The most common source of Salmonella infections in humans is food of poultry origin. Salmonella enterica serovar Enteritidis has a particular affinity for the contamination of the egg supply. In this study, the medium-chain fatty acids (MCFA), caproic, caprylic, and capric acid, were evaluated for the control of Salmonella serovar Enteritidis in chickens. All MCFA were growth inhibiting at low concentrations in vitro, with caproic acid being the most potent. Contact of Salmonella serovar Enteritidis with low concentrations of MCFA decreased invasion in the intestinal epithelial cell line T84. By using transcriptional fusions between the promoter of the regulatory gene of the Salmonella pathogenicity island I, hilA, and luxCDABE genes, it was shown that all MCFA decreased the expression of hilA, a key regulator related to the invasive capacity of Salmonella. The addition of caproic acid (3 g/kg of feed) to the feed of chicks led to a significant decrease in the level of colonization of ceca and internal organs by Salmonella serovar Enteritidis at 3 days after infection of 5-day-old chicks. These results suggest that MCFA have a synergistic ability to suppress the expression of the genes required for invasion and to reduce the numbers of bacteria in vivo. Thus, MCFA are potentially useful products for reducing the level of colonization of chicks and could ultimately aid in the reduction of the number of contaminated eggs in the food supply.

Short-chain fatty acids have been widely used as feed additives to control Salmonella in poultry. Data on the use of butyric acid in poultry are lacking. In this study, powder form and coated butyric acid were compared in their ability to reduce Salmonella colonization of ceca and internal organs shortly after infection of young chickens with Salmonella enteritidis. In the first trial, 4 groups of 25 specific pathogen free layer chickens were given feed either supplemented with powder form butyric acid, coated butyric acid, a combination of powder form and coated butyric acid (all groups received a total of 0.63 g of butyric acid/kg) or nonsupplemented feed. The specific pathogen free layer chickens were orally infected with 10(6) cfu of S. enteritidis. Coated butyric acid significantly decreased cecal colonization 3 d post-infection compared with control chickens, and powder form butyric acid had no effect. To study long-term shedding and colonization of Salmonella in broilers given coated butyric acid as feed additive (0.63 g of active product butyric acid/kg), 10 Ross broiler chickens were infected at d 5 with 10(5) cfu of S. enteritidis and housed together with 40 noninfected broilers. A control group received nonsupplemented feed. The group of broilers receiving coated butyric acid had a significantly lower number of broilers shedding Salmonella bacteria, but cecal colonization at slaughter age was equal for both groups. In conclusion, butyric acid decreases cecal colonization shortly after infection, decreases fecal shedding, and as a consequence, decreases environmental contamination by S. enteritidis-infected broilers. However, complete elimination can probably only be achieved with a combined approach using both hygienic measures and different protection measures, as the broilers still carried S. enteritidis bacteria in the ceca at slaughter age, although at enrichment level.

Poultry are very likely to become infected with Salmonella in the early posthatch period, due to environmental contamination. The purpose of this study was to evaluate the effect of infection dose on the risk of persistent infection in laying hens. In this study, young layer chicks were orally infected with a low (10(2) at 1 d posthatch) or a high dose (10(9) cfu at 1 wk posthatch) of Salmonella Enteritidis. The pattern and duration of fecal shedding was studied for 18 wk. All chickens shed Salmonella early after infection and shed Salmonella intermittently during the whole study period. There were more positive birds in the high-dose group than in the low-dose group in the first weeks following Salmonella exposure. From 10 wk postinfection onwards, however, birds that were orally infected with the low dose of Salmonella Enteritidis shed more Salmonella than the birds that received the high dose. At 18 wk of age, there was no difference in cecal colonization between the treatment groups. It can be concluded that infection of newly hatched chicks with a low dose of Salmonella Enteritidis can lead to persistent infection until onset of lay, hereby excreting Salmonella bacteria intermittently.

No abstract

No abstract