Evaluation of direct immunofluorescence test for campylobacter fetus in Bulls experimentally infected and comensal bacteria from the reproductive tract of bulls

Abstract

Campylobacter fetus is a Gram negative bacterium, with 2 relevant subspecies for cattle health: C. fetus subsp. fetus (Cff) and C. fetus subsp. venerealis (Cfv) which cause important reproductive losses. In the present work, four groups of bulls were used: one group to characterize the genital microbiota (G1; n=3) and the other three to evaluate the direct immunofluorescence (DIF) test for the diagnosis of bovine campylobacteriosis in preputial samples (PS) from experimentally infected bulls with Cff (G2; n=3) and Cfv (G3; n=3), and controls (G4; n=4). Seven bacterial strains of different genera were identified in the PS from G1. Other 11 laboratory bacterial strains were included: Cff, Cfv and Cfv biovar Intermedius, 3 Campylobacter non-fetus, 3 Gram negative and 2 Gram positive. Only the C. fetus strains presented positive immunostaining. The sensitivity and specificity of the DIF test were 79 % and 100 %, respectively. Concordance between DIF test and bacteriological culture was 83 % (Kappa index: 0.65). The present study shows the high specificity of the DIF test for detection of C. fetus using a fluorescent conjugate elaborated in Argentina, and highlights the relevance of no cross reaction against 15 bacterial strains normally present in bull preputial microbiota.

Campylobacter fetus es una bacteria Gram negativa que incluye 2 subespecies de relevancia sanitaria para el bovino: C. fetus subsp. fetus (Cff) y C. fetus subsp. venerealis (Cfv), causantes de importantes pérdidas reproductivas. En el presente estudio, se utilizaron cuatro grupos de toros: un grupo (G1) para caracterizar la microbiota genital, y otros tres (G2, G3, G4) (n=10) para evaluar el test de inmunofluorescencia directa (IFD) para el diagnóstico de la campilobacteriosis bovina en esmegma prepucial (EP) de toros experimentalmente infectados con Cff y Cfv. Se identificaron siete cepas bacterianas de distinto género del G1. Otras 11 cepas bacterianas de laboratorio fueron incluidas: Cff, Cfv, Cfv biovar Intermedius, 3 Campylobacter no-fetus, 3 Gram negativo y 2 Gram positivo. Solo las cepas de C. fetus presentaron inmunofluorescencia positiva. La sensibilidad y especificidad de la IFD fue de 79 % y 100 %, respectivamente. La concordancia entre la IFD y el cultivo bacteriológico fue de 83 % (Kappa: 0,65). Se demuestra la alta especificidad de la IFD para la detección de C. fetus con un conjugado fluorescente elaborado en Argentina, y se destaca la no reacción cruzada contra 15 cepas bacterianas normalmente presentes en la microbiota prepucial del toro.