Establishment of the denaturing high-performance liquid chromatography combined with multiplex nucleic acid amplification method for rapid identification of four important pathogenic mycobacteria / 中国人兽共患病学报

A new molecular method for simultaneously rapid detection and differentiation of Mycobacterium tuberculosis, Mycobacterium bovis, Mycobacterium avium and Mycobacterium paratuberculosis was established by using denaturing high-performance liquid chromatography (DHPLC) combined with multiplex nucleic acid amplification. These 4 important pathogenic mycobacteria were identified by separation of 4 specific PCR-amplified target fragments by DHPLC analysis. A total of 51 Mycobacterium strains and 22 other bacterial species were tested to confirm the specificity of the multiplex PCR-DHPLC assay. The sensitivity of the assay was as low as 10~2-10~3 gene copies. This method rapidly identify the positive clinical samples from human and bovine with higher detection ratio than traditional culture method and was able to identify simultaneously four pathogenic Mycobacterium, which provided a new molecular tool for rapid detection of tuberculosis and paratuberculosis in human and animals.

Tactics of Mycobacterium avium subsp. paratuberculosis for intracellular survival in mononuclear phagocytes

Johne's disease is a condition that refers to chronic granulomatous enteritis in ruminants. It is believed that survival and replication of Mycobacterium (M.) paratuberculosis in mononuclear phagocytes plays an important role in the pathogenesis of Johne's disease. However, it is not clear how M. paratuberculosis survives for long time periods in mononuclear phagocytes, nor is it clear which factors trigger multiplication of these bacilli and result in the development of Johne's disease. Investigating the intracellular fate of M. paratuberculosis is challenging because of its very slow growth (more than two months to form visible colonies on media). Existing animal models also have limitations. Despite those obstacles, there has been progress in understanding the intracellular survival tactics of M. paratuberculosis and the host response against them. In this review, we compare known aspects of the intracellular survival tactics of M. paratuberculosis with those of other mycobacterial species, and consider possible mycobactericidal mechanisms of mononuclear phagocytes.

Analysis of the seroprevalence of bovine paratuberculosis and the application of modified absorbed ELISA to field sample testing in Korea

Paratuberculosis (PTB) is a major disease problem worldwide, and causes major economic losses in the dairy industry. Although PTB has been reported in Korea, no studies have been conducted to determine its prevalence and no program has been developed to control the disease. In this study, the sera of beef (n = 1,056) and dairy cattle (n = 1,105) from all provinces in Korea were tested to determine the prevalence of PTB using two different ELISA: an 'in house' modified absorbed ELISA (P-ELISA) based on sonicated antigen from Mycobacterium avium subsp. paratuberculosis ATCC 19698, and a commercial ELISA (C-ELISA). Receiver operating characteristic analysis was used to determine the cutoff point for P-ELISA. Based on C-ELISA results, the area under the curve for P-ELISA was 0.913 (95% CI, 0.883 to 0.943). Using a cutoff point of 0.100, P-ELISA showed a sensitivity of 62.0% and a specificity of 93.7%. The kappa value and the percent agreement between the two ELISAs were 0.322 and 92.5%, respectively. Both ELISAs showed a significant correlation between age and seropositivity (p < 0.01). According to C-ELISA, 71 of 2,161 sera (3.3%, 95 CI, 2.6% to 4.1%) were test-positive. The national true prevalence of PTB was estimated to be 7.1%. The findings suggest that a control program should be implemented to limit the spread of this disease, and that P-ELISA could be used as a screening test that produces results similar to C-ELISA.

Estimation of Paratuberculosis Prevalence in Dairy Cattle in a Province of Korea using an Enzyme-linked Immunosorbent Assay: Application of Bayesian Approach

To draw inferences about the sensitivity and specificity of the newly developed ELISA test for bovine paratuberculosis (PTB) diagnosis and posterior distribution on the prevalence of PTB in a province of Korea, we applied Bayesian approach with Gibbs sampler to the data extracted from the prevalence study in 1999. The data were from a single test results without a designated gold test. The prevalence estimates for PTB in study population ranged 3.2~5.3% for conservative and 6.7~7.1% for liberal, depending on the priors used. The simulated specificities of the ELISA close to one another, ranging 84.7~90.6%, whereas the sensitivity was somewhat spread out depending largely on the priors with a range of 46.4~88.2%. Our findings indicate that the ELISA method appeared useful as a screening tool at a minimum level in comparison to other diagnostic tests available for this disease in terms of sensitivity. However, this advantage comes at a cost of having low specificity of the test.