Abstract The aim of this study was to standardize a diagnosis procedure to detect Mycobacterium avium subsp. paratuberculosis (Map) DNA in raw cow milk samples under field conditions. A procedure that combines both immunomagnetic separation and IS900 -PCR detection (IMS-IS1 PCR) was employed on milk samples from 265 lactating Holstein cows from Map infected and uninfected herds in Argentina. IMS-IS1 PCR results were analyzed and compared with those obtained from milk and fecal culture and serum ELISA. The extent of agreement between both tests was determined by the Kappa test. IMS-IS1 PCR showed a detection limit of 101 CFU of Map/mL of milk, when 50:50 mix of monoclonal and polyclonal antibodies were used to coat magnetic beads. All of the 118 samples from the Map uninfected herds were negative for the set of the tests. In Map infected herds, 80 out of 147 cows tested positive by milk IMS-IS1 PCR (55%), of which 2 (1.4%) were also positive by milk culture, 15 (10%) by fecal culture, and 20 (14%) by serum ELISA. Kappa statistics (95% CI) showed a slight agreement between the different tests (<0.20), and the proportions of agreement were ≤0.55. The IMS-IS1 PCR method detected Map in milk of the cows that were not positive in other techniques. This is the first report dealing with the application of IMS-IS1 PCR in the detection of Map in raw milk samples under field conditions in Argentina.

This study aimed to evaluate the immune response in bovines following immunization with a mycobaterial Lipoarabinomannan extract (LAMe) and the effect of Map challenge. LAMe vaccine induced specific antibody levels that diminished after the challenge and affected Map excretion at least for 100 days thereafter.

Mycobacterium avium subsp. paratuberculosis (Map) is the etiologic agent of paratuberculosis or Johne's disease. It is a chronic enteritis affecting ruminants, domestic and wild species. Goats and cows infected with Map can excret can excret mycobacteria in their milk. This fact represents a potential risk when people consume raw milk or non-pasteurized cheese. The objective of this work was to determine the viability of Map in cheese elaborated with experimentally infected caprine and bovine milk with different thermal treatments (65 °C or 37 °C). During maturity, Map was isolated in cheese with only treatment of milk with 37 °C, keeping its viability until days 60 and 45 days in caprine and bovine cheese respectively. In caprine cheese the highest pH value was found between days 30 and 45 of maturity in agreement with the biggest number of Map's isolates. The maturity decreases the Map viability in elaborated cheese without thermal treatment, and the treatment with 65 °C of temperature plus cheese maturity process would be beneficial for the mycobacteria elimination in these products.

Mycobacterium avium subsp. paratuberculosis (Map) es el microorganismo causante de la paratuberculosis o Enfermedad de Johne, enteritis crónica que afecta a rumiantes y a otros animales domésticos y silvestres. También ha sido vinculado a la enfermedad de Crohn en humanos. Hembras caprinas y bovinas infectadas con Map pueden excretar micobacterias en su leche, que consumida cruda o usada para la elaboración de quesos sin pasteurizar podría constituir una fuente potencial para la infección humana. El objetivo del trabajo fue determinar la viabilidad de Map en quesos elaborados con leche caprina y bovina infectada experimentalmente y sometida o no a tratamiento térmico. Durante la maduración, Map fue aislado sólo en los quesos elaborados con leche sin tratamiento térmico, manteniendo su viabilidad hasta los 60 días para los quesos caprinos y hasta los 45 días en los bovinos. En quesos caprinos los mayores valores de pH se hallaron entre los 30 y 45 días de maduración, coincidiendo con los aislamientos más numerosos de Map; en cambio, en los quesos bovinos no se observó relación alguna. La maduración de los quesos contribuiría a disminuir la viabilidad de Map en quesos elaborados con leche sin tratamiento térmico y el calentamiento de la leche a 65 ºC durante 20 min, seguido por la maduración de los quesos, resultaría beneficioso ya que eliminaría las micobacterias presentes, mejorando la calidad higiénico-sanitaria del alimento.