No description available.

Brucella abortus (BA) are gram-negative, facultative intracellular bacteria that cause abortions in cattle and debilitating illness in humans. The US is now virtually free of bovine brucellosis, but the disease is endemic in wildlife. The official brucellosis vaccine in the US is strain RB51 (RB51). It elicits protective cell-mediated immunity (CMI) against BA infections. Mycobacterium avium subspecies paratuberculosis (MAP) causes paratuberculosis in ruminants. It is a slow growing intracellular parasite that requires CMI for its control, belongs to the genus Mycobacterium, and is closely related to M. avium avium (MA). Using RB51 as a vector that induces strong protective CMI may be useful to protect against MAP if it expresses MAP protective antigens. Therefore, MAP 85A and 35kDa proteins were expressed at low levels in RB51, and the immune responses elicited by these vaccines in BALB/c mice were evaluated. Strong anti-Brucella immunity was generated, but the anti-mycobacterial response was low. To evaluate protective efficacy, a BALB/c model using MA was developed. When mice were challenged with MA, protection was obtained in some experiments but was inconsistent. This may be due to the low expression of MAP antigens in RB51. Another objective was to evaluate the effect of an ongoing Brucella-infection on the efficacy of RB51 vaccination, and whether vaccination of already infected animals could have a curative effect. Mice acutely or chronically infected with virulent BA, rapidly cleared the RB51 vaccine organisms, but there was no significant decrease in the number of virulent BA. Brucella spp. have been developed as biological weapons, but there are no vaccines to protect humans. The development of a very attenuated protective vaccine is necessary to prevent human infections, as well as to protect wildlife. To generate such a vaccine, RB51 based vaccines were irradiated to render them non-replicative, but metabolically active. We demonstrated that in general, irradiated and non-irradiated RB51 vaccines remain protective at levels similar to those elicited by the live vaccines. Therefore, irradiation of strain RB51 is an effective means of attenuating the strain without affecting its protective characteristics, and could eventually be used as a vaccine for wildlife and humans. / Ph. D.

Mycobacterium avium ssp. paratuberculosis (Map) est responsable de la maladie de Johne chez les ruminants en particulier chez le bovin. Les scientifiques ont émis l'hypothèse que Map pourrait être l'agent étiologique de la maladie de Crohn chez l'humain, ce qui a soulevé des inquiétudes en santé publique. Map est particulièrement résistant à la chaleur dans le lait, mais l'état des connaissances est pratiquement limité dans les matrices de viande. Les valeurs D (temps de réduction décimal) et z (sensibilité à la température) ont été déterminées dans du boeuf haché préparé aseptiquement à partir du muscle semi membranosus pour Map, Escherichia coli et Enterococcus faecalis. L'objectif de ce travail est de déterminer l'effet de divers traitements thermiques sur la cinétique de destruction de Map dans la viande afin d'évaluer si les procédés thermiques industriels (la pasteurisation, cuisson) sont adéquats pour contrôler la Map dans les produits de viande.

Mycobacterium avium and Mycobacterium intracellulare, (M. avium complex, MAC) are human pathogens causing disease in individuals with acquired immunodeficiency syndrome (AIDS) or with thoracic abnormalities. MAC bacteria are difficult to kill because of the resistance of the pathogens to chemotherapeutic agents. One factor affecting treatment of MAC disease is the presence of interconvertible colonial variants. Transparent (T) variants have greater resistance to antibiotics and higher pathogenicity; opaque (O) variants are more susceptible to antibiotics and less pathogenic. The overall goal of this study was to investigate the mechanism for colonial variation. Based on an observation that T variants of M. intracellulare strain Va14 contained a plasmid which was 6 kb smaller than the 68 kb plasmid in O variants, it had been suggested that a transposable element might be responsible for colonial variation. The first objective was to clone the unique DNA fragment present in the 68 kb plasmid but absent from the 62 kb plasmid. The second and third objectives were to determine if the unique fragment contained a transposable element and to analyze the role of that element in the mechanism of colonial variation in M. intracellulare strain Va14. The fourth objective was to determine the distribution of IS1141 in MAC isolates. Fragments containing copies of the putative element were sequenced and a region 1596 basepairs in length with 23 basepair imperfect inverted repeats was designated as insertion sequence IS1141. IS1141 is the first insertion sequence identified in M. intracellulare. Data base searches using open reading frames (ORF) of IS1141, identified ORFb as significantly similar to the transposases of the IS3 family. The presence or absence of IS1141 in strain Va14 plasmids appeared unrelated to colonial variation, but IS1141 was present in another plasmid and the chromosome of the Va14 variants. Hybridization studies with IS1141 identified three chromosomal copies in O variants and two chromosomal copies in T variants. Va14 T variants each had a common IS1141 restriction fragment length polymorphism (RFLP) pattern which was different than the single RFLP pattern found in opaque variants. Based on these differences, it appears that IS1141 may integrate into the gene(s) responsible for the T phenotype preventing their expression. A survey of 64 James River basin non-AIDS, clinical and James River environmental MAC isolates identified 4 of 24 (17%) M. intracellulare isolates as containing IS1141. IS1141 has not been detected in any clinical or environmental M. avium or Mycobacterium species X isolates and may be limited to M. intracellulare. / Ph. D.

La malattia di Johne o paratubercolosi è un’enterite cronica granulomatosa provocata dal Mycobacterium avium subsp paratubercolosis (MAP), che colpisce i ruminanti ed in particolare i bovini da latte ed ha un grande impatto economico a livello mondiale. Il MAP sembra anche avere un ruolo nella malattia umana di Crohn. Tale patogeno è capace di sopravvivere molto bene all’interno dei macrofagi dell’ospite dove previene la loro attivazione, blocca l’acidificazione e la maturazione del fagosoma, e interferisce con la presentazione degli antigeni al sistema immunitario. Al fine di analizzare la complessa interazione tra l’ospite e il patogeno, è stata valutata la risposta dopo 2h, 6h, e 24h di macrofagi derivati da monociti bovini (MDM), coltivati in vitro e infettati con il ceppo L1 di MAP utilizzando un approccio di RNA-Seq. L’analisi statistica dei dati di sequenza ha mostrato un aumento del numero di geni differenzialmente espressi durante l’esperimento in risposta all’infezione. Inoltre i geni sottoespressi negli MDM infettati sono stati individuati solo a 24h post-infezione. L’analisi dei pathway ha evidenziato tre network che sono associati alla risposta immunitaria e al processo infiammatorio. Inoltre lo studio dei geni sottoespressi a 24h ha mostrato il ruolo centrale del complemento e del complesso maggiore di istocompatibilità nella patogenesi della malattia. / Johne’s disease (paratuberculosis) is a chronic granulomatous enteritis caused by Mycobacterium avium subsp paratubercolosis (MAP), affecting ruminants worldwide with a significant economic impact. MAP has also been speculated as a cause of human Crohn’s disease. MAP is a pathogen highly adapted for survival within host macrophages due to the organism's capacity to prevent macrophage activation, block phagosome acidification and maturation, and attenuate presentation of antigens to the immune system. The consequence is a very long silent infection and subclinical phases. To decipher the complex interaction between host and MAP, the response of in vitro bovine monocyte-derived macrophages (MDM) after 2h, 6h and 24h of infection with L1 strain of MAP was explored using RNA-Seq approach. Statistical analysis of sequence data revealed an increasing number of differentially expressed genes in MDM following infection through the three time points analysed. Furthermore down-regulated genes were only found at 24 h post-infection. Ingenuity Pathways Analysis of differentially expressed genes showed that “cell-mediated immune response” was the most significant network related to 2hpi dataset, “immune cell trafficking” for 6hpi, and “inflammatory response” for 24hpi. Finally the analysis of down-regulated genes at 24hpi confirmed the role of complement and major histocompatibility complex (MHC) in the pathogenesis of MAP in cattle.

Mycobacterium avium ssp. paratuberculosis (Map), agent étiologique de la paratuberculose, a évolué en deuxtypes dénommés, S pour« Sheep » et C pour « Cattle ». L’intestin grêle est le site primaire de l’infection à Map mais les mécanismes moléculaires impliqués dans l’implantation du bacille restent largement méconnus. L’objectif de mon projet de thèse visait à identifier et caractériser les adhésines exprimées par Map par des approches génétiques et biochimiques. J’ai ainsi purifié la HBHA et la LBP par chromatographie d’affinité puis les ai identifiés en spectrométrie de masse. L’originalité de ce travail repose sur le polymorphisme de ces adhésines observé entre les souches de type C et S. Cette variabilité a été mise en évidence sur le domaine d’interaction avec les sucres sulfatés de la cellule hôte influençant l’affinité des adhésines pour l’héparine. Ce travail de thèse a permis de caractériser pour la première fois ces deux adhésines produites par Map. Le polymorphisme de la HBHA et de la LBP, discriminant les types C et S, ouvre de nombreuses perspectives sur l’évolution de l’espèce M. avium et le rôle de ces adhésines sur le tropisme intestinal, la préférence d’hôte de Map ou encore leur potentiel diagnostic. / Mycobacterium avium subsp. paratuberculosis (Map), the etiological agent of paratuberculosis, has evolved into two types called, S for "Sheep" and C for "Cattle." The small intestine is the primary site of Map infection but the molecular mechanisms involved in the establishment of bacilli are still unknown. The aim of my thesis was to identify and characterize the adhesins expressed by Map by genetic and biochemical approaches. I purified HBHA and LBP by affinity chromatography then identified them by mass spectrometry. The originality of this work is based on the polymorphism of these adhesins observed between strains of type C and S. This variability has been demonstrated in the binding domain involved in interaction with sulfated sugars of host cell influences adhesins affinity for heparin. This thesis has characterized for the first time these two adhesins produced by Map. Specific polymorphism highlighted related to the evolution of the species avium, opens large number questions on their role on the pathogenesis of Map including the cellular tropism, host preference or interest of these antigens to improve diagnostic.

No description available.

The goal of this project was to incorporate bacteriophage with Bioluminescent Assay in Real-Time Loop-mediated isothermal amplification (BART-LAMP) for the rapid detection of Mycobacterium avium subspecies paratuberculosis (MAP). As the causative agent of Johne’s Disease, there are no rapid detection methods that are suitable in specificity and sensitivity. A screening assay for phage isolation was developed, and over 400 samples were screened for the isolation of a bacteriophage against MAP. One novel Mycobacterium phage was isolated and characterized using transmission electron miscroscopy, host range studies, restriction enzyme digestion, and pH and temperature stability. It was sequenced, annotated, and underwent an in silico protein analysis. No pathogenic or lysogenic genes were detected, and it was found to be related to Gordonia phage GTE2. BART-LAMP was applied to the detection of the isolated phage using purely extracted DNA and crude phage lysate, showing that phages could be detected successfully. / Beef Cattle Research Council; Agriculture and AgriFood Canada through Growing Forward initiative

Tesis para optar al Título Profesional de Ingeniero Agrónomo y al Grado de Magíster en Ciencias Agropecuarias, Mención Producción Frutícola / Chile es uno de los principales productores de cerezas a nivel mundial, encontrándose en una posición privilegiada como abastecedor de cerezas para los mercados del Hemisferio Norte, cuando estos se encuentran sin producción, lo que permite a los productores alcanzar mayores precios (Muñoz, 2015). Se estima que la industria exportadora factura por sobre USD 400 millones, lo que podría ubicar a las exportaciones de cerezas como el tercer mayor generador de valor exportado frutícola (Bravo, 2013); esto conlleva una mayor generación de empleos en el sector, en especial en los momentos de cosecha del producto, aumentando el ingreso a las personas, socialmente, más vulnerables.

No description available.