A Rapid, Simple and Specific Fluorescence Polarization Assay to Diagnose Goat Brucellosis using the Brucella melitensis Native Hapten

Campo Experimental Río Bravo. Instituto Nacional de Investigaciones Forestales y Agropecuarias, Rio Bravo, Tam., México; Laboratorio de Bacteriología. Centro Nacional de Investigaciones Disciplinarias en Microbiología. Instituto Nacional de Investigaciones Forestales y Agropecuarias. México D.F., México; Universidad Autónoma de Nuevo León. Departamento de Inmunología y Virología. Facultad de Ciencias Biológicas. San Nicolás de los Garza, N. L., México; Campo Experimental General Terán. Instituto Nacional de Investigaciones Forestales y Agropecuarias, General Terán, N.L., México; Consorcio Técnico del Norte de México, Guadalupe Nuevo León, México; Campo Experimental Sur de Tamaulipas. Instituto Nacional de Investigaciones Forestales y Agropecuarias, Altamira, Tamaulipas., México

^* To whom correspondence should be addressed. Email: rgomez60{at}hotmail.com.

	Abstract

The fluorescence polarization assay (FPA) performance using the recently described Brucella melitensis NH and the B. abortus OPS tracer was evaluated and compared with The World Organization for Animal Health tests related to the indirect and competitive enzyme linked immunosorbent assays as classification variable for goat sera obtained from a high prevalence and vaccination area; test series were also evaluated to increase the final specificity of tests. Our results showed that the respective relative sensitivity and specificity were 99.7% and 32.5% for rose Bengal test with 3% of cell concentration (RBT3), 92.8% and 68.8% for rose Bengal test with 8% of cell concentration (RBT8), 98.4% and 84.9% for Canadian complement fixation test (CFT), 83.7% and 65.5% for Mexican CFT, 98.4% and 81.0% for buffered plate agglutination test (BPAT), and 78.1% and 89.3% for FPA. The use of FPA as the secondary test significantly increased the final specificities of test combinations; screening tests BPAT, RBT3 and RBT8n plus FPA resulted in 90%, 91.2% and 91.3% final specificities, respectively, whereas for the combinations RBT3+Mexican CFT, RBT8+Mexican CFT, and BPAT+Canadian CFT, specificities were 65.5%, 63.2% and 91.7%, respectively. Results suggested that FPA may be routinely applied as an adaptable screening test for diagnosis of goat brucellosis, since its cutoff can be adjusted to improve its sensitivity or specificity, is a rapid and simple test, can be a test of choice when specificity is relevant or when an alternative confirmatory test is not available, and is not affected by vaccination, thus reducing the number of wrongly slaughtered goats due to misdiagnosis.