INVM 2 was found in six countries and INVM 1 in five. Further investigations will be required to determine if this distribution is a consequence of animal movements, increased

virulence or whether these isolates have characteristics that allow them to transmit more readily. There is evidence to suggest that different mycobacterial strain types vary in their ability to cause disease. Caws et al. [34] provided evidence that M. tuberculosis genotype influences clinical disease phenotype and demonstrated a significant interaction between host and bacterial PFT�� in vitro genotypes and the development of tuberculosis. Gollnick et al. [35] reported that the survival of Map in bovine monocyte-derived macrophages

was not affected by host infection status but by the infecting strain type. Two recent studies suggest that different Map strain types may play a role in polarizing the host immune responses during infection PF-6463922 supplier [36, 37]. Also, different Map strains have been found to differ in virulence in experimental infections of deer [38] and in a mouse model (KS, unpublished data) and Verna et al. have provided data to show how the strain type may influence the pathology of ovine paratuberculosis [39]. Surprisingly, no Type I strains (corresponding to S Type strains in the literature [40]) were identified within the 27 sheep and 33 goat field isolates submitted by the partners. This may be a reflection of the difficulties encountered in isolating and growing these strains in vitro. Typically,

isolates of strain Type I are slow-growing, taking longer than 16 weeks and sometimes as long as 18 months to isolate on solid medium. Cultures are often not retained Glutamate dehydrogenase this long in diagnostic laboratories. Furthermore, studies have shown that the decontamination procedures or media used for isolation can significantly affect recovery of these strains. Reddacliff et al. [41] reported the detrimental effects of various decontamination protocols on the recovery of Type I strains from tissues and faeces. The addition of egg yolk and mycobactin J to BACTEC 12B or 7H9 broth was found to be essential for the isolation of Australian sheep strains from faeces and to enhance their recovery from tissue samples [42]. Other workers have successfully isolated Type I or III strains on LJ or Middlebrook 7H11 supplemented with mycobactin J [43, 44]. The addition of antibiotics can also affect growth. Both ampicillin and vancomycin hydrochloride can retard growth of Type I strains [45]. The various laboratories participating in this study used a range of decontamination procedures and culture media but it is not possible to rule out a culture bias. The results of this survey highlight an interesting difference between the epidemiology of Map in Europe and Australia.