Comparison between tests for tuberculosis diagnosis in slaughtered bovines

Abstract

RESUMO:O objetivo deste estudo foi a comparação entre diferentes testes de diagnóstico para tuberculose bovina. Foram realizados o isolamento bacteriano, a caracterização histopatológica, a identificação de bacilos álcool-ácido resistentes e a detecção do DNA de M. bovis pela reação em cadeia da polimerase, em bovinos adultos abatidos em matadouros frigoríficos sob o Serviço de Inspeção Federal, valendo-se de amostras de linfonodos com lesões macroscópicas sugestivas de tuberculose, identificadas e coletadas durante o abate. O isolamento bacteriano foi realizado pelo cultivo em meios de cultura sólidos; a caracterização histopatológica, pela coloração com hematoxilina-eosina; e a identificação de bacilos álcool-ácido resistentes foi feita pela coloração de Ziehl-Neelsen. A detecção de DNA foi realizada em amostra extraída das lesões sugestivas de tuberculose pela reação em cadeia da polimerase, seguida da nested reação em cadeia da polimerase e por meio das colônias isoladas para identificação do M. bovis, utilizando-se também da reação em cadeia da polimerase . Os resultados obtidos permitiram concluir que os testes histopatológicos, o isolamento bacteriano e a identificação de bacilos álcool-ácido resistentes são aconselháveis para o diagnóstico da tuberculose bovina. Além disso, ensaios de reação em cadeia da polimerase utilizando amostras de lesões sugestivas de tuberculose são um modo mais rápido e promissor para diagnosticar a enfermidade, no entanto não deve ser utilizado sozinho, em virtude da baixa sensibilidade apresentada neste estudo. PALAVRAS-CHAVE: doenças infecciosas; Mycobacterium bovis;tuberculose; zoonose. ABSTRACT:Our goal for this article is to compare several different diagnosis tests for bovine tuberculosis identification. We have performed bacterial isolation, histopathological characterization, acid-fast bacilli (AFB) identification and M. bovis DNA detection. Lesions suggestive of Tuberculosis were sampled from bovine lymph nodes during slaughtering of bovines at an abattoir that operates under federal inspection. The bacterial isolation was performed in solid culture mediums, the histopathological characterization was made by Hematoxylin-eosinstaining, and AFB identification by Ziehl-Neelsen staining. Bacterial DNA detection was performed by Polymerase Chain Reaction (PCR) using DNA from two different sources, directly collected from the tuberculosis-like lesions (PCR followed by nested PCR) and from isolated bacteria. We have concluded that the multi-step approach, including histopathological characterization, bacterial isolation and AFB identification, is strongly recommended to diagnose tuberculosis in bovines. Furthermore, PCR assays using specimens of lesions suggestive of tuberculosis are a faster and more promising way to diagnose the disease. However, it should not be used alone due to the low sensitivity shown in this study.

Detection of Mycobacterium bovis in cattle lungs from two abattoirs in Western and North Central provinces of Sri Lanka

“…No bacterial growths were observed from the cultured lung, liver and kidney tissues after 8 weeks of incubation using the same NaOH decontamination and LJ medium similar to the ones used in the present study (Ereqat et al, 2013). Similarly, in another study that sampled cattle with gross BTB lesions, only 56 % (28/50) of lymph node samples having caseous tuberculous lesions had positive cultures while granuloma formation was observed in 64 % of the samples (Silva et al, 2018a). Only 12 % of the samples was positive for AFB.…”

“…Only 12 % of the samples was positive for AFB. Mycobacterium bovis was detected by PCR only in 20 % of the samples (Silva et al, 2018a). Contrary to these results, several other studies that sampled cattle with gross BTB lesions have reported good agreement between culture and PCR (Cardoso et al, 2009;Proano-Perez et al, 2011;Gizaw et al, 2017;Yahyaoui-Azami et al, 2017;Silva et al, 2018b).…”

Review of Methods Used for Diagnosing Tuberculosis in Captive and Free-Ranging Non-Bovid Species (2012–2020)

“…Conventional diagnostic tests for TB are considered the gold-standard and comprise of bacterial culture, histopathology, and post-mortem examination [ 8 ]. Often, these conventional tests are used in combination with one another or are used as a confirmatory test for newer immunological diagnostics, as discussed by Salfinger and Pfyffer [ 9 ].…”

Mycobacterium tuberculosis complex in wildlife: Review of current applications of antemortem and postmortem diagnosis

“…The detection of bacterial organisms from the tissues, feces, or other biological substances by this method is reduced because of few MTBC and possible contamination with other related organisms. Direct staining could not shed light on the members of the MTBC, producing the infection or show variation among viable and non-viable cells [ 76 , 77 ].…”

“…relies on gross findings and histopathological analyses. One reliable method is histopathological analysis with hematoxylin and eosin staining [ 77 ]. This technique has high specificity and the additional advantage of producing results within a few days.…”