Probiotic yeast as part of salmonella control programs
In 2003, the European Union introduced Salmonella control programs for poultry flocks (regulation (EC) No. 2160/2003) with a goal of preventing the spread of this significant foodborne pathogen to humans. The number of human S. enteritidis cases then dropped by 60% between 2007 and 2011(1). But since 2014, the trend has reversed, as confirmed in another recent EFSA repport(2) (Fig. 1).
Foodborne pathogen control is a multi-factorial issue, that concerns the whole poultry production chain, from farm to fork. It has led the industry to develop integrated prevention programs that are implemented from the feed mill to the farm building. Today, a new nutritional tool can be integrated within a comprehensive pathogen control strategy. The European Union has authorized the live yeast probiotic strain Saccharomyces cerevisiae var. boulardii CNCM I-1079 as a feed additive for the reduction of carcass contamination by Salmonella spp. in broiler chickens (3).
Figure 1: Trend in reported confirmed human cases of non-typhoidal salmonellosis in the EU/EEA, by month, 2012-2016.
Salmonella key figures
HUMAN: In 2017, close to 92,662 cases of salmonellosis were reported in humans, posing an important public health concern. A seasonal trend was observed for confirmed salmonellosis cases in the EU/EEA in 2013–2017, with more cases reported during summer months. S. enteritidis is by far the main species involved in human foodborne diseases (49.1 % of cases) and continues to increase.
BROILERS: The poultry monitoring data in compliance with the Salmonella National Control Programmes shows that Salmonella was found in 3.31% of the broilers flocks in 2017.
FEED: 1.32% of all poultry feed samples taken from 24 countries tested positive for Salmonella. It is a very resistant bacteria, able to survive for more than 9 days in the poultry faeces. Feed or water contaminated through a feces excretion are the major vectors suspected of spreading disease in poultry.
Salmonella enteriditis control strategies
Salmonellacontrol strategies involve the whole chain, from farm to fork (Fig. 2). It represents an important economic burden for the whole industry due to strict prevention and control procedures required at each level.
Figure 2: Salmonellal prevention from farm to fork
1/- PRODUCTION: Salmonellacan colonize the entire poultry digestive tract from the crop to the caecum. It colonizes the lumen, interacts closely with the mucosa and can penetrate the epithelium barrier, triggering immune responses. At the farm level, chickens natural defenses are essential. Salmonellacontrol program includes(4):
• Biosecurity: Strict control of farm hygiene, buildings, feed, water and all potential disease carriers entering the farm–especially rodents, as they can be main sources of infection, insects and personnel.
• Farm management practices to limit contamination (vaccination, ventilation and litter management, etc).
• Monitoring and sampling: Sampling of the farm environment through boot swabs is conducted to detect positive flocks. In broilers, official control sampling is mandatory three weeks before slaughtering (preferably as close as possible to slaughter). Several automatic controls are recommended for each building. For flocks over 5,000 broilers, random sampling is conducted by the national vet services.
• Cleaning and disinfection of the farm building and equipment after emptying the poultry house and/or site. This includes water and feeding systems. When Salmonella has been found, it might be advisable to consult an expert or veterinarian as routine disinfectant concentrations, are not suitable to address Salmonella, which is relatively resistant to disinfectants. In addition, vermin, insect and wild animals are important to consider when the barn is emptied.
• Another imperative part of the prevention program concerns the catching, loading and transportation of the live birds, where strict hygiene procedures should be in place.
2/- FEED-MILL LEVEL
As feed can be a potential vector, strict preventive measures and controls are obviously implemented at the feed mill level, in accordance with the prescriptions provided by national authorities. In Europe, feed suppliers are required to implement permanent procedures based on the HACCP principles includes Salmonellacontrol. Salmonella sppis killed by 121 min at 54.4°C or 5 min at 72.2°C., or acid treatment (formic and/or propionic acid). Finished feed should ideally be delivered to the farm in dedicated vehicles that are not back loaded with raw ingredients, other feeds or materials, or thoroughly cleaned and disinfected before loading finished feed.
3/- PROCESSING & TRANSPORTATION
There the evisceration process must be strictly establish to avoid the carcass contamination. Official measures require control samplings (HACCP and internal checks) by the food business operators. Processed food transportation follows strict procedures including truck cleaning and disinfection, prescriptive temperatures during transport and more.
4/- RETAILERS: Official control monitoring includes sampling by food business operators, storage conditions restriction, cooking prevention measures such as handling and cooking raw chicken meat separately.
5/- CONSUMERS AND RESTAURANTS: Measures require storage restrictions, cooking prevention measures, staff training on safe handling practices and more.
How to assess Salmonella prevalence of contamination at slaughterhouses?
Salmonella is isolated and serotyped on the carcasses. Prevalence of contamination is assessed by sampling and microbial counting directly on the carcass in three areas: neck, breast and cloacal skin. Caecal samples can also be analyzed in addition to, or in place of, skin sampling. In case of contamination, carcass heating is used in Europe for decontamination. Good hygiene procedures must be carried throughout slaughtering, processing, transportation, retail sales locations and even into the consumer's home.
Probiotic yeast, an extra tool
Documented probiotics can help balance the digestive microbiota and reinforce the hosts' natural defenses, contributing to a more positive microbial balance. As a result, this could contribute to reduced foodborne pathogen carriage. This is the case of the specific live yeast strain S. c. boulardii CNCM I-1079. It is today the first and only probiotic authorized in the European Union as a feed additive for the "reduction of Salmonella contamination on carcasses through its decrease in the feces."
This regulatory breakthrough is based on an extensive knowledge of the S. c. boulardiiCNCM I-1079 mode of action and its positive effects in the digestive tract (see boxed text page 4).
Robust studies have been conducted in research stations across Europe with both experimental and naturally occurring Salmonellachallenges. All show a significant reduction of Salmonellaprevalence on the broilers carcasses when fed the probiotic yeast. A recently communicated multi-analysis (6) compiles results of five studies in broiler chickens from the scientific literature (3 with experimental Salmonella challenges and two with natural occurrence). This analysis concluded that feeding the live yeast lead to a significant reduction of the number of animals positive for Salmonella carriage (P<0.05) and of the number of carcasses contaminated with the foodborne pathogen (P<0.05). (Fig. 3).
Figure 3: Effect of S. c. boulardii CNCM I-1079 supplementation on Salmonella prevalence following Salmonella spp. challenge.
In addition, trials conducted under Salmonellaand Campylobacterpathogen challenges and supplemented with S. cerevisiae boulardiiCNCM I-1079 indicate the probiotics enabled broilers to preserve zootechnical performances (body weight and feed conversion rate) despite challenging conditions. On the other hand, the control birds suffered from reduced growth performance.
About S. c. boulardiiCNCM I-1079
There are thousands of different yeast strains. S. cerevisiae boulardiiis the yeast documented in human medicine and recognized to be effective in preventing digestive pathologies such as traveler’s diarrhea, antibiotic-associated diarrheas and pseudomembranous colitis (nosocomial disease) with more than 300 publications describing its health benefits and specific mode of action.
The mode of action of S.c. boulardii CNCM I-1079 is based on a three-fold strategy, targeting the three lines of defenses:
1) Intestinal microbiota balance:
S. c. boulardiiCNCM I-1079 helps support the development of beneficial bacteria and neutralizes the growth of certain undesirable bacteria in the gut, in particular thanks to its ability to consume residual oxygen in the gut (oxygen scavenging), inducing a favorable environment for beneficial flora. This way, the growth of pathogens such as Salmonellaand Campylobactercan be reduced.
2) Preserved intestinal integrity and gut morphology:
S. c. boulardiiCNCM I-1079 helps improve the surface absorption area with an increase of the villus height and the ratio villus height/crypt depth. It also exerts a positive effect on intestinal permeability through reinforcing tight junctions between gut epithelial cells and by reducing the bacteria adherence capacity to the epithelial cells. Salmonellaand Campylobacterbeing hosted in the digestive tract, the integrity of the gut barrier is a very important parameter to limit the risk of contamination from the digestive content to the meat at slaughtering.
3) Natural defenses modulation:
Birds' natural defenses are reinforced with S. c. boulardiiCNCM I-1079, through local immune system modulation. This is translated into the reduction of pro-inflammatory cytokines such as TNF-α, Il-1β, Il-6, Il-8 while the production of protective IgA antibodies and anti-inflammatory cytokines (Il-10) is enhanced.
This triple action strengthens the barrier functions of the gut and improves the microflora balance, resulting in better resistance to digestive challenges and zootechnical performance.
In the global context of fighting antimicrobial resistance in the EU, the reduction of antimicrobial usage in livestock production is a key target while increased emphasis is placed on food safety and food quality. Salmonellosis is one of the major foodborne diseases facing the poultry industry worldwide. Salmonellacontrol is a multi-factorial issue that should concern the whole production chain, from farm to fork. Having a new additive with substantial technical and scientific research — and that is recognized to help reduce the risk of Salmonellacarcass contamination — is good news for the whole food chain.
For more of the article, please click here.
Article made possible through the contribution of Lallemand