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Comparative study of two deleted Mycobacterium bovis strains in experimental animal models

X Ferrara Muñiz(1) F Blanco(1) E García(1) F Delgado(2) M J Marfil(3) M Zumárraga(1) A A Cataldi(1) M E Eirin(1)

1:Instituto de Agrobiotecnología y Biotecnología Molecular (IABIMO), UEDD INTA-CONICET; CICVyA, Instituto Nacional de Tecnología Agropecuaria; 2:Instituto de Patobiología Veterinaria (IPVeT), UEDD INTA-CONICET; CICVyA, Instituto Nacional de Tecnología Agropecuaria; 3:Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Cátedra de Enfermedades Infecciosas

Complementary tools such as vaccines could improve the control and eradication of bovine tuberculosis. Two attenuated strains, M. bovis ∆mce2 and M. bovis ∆mce2-phoP, were inoculated subcutaneously in mice (60 and 90 days, 1,105 CFU, n=24) and guinea pigs (178 days, 1,105 CFU, n=12), and remained in biosafety facilities (Protocols: 2018/36-2021/33 CICUAL-FCV-UBA). Survival (days), pathology (granulomas), bacteriology and tissue-IS6110-PCR (lung, liver, lymph nodes and spleen) led to comprehend its virulence and safety. For the M. bovis ∆mce2 strain, survival was 100% in mice and 66.7% in guinea pigs. In mice, neither lesions nor bacterial isolation were recorded, but a 37.5% positivity for tissue-IS6110-PCR was observed. All guinea pigs presented granulomas, 50% positive for tissue-PCR and 66.7% for bacteriology. For the M. bovis ∆mce2-phoP strain, 100% survival was observed in mice and guinea pigs, with no evidence of granulomas. No viable mycobacteria were recovered in mice, while 16.7% was observed in guinea pigs. However, tissue-IS6110-PCR positivity was confirmed in both cases (25% mice, 50% guinea pigs). A higher attenuation degree of M. bovis ∆mce2-phoP compared to M. bovis ∆mce2 was confirmed, especially evident in a highly susceptible model such as guinea pigs, even when these strains were inoculated subcutaneously.

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