Tuberculosis Caused by Mycobacterium bovis in a Capybara (Hydrochoerus hydrochaeris).

Tuberculosis, associated with Mycobacterium bovis, was diagnosed post mortem in an adult female capybara (Hydrochoerus hydrochaeris), kept at the Pampulha Ecological Park, Belo Horizonte, Brazil, in a large metropolitan area. On post-mortem examination, there were numerous firm white nodules scattered throughout all lobes of both lungs. Tissue samples were collected for histological and microbiological examination. Microscopically, the pulmonary nodules were multifocal to coalescing granulomas and intralesional acid-fast bacilli were evident in Ziehl-Neelsen-stained sections of the lung and spleen. Colonies with morphological features of Mycobacterium spp. were isolated from lung samples and conventional polymerase chain reaction (PCR) with genomic DNA from the isolates was positive for M. bovis; sequencing indicated 100% identity with the region of difference 4 (RD4) of M. bovis. In addition, M. bovis DNA was detected in the lung by quantitative PCR. The finding of M. bovis in a capybara indicates a potential public health risk in a zoological collection.

Validation of two real-time PCRs targeting the PE-PGRS 20 gene and the region of difference 4 for the characterization of Mycobacterium bovis isolates.

This study aimed to develop and validate real-time PCR for the diagnosis of Mycobacterium bovis isolates. Two hundred and seventy-four M. bovis isolates and 156 M. tuberculosis isolates were tested. Both qPCRs amplified all of the 274 M. bovis samples, but none of the 156 M. tuberculosis samples. The qPCR for PE-PGRS 20 had 91% efficiency and a detection limit of 0.32 ng (sensitivity and specificity for qPCR "Mbovis.100" were 99.64 and 100%, respectively). The qPCR for RD4 had 100% efficiency, and a detection limit of 4 pg (diagnostic sensitivity and specificity were 100 and 100%. The qPCR tests were performed using 4 extraction sets, 3 qPCR kits, and with a range of equipment; yet, all combinations produced similar results in a diagnostic test, demonstrating the robustness of this method. The techniques proved to be efficient, robust, sensitive, and specific for the diagnosis of M. bovis.