Mycobacterium goodii is a rapidly growing non‐tuberculous mycobacterium that has recently been associated with severe infections in animals and humans. The ecological niche of M. goodii remains unclear, and cases in large animals remain either undiagnosed or misdiagnosed.
Case presentation:
We present a case of a 5‐year‐old Holstein cow showing mastitis signs of pronounced glandular hardening that did not respond to antibiotic therapy. During the milk bacteriological culture, we observed Gram‐positive and acid‐fast rods with an unusual profile in the milk diagnostic routine. Biochemical tests were performed and the results showed a bacterium belonging to the group Mycobacterium smegmatis. Antimicrobial susceptibility testing was performed, and the result for tobramycin indicated the presence of M. goodii. In order to confirm its identity, 16S rRNA gene sequencing and phylogenetic analysis were performed, showing 100 % nucleotide similarity with M. goodii. Histological analyses of a biopsy specimen obtained from the affected mammary quarter showed evidence of pyogranulomatous and diffuse mastitis, both suggestive of bacterial intracellular infection.
Conclusion:
To the best of our knowledge, this is the first confirmed case of mycobacterial mastitis caused by M. goodii infection in cows, identified through isolation of the bacteria and 16S rRNA gene sequencing. Although the role of this agent in bovine mastitis remains unclear, we highlight its potential source for humans and the implications for the dairy industry.
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