Administration of a Salmonella Enteritidis ΔhilAssrAfliG strain by coarse spray to newly hatched broilers reduces colonization and shedding of a Salmonella Enteritidis challenge strain.

Consumption of contaminated poultry meat is still an important cause of Salmonella infections in humans. Colonization inhibition (CI) occurs when a live Salmonella strain is administered to chickens and subsequently protects against challenge with another Salmonella strain belonging to the same serotype. A Salmonella Enteritidis hilAssrAfliG deletion mutant has previously been proven to reduce colonization and shedding of a wild-type Salmonella Enteritidis strain in newly hatched broilers after experimental infection. In this study, we compared two administration routes for this strain. Administering the Salmonella Enteritidis ΔhilAssrAfliG strain through drinking water on the first day of life resulted in decreased fecal shedding and cecal colonization of a wild-type Salmonella Enteritidis challenge strain administered 24 h later using a seeder-bird model. When administering the CI strain by coarse spray on newly hatched broiler chicks, an even more pronounced reduction of cecal colonization was observed, and fecal shedding of the Salmonella Enteritidis challenge strain ceased during the course of the experiment. These data suggest that administering a Salmonella Enteritidis ΔhilAssrAfliG strain to newly hatched chicks using a coarse spray is a useful and effective method that reduces colonization and shedding of a wild-type Salmonella Enteritidis strain after early challenge.

De Cort W ，Haesebrouck F ，Ducatelle R ，van Immerseel F ... -  《-》

A Salmonella Enteritidis hilAssrAfliG deletion mutant is a safe live vaccine strain that confers protection against colonization by Salmonella Enteritidis in broilers.

Consumption of contaminated poultry meat is an important cause of Salmonella infections in humans. Therefore, there is a need for control methods that protect broilers from day-of-hatch until slaughter age against infection with Salmonella. Colonization-inhibition, a concept in which a live Salmonella strain is orally administered to day-old chickens and protects against subsequent challenge, can potentially be used as control method. In this study, the safety and efficacy of a Salmonella Enteritidis ΔhilAssrAfliG strain as a colonization-inhibition strain for protection of broilers against Salmonella Enteritidis was evaluated. After administration of the Salmonella Enteritidis ΔhilAssrAfliG strain to day-old chickens, this strain could not be isolated from the gut, internal organs or faeces after 21 days of age. In addition, administration of this strain to one-day-old broiler chickens decreased faecal shedding and caecal and internal organ colonization of a Salmonella Enteritidis challenge strain administered one day later using a seeder bird model. To our knowledge, this is the first report of an attenuated Salmonella strain for which both the safety and efficacy has been shown in long-term experiments (until slaughter age) in broiler strain can potentially be used as a live colonization-inhibition strain for controlling Salmonella Enteritidis infections in broilers.

De Cort W ，Geeraerts S ，Balan V ，Elroy M ，Haesebrouck F ，Ducatelle R ，Van Immerseel F ... -  《-》

A colonisation-inhibition culture consisting of Salmonella Enteritidis and Typhimurium ΔhilAssrAfliG strains protects against infection by strains of both serotypes in broilers.

Consumption of contaminated poultry meat is still an important cause of Salmonella infections in humans and there is a need for control methods that protect broilers from day-of-hatch until slaughter age against infection with Salmonella. Colonisation-inhibition, a concept in which a live Salmonella strain is orally administered to day-old chickens and protects against subsequent challenge, can potentially be used as control method. In this study, the efficacy of a Salmonella Typhimurium ΔhilAssrAfliG strain as a colonisation-inhibition strain for protection of broilers against Salmonella Typhimurium was evaluated. Administration of a Salmonella Typhimurium ΔhilAssrAfliG strain to day-old broiler chickens decreased faecal shedding and strongly reduced caecal and internal organ colonisation of a Salmonella Typhimurium challenge strain administered one day later using a seeder bird model. In addition, it was verified whether a colonisation-inhibition culture could be developed that protects against both Salmonella Enteritidis and Typhimurium. Therefore, the Salmonella Typhimurium ΔhilAssrAfliG strain was orally administered simultaneously with a Salmonella Enteritidis ΔhilAssrAfliG strain to day-old broiler chickens, which resulted in a decreased caecal and internal organ colonisation for both a Salmonella Enteritidis and a Salmonella Typhimurium challenge strain short after hatching, using a seeder bird model. The combined culture was not protective against Salmonella Paratyphi B varietas Java challenge, indicating serotype-specific protection mechanisms. The data suggest that colonisation-inhibition can potentially be used as a versatile control method to protect poultry against several Salmonella serotypes.

De Cort W ，Mot D ，Haesebrouck F ，Ducatelle R ，Van Immerseel F ... -  《-》

Orally administered attenuated Salmonella enteritidis reduces chicken cecal carriage of virulent Salmonella challenge organisms.

Cerquetti MC ，Gherardi MM 《VETERINARY MICROBIOLOGY》

Comparative study of the protective effect against Salmonella colonisation in newly hatched SPF chickens using live, attenuated Salmonella vaccine strains, wild-type Salmonella strains or a competitive exclusion product.

There is a need to prevent intestinal colonisation by Salmonella enteritidis and S. typhimurium in newly hatched chicks. Treatment with an undefined bacterial flora is not acceptable to regulatory agencies in some countries because of the potential risk of transmitting pathogens. A defined culture with a potency and stability equivalent to those of an undefined culture has not yet been developed. Since attenuated Salmonella vaccine strains could possess the colonisation characteristics but not the virulence of Salmonella wild-type strains, they could inhibit colonisation of the challenge organism. S. typhimurium live vaccines registered in Germany (Zoosaloral H, Salmonella vac T), S. enteritidis aroA and S. typhimurium aroA strains, S. enteritidis, S. typhimurium and S. infantis wild-type strains or a competitive exclusion product (Broilact) were used as pretreatment cultures and evaluated for their inhibitory effects against S. enteritidis and S. typhimurium colonisation in newly hatched SPF chickens. Day-old chicks were administered a pretreatment culture and infected orally with variants of S. enteritidis or S. typhimurium wild type-strains resistant to nalidixic acid or rifampicin 1 day after pretreatment. On days 2 and 6 after infection, viable numbers of the challenge strain in liver and caeca were determined. The results for birds pretreated with Broilact showed a distinct protective effect against both S. enteritidis and S. typhimurium at a challenge dose of 10(4) cfu/bird. After pretreatment of chicks with S. enteritidis and S. typhimurium wild-type strains, the greatest degree of inhibition of caecal colonisation was produced using isogenic strains. Colonisation after infection with non-isogenic strains could not be prevented but only reduced for a brief period. These effects were also observed after administration of aroA strains of S. enteritidis and S. typhimurium but the protective effect was considerably lower than after pretreatment with wild-type Salmonella strains. Inoculation with attenuated S. typhimurium vaccines resulted in a weak but significantly reduced colonisation by S. typhimurium. Colonisation by S. enteritidis could not be diminished by either of the S. typhimurium vaccine strains. The results indicate in principle the potency of Salmonella vaccine strains to inhibit Salmonella wild-type colonisation in newly hatched chicks. Potential vaccine candidates should be tested for their capacity to prevent intestinal colonisation in newly hatched chicks.

Methner U ，Barrow PA ，Martin G ，Meyer H ... -  《INTERNATIONAL JOURNAL OF FOOD MICROBIOLOGY》