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Biomedical subjects

A P van Dam

Publications and source records attributed to A P van Dam.

At least 19 recordsLinked to original sources
PubMed2006

Evaluation of an internally controlled real-time PCR targeting the ospA gene for detection of Borrelia burgdorferi sensu lato DNA in cerebrospinal fluid.

This study reports the development and evaluation of an internally controlled real-time PCR targeting the ospA gene for detection of Borrelia burgdorferi sensu stricto, Borrelia garinii, Borrelia afzelii and Borrelia valaisiana. DNA was extracted using QIAamp DNA Blood Mini kit columns. DNA from 33 B. burgdorferi sensu lato strains reacted in the assay, whereas no reactivity was observed with DNA from four relapsing fever Borrelia spp., 11 unrelated spirochaetes, and 31 unrelated microorganisms. The quantitative sensitivity of the assay was 1-10 fg of Borrelia DNA and one to five cultured Borrelia spirochaetes. Cerebrospinal fluid (CSF) specimens from 70 patients sent for routine testing for neuroborreliosis, and three CSF specimens containing B. garinii were also tested. Positive PCR results were obtained with all three culture-confirmed neuroborreliosis specimens, five of ten neuroborreliosis specimens with specific antibodies in CSF and pleocytosis, none of nine specimens from possible cases of early neuroborreliosis (antibodies in serum, CSF pleocytosis, no antibodies in CSF), one of 15 specimens from patients with active or past Lyme disease with neurological signs (antibodies in serum, no pleocytosis or antibodies in CSF), and none of 36 specimens from patients without Lyme borreliosis (no antibodies in serum or CSF). Overall, the real-time PCR assay enabled sensitive and specific detection of all B. burgdorferi sensu lato species tested. The PCR had a sensitivity of 50% in patients with neuroborreliosis. The main diagnostic role of the assay could be to confirm neuroborreliosis in patients for whom the diagnosis is doubtful.

Adolescent↗
PubMed2006

Specific and sensitive diagnosis of syphilis using a real-time PCR for Treponema pallidum.

A real-time PCR assay with a Taqman probe was developed that targeted the polA gene of Treponema pallidum. The test was validated using an analytical panel (n = 140) and a clinical panel of genital samples (n = 112) from patients attending a sexually transmitted infections clinic. High sensitivities and specificities of 94-100% were achieved using two real-time PCR platforms, the Rotor-Gene and the iCycler. The assay can be completed within 2 h, enabling reporting in <8 h. This fast and robust assay is suitable for implementation in routine laboratories for diagnosing primary syphilis.

DNA Polymerase III↗
PubMed2005

Differential diagnosis of stroke in a setting of high HIV prevalence in Blantyre, Malawi.

BACKGROUND AND PURPOSE: The differential diagnosis of stroke in Africa in areas with high HIV prevalence includes brain infections. We studied causes of stroke in Blantyre, Malawi, where HIV prevalence among medical inpatients is 70%. METHODS: In a descriptive study of 8-month duration, all patients presenting at Queen Elizabeth Central Hospital, Blantyre, with central neurological deficit of acute onset (<24 hours) had baseline investigations, including full blood count, blood glucose, serology for toxoplasmosis, syphilis, and HIV, ECG, echocardiogram, ultrasound of the carotid arteries, and computerized tomography scan of the brain. A lumbar puncture was performed unless contraindicated. RESULTS: Ninety-eight consecutive patients (49 males) were studied. In those who were HIV positive (48%), the mean age was 37.5 years; ischemic stroke was the commonest diagnosis (n=25; 58%), followed by infection (n=11; 23%; including tuberculous [n=4] and cryptococcal [n=2] meningitis; toxoplasmic encephalitis [n=1]; neurocysticercosis [n=1]; brain abscess [n=1]; and progressive multifocal leucoencephalopathy [n=2]). No clinical or laboratory parameters could be identified as predictors for infection, but 3 of 5 patients with fever on admission had tuberculous meningitis. In HIV-negative patients (mean age 58.6 years), 55% had ischemic stroke and 31% had intracerebral hemorrhage; no brain infection was diagnosed. Presence of vascular disease correlated with age but not with HIV status. CONCLUSIONS: Ischemic stroke was found in half of patients irrespective of HIV status. In those who are HIV positive, brain infection should be considered for which the presence of fever and examination of cerebrospinal fluid seem most useful in diagnosis.

Adolescent↗
PubMed2005

Pneumonia involving Aspergillus and Rhizopus spp. after a near-drowning incident with subsequent Nocardia cyriacigeorgici and N. farcinica coinfection as a late complication.

Reported here is the case of a 22-year-old man who developed pneumonia with unusual pathogens after a near-drowning incident. On day 7 following admission, Rhizopus spp. and Aspergillus fumigatus were cultured from the patient's bronchoalveolar lavage fluid. One week later, sputum cultures revealed N. cyriacigeorgici as well as N. farcinica. The patient recovered fully after prolonged therapy with liposomal amphotericin B, amikacin, meropenem and cotrimoxazole.

Adult↗
PubMed2004

[Sharp increase in the number of syphilis cases in The Netherlands: early recognition and treatment is of great importance].

Syphilis was diagnosed in three men having sex with men, aged 36, 38 and 58 years, who had a variety of skin lesions and other symptoms. In a woman aged 38 years and her 39-year-old husband, syphilis was found during routine pregnancy screening. All patients were successfully treated with intramuscular (benzathin) benzylpenicillin. Early recognition and treatment as well as advice on avoiding high-risk sexual behaviour are important in preventing further spread of the disease. Although generally the risk of HIV transmission during unprotected oral sexual contact is believed to be low, the transmission of Treponema pallidum during this type of contact is possible and is probably the most important transmission route amongst men having sex with men.

Adult↗
PubMed2003

[A case of diphtheria in the Netherlands due to an infection with Corynebacterium ulcerans].

A 58-year-old woman was admitted due to a pseudomembranous pharyngitis. The patient had not been vaccinated against diphtheria. Corynebacterium ulcerans was cultured from a throat swab. The production of diphtheria toxin by these bacteria was demonstrated with PCR and an immunoprecipitation test. The patient was cared for in respiratory isolation and was treated with benzylpenicillin. She quickly recovered and was discharged four days after admission. A contact investigation did not reveal any dissemination of the toxin-producing C. ulcerans and a source was not found. In spite of the large-scale vaccination against diphtheria which has taken place in the Netherlands since 1953, a physician has to consider diphtheria in the differential diagnosis of patients who present with a clinical syndrome compatible with this disease. Either Corynebacterium diphtheriae or C. ulcerans could be the pathogen responsible.

Corynebacterium↗
PubMed2001

Analysis of a VMP-like sequence (vls) locus in Borrelia garinii and Vls homologues among four Borrelia burgdorferi sensu lato species.

The VMP-like sequence (vls) locus that consists of one expressed vlsE gene and 15 silent vls cassettes has been described in Borrelia burgdorferi sensu stricto B31. In the present study, the vls locus from a Borrelia garinii isolate A87SA was analyzed. DNA fragments that contained three complete and five partial vls cassettes were cloned and sequenced. Pulsed-field gel electrophoresis (PFGE) analysis and Southern hybridization of the PFGE blot indicated that the vls locus of B. garinii A87SA, consisting of at least eight vls cassettes, was located on a 21-kb linear plasmid. The size of the three complete vls cassettes varied from 573 to 612 bp. They had 93.8-94.3% identity at the nucleotide level and 84.9-87.3% amino acid identity. The amino acid sequences of the three vls cassettes of B. garinii A87SA exhibited 45.9-50.8% identity to the VlsE sequence of B. burgdorferi B31, and 30.0-33.8% identity to the VMP17 sequence of B. hermsii HS1. Homologues of the vls locus of B. garinii were detected by dot blot hybridization among 24 of the 30 (80.0%) isolates representing four B. burgdorferi sensu lato species distributed widely in Europe. Our findings indicate that B. garinii might possess a similar vls structure to that described in B. burgdorferi sensu stricto. The highly conserved nature of the vls locus among various B. burgdorferi sensu lato species suggests that it may be important in the physiology and pathogenesis of Lyme disease spirochetes.

Amino Acid Sequence↗
PubMed2001

Nosocomial outbreak of Clostridium difficile-associated diarrhoea due to a clindamycin-resistant enterotoxin A-negative strain.

A clindamycin-resistant toxin A-negative, toxin B-positive Clostridium difficile strain caused an outbreak among 24 hospitalized patients at the Department of Surgery, the Intensive Care unit, and the Department of Internal Medicine of an 800-bed academic hospital. Nineteen patients had undergone a surgical intervention and all 24 patients received at least one dose of antibiotics prior to the development of Clostridium difficile-associated diarrhoea. Twenty-seven episodes of Clostridium difficile-associated diarrhoea in 24 patients were categorized as mild (n=19), severe (n=7), or fatal (n=1). Relapses occurred in three patients. Nineteen of the 27 episodes required anti-Clostridium difficile treatment. Molecular typing performed by arbitrary primer polymerase chain reaction (PCR) and PCR amplification of rRNA intergenic spacer regions revealed that the outbreak strains recovered from culture were identical. The outbreak strain belonged to serogroup F and was resistant to erythromycin, clindamycin, and tetracycline, whereas susceptibility to chloramphenicol varied. No phenotypic activity of enterotoxin A was detected. A deletion of approximately 1.7 kb was found in the toxin A gene. Cytotoxin B had an unusual effect on cell culture assays that, at first, was not recognized as Clostridium difficile specific but could be neutralized with anti-Clostridium difficile B cytotoxin.

Adult↗
PubMed2001

Diagnostic and biological significance of anti-p41 IgM antibodies against Borrelia burgdorferi.

We performed a prospective study to investigate the biological significance and diagnostic specificity of anti-p41 immunoglobulin (Ig)M antibodies against Borrelia burgdorferi. During a 1-year interval 2403 patients were referred to our department for B. burgdorferi serology. Sixty-three patients had repetitive positive tests for IgM anti-p41 antibodies and negative tests for anti-p41 IgG antibodies. Ten of the 63 patients recently had symptoms of erythema migrans. A confirmatory IgM Western blot gave a positive reaction in 5 patients out of 53 patients with little or no clinical evidence of B. burgdorferi infection. The remaining 48 patients were negative in this test and were considered as false-positives. Two whole cell enzyme-linked immunosorbent assay (ELISAs), two immunofluorescence assays and Western blotting were not useful as confirmatory tests. Sera from 330 blood donors and 72 cord sera were also screened for anti-p41 IgM. Five blood donor sera and five cord sera showed an IgM reactivity against p41. Based on our data we hypothesize that up to 1.5% of the population may have natural IgM antibodies against p41 in their sera. We observed that six out of nine sera with such antibodies could immobilize a B. afzelii reference strain in vitro. Whether anti-p41 IgM antibodies are capable of inactivating infective spirochetes and thereby prevent infection in vivo is, however, not yet clarified. The paradoxical conclusion that anti-p41 IgM antibodies may be a sign of resistance to infection rather than a sign of infection should be given consideration.

Adolescent↗
PubMed2001

Recent advances in the diagnosis of Lyme disease.

Diagnosis of human Lyme borreliosis is usually based on serology, which has a number of pitfalls. In the early phase of the disease serology can still be negative, whereas false-positive results are also common. The interpretation of confirmatory Western blot tests is not always easy. Furthermore, routine serology cannot discriminate between active and past infection. In addition, recombinant antigens are being introduced to improve serologic tests. New developments in the diagnosis of Lyme disease are the development of PCR tests. This review gives an overview of the molecular diagnostic possibilities of Lyme borreliosis, mainly by PCR, and describes some interesting possibilities for future serology.

Animals↗
PubMed2000

Two distinct ospA genes among Borrelia valaisiana strains.

Borrelia valaisiana is a recently described bacterial species in the Borrelia burgdorferi sensu lato complex. To further characterize this bacterium, the plasmid-encoded ospA genes from eight B. valaisiana isolates were amplified by PCR, cloned and sequenced. All B. valaisiana isolates studied possessed an ospA gene with a size of 822-825 bp. The identity of the predicted amino acid sequences of the OspA proteins among B. valaisiana isolates was 69.1-100%, and ranged from 68.2 to 79.1% between B. valaisiana and other B. burgdorferi sensu lato species. Based on the OspA protein sequences, the eight B. valaisiana isolates could be distinguished into two subgroups. Subgroup I contained six B. valaisiana isolates of which OspA sequences were almost identical, but clearly differed from other LB spirochetes. Subgroup II consisted of two isolates with identical OspA sequences which were only 70% identical to subgroup I B. valaisiana isolates and similarly distant from the OspA sequences of other B. burgdorferi sensu lato genospecies. Phylogenetic analysis indicates that B. valaisiana isolates belonging to subgroups I and II possibly evolved from two distinct ancestors. Our data showed for the first time a major difference in OspA proteins within a well-defined B. burgdorferi sensu lato species at the evolutionary level, suggesting that it is not always reliable to assign Borrelia isolates to a definite species solely based on data from ospA gene sequence analysis.

Amino Acid Sequence↗
PubMed2000

Antibodies against specific proteins of and immobilizing activity against three strains of Borrelia burgdorferi sensu lato can be found in symptomatic but not in infected asymptomatic dogs.

In an area where Lyme disease is endemic in The Netherlands all dogs had positive titers by whole-cell enzyme-linked immunosorbent assay and appeared to be naturally infected by Borrelia burgdorferi sensu lato. To compare the antibody responses of symptomatic dogs and asymptomatic controls, we performed Western blots and in vitro immobilization assays to study antibody-dependent bactericidal activity. Strains from three different genospecies were employed as the antigen source: B. burgdorferi strain B31, Borrelia garinii strain A87S, and Borrelia afzelii strain pKo. Antibodies against flagellin (p41) and p39 for three strains were found in sera from both symptomatic and asymptomatic dogs and were therefore considered to be markers of exposure. Antibodies against p56 and p30 of strain B31, against p75, p58, p50, OspC, and p<19 of strain A87S, and against p56, p54, p45, OspB, p31, p26, and p<19 of strain pKo were found significantly more frequently in sera from symptomatic dogs younger than 8 years when the first symptoms were observed than in those from age-matched controls (P<0.01). These antibodies were not found in preclinical sera and appeared during development of disease. Antibodies against OspA of strains B31 and A87S were only seen in acute-phase and convalescent sera from three dogs that recovered from disease. Incubation with 25% normal canine serum did not result in the immobilization of strains B31 and pKo, but partial immobilization of strain A87S (61%+/-24% [standard deviation] at 5 h) occurred. Seven of 15 sera from symptomatic dogs but none of the sera from 11 asymptomatic dogs had antibody-dependent immobilizing activity against one of the strains. Consecutive sera from one of these dogs immobilized two different strains. Antibody-mediated bactericidal serum was not seen before onset of disease, was strongest in the acute phase of disease, and fluctuated during chronic disease. From seven out of eight symptomatic dogs Borrelia DNA was amplified by PCR; in three of them the bactericidal activity was directed against one of the genospecies amplified from that dog; however, four PCR-positive dogs lacked bactericidal activity. In conclusion, dogs with symptomatic canine borreliosis have more-extensive antibody reactivity against Borrelia, as shown by both Western blotting and immobilization assays.

Animals↗
PubMed1999

Evidence for frequent OspC gene transfer between Borrelia valaisiana sp. nov. and other Lyme disease spirochetes.

Molecular polymorphism of the ospC gene has been reported in Borrelia burgdorferi sensu stricto, Borrelia garinii and Borrelia afzelii, the spirochetes causing human Lyme borreliosis. To assess the genetic relationship between ospC genes from the recently described Borrelia valaisiana sp. nov. and other B. burgdorferi sensu lato species, the ospC genes from eight B. valaisiana isolates were amplified by PCR, cloned and sequenced. The ospC genes of three B. valaisiana isolates were identical, but clearly distinct from ospC genes from other Borrelia species. Four B. valaisiana isolates possessed ospC genes more related to those of B. garinii, and fell into a cluster representing B. garinii species in the phylogenetic tree. One isolate had an ospC gene encoding a protein identical to that of B. afzelii strain. Since five of the eight (62.5%) B. valaisiana isolates contained a gene highly homologous or even identical to ospC genes found among B. garinii and B. afzelii strains, our findings indicate that ospC gene transfer occurs between B. valaisiana and other Lyme disease spirochetes.

Amino Acid Sequence↗
PubMed1999

Molecular typing of Borrelia burgdorferi sensu lato: taxonomic, epidemiological, and clinical implications.

Borrelia burgdorferi sensu lato, the spirochete that causes human Lyme borreliosis (LB), is a genetically and phenotypically divergent species. In the past several years, various molecular approaches have been developed and used to determine the phenotypic and genetic heterogeneity within the LB-related spirochetes and their potential association with distinct clinical syndromes. These methods include serotyping, multilocus enzyme electrophoresis, DNA-DNA reassociation analysis, rRNA gene restriction analysis (ribotyping), pulsed-field gel electrophoresis, plasmid fingerprinting, randomly amplified polymorphic DNA fingerprinting analysis, species-specific PCR and PCR-based restriction fragment length polymorphism (RFLP) analysis, and sequence analysis of 16S rRNA and other conserved genes. On the basis of DNA-DNA reassociation analysis, 10 different Borrelia species have been described within the B. burgdorferi sensu lato complex: B. burgdorferi sensu stricto, Borrelia garinii, Borrelia afzelii, Borrelia japonica, Borrelia andersonii, Borrelia valaisiana, Borrelia lusitaniae, Borrelia tanukii, Borrelia turdi, and Borrelia bissettii sp. nov. To date, only B. burgdorferi sensu stricto, B. garinii, and B. afzelii are well known to be responsible for causing human disease. Different Borrelia species have been associated with distinct clinical manifestations of LB. In addition, Borrelia species are differentially distributed worldwide and may be maintained through different transmission cycles in nature. In this paper, the molecular methods used for typing of B. burgdorferi sensu lato are reviewed. The current taxonomic status of B. burgdorferi sensu lato and its epidemiological and clinical implications, especiallly correlation between the variable clinical presentations and the infecting Borrelia species, are discussed in detail.

Bacterial Typing Techniques↗
PubMed1999

Tick-borne relapsing fever imported from West Africa: diagnosis by quantitative buffy coat analysis and in vitro culture of Borrelia crocidurae.

West African tick-borne relapsing fever (TBRF) is difficult to diagnose due to the low number of spirochetes in the bloodstream of patients. Previously, the causative microorganism, Borrelia crocidurae, had never been cultured in vitro. TBRF was rapidly diagnosed for two patients returning from western Africa with fever of unknown origin by quantitative buffy coat (QBC) analysis. Diagnosis was confirmed by intraperitoneal inoculation of blood specimens from patients into laboratory mice. In vitro experiments showed that QBC analysis may be as much as 100-fold more sensitive than thick smear. Spirochetes were also cultured from blood samples from both patients in modified Kelly's medium and were identified as B. crocidurae by partial sequencing of the PCR-amplified rrs gene.

Acridine Orange↗
PubMed1999

Phenotypic and genetic characterization of a novel Borrelia burgdorferi sensu lato isolate from a patient with lyme borreliosis.

Borrelia burgdorferi sensu lato A14S was cultured from a skin biopsy specimen of a patient with erythema migrans in The Netherlands. This isolate had a unique DNA fingerprint pattern compared to 135 other B. burgdorferi sensu lato isolates. In this study, the isolate A14S was further characterized by protein analysis with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and reactivity with various monoclonal antibodies. In addition, the 16S rRNA, ospA, and ospC genes, as well as the 5S-23S rRNA intergenic spacer DNA, were amplified by PCR, cloned, and sequenced. SDS-PAGE protein profiles and phylogenetic analysis based on all of the analyzed genes confirmed that B. burgdorferi sensu lato A14S was phenotypically and genetically different from the three human pathogenic species B. burgdorferi sensu stricto, Borrelia garinii, and Borrelia afzelii, as well as from other B. burgdorferi sensu lato species. Our findings indicate that Borrelia genomic groups or isolates other than the three well-known human pathogenic species may also cause human Lyme borreliosis.

Antigens, Bacterial↗
PubMed1998

Improved envelope function selected by long-term cultivation of a translation-impaired HIV-1 mutant.

The untranslated leader region of the human immunodeficiency virus (HIV) RNA genome contains multiple regulatory elements that fold into stable hairpin structures. Because extensive secondary structure can block the scanning of ribosomes, an alternative mechanism for HIV translation seems feasible. To study the mechanism of HIV-1 mRNA translation, a start codon was introduced in the leader region that will usurp scanning ribosomes. This upstream AUG mutation (uAUG) inhibited HIV gene expression, indicating that HIV-1 mRNA translation occurs via the regular scanning mechanism. Revertant viruses with increased replication capacity were obtained upon prolonged culturing of the mutant virus. To our surprise, the introduced start codon had not been inactivated in these phenotypic revertants. Instead, these revertants contain additional mutations in the envelope (Env) protein that stimulated HIV-1 replication. These second-site Env mutations did not specifically overcome the gene expression defect of the uAUG mutant, as the replication capacity of other HIV-1 mutants with an unrelated defect could also be improved. The uAUG construct appears to be a unique tool in forced HIV-1 adaptation studies because the deleterious uAUG mutation is stably maintained in the progeny, yielding phenotypic revertants with second-site mutations elsewhere in the viral genome.

Base Sequence↗