Individual effect of the steps preceding slaughtering on Salmonella contamination of pigs

The influence of the different steps preceding pig slaughtering (waiting in the herd, transport and lairage) was studied regarding deep (organs) and surface (carcass) Salmonella contamination, by mixing SPF with contaminated pigs at the different steps. For a lairage of 2 hours and a transport of 1 hour, the caecal contamination concerned the conventional pigs and the long time mixed groups (more than lairage time). The isolated strains were from herd origin according to serotyping. After the slaughtering process, it was not possible to differentiate carcasses contamination rate for the conventional batch from those of the control group pigs (transport and lairage in Salmonella-free conditions). This study showed that without efficient control measures during slaughtering, implementation of control measures in the herd would be inefficient regarding carcass contamination rate

Modification of PCV-2 virulence by substitution of the genogroup motif of the capsid protein

Porcine circovirus type 2 (PCV-2) is the causal agent of the post-weaning multisystemic wasting syndrome (PMWS). PCV-2 are small single-stranded circular DNA viruses clustered into two main genogroups: PCV-2a and PCV-2b. Each genogroup present a specific highly-conserved motif of six amino acids (between amino acids 86 and 91) in the PCV-2 capsid protein. The aim of this study was to verify whether the motif located in the capsid protein and specific to each PCV-2 genogroup contributes to virulence. Two parental DNA clones, PCV-2a and PCV-2b, were constructed as well as two mutants DNA clones, PCV-2a/motif 2b and PCV-2b/motif 2a by exchanging the capsid motif of each genogroup. The four DNA clones were characterized in vitro as well as in vivo. Cells transfected by the four DNA clones produced infectious viruses. In specific-pathogen-free piglets transfected by the four infectious DNA clones, PCV-2b/motif 2a virulence was not attenuated while the PCV-2a/motif 2b virulence was drastically reduced compared to their parent virulence. These results suggest that the amino acids between positions 86 and 91 of the capsid protein are determinant for the virulence of isolates. However, the environment of this motif seems also involved

Estimation of transmission parameters of a fluoroquinolone-resistant Escherichia coli strain between pigs in experimental conditions

Antimicrobial resistance is of primary importance regarding public and animal health issues. Persistence and spread of resistant strains within a population contribute to the maintenance of a reservoir and lead to treatment failure. An experimental trial was carried out to study the horizontal transmission of a fluoroquinolone-resistant Escherichia coli strain from inoculated to naïve pigs. All naïve contact pigs had positive counts of fluoroquinolone-resistant E. coli after only two days of contact. Moreover, re-infections of inoculated pigs caused by newly contaminated animals were suspected. A maximum likelihood method, based on a susceptible-infectious-susceptible (SIS) model, was used to determine the transmission parameters. Two transmission levels were identified depending on the quantity of bacteria shed by infected individuals: (i) low-shedders with bacterial counts of resistant E. coli in the faeces between 5*103 and 106 CFU/g (βL = 0.41 [0.27; 0.62]), (ii) high shedders with bacterial counts above 106 CFU/g (βH = 0.98 [0.59; 1.62]). Hence, transmission between animals could be pivotal in explaining the persistence of resistant bacteria within pig herds

Acute induction of cell death-related IFN stimulated genes (ISG) differentiates highly from moderately virulent CSFV strains

Classical swine fever (CSF) severity is dependent on the virulence of the CSF virus (CSFV) strain. The earliest event detected following CSFV infection is a decrease in lymphocytes number. With some CSFV strains this leads to lymphopenia, the severity varying according to strain virulence. This lymphocyte depletion is attributed to an induction of apoptosis in non-infected bystander cells. We collected peripheral blood mononuclear cells (PBMC) before and during 3 days post-infection with either a highly or moderately virulent CSFV strain and subjected them to comparative microarray analysis to decipher the transcriptomic modulations induced in these cells in relation to strain virulence. The results revealed that the main difference between strains resided in the kinetics of host response to the infection: strong and immediate with the highly virulent strain, progressive and delayed with the moderately virulent one. Also although cell death/apoptosis-related IFN stimulated genes (ISG) were strongly up-regulated by both strains, significant differences in their regulation were apparent from the observed differences in onset and extent of lymphopenia induced by the two strains. Furthermore, the death receptors apoptotic pathways (TRAIL-DR4, FASL-FAS and TNFa-TNFR1) were also differently regulated. Our results suggest that CSFV strains might exacerbate the interferon alpha response, leading to bystander killing of lymphocytes and lymphopenia, the severity of which might be due to the host’s loss of control of IFN production and downstream effectors regulation

Effect of fumonisins and Salmonella on digestive flora profiles assessed using a molecular tool (CE-SSCP).

Fumonisins (FB) are mycotoxins frequently found in vegetal feedstuffs, especially in maize used for pig feeding. Among fumonisins, FB1 was the better described toxin. It caused pulmonary and hepatic damages as well as immune response disorders in pigs that were recognised as especially sensitive to FB Intoxication. The FB1 immunosuppressor induced a higher susceptibility of pigs to gut pathogens such as E coli. Effects on Salmonella have poorly been studied despite the frequent asymptomatic carnage in pigs and the presumptive role of nora equilibrium on prevention of Salmonella excretion or re-excretion. To determine the influence of Salmonella carriage, fumonisins or both on digestive flora equilibrium, the use of a molecular technique CE-SSCP (Capillary-Electrophoresis Single Strand Conformation Polymorphism) appeared a good complement to the conventional bacteriological techniques. The objective was to assess the perturbation of nora associated with co-exposition in experimental conditions in absence of clinical sign

Utilisation de la PCR-SSCP capillaire pour l’étude de la flore digestive de groupes de porcs EOPS

Utilisation de la PCR-SSCP capillaire pour l’étude de la flore digestive de groupes de porcs EOPS. 39. Journées de la Recherche Porcin

Individual effect of the steps preceding slaughtering on Salmonella contamination of pigs

The influence of the different steps preceding pig slaughtering (waiting in the herd, transport and lairage) was studied regarding deep (organs) and surface (carcass) Salmonella contamination, by mixing SPF with contaminated pigs at the different steps. For a lairage of 2 hours and a transport of 1 hour, the caecal contamination concerned the conventional pigs and the long time mixed groups (more than lairage time). The isolated strains were from herd origin according to serotyping. After the slaughtering process, it was not possible to differentiate carcasses contamination rate for the conventional batch from those of the control group pigs (transport and lairage in Salmonella-free conditions). This study showed that without efficient control measures during slaughtering, implementation of control measures in the herd would be inefficient regarding carcass contamination rate.</p