T. gondii strains and their dosage influence the parasitic load in tissues of experimentally infected pigs

One of the major routes of a Toxoplasma gondii infection in humans is the consumption of raw or undercooked meat. In the present study, we compared the parasitic load induced by 2 different T. gondii strains in the tissues of experimentally infected 6 weeks old pigs. In the first experiment, pigs were orally infected with 3000 tissue cysts of IPB-Gangji strain. The pigs were euthanized 2 and 6 months after infection, and the following samples were tested by bio-assay and qPCR: brain, heart and several skeletal muscles. Two months after infection, all samples tested positive with both tests. Remarkably, after 6 month no cysts were detected in tenderloin and ham, while brain and heart tissue remained infectious. In the second experiment, pigs were infected orally with a low (700 cysts) and a high (6000) dose of T. gondii IPB-Gangji cysts and euthanized after 4 months. The parasitic load was much higher in the low dose group than in the high dose group, as determined by qPCR. In most animals various samples tested negative in both groups, with the exception of the intercostals muscles. Last experiment was repeated with a low and a high dose of the T. gondii IPB-LR strain. Here, all samples remained infectious with no significant difference in parasitic load between both groups. The parasitic load was higher in brain and heart tissue compared to the skeletal muscles. In bio-assay, numerous mice died from the inoculated samples from pigs infected with the IPB-Gangji strain. Ascites and lungs tested T. gondii positive by qPCR. When inoculated with samples from pigs infected with the IPB-LR strain, no mice died from acute T. gondii infection

Strain- and dose-dependent reduction of Toxoplasma gondii burden in pigs is associated with interferon-gamma production by CD8+ lymphocytes in a heterologous challenge model

Toxoplasma gondii is a worldwide prevalent parasite of humans and animals. The global infection burden exceeds yearly one million disability-adjusted life years (DALY's) in infected individuals. Therefore, effective preventive measures should be taken to decrease the risk of infection in humans. Although human toxoplasmosis is predominantly foodborne by ingestion of tissue cysts in meat from domestic animals such as pigs, the incidence risk is difficult to estimate due to the lack of screening of animals for infection and insights in location and persistence of the parasite in the tissues. Hence, experimental infections in pigs can provide more information on the risk for zoonosis based on the parasite burden in meat products intended for human consumption and on the immune responses induced by infection. In the present study, homo-and heterologous infection experiments with two distinct T. gondii strains ( IPB-LR and IPB-Gangji) were performed. The humoral and cellular immune responses, the presence of viable parasites and the parasite load in edible meat samples were evaluated. In homologous infection experiments the parasite persistence was clearly strain-dependent and inversely correlated with the infection dose. The results strongly indicate a change in the amount of parasite DNA and viable cysts in porcine tissues over time. Heterologous challenge infections demonstrated that IPB-G strain could considerably reduce the parasite burden in the subsequent IPB-LR infection. A strong, however, not protective humoral response was observed against GRA7 and TLA antigens upon inoculation with both strains. The in vitro IFN-gamma production by TLA-stimulated PBMCs was correlated with the infection dose and predominantly brought about by CD3+ CD4-CD8 alpha bright T-lymphocytes. The described adaptive cellular and humoral immune responses in pigs are in line with the induced or natural infections in mice and humans. Previous studies underscored the heterogeneity of T. gondii strains and the corresponding virulence factors. These findings suggest the potential of the IPB-G strain to elicit a partially protective immune response and to reduce the parasite burden upon a challenge infection. The IPB-G strain could be used as a promising tool in limiting the number of viable parasites in edible tissues and, hence, in lowering the risk for human toxoplasmosis

Trend analysis of antimicrobial resistance in Campylobacter jejuni and Campylobacter coli isolated from Belgian pork and poultry meat products using surveillance data of 2004-2009

The purpose of this study was to analyze and compare antimicrobial resistance in Campylobacter spp. isolated from pork and poultry carcasses and pork and poultry meat(at slaughterhouse level, during meat cutting and at retail) in Belgium, using available surveillance data over the period 2004-2009. The susceptibilities of 1724 Campylobacter isolates for ampicillin, ciprofloxacin, nalidixic acid, tetracycline, erythromycin and gentamicin were tested by E-test. Gentamicin resistance was low (near 0%) till 2007, with an increase to over 20% by 2009 for all species-matrix combinations. Resistance to tetracycline fluctuated around the same level during the entire study period and was significantly higher (p-value <0.05) in C. coli than in C. jejuni. Erythromycin resistance was low and showed a slight decrease between 2004 and 2007, but increased from 2007 till 2009. Fluoroquinolone and ampicillin resistance was significantly higher in isolates derived from poultry, compared to pork-related isolates. This correlates with the higher use of these antimicrobials in poultry husbandry. With one out of four, C. coli from poultry showed the most apparent multiresistance (resistance to four or more antimicrobials). Approximately 1% of the poultry-derived isolates (both C. coli and C. jejuni) showed resistance to all tested antimicrobials, while none was found in pork product

T. gondii strains and their dosage influence the parasitic load in tissues of experimentally infected pigs

One of the major routes of a Toxoplasma gondii infection in humans is the consumption of raw or undercooked meat. In the present study, we compared the parasitic load induced by 2 different T. gondii strains in the tissues of experimentally infected 6 weeks old pigs. In the first experiment, pigs were orally infected with 3000 tissue cysts of IPB-Gangji strain. The pigs were euthanized 2 and 6 months after infection, and the following samples were tested by bio-assay and qPCR: brain, heart and several skeletal muscles. Two months after infection, all samples tested positive with both tests. Remarkably, after 6 month no cysts were detected in tenderloin and ham, while brain and heart tissue remained infectious. In the second experiment, pigs were infected orally with a low (700 cysts) and a high (6000) dose of T. gondii IPB-Gangji cysts and euthanized after 4 months. The parasitic load was much higher in the low dose group than in the high dose group, as determined by qPCR. In most animals various samples tested negative in both groups, with the exception of the intercostals muscles. Last experiment was repeated with a low and a high dose of the T. gondii IPB-LR strain. Here, all samples remained infectious with no significant difference in parasitic load between both groups. The parasitic load was higher in brain and heart tissue compared to the skeletal muscles. In bio-assay, numerous mice died from the inoculated samples from pigs infected with the IPB-Gangji strain. Ascites and lungs tested T. gondii positive by qPCR. When inoculated with samples from pigs infected with the IPB-LR strain, no mice died from acute T. gondii infection

QuilA-adjuvanted T. gondii lysate antigens trigger robust antibody and IFNγ+ T cell responses in pigs leading to reduction in parasite DNA in tissues upon challenge infection

Toxoplasma gondii is an intracellular parasite of all mammals and birds, responsible for toxoplasmosis. In healthy individuals T. gondii infections mostly remain asymptomatic, however this parasite causes severe morbidity and mortality in immunocompromised patients and congenital toxoplasmosis in pregnant women. The consumption of raw or undercooked pork is considered as an important risk factor to develop toxoplasmosis in humans. Since effective therapeutic interventions to treat toxoplasmosis are scarce, vaccination of meat producing animals may prevent T. gondii transmission to humans. Here, we evaluated the elicited immune responses and the efficacy of a potential vaccine candidate, generated by size fractionation of T. gondii lysate proteins, to reduce the parasite burden in tissues from experimentally T. gondii infected pigs as compared to vaccination with total lysate antigens (TLA). Our results show that both the vaccine candidate and the TLA immunization elicited strong serum IgG responses and elevated percentages of CD4+CD8+IFNγ+ T cells in T. gondii infected pigs. However, the TLA vaccine induced the strongest immune response and reduced the parasite DNA load below the detection limit in brain and skeletal muscle tissue in most animals. These findings might inform the development of novel vaccines to prevent T. gondii infections in livestock species and humans

Early intestinal infection kinetics and immune responses to Toxoplasma gondii in pigs

Toxoplasma gondii is an obligate intracellular parasite, able to infect all homeothermic animals mostly through ingestion of food or drinks contaminated with tissue cysts or oocysts. Recently, we showed a T. gondii strain-specific clearance from tissues upon infection in pigs. While the swine-adapted LR strain persisted in muscle tissues, the human-adapted Gangji strain was cleared from these tissues. We hypothesized that intestinal immune responses short after infection might play a role in this strain-specific clearance. To assess this possibility, the parasite load in duodenal, jejunal and ileal lymph node cells and blood immune cells (PBMCs) as well as the IFNγ secretion by these cells were evaluated at 2, 4, 8, 14 and 28 days post oral inoculation of pigs with both strains. Interestingly, at day 4 post inoculation with the LR strain the parasite was only detected by qPCR in the duodenal lymph node cells, while in the jejunal and ileal lymph node cells and PBMCs the parasite was detected from day 8 post inoculation onwards. Although we observed a similar profile upon inoculation with the Gangji strain, the parasite load in the examined cells was much lower. This was reflected in a significantly higher T. gondii-specific serum IgG response in LR than Gangji infected pigs at day 28 post inoculation. Unexpectedly, this was not reflected in the IFNγ secretion upon re-stimulation of the cells. However, the recall test most likely does not pick up the IFNγ production by innate immune cells, which might have been more important for clearance. In conclusion, our results show that T. gondii first enters the host at the duodenum and then probably disseminates from this site to the other host tissues

Early kinetics of intestinal infection and immune responses to two Toxoplasma gondii strains in pigs

Toxoplasma gondiiis an obligate intracellular parasite, able to infect all homeothermicanimals mostly through ingestion of (oo)cysts contaminated food or water. Recently,we observed aT. gondiistrain-specific clearance from tissues upon infection in pigs:while the swine-adapted LR strain persisted in porcine tissues, a subsequent infectionwith the human-isolated Gangji strain cleared parasites from several tissues. Wehypothesized that intestinal immune responses shortly after infection might play a rolein this strain-specific clearance. To assess this possibility, the parasite load in smallintestinal lymph node cells and blood immune cells as well asthe IFNγsecretion bythese cells were evaluated at 2, 4, 8, 14, and 28 days post oralinoculation of pigs withtissue cysts of both strains. Interestingly, at day 4 post inoculation with the LR strainthe parasite was detected by qPCR only in the duodenal lymph node cells, while in thejejunal and ileal lymph node cells and PBMCs the parasite wasdetected from day 8post inoculation onwards. Although we observed a similar profile upon inoculation withthe Gangji strain, the parasite load in the examined cells was much lower. This wasreflected in a significantly higherT. gondii-specific serum IgG response in LR comparedto Gangji infected pigs at day 28 post inoculation. Unexpectedly, this was not reflected inthe IFNγsecretion upon re-stimulation of the cells where almost equal IFNγsecretion wasobserved in both groups. In conclusion, our results show thatT. gondiifirst enters thehost at the duodenum and then probably disseminates from this site to the other tissues.How the early immune response influences the clearance of parasite from tissues needsfurther study

A genoserotyping system for a fast and objective identification of Salmonella serotypes commonly isolated from poultry and pork food sectors in Belgium

Humans are mostly contaminated by Salmonella through the consumption of pork- and poultry-derived food products. Therefore, a strict monitoring of Salmonella serotypes in food-producing animals is needed to limit the transmission of the pathogen to humans. Additionally, Salmonella can lead to economic loss in the food sector. Previously, a genoserotyping method using the MOL-PCR and Luminex technology was developed for the identification of the 6 Salmonella serotypes, and their variants, subjected to an official control in the Belgian food sector. In this study, 3 additional assays using the same technology were developed for the rapid and cost-effective detection of 13 dangerous highly invasive serotypes or other serotypes frequently isolated from the Belgian poultry and pork sector, i.e. Agona, Anatum, Brandenburg, Choleraesuis, Derby, Enteritidis vaccine strains, Gallinarum var. Gallinarum/Pullorum, Livingstone, Mbandaka, Minnesota, Ohio, Rissen and Senftenberg. Moreover, the previously developed first MOL-PCR assay was improved for S. Paratyphi B and serogroup O:3 detection. Finally, a Decision Support System hosted by a web application was created for an automatic and objective interpretation of the Luminex raw data. The 3 new assays and the modifications of the first assay were validated with a 100% accuracy, using 553 Salmonella and non-Salmonella strains in total

Novel norovirus recombinants and of GII.4 sub-lineages associated with outbreaks between 2006 and 2010 in Belgium

<p>Abstract</p> <p>Background</p> <p>Noroviruses (NoVs) are an important cause of acute gastroenteritis in humans worldwide. To gain insight into the epidemiologic patterns of NoV outbreaks and to determine the genetic variation of NoVs strains circulating in Belgium, stool samples originating from patients infected with NoVs in foodborne outbreak investigations were analysed between December 2006 and December 2010.</p> <p>Results</p> <p>NoVs were found responsible of 11.8% of all suspected foodborne outbreaks reported in the last 4 years and the number of NoV outbreaks reported increased along the years representing more than 30% of all foodborne outbreaks in 2010. Genogroup II outbreaks largely predominated and represented more than 90% of all outbreaks. Phylogenetic analyses were performed with 63 NoV-positive samples for the partial polymerase (N = 45) and/or capsid gene (N = 35) sequences. For 12 samples, sequences covering the ORF1-ORF2 junction were obtained. A variety of genotypes was found among genogroups I and II; GII.4 was predominant followed in order of importance by GII.2, GII.7, GII.13, GI.4 and GI.7. In the study period, GII.4 NoVs variants 2006a, 2006b, 2007, 2008 and 2010 were identified. Moreover, phylogenetic analyses identified different recombinant NoV strains that were further characterised as intergenotype (GII.e/GII.4 2007, GII.e/GII.3 and GII.g/GII.1) and intersub-genotype (GII.4 2006b/GII.4 2007 and GII.4 2010/GII.4 2010b) recombinants.</p> <p>Conclusions</p> <p>NoVs circulating in the last 4 years in Belgium showed remarkable genetic diversity either by small-scale mutations or genetic recombination. In this period, GII.4 2006b was successfully displaced by the GII.4 2010 subtype, and previously reported epidemic GII.b recombinants seemed to have been superseded by GII.e recombinants in 2009 and GII.g recombinants in 2010. This study showed that the emergence of novel GII.4 variants together with novel GII recombinants could lead to an explosion in NoV outbreaks, likewise to what was observed in 2008 and 2010. Among recombinants detected in this study, two hitherto unreported strains GII.e/GII.3 and GII.g/GII.1 were characterised. Surveillance will remain important to monitor contemporaneously circulating strains in order to adapt preventive and curative strategies.</p