Salmonella typhimurium (ST) infection not only causes salmonellosis in humans, but also can result in great economic losses in the typically narrow-margin, high-volume broiler business due to reduced growth rates and mortalities. Over the last decade, the use of antibiotics and attenuated vaccines to restrain or prevent bacterial infections in domestic animals has been criticised because of the possible development of antibiotic resistance and the potential dangers of residual antibiotics and vaccines in animal-derived food products for human consumption. For these reasons, many countries have begun phasing out growth promoting antibiotics in broiler diets. It is therefore essential for the poultry production industry to develop feed additives and processing techniques as alternatives for sub-therapeutic dietary supplementation of antibiotics. However, innovative research is needed to evaluate the efficacy of new and existing alternative products. The general aim of this trial was to determine the effects of Salmonella typhimurium colonisation of the gastrointestinal tract of broiler chicks on gastrointestinal health and production performance. The effect of Zinc-Bacitracin (Zn-BC), a commonly used antibiotic growth promoter in the poultry industry, on Salmonella colonisation was also measured. A pilot trial was first conducted to determine the level of Salmonella typhimurium required to infect broiler chicks, and the necessity of administering an immunosuppressive agent in order to obtain infection. The main trial followed to determine the effects of Salmonella typhimurium on gastrointestinal health and function. The ultimate aim of the study was to obtain baseline values of various parameters that could be used in future trials for the evaluation of antibiotic alternative products. The results obtained from the pilot trial showed that it was not necessary to administer cyclophosphamide as the Salmonella typhimurium proved to be highly virulent. The cloacal swabs taken in the second trial showed that the use of Zn-BC as an antibiotic did not inhibit Salmonella colonisation in the challenged birds. The inclusion of Zn-BC in this trial inhibited the growth of the gut microflora allowing the Salmonella to proliferate in the body of the chicken, which lead to the conclusion that the routine inclusion of Zn-BC at sub-clinical levels as a growth promoter may be detrimental when the bird gets exposed to Gram(-) bacteria, such as Salmonella. In both of the trials, Salmonella challenge resulted in enlargement of the organs with a consequent increase in the organ weights. In the pilot trial there was a significant difference (P<0.0033) of the control weights for the duodenum, ileum, caeca and liver and those of the Salmonella infected birds. Control birds that did not receive CY had duodenum weights of 1.00 (±0.236) while the birds infected with 1 x 108 CFU/mL had weights of 1.99 (±0.310), while the control birds that did receive CY had duodenum weights of 0.98 (±0.244) with the Salmonella infected birds having weights of between 1.79 (±0.299) and 2.13 (±0.006). Significant results (P<0.016) in the main trial were found to occur predominantly at 7 days of age for the duodenum, jejenum, ileum and caeca weights. Control birds in the group that did receive antibiotics had 7 day duodenum weights of 1.80 (±0.301) compared to the Salmonella infected bird which had weights of between 2.33 (±0.376) and 2.51 (±0.424). In general Salmonella did not affect the growth and performance of the challenged birds. Birds challenged with Salmonella showed a tendency to have enlarged livers, possibly due to hepatic damage. In the main trial there was a significant difference (P<0.016) in liver weights at 28 days of age between the control and Salmonella infected groups regardless of whether the birds received antibiotics or not. The control birds that received antibiotics had liver weights of 3.24 (±0.234) while the birds infected with the higher level of Salmonella had weights of 3.86 (±0.542). This finding, together with the noticeable, although mainly insignificant, trend of decreased serum albumin levels and increased serum globulin and total serum protein levels noted in infected birds can be used in conjunction to measure the effect of ST on liver damage. Salmonella colonisation resulted in an increase in the severity of lesions seen in the gastrointestinal tract (P<0.0016). Histopathology results proved to be inconsistent and did not provide any conclusive evidence on the effect of Salmonella on the organs. Villi measurements taken in the second trial showed that Salmonella significantly (P<0.016) shortened the length of the villi in the duodenum and jejenum of challenged birds when measured at 28 days of age. Control birds had duodenum villi length of 662.5 (±56.79) while those birds infected with Salmonella had lengths of between 558.9 (±77.74) and 537.0 (±51.66). There was a significant difference in the duodenum villi length regardless of antibiotic inclusion into the diet. In the birds that did receive antibiotics, there was a significant difference (P<0.016) in the jejenum villi length with the control birds having the longest villi 725.7 (±90.92) while the birds infected with the higher level of Salmonella having the shortest villi 557.2 (±124.5). It would appear that using all of the information and results obtained for liver weights, broiler performance, serum biochemical level, lesion scoring, histopathology and villous morphological measurements should be used in conjunction with one another to measure the effect of Salmonella on the broiler chicken. The results obtained in this trial clearly show just how significant a problem Salmonella infection can be in the poultry industry due to seemingly healthy adult birds displaying little or no systemic disease being non-symptomatic carriers. Many of the Para-typhoid salmonellae do not always produce clinical signs in chicks, and their presence in the poultry industry may go unrecognised for this reason. / Dissertation (MSc(Agric))--University of Pretoria, 2011. / Animal and Wildlife Sciences / unrestricted

Salmonella enterica is a facultative intracellular pathogen, able to invade various hosts and successfully replicate within them. Invasion of polarized cells by S. enterica serovar Typhimurium (STM) occurs in dependence of the type 1 secretion system (T1SS), encoded on Salmonella Pathogenicity Island 4 (SPI4). The 595 kDa non-fimbrial adhesin SiiE is the substrate of the SPI4-T1SS and mediates the first close contact to the host cells apical side. This allows for the type 3 secretion system (T3SS) of the SPI1 to translocate its effector proteins into the host cells cytosol, leading to actin remodeling, membrane ruffle formation and finally uptake of the pathogen. The SPI4-T1SS belongs to the family of ATP-binding cassette (ABC) transporters and is characteristically composed of the ATPase SiiF in the inner membrane (IM), the periplasmic adaptor protein (PAP) SiiD and the secretin SiiC. Further there are two non-canonical proteins encoded, namely SiiA and SiiB, which are known to form a proton channel in the IM. Every single subunit was found to be essential for invasion of polarized cells. The substrate SiiE is transiently retained on the cell surface during secretion process and protrudes the lipopolysaccharide (LPS) layer, a step essential for adhesion. Following translocation of the SPI1-T3SS effector proteins, SiiE is released into the extracellular space. Utilizing a variety of techniques, I was able to show that the transient retention of SiiE only occurs in the outer membrane (OM) protein SiiC and not in the whole two membrane-spanning T1SS. My analyses showed that the proton channel SiiAB is involved in initial steps of secretion and not necessary for release of SiiE, further narrowing down possible modes of action. I found a potential proteolytic cleavage site in the N-terminal part of SiiE, essential for release of the adhesin and discovered a potential retention domain in its N-terminus, too bulky to pass through the secretin. Additionally, I gained first hints that the large cytosolic domain of SiiB is not only involved in SiiE retention mechanism, but also in flagellar-dependent movement under swarming conditions. Using dual-color 3D direct stochastic optical reconstruction microscopy (dSTORM), I was able to localize SiiAB in the IM and SiiB not only at the SPI4-T1SS, but during SiiE retention maximum primarily at the flagellum. Intriguingly, the synthetic expression of siiAB as well as synthetic expression of the flagellar stator unit motAB both showed an increase of velocity. Furthermore, I successfully established murine and human intestinal organoid cell culture for microscopic and quantitative analyses of STM and S. Paratyphi A (SPA) invasion processes. Thus, with this work I was able to reveal new insights of the SPI4-T1SS, its substrate SiiE and the non-canonical subunits SiiAB that pave the way for further SPI4-T1SS investigations and also other secretion systems and their associated subunits.

No description available.

The interaction of bacterial pathogens and the human host is a complex process that has shaped both organisms on a molecular, cellular and population level. When pathogenic bacteria infect the human body, a battle ensues between the host immune system and the pathogen. In order to escape an immune response and to colonize the host, pathogenic bacteria have developed diverse virulence strategies and some pathogens even replicate within host cells. For survival and propagation within the dynamic environment of a host cell, these bacteria interfere with the regulation of host pathways, such as the cell cycle, for their own benefit. The intracellular pathogen Salmonella Typhimurium invades eukaryotic cells and resides and replicates in a modified vacuolar compartment in which it is protected from the innate immune response. To this end, it employs a set of virulence factors that help to invade cells (SPI-1 effectors) and to hijack and modify the host endolysosomal system, in order to stabilize and mature its vacuolar niche (SPI-2 effectors). Previous studies have shown that Salmonella arrests host cells in G2/M phase and that Salmonella infected cells progress faster from G1 into S phase, suggesting that the G1 phase is disadvantageous for Salmonella infection. In fact, it has already been observed that Salmonella replication is impaired in G1 arrested cells. However, the reason for this impairment remained unclear. The current study addressed this question for the first time and revealed that the highly adapted, intracellular lifestyle of Salmonella is drastically altered upon G1 arrest of the host cell. It is shown that proteasomal degradation in G1 arrested cells is delayed and endolysosomal and autophagosomal trafficking is compromised. Accordingly, processing of lysosomal proteins is insufficient and lysosomal activity is decreased; resulting in uneven distribution and accumulation of endolysosomes and autophagosomes, containing undegraded cargo. The deregulation of these cellular signaling pathways affects maturation of the Salmonella containing vacuole (SCV). For the first time it is shown that acidification of SCVs is impaired upon G1 arrest. Thus, an important environmental factor for the switch from SPI-1 to SPI-2 gene expression is missing and the SPI-2 system is not activated. Consequently, targeting and modification of host cell structures by SPI-2 effectors e.g. recruitment of endolysosomal membrane proteins, like LAMP1, or exchange of endosomal cargo, is compromised. In addition, degradation of Salmonella SPI-1 effectors by the host proteasome is delayed. Their prolonged presence sustained the recruitment of early endosomes and contributed to the SCV remaining in an early, vulnerable maturation stage. Finally, it was shown that SCV membrane integrity is compromised; the early SCV ruptures and bacteria are released into the cytoplasm. Depending on the host cell type, SPI-2 independent, cytoplasmic replication is promoted. This might favor bacterial spreading, dissemination into the tissue and provide an advantage in host colonization. Overall, the present study establishes a link between host cell cycle regulation and the outcome of Salmonella infection. It fills the gap of knowledge as to why the host cell cycle stage is of critical importance for Salmonella infection and sheds light on a key aspect of host-pathogen interaction. / Die Interaktion zwischen bakteriellen Krankheitserregern und dem menschlichen Wirt ist ein komplexer Prozess, der beide Organismen auf molekularer, zellulärer und Populationsebene geprägt hat. Wenn pathogene Bakterien den menschlichen Körper infizieren, kommt es zu einem Kampf zwischen dem Immunsystem des Wirtes und dem Krankheitserregers. Um einer Immunantwort zu entgehen und den Wirt zu besiedeln, haben pathogene Bakterien diverse Strategien entwickelt und einige Erreger vermehren sich sogar innerhalb von Wirtszellen. Zum Überleben und zur Vermehrung innerhalb der dynamischen Umgebung einer Wirtszelle, manipulieren diese Bakterien die Regulation zellulärer Netzwerke, wie zum Beispiel den Zellzyklus, zu ihrem eigenen Vorteil. Salmonella Typhimurium, ein intrazelluläres Bakterium, dringt in eukaryotische Wirtszellen ein und vermehrt sich in einem modifizierten, vakuolären Kompartiment, welches gleichzeitig vor der angeboren Immunantwort des Wirtes schützt. Zu diesem Zweck entwickelten Salmonellen eine Reihe von Virulenzfaktoren. Diese sind zum einen für die Invasion von Zellen verantwortlich (SPI-1 Faktoren), zum anderen greifen sie das endolysosomale System der Wirtszelle an und modifizieren es, mit dem Ziel die intrazelluläre Salmonellen-enthaltende Vakuole (SCV) zu stabilisieren und reifen zu lassen (SPI-2 Faktoren). Frühere Studien haben gezeigt, dass Salmonellen ihre Wirtszellen in der G2/M Phase blockieren. Zudem gehen Salmonellen-infizierte Zellen schneller von der G1 in die S-Phase über, was auf einen Nachteil der G1-Phase für die Salmonelleninfektion hindeutet. In der Tat wurde bereits beobachtet, dass die Vermehrung von Salmonellen in G1-arretierten Zellen beeinträchtigt war. Der Grund für diese Beeinträchtigung blieb jedoch unklar. Die vorliegende Studie befasst sich zum ersten Mal mit dieser Frage und zeigt auf, dass der hoch angepasste, intrazelluläre Lebensstil von Salmonellen während des G1-Arrest der Wirtszelle dramatisch verändert wird. Im Rahmen der hier vorgelegten Arbeit wurde gezeigt, dass der proteasomale Abbau in G1-arretierten Zellen verzögert und die endolysosomalen und autophagosomalen Transportnetzwerke beeinträchtigt sind. Dementsprechend ist die Prozessierung lysosomaler Proteine unzulänglich und die lysosomale Aktivität herabgesetzt; was zu einer ungleichmäßigen Verteilung und Anreicherung von Endolysosomen und Autophagosomen führt, die nicht abgebaute Stoffwechselprodukte akkumulieren. Die Deregulierung der genannten zellulären Signalwege beeinflusst die Reifung der SCV. Es konnte hier zum ersten Mal gezeigt werden, dass die Ansäuerung der SCV in G1-arretierten Zellen inhibiert ist. Somit fehlt ein essentieller Faktor für den Wechsel von SPI-1 zu SPI-2-Genexpression und das SPI-2 System wird nicht aktiviert. Folglich findet keine Modifikation der Wirtszelle durch SPI-2-Effektoren, z.B. die Rekrutierung endolysosomaler Membranproteine, wie LAMP1 oder der Austausch endosomaler Fracht statt. Zudem ist der Abbau von bakteriellen SPI-1-Effektoren durch das Wirtsproteasom verzögert. Die verlängerte Präsenz der SPI-1 Effektoren fördert eine anhaltende Rekrutierung von frühen Endosomen und trägt zum Verbleib der SCV in einem frühen, sehr instabilen Reifestadium bei. Schließlich wurde gezeigt, dass die Integrität der SCV Membran kompromittiert ist, die Vakuole aufbricht und die Bakterien ins Zytoplasma entlassen werden. In Abhängigkeit des Wirtszelltyps wird eine SPI-2 unabhängige, zytoplasmatische Vermehrung begünstigt, was möglicherweise die Ausbreitung der Bakterien ins Gewebe erleichtert und somit einen Vorteil bei der Besiedelung des Wirtes darstellt. Insgesamt etabliert die vorliegende Studie einen Zusammenhang zwischen der Regulation des Wirtszellzyklus und dem Ergebnis einer Salmonelleninfektion. Es wird aufgezeigt, warum der Zellzyklus der Wirtszelle von entscheidender Bedeutung für den Verlauf der Salmonelleninfektion ist und beleuchtet somit einen essentiellen Aspekt der Wirt-Pathogen-Interaktion.

Small proteins, often defined as shorter than 50 amino acids, have been implicated in fundamental cellular processes. Despite this, they have been largely understudied throughout all domains of life, since their size often makes their identification and characterization challenging. This work addressed the knowledge gap surrounding small proteins with a focus on the model bacterial pathogen Salmonella Typhimurium. In a first step, new small proteins were identified with a combination of computational and experimental approaches. Infection-relevant datasets were then investigated with the updated Salmonella annotation to prioritize promising candidates involved in virulence. To implement the annotation of new small proteins, predictions from the algorithm sPepFinder were merged with those derived from Ribo-seq. These were added to the Salmonella annotation and used to (re)analyse different datasets. Information regarding expression during infection (dual RNA-seq) and requirement for virulence (TraDIS) was collected for each given coding sequence. In parallel, Grad-seq data were mined to identify small proteins engaged in intermolecular interactions. The combination of dual RNA-seq and TraDIS lead to the identification of small proteins with features of virulence factors, namely high intracellular induction and a virulence phenotype upon transposon insertion. As a proof of principle of the power of this approach in highlighting high confidence candidates, two small proteins were characterized in the context of Salmonella infection. MgrB, a known regulator of the PhoPQ two-component system, was shown to be essential for the infection of epithelial cells and macrophages, possibly via its stabilizing effect on flagella or by interacting with other sensor kinases of twocomponent systems. YjiS, so far uncharacterized in Salmonella, had an opposite role in infection, with its deletion rendering Salmonella hypervirulent. The mechanism underlying this, though still obscure, likely relies on the interaction with inner-membrane proteins. Overall, this work provides a global description of Salmonella small proteins in the context of infection with a combinatorial approach that expedites the identification of interesting candidates. Different high-throughput datasets available for a broad range of organisms can be analysed in a similar manner with a focus on small proteins. This will lead to the identification of key factors in the regulation of various processes, thus for example providing targets for the treatment of bacterial infections or, in the case of commensal bacteria, for the modulation of the microbiota composition. / Kleine Proteine, oft definiert als kürzer als 50 Aminosäuren, sind in fundamentale zelluläre Prozesse involviert. Trotzdem sind sie in allen Domänen des Lebens noch weitgehend unerforscht, da ihre Größe ihre Identifizierung und Charakterisierung oft schwierig macht. Diese Arbeit adressiert die Wissenslücke um kleine Proteine mit einem Fokus auf das bakterielle Modellpathogen Salmonella Typhimurium. In einem ersten Schritt wurden neue kleine Proteine mit einer Kombination aus bioinformatischen und experimentellen Ansätzen identifiziert. Anschließend wurden infektionsrelevante Datensätze mit der aktualisierten Salmonella-Annotation untersucht, um vielversprechende Kandidaten zu priorisieren, die an der Virulenz beteiligt sind. Um die Annotation neuer kleiner Proteine zu implementieren, wurden die Vorhersagen aus dem Algorithmus sPepFinder mit denen aus Ribo-seq kombiniert. Diese wurden der Salmonella-Annotation hinzugefügt und zur (Re-)Analyse verschiedener Datensätze verwendet. Für jede gegebene kodierende Sequenz wurden Informationen zur Expression während der Infektion (duale RNA-seq) und zum Beitrag zur Virulenz (TraDIS) gesammelt. Parallel dazu wurden Grad-seq-Daten ausgewertet, um kleine Proteine zu identifizieren, die an intermolekularen Interaktionen beteiligt sind. Die Kombination von dualer RNA-seq und TraDIS führte zur Identifizierung von kleinen Proteinen mit Merkmalen von Virulenzfaktoren, nämlich einer hohen intrazellulären Induktion und einem Virulenz-Phänotyp nach Transposon- Insertion. Als Beweis für die Leistungsfähigkeit dieses Ansatzes Identifikation von vielversprechenden Kandidaten wurden zwei kleine Proteine im Kontext einer Salmonella-Infektion charakterisiert. MgrB, ein bekannter Regulator des PhoPQ-Zweikomponentensystems, erwies sich als ein für die Infektion von Epithelzellen und Makrophagen essentielles Protein, möglicherweise über seine stabilisierende Wirkung von Flagellen oder durch Interaktion mit Sensorkinasen von Zweikomponentensystemen. YjiS, das in Salmonella bisher nicht charakterisiert wurde, hatte eine entgegengesetzte Rolle bei der Infektion, wobei seine Deletion Salmonella hypervirulent macht. Der Mechanismus, der dem zugrunde liegt, ist zwar noch unklar, beruht aber wahrscheinlich auf der Interaktion mit inneneren Membranproteinen. Insgesamt liefert diese Arbeit eine globale Beschreibung der kleinen Salmonella- Proteine im Kontext der Infektion mit einem kombinatorischen Ansatz, der die Identifizierung interessanter Kandidaten beschleunigt. Verschiedene Hochdurchsatz- Datensätze, die für ein breites Spektrum von Organismen verfügbar sind, können auf ähnliche Weise mit einem Fokus auf kleine Proteine analysiert werden. Dies wird zur Identifizierung von Schlüsselfaktoren in der Regulation verschiedener Prozesse führen und damit z. B. Targets für die Behandlung bakterieller Infektionen oder, im Falle kommensaler Bakterien, für die Modulation der Mikrobiota- Zusammensetzung liefern.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

No description available.

No description available.

To compare the optimum recoveries of an inoculation of <i>Salmonella enterica</i> serotype Typhimurium, fluorescent microspheres (1.0 μm diameter, carboxylate-modified, crimson FluoSpheres®, Molecular Probes, Eugene, OR), or a combination of both from stainless steel, three recovery methods, including a standard rinse, a one-ply composite tissue (Kimwipe®) or a sonicating brush were used. Findings were used to assess the effectiveness of fluorescent microspheres as surrogates for <i>S.</i> Typhimurium. For each method, ten coupons (304 grade, 2.5 x 8 cm) were inoculated with either 100 μl of a <i>S.</i> Typhimurium culture, or a solution of fluorescent microspheres, or both, at approximate concentrations of 10⁶. After drying for one hour, coupons were sampled using either a rinse of 100 ml of phosphate buffered saline solution (PBS) for one min, a Kimwipe® tissue method, or submerged in PBS and subjected to a sonicating brush for one min. After treatments, PBS solutions were analyzed using duplicate plate counting (<i>Salmonella</i>) or hemacytometry (microspheres). For microspheres and <i>Salmonella</i>, recovery by sonicating brush > rinse > Kimwipe® method. Additionally, the retention of microspheres on the steel ranged from 16 to 25% (mean from five coupons each recovery method). Microspheres yielded a significantly higher recovery rate (11 – 60%) than <i>Salmonella</i> (~1%) for each recovery method, therefore the microspheres used in this study, are not appropriate surrogates for <i>S.</i> Typhimurium for future recovery studies on stainless steel. However, due to their low standard deviations for their mean percent recovery, they hold the opportunity to provide better accuracy and reproducibility. / Master of Science

O experimento associando probióticos no aleitamento e creche utilizou 144 leitões do nascimento até aos 62 dias de idade no Laboratório de Pesquisa em Suínos (FMVZ USP). No aleitamento, o delineamento experimental foi inteiramente casualizado com dois tratamentos e na creche em blocos casualizados formando o esquema fatorial 2x3 com seis tratamentos. A unidade experimental no aleitamento foi a baia maternidade constituída de grade de parição e na creche gaiola suspensa com 3 animais cada, constituindo, 8 repetições por tratamento. Aos 35 dias de idade os animais da creche foram inoculados com cepa de Salmonella Typhimurium via oral. Na maternidade os tratamentos foram: Placebo (PLA), 1mL de água destilada e Probiótico A (ProbA), 5g em 15mL de água destilada. O ProbA foi aplicado em duas ocasiões, ao nascimento e 12 horas antes do desafio e os animais que não receberam ProbA, receberam PLA. Os tratamentos na creche foram: Probiótico A Probiótico B (ProbA ProbB) 30g/tonelada de ProbB na ração; Controle Probiótico B (CTL ProbB): 30g/tonelada de ProbB na ração; Probiótico A Probiótico A(ProbA ProbA); Controle Controle (CTL CTL); Probiótico A Desafio (ProbA DES); Controle Desafio (CTL DES). As variáveis; peso, consumo, ganho de peso e conversão alimentar, foram analisadas em medidas repetidas no tempo com contrastes e o escore de fezes submetido à análise de variância pelo teste de Tukey. Foi utilizado o programa computacional Statistical Analysis System SAS. Na maternidade o peso médio do ProbA foi superior ao PLA, não observando-se diferenças no ganho de peso. Na creche o ProbA mostrou-se significativamente melhor em comparação aos demais tratamentos na conversão alimentar. No escore fezes, os animais desafiados apresentaram mais diarréia, e mais eliminação de S. Typhimurium, evidenciando o efeito positivo do desafio programado. A avaliação histológica aos 63 dias revelou aspecto similar nos diferentes grupos com e sem desafio. A eficiência econômica destacou o CTL ProbB.. O estudo indicou ação positiva dos probióticos quando aplicado logo ao nascimento, por influenciar diretamente na formação da microbiota intestinal, em fases mais adiantadas como na creche os efeitos são menos diretos. / The experiment involving probiotics in lactation and nursery were used one hundred and forty four piglets were used from birth to 62 days of age at Swine Research Laboratory (USP FMVZ). In the lactation, the experimental design was randomized with two treatments and in the nursery were randomized blocks forming a 2x3 factorial, consisting of six treatments. The experimental unit considered was the pen with 3 animals, with 8 repetitions per treatment. At 35 days of age the nursery animals were inoculated with a Salmonella Typhimurium strain orally. The treatments in the maternity were: Placebo (PLA): 1mL of distilled water and Probiotic A (ProbA): 5g in 15ml of distilled water. The ProbA was applied twice, at birth and 12 hours before the challenge and the animals that received no ProbA, received PLA. At the nursery twelve hours before the challenge, the same group of piglets that received ProbA and PLA in the maternity, received reinforcement for ProbA and PLA. In the nursery: Probiotic A Probiotic B (ProbA ProbB): 30g/ton of diet; Control Probiotic B (ProbB CTL): 30g/ton of diet; Probiotic A probiotic A (ProbA probA) Control Control (CTL CTL) Probiotic Challenge (DES ProbA) Control Challenge (CTL DES).The variables analyzed were weight, consumption, weight gain and feed conversion. The variables were analyzed with repeated measures contrasts and fecal score variable was subjected to analysis of variance by Tukey test. We used the computer program Statistical Analysis System SAS. In maternity, ProbA was superior to PLA treatment and did not observe differences in weight gain. At nursery the ProbA ProbA was significantly better compared to the other treatments in feed conversion. In the feces score, challenged animals showed high scores and greater elimination of S. Typhimurium, showing the effects of the programmed challenge. Histological evaluation at 63 days showed similar appearance within different groups (challenged or not). Economic evaluation shows CTL ProbB. The study indicated positive action of probiotics applied shortly after birth, by directly influencing the formation of the intestinal tract and in nursery as the effects are less direct.