Search

Mycobacterium boviscauses tuberculosis (TB) in cattle, which in turn can transmit the pathogen to humans. Tuberculosis in dairy cattle is of particular concern where the consumption of raw milk and dairy products is customary. Baja California (BCA), Mexico, presents high prevalence of TB in both cattle and humans, making it important to investigate the molecular epidemiology of the disease in the region. A long-term study was undertaken to fully characterize the diversity ofM. bovisgenotypes circulating in dairy cattle, cheese and humans in BCA by whole-genome sequencing (WGS). During a 2-year period, 412 granulomatous tissue samples were collected from local abattoirs and 314 cheese samples were purchased from local stores and vendors in BCA and sent to the laboratory for mycobacterial culture, histology, direct PCR and WGS. For tissue samplesM. boviswas recovered from 86.8%, direct PCR detected 90% and histology confirmed 85.9% as mycobacteriosis-compatible. For cheese,M. boviswas recovered from 2.5% and direct PCR detected 6% of the samples. There was good agreement between diagnostic tests. Subsequently, a total of 345 whole-genome SNP sequences were obtained. Phylogenetic analysis grouped these isolates into 10 major clades. SNP analysis revealed putative transmission clusters where the pairwise SNP distance between isolates from different dairies was ≤3 SNP. Also, human and/or cheese isolates were within 8.45 (range 0–17) and 5.8 SNP (range 0–15), respectively, from cattle isolates. Finally, a comparison between the genotypes obtained in this study and those reported previously suggests that the genetic diversity ofM. bovisin BCA is well-characterized, and can be used to determine if BCA is the likely source ofM. bovisin humans and cattle in routine epidemiologic investigations and future studies. In conclusion, WGS provided evidence of ongoing local transmission ofM. bovisamong the dairies in this high-TB burden region of BCA, as well as show close relationships between isolates recovered from humans, cheese, and cattle. This confirms the need for a coordinated One Health approach in addressing the elimination of TB in animals and humans. Overall, the study contributes to the knowledge of the molecular epidemiology ofM. bovisin BCA, providing insight into the pathogen's dynamics in a high prevalence setting.

Veterinaria Mexico OA ISSN: 2448-6760 Cite this as: Carrisoza Urbina J, Flores Velazquez E, Gutierrez Reyes JA, Juarez Lopez NO. Assessment of the degree of concordance between the results of histopathological examination and bacterial culture in the diagnosis of bovine tuberculosis in Mexico. Veterinaria Mexico OA. 2015;2(3). doi: 10.21753/vmoa.2.3.348 . Bovine tuberculosis is a complex disease that is difficult to diagnose, control and eradicate and negatively impacts many farms. The objective of this study was to assess the degree of concordance between the results of histopathological examination and bacterial culture in the diagnosis of bovine tuberculosis lesions obtained in the laboratories certified by the Secretaria de Agricultura, Ganaderia, Desarrollo Rural, Pesca y Alimentacion (Ministry of Agriculture, Animal Production, Rural Development, Fisheries and Feeding) at the national level between January 2009 and December 2012 in Mexico. Tissue samples (10,818) from regular slaughter cattle that did not have tuberculin tests but had lesions suspected of having been caused by tuberculosis were sent to 10 authorized laboratories. Using Cohen’s kappa to measure the reliability of the diagnosis, a general concordance was obtained between the histopathological examination and bacterial culture results with a kappa of 0.634 and a 95% (0.618 – 0.650) confidence interval (CI), which shows good concordance between the two techniques at the national level. The laboratory in Chihuahua had the highest kappa [k=0.784, 95% CI (0.754–0.814)] and the laboratory of the La Laguna Region in the state of Coahuila had a low value of global concordance [k= 0.334, 95% CI (0.257–0.412)]. The number of positive samples in bacterial culture was low in Tamaulipas (21 samples), Sonora (41 samples), and Yucatan (45 samples) because tuberculosis prevalence in those states is ≤ 0.04%. The number of positive samples in bacterial culture was low in Tamaulipas (21 samples), Sonora (41 samples), and Yucatan (45 samples) because tuberculosis prevalence in those states is ≤ 0.04%. The reason for the disagreement between the two tests among some laboratories includes factors such as a lack of economic resources, infrastructure or personnel training. Correct sampling procedures, storage facilities, and shipping and sample processes are important in optimizing the bacteriological and histopathological results and obtaining correct diagnoses and differential diagnoses of bovine tuberculosis.

"La tuberculosis bovina es una enfermedad compleja, difícil de diagnosticar, controlar y erradicar y tiene un impacto negativo en el sector ganadero. El objetivo de este estudio fue evaluar el grado de concordancia entre los resultados del examen histopatológico y del cultivo bacteriológico en el diagnóstico de lesiones de tuberculosis bovina realizado en los laboratorios certificados por la Secretaría de Agricultura, Ganadería, Desarrollo Rural, Pesca y Alimentación (sagarpa) a nivel nacional, en el periodo comprendido entre enero de 2009 y diciembre de 2012 en México. La información se obtuvo de 10,818 muestras de bovinos de matanza regular, a las cuales no se los sometió a la prueba de tuberculina, pero tenían lesiones que sugerían tuberculosis. Esas muestras se enviaron a diez laboratorios autorizados. Mediante el coeficiente kappa de Cohen, se midió la confiabilidad del diagnóstico; se obtuvo una concordancia general entre los resultados del examen histopatológico y del cultivo bacteriológico de k= 0.633, con un intervalo de confianza (IC) del 95% (0.618–0.649), lo cual indica una concordancia buena entre las dos pruebas a nivel nacional. El laboratorio de Chihuahua obtuvo el valor más alto de kappa [k = 0.784; IC del 95% (0.754–0.814)] y el laboratorio de la Región Lagunera en el estado de Coahuila obtuvo un valor bajo de concordancia [k = 0.334; IC del 95% (0.257–0.412)]. El número de muestras positivas en el cultivo bacteriológico fue bajo en Tamaulipas (21 muestras), Sonora (41 muestras) y Yucatán (45 muestras), ya que la prevalencia de tuberculosis en esos Estados es ≤ 0.04%. El grado de discordancia en algunos laboratorios involucra factores como la falta de recursos económicos, de infraestructura y de capacitación. El procedimiento correcto para la toma, conservación, envío y procesamiento de las muestras es crucial para optimizar los resultados bacteriológicos e histopatológicos y, así, llegar al correcto diagnóstico de la tuberculosis bovina y de diagnósticos diferenciales."