A comparison of Mycobacterium tuberculosis complex isolates from seals (pinnipeds) in Australia, Argentina, Uruguay, Great Britain and New Zealand was undertaken to determine their relationships to each other and their taxonomic position within the complex. Isolates from 30 cases of tuberculosis in six species of pinniped and seven related isolates were compared to representative and standard strains of the M. tuberculosis complex. The seal isolates could be distinguished from other members of the M. tuberculosis complex, including the recently defined 'Mycobacterium canettii ' and 'Mycobacterium caprae', on the basis of host preference and phenotypic and genetic tests. Pinnipeds appear to be the natural host for this 'seal bacillus', although the organism is also pathogenic in guinea pigs, rabbits, humans, Brazilian tapir (Tapirus terrestris) and, possibly, cattle. Infection caused by the seal bacillus is predominantly associated with granulomatous lesions in the peripheral lymph nodes, lungs, pleura, spleen and peritoneum. Cases of disseminated disease have been found. As with other members of the M. tuberculosis complex, aerosols are the most likely route of transmission. The name Mycobacterium pinnipedii sp. nov. is proposed for this novel member of the M. tuberculosis complex (the type strain is 6482 T =ATCC BAA-688 T =NCTC 13288 T ).Abbreviations: BCG, Bacille Calmette-Gué rin; FAFLP, fluorescent amplified fragment length polymorphism; PZA, pyrazinamide; SS, seal spoligotype; TCH, thiophen-2-carboxylic acid hydrazide.

The first case of tuberculosis is described in a wild subantarctic fur seal (Arctocephalus tropicalis) found on the Argentine coast. There was hydrothorax and white firm granulomatous lesions of 40-50 mm in diameter in the lungs. Lesions consisted of a central area of caseous necrosis, an intermediate zone of epithelioid and lymphocytic mononuclear cells, and a peripheral zone of connective tissue. Biochemical and drug sensitivity tests and inoculation of Guinea pigs confirmed the identification as Mycobacterium tuberculosis complex. Arctocephalus tropicalis is the fifth pinniped species in which the M. tuberculosis complex has been detected. Since subantarctic fur seals are widely distributed in the Southern Hemisphere, it is possible that the tuberculosis cases may have a common origin and could spread to other austral regions and species.

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Tuberculosis (TB) was diagnosed in 10 seals from three species (Arctocephalus australis, Arctocephalus tropicalis and Otaria flavescens) found in South America. The mycobacteria isolated from these cases belonged to the Mycobacterium tuberculosis complex, as determined by RFLP using an IS6110 probe, spoligotyping, analysis of the 16S rRNA gene sequence and by PCRrestriction analysis of hsp65. Polymorphisms in gyrA, katG, oxyR and pncA were investigated in some of the isolates, as well as the presence of the MPB70 antigen. The insertion sequence IS6110 was present in three to seven copies in the genome of the mycobacteria isolated from seals. Using the IS6110 probe, six patterns (designated A, B, C, D, E and F) were identified from 10 different isolates. Patterns A and B were found for the mycobacteria isolated from two and four seals, respectively, indicating an epidemiological relationship between isolates grouped according to their IS6110 RFLP. The mycobacteria isolated from seals shared the majority of their IS6110 DNAcontaining restriction fragments, and nine isolates had an identical spoligotype ; only one isolate showed a minor difference in its spoligotype. In addition, none of these spoligotypes were found in other M. tuberculosis complex strains. These results suggest that the isolates from seals constitute a unique group of closely related strains. The mycobacteria isolated from seals showed polymorphisms at gyrA codon 95 and katG codon 463, as do group 1 M. tuberculosis, and M. bovis. Group 1 mycobacteria are associated with cluster cases. The spoligotypes found in the mycobacteria isolated from seals lack spacers 39-43, as does M. bovis, but the MPB70 antigen, which is highly expressed in M. bovis and minimally expressed in M. tuberculosis, was not detected in these mycobacteria. The mycobacteria isolated from seals also showed oxyR and pncA polymorphisms specific to M. tuberculosis. In conclusion, the mycobacteria that cause TB in seals in the South-Western Atlantic are a related group, and based on the combination of genetic characteristics, belong to a unique genotypic group within the M. tuberculosis complex.

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