Biomedical subjects

Sascha Al Dahouk

Publications and source records attributed to Sascha Al Dahouk.

22 records · Page 2Linked to original sources

PubMed2003

Rapid detection of Yersinia pestis with multiplex real-time PCR assays using fluorescent hybridisation probes.

The objective of the present study was to establish a system of real-time polymerase chain reactions (PCRs) for the specific detection of Yersinia pestis using the LightCycler (LC) instrument. Twenty-five strains of Y. pestis, 94 strains of other Yersinia species and 33 clinically relevant bacteria were investigated. Assays for the 16S rRNA gene target and the plasminogen activator gene (resides on the 9.5-kb plasmid) and for the Y. pestis murine toxin gene and the fraction 1 antigen gene (both on the 100-kb plasmid) were combined for the use in two multiplex assays including an internal amplification control detecting bacteriophage lambda-DNA. Applying these multiplex assays, Y. pestis was selectively identified; other bacteria yielded no amplification products. The lower limit of detection was approximately 0.1 genome equivalent. Rat or flea DNA had no inhibitory effects on the detection of Y. pestis. The results obtained using the multiplex real-time assays showed 100% accuracy when compared with combinations of conventional PCR assays. We developed and evaluated a highly specific real-time PCR strategy for the detection of Y. pestis, obtaining results within 3 h including DNA preparation.

Animals↗

PubMed2003

Laboratory-based diagnosis of brucellosis--a review of the literature. Part I: Techniques for direct detection and identification of Brucella spp.

Brucellosis is a world-wide re-emerging zoonosis and the most frequent laboratory-acquired bacterial infection, causing severe disease in humans with unspecific clinical signs affecting numerous organs. Contact with infected animals, ingestion of contaminated animal products and handling of Brucella isolates in laboratories are risk factors. Various other febrile illnesses, e.g. malaria, tuberculosis, typhoid fever and tularemia may present with the same symptoms. Therefore, clinical diagnosis is difficult to establish but effective therapy requires an early diagnosis. Vaccines for humans are still not commercially available. Blood culturing of Brucella is time-consuming and not reliable. Thus diagnosis is usually based on indirect serological tests, i.e. serum agglutination test, complement fixation or the Coombs test. However, these 'conventional' serological tests lack sensitivity and specificity. Hence, a combination of various tests is mandatory for a definite diagnosis. Enzyme-linked immunosorbent assays can be used for screening and confirmation of brucellosis in one step. Molecular techniques like the polymerase chain reaction and restriction fragment length polymorphism are needed to differentiate species and strains within the genus Brucella. This review will summarize advantages and disadvantages of the techniques used in clinical laboratories for direct detection and identification of Brucella spp.

Animals↗

PubMed2003

Laboratory-based diagnosis of brucellosis--a review of the literature. Part II: serological tests for brucellosis.

Brucellosis is a common zoonotic disease transmittable to humans from infected animal reservoirs. Malta, Rock, Gibraltar, Cyprus or Mediterranean fever, Bang's disease, intermittent typhoid or typho-malarial fever, undulant fever, etc. are just various synonyms for brucellosis. Patients suffering from this disease show unspecific symptoms, e.g. fever, chills, malaise, arthralgia, headache, tiredness and weakness. Human brucellosis may be caused by four of totally six genetically and phenotypically closely related Brucella species, i.e. B. melitensis, B. abortus, B. suis and B. canis. Although many organ systems may be involved, brucellosis is rarely fatal. Therapeutic failure and relapses, chronic courses and severe complications like bone and joint involvement, neurobrucellosis and endocarditis are characteristic for the disease. A definite diagnosis requires the isolation of Brucellae from blood, bone marrow or other tissues. However, cultural examinations are time-consuming, hazardous and not sensitive. Thus, clinicians often rely on the indirect proof of infection. The detection of high or rising titers of specific antibodies in the serum allows a tentative diagnosis. A variety of serological tests has been applied, but at least two serological tests have to be combined to avoid false negative results. Usually, the serum agglutination test is used for a first screening and complement fixation or Coombs' test will confirm its results. As Brucella ELISAs are more sensitive and specific than other serological tests, they may replace them step by step. This review will summarize advantages and disadvantages of the serological techniques used in clinical laboratories for indirect verification of human brucellosis.

Agglutination Tests↗

PubMed2002

Induction of autoimmune diabetes through insulin (but not GAD65) DNA vaccination in nonobese diabetic and in RIP-B7.1 mice.

Insulin has been used to modify T-cell autoimmunity in experimental models of type 1 diabetes. In a large clinical trial, the effect of insulin to prevent type 1 diabetes is currently investigated. We here show that insulin can adversely trigger autoimmune diabetes in two mouse models of type 1 diabetes, using intramuscular DNA vaccination for antigen administration. In female nonobese diabetic (NOD) mice, diabetes development was enhanced after preproinsulin (ppIns) DNA treatment, and natural diabetes resistance in male NOD mice was diminished by ppIns DNA vaccination. In contrast, GAD65 DNA conferred partial diabetes protection, and empty DNA plasmid was without effect. In RIP-B7.1 C57BL/6 mice (expressing the T-cell costimulatory molecule B7.1 in pancreatic beta-cells), autoimmune diabetes occurred in 70% of animals after ppIns vaccination, whereas diabetes did not develop spontaneously in RIP-B7.1 mice or after GAD65 or control DNA treatment. Diabetes was characterized by diffuse CD4(+)CD8(+) T-cell infiltration of pancreatic islets and severe insulin deficiency, and ppIns, proinsulin, and insulin DNA were equally effective for disease induction. Our work provides a new model of experimental autoimmune diabetes suitable to study mechanisms and outcomes of insulin-specific T-cell reactivity. In antigen-based prevention of type 1 diabetes, diabetes acceleration should be considered as a potential adverse result.

Aging↗