Evaluation of the Fluorescence Polarization Assay (FPA) for diagnosis of brucella melitensis infection of goats in Argentina

AIM

Determine the optimal cut-off and the use of Fluorescence Polarization Assay (FPA) to improve the detection of brucellosis in individual goats in Argentina.

METHODS

Sera from 96 goats from a flock with abortion due to B. melitensis biovar 1 were used to assess the efficacy of the FPA to detect brucellosis in goats. FPA results were compared with those of the Buffered Antigen Plate Agglutination test (BPAT) confirmed by Seroagglutination in tube (SAT), the competitive enzyme-linked immunosorbent assay (c-ELISA) and the indirect enzyme-linked immunosorbent assay (i-ELISA). Sera from 554 goats free from brucellosis were tested with the BPAT, SAT, c-ELISA and i-ELISA to determine its Specificity. Vaccination had not been performed in the flocks evaluated.

RESULTS

The most appropriate cut-off was selected for the FPA by using MedCalc software. It was fixed at 87 mP giving a sensitivity and specificity of 98.1% (CI 89.9-99.7) and 92.8% (CI 90.4-94.7). The relative sensitivity compared with i-ELISA and c-ELISA was 97% and 92.9% respectively. The relative specificity compared with i-ELISA and c-ELISA was 97.5% and 98% respectively. The kappa measures of agreement between tests was higher than 0.75 CONCLUSION: The high correlation between FPA results and other serological methods with sera goats is indicative of the excellent performance of FPA technique in diagnosis of caprine brucellosis and we endorse it as a recommended method.

Transcriptome characterization of the dimorphic and pathogenic fungus Paracoccidioides brasiliensis by EST analysis

Paracoccidioides brasiliensis is a pathogenic fungus that undergoes a temperature-dependent cell morphology change from mycelium (22 degrees C) to yeast (36 degrees C). It is assumed that this morphological transition correlates with the infection of the human host. Our goal was to identify genes expressed in the mycelium (M) and yeast (Y) forms by EST sequencing in order to generate a partial map of the fungus transcriptome. Individual EST sequences were clustered by the CAP3 program and annotated using Blastx similarity analysis and InterPro Scan. Three different databases, GenBank nr, COG (clusters of orthologous groups) and GO (gene ontology) were used for annotation. A total of 3,938 (Y = 1,654 and M = 2,274) ESTs were sequenced and clustered into 597 contigs and 1,563 singlets, making up a total of 2,160 genes, which possibly represent one-quarter of the complete gene repertoire in P. brasiliensis. From this total, 1,040 were successfully annotated and 894 could be classified in 18 functional COG categories as follows: cellular metabolism (44%); information storage and processing (25%); cellular processes-cell division, posttranslational modifications, among others (19%); and genes of unknown functions (12%). Computer analysis enabled us to identify some genes potentially involved in the dimorphic transition and drug resistance. Furthermore, computer subtraction analysis revealed several genes possibly expressed in stage-specific forms of P. brasiliensis. Further analysis of these genes may provide new insights into the pathology and differentiation of P. brasiliensis.