Deoxyribonucleic Acid Relatedness of Mycobacterium paratuberculosis to Other Members of the Family Mycobacteriaceae

Abstract

Deoxyribonucleic acid (DNA)-DNA hybridization was used to determine the relationships of Mycobacterium paratuberculosis and Mycobacterium avium to 24 mycobacterial strains representing seven species. Our results indicate that M . paratuberculosis should be considered a member of the same genomic species as M. avium and the wood pigeon bacillus. Mycobacterium scrofulaceum, which has been considered a member of the M . avium-Mycobacterium intracellulare-M. scrofulaceum complex on the basis of phenotypic characteristics, shows little DNA similarity to M . avium, M. intracellulare, or M. paratuberculosis.Classification of the slow-growing mycobacteria on the basis of phenotypic characteristics has been a complicated and uncertain process. There is relatively little variability among strains thought to typify separate species, and there is significant variation in the phenotypic characteristics of isolates which appear to belong to the same species (26,(33)(34)(35). This is particularly true of Mycobacterium paratuberculosis. Phenotypic variation within the species precludes identification of a clear pattern of biochemical responses in an Adansonian system. The characteristics exhibited by fresh isolates may change with storage or repeated passage (9, 26). Mycobactin dependency, hydrolysis of Tween 80, and catalase activity at pH 5 after heating are the characteristics which have been used to distinguish M . paratuberculosis from Mycobacterium avium. When these criteria are used, the wood pigeon bacillus (22, 33) resembles M . paratuberculosis rather than M . avium, as do some other M . avium isolates cultured from swine lymph nodes and lesions in birds (8,22,26,33).Antibiotic susceptibility patterns have been used in attempts to distinguish M . paratuberculosis from M . avium. M . paratuberculosis is often susceptible to streptomycin and rifampin, as well as to neotetrazolium chloride, whereas M . avium is usually resistant to all three antibiotics. These responses are also variable (9,34).Mycobacterium scrofulaceum has often been included as a member of the M . avium-Mycobacterium intracellulare-M. scrofulaceum (MAIS) complex on the basis of phenotypic characteristics (35), although the relationship of M. scrofulaceum to M . paratuberculosis has not been examined by other investigators.There is a need for better methods of defining the relationship of M . paratuberculosis to other mycobacterial species. Although numerous investigations on mycobacterial deoxyribonucleic acid (DNA)-DNA hybridization have been reported (3)(4)(5)7, 10, 13,16,17) MATERIALS AND METHODSBacterial strains. The 24 mycobacterial strains used in this study are listed in Table 1. The cells were grown in Middlebrook 7H9 medium supplemented with Dubos oleic-albumin complex (100 ml/liter) and 0.05% Tween 80 and were cultivated by standard methods (9). The M . paratuberculosis cultures were further supplemented with 2 mg of mycobactin J (Allied Laboratories, Inc., Ames, Iowa) per liter. Cells were pelleted by centrifugation at 6,000 x g for 15 min...

Mycobacterium aviumsubsp.paratuberculosisin Veterinary Medicine

“…silvaticum (M. silvaticum). The subspecies designation of M. paratuberculosis is based on DNA-DNA hybridization studies (159,259,298,328) and numerical taxonomy analysis (298). Although commonly grouped with M. avium in the Mycobacterium aviumintracellulare complex, M. intracellulare is a genetically distinct species (7,256).…”

Mycobacterium avium in the Postgenomic Era

“…A milestone in the characterization and definition of M. avium occurred in 1990 with a publication by Thorel et al which defined three principal subsets of M. avium, as revealed by prior molecular analyses, such as DNA-DNA hybridization (122,231,307), on the basis of growth characteristics and biochemical tests (numerical taxonomy analysis) (267). These three subsets consist of M. avium subsp.…”

Paratuberculosis

“…The base composition of M. paratuberculosis DNA is 66 to 67% G+C (103,130), and that of other pathogenic mycobacteria is as follows: 66 (Table 2). Nearly 100% homology between most strains of M. paratuberculosis and M. avium has been reported (100,103,174,231). The DNA of M. paratuberculosis was also found to be highly homologous to the DNA from several wood pigeon mycobacteria, organisms genetically related to some M. avium and M. intracellulare strains (100,231).…”