterium. A chromosomal...

The aim of the study was to monitor the course of digital dermatitis after local antibiotic treatment in an experimental group (treated on diagnosis) and a control group (treated 5 days later). The present study was carried out on 2 farms involving 18 animals. Monitoring was performed by means of clinical findings and detection of spirochetes on th...

Thirty-three family dogs were monitored for antibodies to Borrelia burgdorferi sensu lato over a 3-year period. Serum samples were collected before and during the season of high tick activity. Antibody levels were measured with an ELISA based on whole-cell antigens and an ELISA with a purified recombinant flagellin (r410). Antibody levels measured...

Most Campylobacter jejuni strains express lipo-oligosaccharides. Some strains also express lipopolysaccharides (LPS), with O-antigen-like carbohydrate repeats. C. jejuni 81116 expresses an LPS containing both lipo-oligosaccharides and O-antigen-like repeats, but nothing is known about the structure or sugar composition of these LPS species. A cosmi...

The rpoD gene encoding the primary sigma-factor of Campylobacter jejuni was amplified from genomic DNA with degenerate oligonucleotide primers. The complete gene encodes a polypeptide of 622 amino acids and has a deduced M(r) of 72.6 kDa. This polypeptide is 40% identical to the RpoD (sigma 70) protein of Escherichia coli and has 66% identity with...

Streptococcus pneumoniae comprises 90 serotypes, each one having its own specific polysaccharide capsule. In order to explore the diversity of capsular polysaccharide synthesis (cps) gene clusters in S. pneumoniae, we performed cross-hybridizations between the 12 cps genes of S. pneumoniae serotype 14 and chromosomal DNA of 26 strains comprising 26...

A promoterless lacZ shuttle vector, which allowed screening of promoters by beta-galactosidase activity in Campylobacter jejuni and Escherichia coli, was developed. Chromosomal DNA fragments from C. jejuni were cloned into this vector; 125 of 1,824 clones displayed promoter activity in C. jejuni. Eleven clones with strong promoter activity in C. je...

LytB of Escherichia coli is an essential gene involved in penicillin tolerance and the stringent response. The lytB gene of Campylobacter jejuni was cloned and characterized. It could complement a temperature-sensitive E. coli lytB mutant. The C. jejuni lytB gene encodes a protein of 277 amino acids that has 34, 36 and 40% amino acid identity with...

Campylobacter spp. are well recognized as primary pathogens in animals and in people. To isolate and define the genetic regions encoding major surface antigens of Campylobacter hyoilei, genomic DNA of the type strain of the species, RMIT-32A, was cloned into a cosmid vector, pLA2917, in Escherichia coli and the resulting genomic library was screene...

We have reported previously on seven genes (cps14B-H) of Streptococcus pneumoniae serotype 14, which are part of the type 14 capsular polysaccharide synthesis (cps14) locus. This study describes the cloning and sequencing of the remaining part of the cps14 locus. The entire cps14 gene cluster consists of 12 open reading genes (cps14A to cps14L), wh...

Bacteria belonging to the species Streptococcus pneumoniae vary in their capsule. Presently, 90 capsular serotypes are known, all possessing their own specific polysaccharide structure. Little is known about the biosynthesis of these capsular polysaccharides. The cps locus of S. pneumoniae serotype 14 was cloned. So far, 7 open reading frames have...

Polymerase chain reaction (PCR) mediated DNA fingerprinting has resulted in the identification of a novel Campylobacter jejuni gene, encoding a GTPase protein. The gene, consisting of 383 amino acids contained semi-conserved GTP-binding sites (designated G-1 to G-4), that are characteristic for members of the GTPase protein superfamily. Remarkably,...

With DNA probes derived from the fimbrial subunit genes fim2 and fim3 of Bordetella pertussis, two homologous subunit genes of Bordetella bronchiseptica were identified and cloned. The nucleotide sequences of these genes were determined. Comparison of these nucleotide sequences with the B. pertussis fimbrial fim2 and fim3 subunit genes showed a pro...

The gene for 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase (aroA) cloned from Campylobacter jejuni (Cj) strain 81116 was identified by complementation of an Escherichia coli (Ec) auxotrophic aroA mutant. The Cj aroA gene has been sequenced. It encodes an enzyme of 428 amino acids (aa), that is homologous to other bacterial EPSP synthases, espe...

The major antigenic protein (MAP1) of Cowdria ruminantium was screened for immunogenic regions by expression of overlapping recombinant DNA clones of the gene encoding the MAP1 protein. Two regions, designated MAP1-A and MAP1-B, were recognized by all antisera to 9 different isolates of C. ruminantium. MAP1-A contained one or more epitopes responsi...

To identify a chromosomal region of Streptococcus pneumoniae serotype 14 involved in capsule polysaccharide synthesis, two strategies were used: (i) Tn916 mutagenesis, followed by the characterization of four unencapsulated mutants, and (ii) cross-hybridization with a capsule polysaccharide synthesis gene (cps) probe from S. agalactiae, which has a...

Enterotoxigenic Escherichia coli (ETEC) are the cause of childhood and travellers' diarrhoea in humans. An important virulence factor of these ETEC is their ability to adhere to the intestinal epithelial cells of the host. This adhesion is mediated by proteinaceous surface appendages called fimbriae, or colonization factors. There is a clear correl...

The ability of Taylorella equigenitalis, the causative agent of contagious equine metritis, to invade and replicate in equine derm cells was studied. The kinetics of invasion and replication were determined for four T. equigenitalis strains. On the basis of these experiments, a simpler assay in which the invasive as well as the replicative properti...

The flagella of Carnpylobacter jejuni play an important role in pathogenicity. Wassenaar et al. 18 and Grant et al. 3 showed that flagella are important for invasion, while Ruiz-Palacios et al. 14 showed that invasiveness is associated with inflammatory diarrhoea. Motility, rather than the presence of flagella, is the major factor involved in invas...

Currently available serological tests for cowdriosis (Cowdria ruminantium infection) in domestic ruminants are hampered by their low specificities because of cross-reactivity with Ehrlichia spp. The use of recombinant major antigenic protein (MAP1) of C. ruminantium for serodiagnosis was investigated. Overlapping fragments of the MAP1 protein were...

Clones expressing fragments of the flagellin protein of Salmonella enteritidis were constructed and screened with a g,m-specific monoclonal antibody. Results showed that the g,m epitope is localized between amino acids 258 and 348 of the flagellin. The fliC gene, encoding the flagellin of S. enteritidis, was proven to be the only flagellin gene pre...

The capacity of Campylobacter jejuni to generate genetic diversity was determined for its flagellar region. Recombination within a genome, as well as recombination after the uptake of exogenous DNA, could be demonstrated. The subunit of the flagellar filament of C. jejuni is encoded by two tandem genes, flaA and flaB, which are highly similar and t...

Flagella production in Campylobacter jejuni 81116 is subject to phase variation; the bacterium is able to switch its flagellum synthesis, and thereby its motility, on and off. Under standard laboratory growth conditions flagellar phase variants can be maintained as stable, pure cultures. We found conditions that efficiently induced a phase shift in...

A disease with the characteristics of transmissible gastroenteritis (TGE) was first reported in 1935 (Smith, 1956). The viral etiology of TGE was demonstrated 11 years later by Doyle and Hutchings (1946) in the United States. During the next 20 years TGE was reported in all other continents (Table I). Apparently, the disease occurred first in those...

Campylobacter jejuni 81116 has two genes coding for flagellin, flaA and flaB. Fully motile wild-type C. jejuni bacteria express the flaA gene, with no flaB message being detected. A nonmotile flaA flaB+ mutant, R1, produced detectable levels of flagellin B which was incorporated into truncated flagella. After R1 had invaded INT-407 cells, a variant...

We have developed an assay for the detection of pathogenic Leptospira that is based on the polymerase chain reaction. With the combination of agarose gel electrophoresis and blotting, pathogenic Leptospira can be discriminated specifically from nonpathogenic Leptospira and other bacterial species. This method, based on the amplification of 16S ribo...

The role of the Serpulina hyodysenteriae hemolysin encoded by the tlyA gene in the pathogenesis of swine dysentery (SD) was studied. tlyA mutants of two S. hyodysenteriae strains (B204 and C5) were tested for virulence in pigs. None of the animals developed SD. However, after infection with wild-type strain B204 or C5, the incidence of SD was 100 o...

The 23S rDNA sequences of Mycobacterium paratuberculosis, M. avium and M. phlei and the sequences of the spacer regions between the 16S and 23S rRNA genes were determined. The overall 23S rDNA sequence identity between M. paratuberculosis and M. avium was 99.7% (nine mismatches), showing the very close relatedness of these mycobacteria. Evolutionar...

Cowdria ruminatium, the causative agent of heartwater disease, expresses an immunodominant and conserved 32-kilodalton protein (MAP1; formerly called Cr32), which is currently in use for serodiagnosis of the disease. The gene encoding this protein, designated map1, was detected, cloned, and characterized. The gene is conserved between four differen...

A PCR for the detection of Taylorella equigenitalis, the causative agent of contagious equine metritis, was developed and evaluated. A genus-specific primer-probe set was derived from the 16S ribosomal DNA sequences. The PCR was specific and amplified a 585-bp product from all 64 available T. equigenitalis isolates. This PCR product hybridized with...

Serpulina hyodysenteriae hemolysin is though to be an important virulence factor in swine dysentery. One gene, tlyA, previously called tly, encoding a hemolysin in S. hyodysenteriae strain B204 has been characterized (Muir et al. Infect Immun 1992; 60: 529-35). Two other genes of S. hyodysenteria strain B204, designated tlyB and tlyC, encoding hemo...

Expression of CFA/I fimbriae of Escherichia coli requires the transcriptional activator CfaD. The mechanism by which CfaD activates the CFA/I promoter is to overcome the repression by H-NS, one of the histone-like proteins in E coli. This study addresses the question of which sequences in the promoter region of CFA/I interact with CfaD and H-NS. In...

Monolayers of intestine 407 (Int-407) cells were infected with the virulent Salmonella typhimurium strain C52, and the adhesion to and invasion of these cells were studied. The effects of the multiplicity of infection and growth phase of the bacteria (logarithmic versus stationary) on the interaction with eukaryotic cells were investigated. In cont...

CFA/I fimbriae on human enterotoxigenic Escherichia coli are composed of the CfaB protein, the product of the second gene of the CFA/I operon. We show here that CfaB is expressed at a higher level than other proteins of the CFA/I operon. mRNA encoding the CfaB protein is much more abundant than mRNA encoding CfaA, the first protein, together with C...

Two methods, natural transformation and electro-transformation, for the introduction of DNA into nine strains of Campylobacter jejuni were compared. Both methods were successful with a limited number of strains. Natural transformation was efficient only for the introduction of C. jejuni chromosomal DNA, while electro-transformation was also applica...

A DNA fragment from Bordetella pertussis, encoding the fim2 fimbrial subunit gene with adjacent sequences, was used as a probe for the detection of homologous sequences in chromosomal DNA of Bordetella avium. A 1.8 kb Sa1I-PstI fragment from the genome of B. avium, which hybridized with the probe, was isolated and sequenced. No fimbrial subunit gen...

An assay that is based on the amplification of 16S rRNA sequences and that was initially developed to detect Mycobacterium paratuberculosis in cattle was used to test 20 serotypes of the Mycobacterium avium complex (MAC) and atypical mycobacterial species not belonging to MAC. Only serotypes 1 to 6 and 8 to 11, designated M. avium, were detected by...

The flaB2 gene encoding a protein located in the core of the periplasmic flagella of Serpulina hyodysenteriae was cloned and sequenced. The FlaB2 protein consists of 285 amino acids and has a calculated molecular mass of 31.1 kDa. Southern blot analysis indicated that at least one, and possibly two genes related to flaB2 are present in the genome o...

The 16S ribosomal DNA sequence of Taylorella equigenitalis (formerly Haemophilus equigenitalis), the causative organism of contagious equine metritis, was determined. A phylogenetic analysis of this sequence revealed a phylogenetic position of T. equigenitalis in the beta subclass of the class Proteobacteria apart from the position of Haemophilus i...

Campylobacter jejuni strain 81116 contains two flagellin genes, flaA and flaB. Wild-type (WT) bacteria express flaA only, but flaB can be expressed under certain conditions. We have determined the importance of flagella for colonization of the avian caecum, which appears to be the natural environment for these bacteria. Mutants in which flaA or fla...

Serpulina (Treponema) hyodysenteriae, an anaerobic beta hemolytic spirochaete, is the etiologic agent of swine dysentery. Not much is known at present about the virulence factors of S. hyodysenteriae. However, the hemolysin production of this bacterium is generally accepted to be a virulence factor. To study the exact role of hemolysin production i...

The chromosomal DNA of spirochetes isolated from human, swine, dog, mouse, rat, and chicken intestine or feces was subjected to restriction enzyme analysis and hybridization with three different DNA probes, derived from a flagellin gene, a hemolysin gene, and the 16S rDNA sequence of the pathogenic swine intestinal spirochete Serpulina hyodysenteri...

Invasion, defined as adhesion to, followed by entrance into HeLa cells by Bordetella bronchiseptica was determined by (i) specific staining of intracellular bacteria and (ii) counting of viable intracellular bacteria after killing extracellular bacteria with colistin. It was demonstrated for the first time that B. bronchiseptica, like Bordetella pe...

Cowdria organisms were purified by density gradient centrifugation. The DNA was used to construct expression libraries. The immunodominant Cr32 protein was purified and its N-terminal amino acid sequence was determined. The expression libraries were screened with Cr32-specific monoclonal antibodies, but did not yield Cr32-positive clones. Therefore...

The major components of the periplasmic flagella of the spirochaete Serpulina (Treponema) hyodysenteriae strain C5 were purified and characterized. We demonstrate that the periplasmic flagella are composed of five major proteins (molecular masses 44, 37, 35, 34 and 32 kDa) and present their location, N-terminal amino acid sequence and immunological...

Salmonella typhimurium is a widely spread Gram negative bacterium that is capable of causing disease in both man and animals. The first step in the infection process is the invasion of the epithelial cells of the gut. This invasion proceeds in two phases. First bacteria adhere to the host cells, then they penetrate these cells. In spite of their re...

Les Cowdria ont été purifiées par centrifugation en gradient de densité. L'ADN a été utilisé pour la construction de banques génomiques d'expression. La protéine immunodominante Cr32 a été purifiée et la séquence N-terminale d'acides aminés déterminée. Les banques génomiques d'expression ont été criblées avec des anticorps monoclonaux spécifiques d...

Genomes of 55 Dutch porcine Serpulina (Treponema) hyodysenteriae and non-pathogenic Serpulina isolates were characterized by restriction endonuclease analysis (REA) and DNA hybridization. The Dutch porcine isolates were compared with American Type Culture Collection (ATCC) strains of S. hyodysenteriae and S. innocens and isolates of S. hyodysenteri...

An Eco RV-Cla I fragment containing the gene encoding the F9 fimbrial subunit of the human uropathogenic Escherichia coli strain C1018 and a PstI-PstI fragment containing the F12 fimbrial subunit gene of the dog uropathogenic strain 1442 have been cloned and the nucleotide sequence of the fragments determined. The structural gene of the F9 fimbriae...

A Serpulina (Treponema) hyodysenteriae expression library was constructed in vector lambda ZAP and screened with a polyclonal antiserum raised against S. hyodysenteriae periplasmic flagella. A single immunoreactive plaque was chosen for further analysis. The recombinant phage from this plaque contained a gene encoding the 44-kDa protein that is on...

The 16S ribosomal DNA sequence of Cowdria ruminantium, the causative agent of heartwater disease in ruminants, was determined. An analysis of this sequence showed that C. ruminantium forms a tight phylogenetic cluster with the canine pathogen Ehrlichia canis and the human pathogen Ehrlichia chaffeensis. Although a close relationship between the gen...

CFA/I fimbriae of enterotoxigenic Escherichia coli are expressed at 37 degrees C and not at 20 degrees C. Expression of CFA/I fimbriae requires two DNA regions (regions 1 and 2) which are separated by 40 kb on the wild type plasmid. Region 2 encodes a protein (CfaD) which activates the promoter in region 1. We investigated whether the histone-like...

Three assays for the specific detection of Mycobacterium paratuberculosis by dot spot hybridization of polymerase chain reaction products were applied to fecal samples of dairy cattle. The first two tests used polymerase chain reaction primers and a DNA probe derived from M. paratuberculosis-specific sequences of the 16S rRNA gene and insertion ele...

The role of Serpula hyodysenteriae hemolysin in the pathogenesis of swine dysentery was studied. The inactivation of a gene, tly, encoding a hemolysin, and the virulence of a tly− mutant in mice is reported. We obtained chromosomal integration of the distrupted tly gene via homologous recombination in a S. hyodysenteriae wild-type strain following...

The presence of multiple DNA elements in pathogenic members of the family Leptospiraceae, similar to the sphA sphingomyelinase gene from Leptospira borgpetersenii, was demonstrated by low-stringency hybridization experiments. These DNA elements were designated putative sphingomyelinase genes. Grouping of strains by similarity of hybridization patte...

A probe based on 16S ribosomal RNA (rRNA) sequences was developed to detect Mycobacterium paratuberculosis, the causative agent of Johne's disease in cattle. Three universal primers were used to sequence the amplified fragments of the 16S rRNA gene of various species of mycobacteria. When the nucleotide sequences were analysed, a deletion was detec...

Neutralizing monoclonal antibodies directed against five antigenic sites on the spike (S) S1 glycopolypeptide of avian infectious bronchitis virus (IBV) were used to select neutralization-resistant variants of the virus. By comparing the nucleotide sequence of such variants with the sequence of the IBV parent strain, we located five antigenic sites...

The production of the plasmid-encoded fimbrial antigen CFA/I of enterotoxigenic Escherichia coli requires two DNA regions: CFA/I region 1 and CFA/I region 2. These two regions are separated by about 40 kb on the wildtype plasmid. CFA/I region 1 contains the structural genes, whereas CFA/I region 2 contains a positive regulator. The first two genes...

A rapid and sensitive method for the detection and unambiguous typing of infectious bronchitis virus (IBV) is described. RNA was isolated from IBV-infected allantoic fluid and was transcribed into cDNA. This cDNA was amplified by the polymerase chain reaction. The polymerase chain reaction products were subsequently analyzed on an agarose gel. The...

A DNA fragment that can functionally substitute for cfaD, the positive regulatory gene involved in expression of CFA/I fimbriae, has recently been cloned from an Escherichia coli strain of serotype O167:H5 that produces CS5 fimbriae. Nucleotide sequence determination showed that the fragment contained a gene, csvR (Coli Surface Virulence factor Reg...

In a previous study, two murine T-cell hybridomas generated after immunization with infectious bronchitis virus (IBV) were shown to be responsive to the internally localized viral nucleocapsid protein. In the present study, the antigenic determinants were mapped using recombinant expression products and synthetic peptides. Both hybridomas recognize...

The role of the Campylobacter jejuni flagella in adhesion to, and penetration into, eukaryotic cells was investigated. We used homologous recombination to inactivate the two flagellin genes flaA and flaB of C. jejuni, respectively. Mutants in which flaB but not flaA is inactivated remain motile. In contrast a defective flaA gene leads to immotile b...

Hybridomas producing monoclonal antibodies (mAb) to Cowdria ruminantium were raised. Four mAbs of the IgG isotype reacted in western blots with a 32-kilodalton Cowdria protein (Cr32), which had previously been shown to be conserved and immunodominant. A fifth mAb of the IgM isotype recognized a 40-kDa Cowdria protein. The latter mAb was negative in...