Live and inactivated vaccine regimens against caecal Salmonella Typhimurium colonisation in laying hens.

In Australia, Salmonella serovar Typhimurium (S. Typhimurium) is the predominant zoonotic serovar in humans and is frequently isolated from layer hens. Vaccination against this serovar has been previously shown to be effective in broilers and the aim of this current study was to assess and determine the best vaccination strategy (live or inactivated) to minimise caecal colonisation by S. Typhimurium. A long-term experiment (56 weeks) was conducted on ISABROWN pullets using a commercial live aroA deleted mutant S. Typhimurium vaccine and an autogenous inactivated multivalent Salmonella vaccine (containing serovars Typhimurium, Infantis, Montevideo and Zanzibar). These vaccines were administered PO or by SC or IM injection, either alone or in combination. Pullets were vaccinated throughout rearing (to 18 weeks of age) and sequentially bled for antibody titre levels. The birds, vaccinated and controls, were challenged orally with a field isolate of S. Typhimurium at different ages, held for 21 days post-challenge, then euthanased and their caeca cultured for the presence of Salmonella. None of the oral live-vaccinated groups exhibited lasting protection. When administered twice, the inactivated vaccine gave significant protection at 17 weeks of age and the live vaccine given by SC injection given twice produced significant protection at 17, 25 and 34 weeks. Vaccination regimens that included parenteral administration of live or inactivated vaccines and thus achieved positive serum antibody levels were able to provide protection against challenge. Hence, vaccination may play a useful role in a management strategy for Salmonella carriage in layer flocks.

Groves PJ ，Sharpe SM ，Muir WI ，Pavic A ，Cox JM ... -  《-》

Oral vaccination with a live Salmonella Enteritidis/Typhimurium bivalent vaccine in layers induces cross-protection against caecal and internal organ colonization by a Salmonella Infantis strain.

Salmonella is an important zoonotic agent, and poultry products remain one of the main sources of infection for humans. Salmonella Infantis is an emerging serotype in poultry worldwide, reflected by an increased prevalence in poultry flocks, on broiler meat and in human foodborne illness cases. In the current study, the efficacy of oral administration of a live monovalent Salmonella Enteritidis and a live bivalent Salmonella Enteritidis/Typhimurium vaccine, against a Salmonella Enteritidis and Infantis infection, was determined. Oral administration of the live vaccines to day-old chickens caused a decrease in caecal colonization by Salmonella Enteritidis, but not Infantis, at day 7, when challenged at day 2. Vaccination with the bivalent vaccine at day 1 resulted in a decreased spleen colonization by both Salmonella Infantis and Enteritidis. Twice (at day 1 and week 6) and thrice vaccination (at day 1, week 6 and 16) of laying hens with the bivalent vaccine resulted in a decreased caecal colonization by Salmonella Enteritidis and Infantis, and significantly lower oviduct colonization levels by Salmonella Enteritidis. These data show cross-protection against Salmonella Infantis by oral administration of live vaccine strains belonging to other serogroups.

Eeckhaut V ，Haesebrouck F ，Ducatelle R ，Van Immerseel F ... -  《-》

Utilization of a novel autologous killed tri-vaccine (serogroups B [Typhimurium], C [Mbandaka] and E [Orion]) for Salmonella control in commercial poultry breeders.

Pavic A ，Groves PJ ，Cox JM 《-》

Evaluation of different live Salmonella enteritidis vaccine schedules administered during layer hen rearing to reduce excretion, organ colonization, and egg contamination.

Salmonellosis caused by Salmonella Enteritidis is a widespread zoonosis and poultry products are an important source of infection. This study was carried out to evaluate the protection of different vaccination schedules in layers using a live commercial attenuated Salmonella Enteritidis vaccine based on strain Sm24/Rif12/Ssq (AviPro® Salmonella Vac E, ELANCO) during rearing and egg production. Three hundred and fifty Salmonella-free chickens were distributed into 7 vaccinated groups and 1 unvaccinated group. Different vaccination schedules were performed combining either 1, 2, or 3 oral gavage doses. Chickens from Group A, B, and C were vaccinated once, either at the first day, at 7 or 16 wk old, respectively. Chickens from Group D were vaccinated twice-at the first day and 7 wk old. Chickens from Group E were vaccinated twice-at the first day and 16 wk old. Chickens from Group F were vaccinated twice-at 7 and 16 wk old. Chickens from Group G were vaccinated 3 times, following the manufacturer's recommendation: at the first day, 7 and 16 wk old. Chickens from Group H remained unvaccinated. Five challenge trials numbered 1 to 5 were carried out at 8, 12, 16, 29, and 55 wk old, respectively. After challenge, chickens were sampled by cloacal swabbing and, after euthanasia, livers, ovaries, spleens, and cecal contents were cultured to isolate S. Enteritidis. Additionally, eggs were collected after challenge and cultured to isolate S. Enteritidis on egg shells (Trials 4 and 5). Protection against experimental infection with a virulent nalidixic acid resistant S. Enteritidis strain K285/94, was evaluated by measuring reduction of excretion, colonization, invasion into organs, eggshell contamination, and egg production. The live S. Enteritidis vaccine protected the hens by reducing S. Enteritidis excretion, isolation from organs, and egg contamination. Higher protection throughout laying period was afforded after administration of three vaccine doses during rearing period.

Huberman YD ，Velilla AV ，Terzolo HR 《POULTRY SCIENCE》

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》