Abstract
Abstract Infections with Mycobacterium microti, a member of the M. tuberculosis complex, have been increasingly reported in humans and in domestic and free-ranging wild animals. At postmortem examination, infected animals may display histopathologic lesions indistinguishable from those caused by M. bovis or M. caprae, potentially leading to misidentification of bovine tuberculosis. We report 3 cases of M. microti infections in free-ranging red deer (Cervus elaphus) from western Austria and southern Germany. One diseased animal displayed severe pyogranulomatous pleuropneumonia and multifocal granulomas on the surface of the pericardium. Two other animals showed alterations of the lungs and associated lymph nodes compatible with parasitic infestation. Results of the phylogenetic analysis including multiple animal strains from the study area showed independent infection events, but no host-adapted genotype. Personnel involved in bovine tuberculosis–monitoring programs should be aware of the fastidious nature of M. microti, its pathogenicity in wildlife, and zoonotic potential.
Highlights
Infections with Mycobacterium microti, a member of the M. tuberculosis complex, have been increasingly reported in humans and in domestic and free-ranging wild animals
Isolates of the animal-adapted ecotype defined as M. microti are characterized by the deletion of the RD1mic in the RD1 region, which includes open reading frame coding for well-known virulence factors, such as early secreted antigenic target (ESAT) 6, locus tag Rv3875, and CFP-10, a culture filtrate protein encoded by the neighboring gene Rv3874 [23]
Multifocal to coalescing granulomas of 4–25 mm diameter were observed on the surface of the epicardium (Figure 1, panel B)
Summary
Cases Three cases of natural M. microti infections in red deer were identified (Table 1). Thereafter, histologic examination and mycobacterial analysis of the lungs were performed. Mycobacterial Analyses and Histologic Examination We isolated mycobacteria following a standardized protocol as described elsewhere [32]. 2–3 g of minced tissue samples were homogenized in 5 mL 0.9% NaCl solution by using a rotating-blade macerator system (Ultra-Turrax IKA, https://www.ika.com). Investigation of Phylogenetic Relationships DVR spoligotyping (direct variable repeat spacer oligonucleotide typing) was performed using a commercial microarray system (Alere Technologies, https://www.globalpointofcare.abbott) with integrated data analysis as described elsewhere [29]. To investigate the phylogenetic relationships between the 3 isolates from red deer, we analyzed 8 additional strains isolated from different wild and domestic hosts that originated from the regions bordering Germany, Austria, and Switzerland by MLVA (Table 2).
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