Development of early diagnostic methodologies of Burkholderia pseudomallei infection in cetaceans

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Development of early diagnostic methodologies of Burkholderia pseudomallei infection in cetaceans

 

Author: Cheung, Kam-yan
Title: Development of early diagnostic methodologies of Burkholderia pseudomallei infection in cetaceans
Degree: M.Sc.
Year: 2011
Subject: Dolphins -- Infections.
Melioidosis -- Diagnosis.
Cetacea -- Diseases -- Treatment.
Marine mammals -- Diseases -- Treatment.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Health Technology and Informatics
Pages: xii, 115 p. : ill. (chiefly col.) ; 30 cm.
InnoPac Record: http://library.polyu.edu.hk/record=b2457876
URI: http://theses.lib.polyu.edu.hk/handle/200/6235
Abstract: Introduction: Fatal infections by Burkholderia pseudomallei (B. Pseudomallei) infection in marine mammals have been reported since 1976, when a group of dolphins died at an oceanarium in Hong Kong (Ocean Park Corporation, OPC). The bacterial infection causes a disease called melioidosis and has been associated with a relatively high causality in the overall mortality over 30 years. Marine mammals and cetaceans in particular, appear to be highly susceptible to infection and disease with B. pseudomallei. Cultivation and biochemical identification of the organism takes time, at least 4-5 days, and often yields a negative culture from non-sterile and blood specimens. Therefore, a supported diagnostic method of antibody capture enzyme-linked immunosorbent assay (ELISA) was developed. However, the average time for a positive finding was 16 days post clinical presentation in cetaceans. Aim: This study was conducted with the aim of developing and evaluating indirect ELISA (IgM) for serological diagnosis in cetaceans kept at OPC as well as other facilities in endemic area. In addition, we explored characterization of cytokines networks in immunopathogical status as a possible sub-diagnostic method for melioidosis. Methods: A total of 209 retrospective sera samples from 26 dolphins (Tursiops aduncas) were tested by direct ELISA for IgM and flow cytometry beads multiplex base technology for 11 cytokines measurement. In the indirect ELISA, the goat anti-human IgM antibody conjugate was used instead of species-specific anti-antibody (because not available); and anti-human cytokine antibodies were chosen for the measurement of cytokines in the study. Results: The antigen-specific IgM ELISA developed achieved a sensitivity and specificity of 100% at ≤7days after clinical presentation from non-vaccinated animals. Moreover, from the vaccinated animals at 8-14 days after clinical signs, the test achieved 100% and 75% sensitivity and specificity respectively. A comparison with IgG determinations, the IgM-ELISA obtained 100% sensitivity and specificity in 15-21 days after clinical presentation on non-vaccinated animals. In the cytokines measurements, statistically significant differences were found for seven cytokines (IL-12p70, IL-2, IL-10, IL-8, IL6, IL-1β, and TNF-α) in animals with melioidosis as compared to normal/healthy animals. In addition, a comparison with non-melioidosis grouped samples from ill animals. We found a cytokine IL-6 was significant up-regulated statistically. Conclusion: In the present study, an early diagnostic method has been developed. The indirect ELISA for IgM measurement is useful for a presumptive diagnosis in suspected cases of melioidosis to help guide veterinarians in medical management of these cases. Moreover, thanks to their high sensitivity and specificity, the IgM ELISA is useful for ruling out their infections. In addition, the quantitative measurement of a number of cytokine may prove useful for sub-diagnostic tool. Among the eleven cytokine measurements, at least two cytokine were found in melioidosis differed from the profile of other infections. And one cytokine was markedly high compared with healthy and other infection cases. The pattern of these cytokines determination could prove useful to assists in diagnosing melioidosis.

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