Determination of the etiology of presumptive feline leprosy by 16S rRNA gene analysis.

PCR-amplified 16S rRNA gene sequences were obtained directly from tissue specimens from eight cats with presumptive feline leprosy. Acid-fast bacilli were observed in sections from all eight specimens, but culture for mycobacteria was successful for one specimen only. Analysis of the V2 variable region of each 16S rRNA PCR product identified a sequence with 100% nucleotide identity to the sequences of Mycobacterium lepraemurium, Mycobacterium avium, and Mycobacterium paratuberculosis in four of the specimens from cats with feline leprosy. Separate M. paratuberculosis- and M. avium-specific PCR amplifications of the four specimens were negative, thus substantiating the identification of M. lepraemurium in these specimens from cats with feline leprosy. Further sequence analysis of the V3 variable region of one of the four specimens provided conclusive evidence of the presence of M. lepraemurium. This is the first report of the definitive identification of M. lepraemurium in cats with feline leprosy by molecular biology-based analyses. M. avium, which is rarely reported in cats, and Mycobacterium chitae, a reported nonpathogenic, rapidly growing mycobacterial species found in the environment, were identified in the specimen from which acid-fast bacilli were cultured. Two of the specimens from cats were infected with a potentially novel species of mycobacteria which had a 16S rRNA gene sequence sharing the closest nucleotide sequence identity with that of Mycobacterium malmoense. Molecular biology-based analyses provided for the accurate and rapid diagnosis of mycobacterial infections in cats and circumvented the problems of culture and misdiagnosis of feline leprosy associated with traditional methods.