Search

Salmonella Typhimurium (including S.Typhimurium 1,4,[5],12:i-) and other enteric pathogens cause acute infection in pigs during the weaning stage, often evolving into chronic infections responsible for the introduction of zoonotic bacteria into the slaughterhouse and thus determining carcass contamination. In addition to being zoonotic hazards, these pathogens are responsible for economic losses in affected farms. Traditionally, antibiotic treatments have been largely administered in order to reduce the infection burden but it favored, as a direct consequence, an increase in the number of multi-drug resistance strains. In order to overcome antibiotic-resistance concerns, new alternative control strategies should be developed. In this context, a blend of organic acids, phytochemicals and a permeabilizing complex, administered in feed (Group A - 459 piglets) or water (Group B - 458 piglets), was tested in field conditions for its capability of reducing Salmonella-infection in weaned piglets of an endemic farm. Data recorded were compared to results of a control group (Group C - 456 piglets). Zootechnical parameters were recorded in all animals, while microbiological, serological and PCR analyses were conducted in 15 piglets for each group. Results demonstrated that additive administered in feed improved animal weight gain (better average daily gain [A.D.G.] and increment), and rapidly reduced Salmonella-shedding in feces. Administration of additive in feed gave better results than in water.

Background: Salmonella enterica serovar Choleraesuis (S. Choleraesuis) infection causes a systemic disease in pigs. Vaccination could represent a solution to reduce prevalence in farms. In this study, we aimed to assess the efficacy of an attenuated strain of Salmonella enterica serovar Typhimurium (S. Typhimurium ΔznuABC) against S. Choleraesuis infection. The vaccination protocol combined priming with attenuated S. Typhimurium ΔznuABC vaccine and boost with an inactivated S. Choleraesuis vaccine and we compared the protection conferred to that induced by an inactivated S. Choleraesuis vaccine., Methods: The first group of piglets was orally vaccinated with S. Typhimurium ΔznuABC and boosted with inactivated S. Choleraesuis, the second one was intramuscularly vaccinated with S. Choleraesuis inactivated vaccine and the third group of piglets was unvaccinated. All groups of animals were challenged with a virulent S. Choleraesuis strain at day 35 post vaccination., Results: The results showed that the vaccination protocol, priming with S. Typhimurium ΔznuABC and boosted with inactivated S. Choleraesuis, applied to group A was able to limit weight loss, fever and organs colonization, arising from infection with virulent S. Choleraesuis, more effectively, than the prime-boost vaccination with homologous S. Choleraesuis inactivated vaccine (group B)., Conclusion: In conclusion, these research findings extend the validity of attenuated S. Typhimurium ΔznuABC strain as a useful mucosal vaccine against S. Typhimurium and S. Choleraesuis pig infection. The development of combined vaccination protocols can have a diffuse administration in field conditions because animals are generally infected with different concomitant serovars.

Salmonella enterica serovar Typhimurium is an important zoonotic gastrointestinal pathogen responsible for foodborne disease worldwide. It is a successful enteric pathogen because it has developed virulence strategies allowing it to survive in a highly inflamed intestinal environment exploiting inflammation to overcome colonization resistance provided by intestinal microbiota. In this study, we used piglets featuring an intact microbiota, which naturally develop gastroenteritis, as model for salmonellosis. We compared the effects on the intestinal microbiota induced by a wild type and an attenuated S. Typhimurium in order to evaluate whether the modifications are correlated with the virulence of the strain. This study showed that Salmonella alters microbiota in a virulence-dependent manner. We found that the wild type S. Typhimurium induced inflammation and a reduction of specific protecting microbiota species (SCFA-producing bacteria) normally involved in providing a barrier against pathogens. Both these effects could contribute to impair colonization resistance, increasing the host susceptibility to wild type S. Typhimurium colonization. In contrast, the attenuated S. Typhimurium, which is characterized by a reduced ability to colonize the intestine, and by a very mild inflammatory response, was unable to successfully sustain competition with the microbiota.

The monophasic variant of Salmonella enterica serovar Typhimurium, namely Salmonella 1,4,[5],12:i-, has been increasingly responsible for foodborne human cases of disease and is most frequently detected in pork, since the variant is widely spread in pig farms. The aim of this study was to assess the efficacy of an autologous vaccine in decreasing the prevalence of Salmonella 1,4,[5],12:i-, in pigs. The trial was performed in a multisite pig production system of Northern Italy. The autogenous vaccine was prepared from the Salmonella 1,4,[5],12:i- strain isolated from the clinical case occurring in the Farm. Different immunization protocols were applied, ranging from interventions only in sows or piglets, or both. Microbiological analysis was performed to assess faecal shedding in sows and their offspring from birth till end of the production cycle and organ colonization of slaughtered pigs. Body weight of pigs was recorded at different time-points. Humoral immune response was evaluated in serum samples of sows and piglets. S. Typhimurium 1,4,[5],12:i- determines reduction of animal growth and farm production, furthermore, contamination of carcasses at the slaughterhouse. The load of bacteria entering into the food processing chain is differently influenced by the regimen of administration of inactivated vaccine. In particular, a combined vaccination of sows and their offspring was able to improve the weight gain of growing pigs, to limit Salmonella colonization of organs and to reduce the number of carrier pigs, and hence lowering the risk of introducing Salmonella organisms in the slaughter process., (Copyright © 2015. Published by Elsevier B.V.)

Meat contamination by Salmonella spp. is emerging as a major cause of human enteric infections in industrialized countries. The attempts to reduce human cases of salmonellosis encompass pre- and post-harvest interventions. In this context, vaccination of pigs may represent an effective instrument in eliminating/reducing Salmonella burden through the food chain. We have previously demonstrated that Salmonella Typhimurium lacking the ZnuABC transporter (S. Typhimurium ΔznuABC) is a promising candidate live vaccine in different mouse models of Salmonella Typhimurium infection. In this study, we confirmed in pigs the attenuation of S. Typhimurium ΔznuABC. Moreover, we evaluated the safety and immunogenicity of S. Typhimurium ΔznuABC administered to pigs by the oral route. We monitored clinical conditions of animals and we conducted a microbiological culture and a quantification of the humoral and cellular immune response, respectively, on fecal and blood samples of pigs. After vaccination with attenuated S. Typhimurium ΔznuABC, pigs showed a modest degree of hyperthermia. In addition, fecal shedding of S. Typhimurium ΔznuABC could not be detected 28 days after the inoculum. Furthermore, vaccination with S. Typhimurium ΔznuABC elicited a distinct production of anti-Salmonella antibodies and IFN-γ. Taken together, these results suggest that S. Typhimurium ΔznuABC is attenuated and immunogenic in pigs. Although the vaccine dosages do not guarantee complete safety there is ample margin to set up better conditions of use, suggesting that S. Typhimurium ΔznuABC could be a promising attenuated strain to be used as live mucosal vaccine for oral delivery., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Highlights: [•] Parenteral administration of Salmonella Typhimurium ΔznuABC is safe and effective versus pig salmonellosis. [•] Natural and experimental infections with Salmonella Typhimurium wild type have different patterns of response. [•] Efficacy of Salmonella Typhimurium ΔznuABC is dose dependent. [Copyright &y& Elsevier]