Variability in the Resistance of Four Chicken Lines to Experimental Intravenous Infection with Salmonella enteritidis Phage Type 4

Abstract

The capacity of four chicken lines (Y11, L2, B13, PA12) to control Salmonella enteritidis (SE) phage type 4 (PT4) systemic colonization was investigated. Thirteen-week-old chickens were intravenously inoculated with 10(6) SE colony-forming units, and the levels of SE colonization were determined at various time intervals after inoculation in liver, spleen, genital organs, and ceca. The course of SE infection showed a rapid contamination of liver, spleen, and genital organs, whereas the ceca were infected later. A significant (P < 0.001) effect of the chicken line on levels of SE was detected on day 3 postinoculation (PI) in liver and ceca, on day 10 PI in ceca, and on day 15 PI in spleen. Because an early control of systemic Salmonella infection by the Ity/Nramp1 gene has been demonstrated in mice, we aimed to study the early resistance of chickens to SE. As a consequence, we then focused our study on the between- and within-line variabilities of SE levels on day 3 PI. According to the SE levels in liver on day 3 PI, the chicken lines could be classified as susceptible (Y11 and L2) or resistant (PA12 and B13). This early variability was explored in resistant B13 and susceptible L2 lines. Differences between these two lines were confirmed in liver but not in ceca. A large within-line variability was observed in all organs of these two lines. The genetic origin of this variability will have to be determined as a prerequisite to an eventual selection.

Heritability of susceptibility to Salmonella enteritidis infection in fowls and test of the role of the chromosome carrying the NRAMP1 gene

“…a maximum of 2 dams per sire with the exception of one sire mated to 3 dams); in the second experiment, 312 animals were studied. They originated from the L2 line described in [9], which is a parent of the commercial cross and were derived from 29 sires mated to a maximum of 4 dams (i.e. a total of 89 dams).…”

“…Strain 1 009 of S. enteritidis PT4, which is resistant to nalidixic acid (Nal) and streptomycin (Sm), was used for the two trials as described in [1,2,6,9,11,14].…”

“…enteritidis strain 1 009 was grown in trypticase soy broth (BioMérieux, France) overnight at 37 • C with shaking at 200 rpm [9]. The bacterial suspension was adjusted to a concentration of 10 9 colony forming units (CFU) per mL by appropriate dilutions in PBS containing glycerol (10%) and was stored at −70 • C. On the inoculation day, the bacterial suspension was diluted in sterile PBS to obtain an inoculum concentration of 2.5 × 10 6 CFU · mL −1 .…”

“…The CFU of S. enteritidis per gram were determined as described in [9] and the numbers of S. enteritidis per organ were calculated from bacterial counts and organ weight values.…”

“…These results were however obtained in very young animals while the main risk of Salmonella to humans is due to the consumption of meat or contaminated eggs from adult animals. Large differences in susceptibility have been observed between poultry lines following inoculation at the peak of lay [14] or a little earlier, at 13 weeks of age [9]. The latter inoculation protocol is easier to perform because animals are younger and intravenous inoculation is more repeatable.…”