Fowl typhoid and pullorum disease are two distinct septicaemic diseases largely specific to avian species and caused by Salmonella Gallinarum and Salmonella Pullorum, respectively. They were first described more than one century ago. Since their discovery, many efforts have been made to control and prevent their occurrence in commercial farming of birds. However, they remain a serious economic problem to livestock in countries where measures of control are not efficient or in those where the climatic conditions favour the environmental spread of these microorganisms. During the past 15 to 20 years there has been an explosion of genetic and immunological information on the biology of these two organisms, which is beginning to contribute to a better understanding of the organisms and their interaction with the host. However, it is not enough simply to understand the pathology in greater and greater detail. What is needed, in addition to this increase in basic knowledge, is creative thinking to challenge existing paradigms and to develop really novel approaches to infection control.

Salmonella enterica in poultry remains a major political issue. S. enterica serovar Enteritidis, particularly, remains a world-wide problem. Control in poultry by immunity, whether acquired or innate, is a possible means of containing the problem. Widespread usage of antibiotics has led to the emergence of multiple antibiotic-resistant bacteria. This problem has indicated an increasing requirement for effective vaccines to control this important zoonotic infection. An attempt is made in the present review to explain the relatively poor success in immunizing food animals against these non-host-specific Salmonella serotypes that usually produce food-poisoning, compared with the success obtained with the small number of serotypes that more typically produce systemic “typhoid-like” diseases. New examinations of old problems such as the carrier state and vertical transmission, observed with S. Pullorum, is generating new information of relevance to immunity. Newer methods of attenuation are being developed. Live vaccines, if administered orally, demonstrate non-specific and rapid protection against infection that is of biological and practical interest. However, from the point of view of consumer safety, there is a school of thought that considers inactivated or sub-unit vaccines to be the safest. The benefits of developing effective killed or sub-unit vaccines over the use of live vaccines are enormous. Recently, there have been significant advances in the development of adjuvants (e.g. microspheres) that are capable of potent immuno-stimulation, targeting different arms of the immune system. The exploitation of such technology in conjunction with the ongoing developments in identifying key Salmonella virulence determinants should form the next generation of Salmonella sub-unit vaccines for the control of this important group of pathogens. There are additional areas of concern associated with the use of live vaccines, particularly if these are generated by genetic manipulation. Infections salmonelliques : protection non immune ou immune avec des vaccinsSalmonella enterica chez les volailles demeure un problème politique majeur. S. serovar Enteritidis, particulièrement, demeure un problème mondial. Le contrôle chez les volailles par l'immunité soit acquise soit innée, est un moyen possible de maîtriser le problème. L'utilisation, à grande échelle, des antibiotiques a conduit à l’émergence de bactéries multirésistantes aux antibiotiques. Ce problème a mis en évidence un besoin croissant de vaccins efficaces pour contrôler cette importante zoonose. Dans cette revue, on a essayé d'expliquer le succès relativement faible de l'immunisation des animaux contre les sérotypes de salmonelles non spécifiques d'hôte qui entraînent généralement des intoxications alimentaires, comparé au succès obtenu avec le petit nombre de sérotypes qui plus typiquement produisent des maladies systémiques de type “typhoïde”. Des examens nouveaux concernant de vieux problèmes tels que le statut de porteur et la transmission verticale, observés avec S. Pullorum sont générateurs de nouvelles informations en rapport avec l'immunité. Des méthodes plus récentes d'atténuation ont été développées. Les vaccins vivants, s'ils sont administrés par voie orale, démontrent une protection rapide et non spécifique contre l'infection, ce qui a un intérêt biologique et pratique. Cependant, du point de vue de la santé du consommateur, il y a une école de pensées qui considère que les vaccins sous-unitaires ou inactivés présentent la meilleure innocuité. Les bénéfices pour le développement de vaccins sous-unitaires ou inactivés efficaces par rapport à l'utilisation de vaccins vivants sont importants. Récemment, il y a eu des progrès significatifs dans le développement des adjuvants, par exemple les microsphères, qui sont capables de puissante stimulation immunitaire ciblant différentes branches du système immunitaire. L'exploitation de telle technologie conjointement avec les développements en cours concernant l'identification des déterminants clefs de la virulence des salmonelles devraient constituer la prochaine génération de vaccins salmonelle sous-unitaires pour la maîtrise de ce groupe important d'agents pathogènes. Il existe par ailleurs d'autres domaines de préoccupation, en relation avec l'utilisation de vaccins vivants, particulièrement s'ils sont issus de manipulation génétique. Salmonelleninfektionen: spezifische und unspezifische Schutzwirkung durch Vakzine Salmonella enterica beim Geflügel ist immer noch ein großes politisches Thema, wobei insbesondere S. serovar Enteritidis weiterhin ein weltweites Problem darstellt. Ein mögliches Mittel, das Problem zu kontrollieren, ist beim Geflügel die Bekämpfung mittels Induzierung einer erworbenen oder angeborenen Immunität. Der weitverbreitete Einsatz von Antibiotika hat zur Entstehung von Bakterienstämmen mit multipler Antibiotikaresistenz geführt. Dieses Problem weist auf einen zunehmenden Bedarf nach effektiven Vakzinen zur Bekämpfung dieser bedeutenden Zoonose hin. Immunisierungen gegen die geringe Anzahl von Salmonella-Serotypen, die typischerweise systemische “Typhus-ähnliche” Erkrankungen verursachen, waren recht erfolgreich. In diesem Übersichtsreferat wird der Versuch gemacht, den im Vergleich dazu relativ geringen Erfolg bei der Immunisierung Lebensmittel produzierender Tiere gegen die nicht wirtsspezifischen Salmonella-Serotypen, die gewöhnlich zu Lebensmittelvergiftungen führen, zu erklären. Neue Untersuchungen alter Probleme wie den Trägerstatus und die vertikale Übertragung im Zusammenhang mit S. Pullorum erbringen neue Informationen über die Bedeutung der Immunität. Neuere Attenuierungsmethoden werden entwickelt. Oral verabreichte Lebendvakzine induzieren einen unspezifischen und schnellen Schutz gegen die Infektion, was sowohl von biologischem als auch praktischem Interesse ist. Aus Sicht der Verbrauchersicherheit wird jedoch die der Standpunkt vertreten, dass inaktivierte oder Subunitvakzinen die sichersten Impfstoffe sind. Der Vorteil der Entwicklung wirksamer Tod- oder Subunitvakzinen ist gegenüber der Verwendung von Lebendvakzinen enorm. Kürzlich sind bedeutende Fortschritte in der Adjuvansentwicklung zum Beispiel mit den Mikrosphären, die eine starke Immunstimulation in verschiedenen Bereichen des Immunsystems auslösen können, gemacht worden. Die Ausnutzung einer derartigen Technologie in Verbindung mit der weitergehenden Forschung hinsichtlich der Identifizierung der Schlüsseldeterminanten der Salmonella-Virulenz sollte die nächste Generation von Salmonella-Subunitvazinen zur Kontrolle dieser wichtigen Erregergruppe gestalten. Es existiert aber weiterhin auch das Interesse an der Verwendung von Lebendvakzinen, insbesondere an solchen, die durch Genmanipulation optimiert werden. Infecciones por Salmonella: protección inmune y no inmune mediante vacunasSalmonella enterica continua siendo en avicultura uno de los mayores temas con repercusión política. En concreto S. serovar Enteritidis, sigue siendo un problema a nivel mundial. El control en las aves a través de la inmunidad, bien sea innata o adquirida, es probablemente una manera de contener el problema. El uso indiscriminado de antibióticos ha permitido la aparición de bacterias multirresistentes. Este problema ha mostrado la necesidad creciente de vacunas efectivas para el control de esta importante infección zoonótica. Esta revisión pretende explicar el poco éxito relativo de la inmunización de animales de abasto frente a los serotipos de Salmonella no específicos de huésped, causantes de las toxiinfecciones alimentarias, en comparación con el éxito obtenido con el bajo número de serotipos que de manera clásica producen las enfermedades de “tifoideas”. La revisión de viejos problemas como el estatus portador y la transmisión vertical, observados en S. pullorum, genera información nueva de relevancia para la inmunidad. Se están desarrollando nuevos métodos de atenuación. Las vacunas vivas, si se administran oralmente muestran una protección rápida y no específica de gran interés biológico y práctico frente a la infección. Sin embargo, desde el punto de vista de la seguridad del consumidor, hay una escuela de pensamiento que considera más seguras las vacunas inactivadas o de subunidades . Los beneficios del desarrollo de vacunas muertas o de subunidades efectivas frente al uso de vacunas vivas son enormes. Recientemente, se han obtenido grandes avances en el desarrollo de adyuvantes, por ejemplo microesferas, que son capaces de potenciar inmunoestimulación, actuando en diferentes vías del sistema inmune. La explotación de esta tecnología junto con los actuales avances en la identificación de los determinantes de la virulencia de Salmonella debería ser la próxima generación de vacunas de subunidades de Salmonella para el control de este grupo tan importante de patógenos. Hay otros puntos de preocupación asociados al uso de vacunas vivas, principalmente si éstas se han generado mediante manipulación genética.

As a part of the 40th anniversary celebrations of Avian Pathology we review the last four decades of Salmonella research which has led to major progress in our understanding of the bacteriology and infection biology of the organism through the huge advances in molecular biology and immunology that have accompanied technical advances in biology generally. In many countries combinations of improvements in management, sometimes under legislative pressure and supported by a number of basic biological interventions, have resulted in reductions in incidence in the Salmonella serovars that are commonly associated with food-poisoning to unprecedented low levels in parent flocks, broilers and layers. Utilisation of the information generated during the past few decades should improve the efficacy of surveillance and biological interventions both for the intestinal carriage that is associated most frequently with human infection and also for systemic diseases, including fowl typhoid and pullorum disease. These two diseases continue to be major economic problems in many countries where the possibilities for improvements in hygiene may be limited but which, nevertheless, are increasingly a significant part of the global economy in poultry meat.

The pattern of global gene expression inSalmonella entericaserovar Typhimurium bacteria harvested from the chicken intestinal lumen (cecum) was compared with that of a late-log-phase LB broth culture using a whole-genome microarray. Levels of transcription, translation, and cell divisionin vivowere lower than thosein vitro.S.Typhimurium appeared to be using carbon sources, such as propionate, 1,2-propanediol, and ethanolamine, in addition to melibiose and ascorbate, the latter possibly transformed tod-xylulose. Amino acid starvation appeared to be a factor during colonization. Bacteria in the lumen were non- or weakly motile and nonchemotactic but showed upregulation of a number of fimbrial andSalmonellapathogenicity island 3 (SPI-3) and 5 genes, suggesting a close physical association with the host during colonization.S.Typhimurium bacteria harvested from the cecal mucosa showed an expression profile similar to that of bacteria from the intestinal lumen, except that levels of transcription, translation, and cell division were higher and glucose may also have been used as a carbon source.

Salmonella enterica is a facultative intracellular pathogen of worldwide importance. Over 2,500 serovars exist and infections in humans and animals may produce a spectrum of symptoms from enteritis to typhoid depending on serovar- and host-specific factors. S. Enteritidis is the most prevalent non-typhoidal serovar isolated from humans with acute diarrhoeal illness in many countries. Human infections are frequently associated with direct or indirect contact with contaminated poultry meat or eggs owing to the ability of the organism to persist in the avian intestinal and reproductive tract. The molecular mechanisms underlying colonisation of poultry by S. Enteritidis are ill-defined. Targeted and genome-wide mutagenesis of S. Typhimurium has revealed conserved and host-specific roles for selected fimbriae in intestinal colonisation of different hosts. Here we report the first systematic analysis of each chromosomally-encoded major fimbrial subunit of S. Enteritidis in intestinal colonisation of chickens.

Salmonella entericainfection affects a wide range of animals and humans, and a small number of serovars cause typhoid-like infections, one characteristic of which is persistent infection in convalescents. Avian-specificS. entericaserovar Pullorum produces systemic disease in young chickens, which is followed by a carrier state in convalescent birds, leading to infection of the ovary at sexual maturity and vertical transmission.