Liesbeth Ceelen - Academia.edu (original) (raw)

Papers by Liesbeth Ceelen

The EU FP6 project carcinoGENOMICS explored the combination of toxicogenomics and in vitro cell c... more The EU FP6 project carcinoGENOMICS explored the combination of toxicogenomics and in vitro cell culture models for identifying organotypical genotoxic- and non-genotoxic carcinogen-specific gene signatures. Here the performance of its gene classifier, derived from exposure of metabolically competent human HepaRG cells to prototypical non-carcinogens (10 compounds) and hepatocarcinogens (20 compounds), is reported. Analysis of the data at the gene and the pathway level by using independent biostatistical approaches showed a distinct separation of genotoxic from non-genotoxic hepatocarcinogens and non-carcinogens (up to 88 % correct prediction). The most characteristic pathway responding to genotoxic exposure was DNA damage. Interlaboratory reproducibility was assessed by blindly testing of three compounds, from the set of 30 compounds, by three independent laboratories. Subsequent classification of these compounds resulted in correct prediction of the genotoxicants. As expected, resu...

the presence of Campylobacter dna was studied by means of Pcr in fecal samples from 37 dogs suffe... more the presence of Campylobacter dna was studied by means of Pcr in fecal samples from 37 dogs suffering from acute or chronic diarrhea and 50 dogs without clinical signs. in total, 47% of the fecal samples were positive for Campylobacter dna, with C. upsaliensis being the predominant species, followed by C. coli, C. jejuni and C. mucosalis. C. helveticus, C. lari, C. hyointestinalis, C. sputorum, C. fetus and C. lanienae DNA was not detected in any of the samples. No significant difference was noted between the healthy dogs and the diarrheic dogs. Dogs younger than 12 months old were significantly more often infected with Campylobacter species than older dogs. although a pathogenic role cannot be excluded, the detection of these organisms in fecal samples is not diagnostic for Campylobacter-associated disease in dogs. however, because of their frequent presence in dog feces, Campylobacter species may constitute a public health

To date, 13 en te ro he pa tic He li co bac ter spe cies have been de tec ted in la bo ra to ry r... more To date, 13 en te ro he pa tic He li co bac ter spe cies have been de tec ted in la bo ra to ry ro dents. Some of the se spe cies, in par ti cu lar He li co bac ter he pa ti cus and He li co bac ter bi lis, cau se dis e a se in im mu no com pro mi sed and im mu no com pe tent la bo ra to ry mice, rats and/or ham sters. In ad di ti on, sub cli ni cal in fec ti ons with the se bac te ria may in ter fe re with re sults ob tai ned from ex pe ri men tal re search in the se ani mals and thus may lead to faul ty in ter pre ta ti on of the data. Some la bo ra to ry ro dent-as so ci a ted He li co bac ter spe cies may also be con si de red zoono tic agents. Apart from He li co bac ter he pa ti cus, the pa tho ge ne sis of He li co bac ter in fec ti ons has not been stu died ex ten si ve ly, a fact which me ans the re are sub stan ti al gaps in the com pre hen si on of the vi ru len ce mecha nisms of en te ro he pa tic He li co bac ter spe cies as so ci a ted with la bo ra to ry ro dents. For...

Stem cell reports, Jan 12, 2016

Induced pluripotent stem cells (iPSCs) hold great potential not only for human but also for veter... more Induced pluripotent stem cells (iPSCs) hold great potential not only for human but also for veterinary purposes. The equine industry must often deal with health issues concerning muscle and cartilage, where comprehensive regenerative strategies are still missing. In this regard, a still open question is whether equine iPSCs differentiate toward muscle and cartilage, and whether donor cell type influences their differentiation potential. We addressed these questions through an isogenic system of equine iPSCs obtained from myogenic mesoangioblasts (MAB-iPSCs) and chondrogenic mesenchymal stem cells (MSC-iPSCs). Despite similar levels of pluripotency characteristics, the myogenic differentiation appeared enhanced in MAB-iPSCs. Conversely, the chondrogenic differentiation was augmented in MSC-iPSCs through both teratoma and in vitro differentiation assays. Thus, our data suggest that equine iPSCs can differentiate toward the myogenic and chondrogenic lineages, and can present a skewed d...

Archives of Toxicology, 2015

analysis protocols. We have conducted an inter-laboratory study for testing chemical carcinogenic... more analysis protocols. We have conducted an inter-laboratory study for testing chemical carcinogenicity evaluating two human in vitro assays: hepatoma-derived cells and hTERTimmortalized renal proximal tubule epithelial cells, representing liver and kidney as major target organs. Cellular systems were initially challenged with thirty compounds, genome-wide gene expression was measured with microarrays, and hazard classifiers were built from this training set. Subsequently, each system was independently established in three different laboratories, and gene expression measurements were conducted using anonymized compounds. Data analysis was performed independently by two separate groups applying different protocols for the assessment of inter-laboratory reproducibility and for the prediction of carcinogenic hazard. As a result, both workflows came to very similar conclusions with respect to (1) identification Abstract The assessment of the carcinogenic potential of chemicals with alternative, human-based in vitro systems has become a major goal of toxicogenomics. The central read-out of these assays is the transcriptome, and while many studies exist that explored the gene expression responses of such systems, reports on robustness and reproducibility, when testing them independently in different laboratories, are still uncommon. Furthermore, there is limited knowledge about variability induced by the data

Hepatology International, 2013

Veterinary Surgery, 2005

Objective-To determine radiocarpal (RC) joint synovial fluid and plasma ceftiofur concentrations ... more Objective-To determine radiocarpal (RC) joint synovial fluid and plasma ceftiofur concentrations after regional intravenous perfusion (RIP) and systemic intravenous (IV) administration. Study Design-Experimental cross-over study. Animals-Five normal adult horses. Methods-One RC joint was randomly selected for RIP and the contralateral RC joint was sampled to determine intrasynovial ceftiofur concentrations after IV administration. Wash-out between IV and RIP was ! 14 days. After surgical introduction of an intraarticular catheter, ceftiofur (2 g) was administered under general anesthesia either IV or by RIP after tourniquet application. Plasma and synovial fluid were collected over 24 hours. Samples were analyzed using high-performance liquid chromatography with ultraviolet detection and the results were statistically analyzed using a linear mixed effect model. Results-Mean synovial fluid ceftiofur concentrations were consistently higher after RIP than after IV administration and were 4 1 mg/mL (minimal inhibitory concentration [MIC] for common pathogens) for 424 hours. Mean synovial fluid peak concentration of ceftiofur after RIP and IV administration was 392.7 AE 103.29 mg/mL at 0.5 hours postinjection (HPI) and 2.72 AE 0.31 mg/mL at 1 HPI, respectively. Large variations in synovial fluid and plasma ceftiofur concentrations were observed between horses regardless of administration technique. RIP did not cause adverse effects. Conclusions-Under the present experimental conditions RIP with ceftiofur (2 g) induced significantly higher intraarticular antibiotic concentrations in the RC joint in comparison with IV administration. Moreover, after RIP, synovial fluid ceftiofur concentrations remain above the MIC for common pathogens (1 mg/mL) for 4 24 hours. No adverse effects from the technique or the antibiotic were observed. Clinical relevance-RIP with high doses of ceftiofur may be a beneficial adjunctive therapy when treating equine synovial infections which are caused by cephalosporin susceptible microorganisms.

Nature Methods, 2013

The need for transparency and good practices in the qPCR literature Two surveys of over 1,700 pub... more The need for transparency and good practices in the qPCR literature Two surveys of over 1,700 publications whose authors use quantitative real-time PCR (qPCR) reveal a lack of transparent and comprehensive reporting of essential technical information. Reporting standards are significantly improved in publications that cite the Minimum Information for Publication of Quantitative Real-Time PCR Experiments (MIQE) guidelines, although such publications are still vastly outnumbered by those that do not.

Microbiological Research, 2006

Cytolethal distending toxin (CDT) is a bacterial protein that is widely distributed among Gram-ne... more Cytolethal distending toxin (CDT) is a bacterial protein that is widely distributed among Gram-negative bacteria including Escherichia coli, Campylobacter spp., enterohepatic Helicobacter spp., Actinobacillus actinomycetemcomitans and Haemophilus ducreyi. In vitro studies demonstrated that it is able to stop proliferation of various cell lines. The toxin is composed of three subunits designated CDTs A, B and C. The B subunit targets the eukaryotic DNA and triggers a signalling pathway involving different protein kinases which results in a cell block before entering into mitosis. To date, the individual role of the A and C subunits has not been totally elucidated. There are indications that the CDT is also produced in vivo. Its exact role in pathogenesis is not yet clear, but possible actions include inhibition of epithelial cell proliferation, apoptosis of immune cells and inhibition of a fibrotic response.

Journal of Morphology, 2009

Helicobacter pullorum infections have been associated with several enterohepatic diseases, but th... more Helicobacter pullorum infections have been associated with several enterohepatic diseases, but the mechanism of action is currently undefined. The present study was therefore set up to investigate possible cytotoxic effects of this pathogen on liver cells. A mouse hepatic cell line was exposed to H. pullorum sonicate and cytotoxicity was observed for all isolates after incubation for 72 h. Features characteristic for mitotic catastrophe characterized by chromatin condensation, formation of multinuclear distended cells and micronucleation, were recorded. In addition, intranuclear pseudoinclusions were seen in sonicate-treated cells. Finally, cells exposed to sonicate eventually underwent cell death with the morphological features of necrosis, which occurred without activation of caspase-3. The toxic factor involved in the cytotoxic activity proved to be soluble, trypsin-sensitive and stable at 56 degrees C and at -70 degrees C with a molecular weight to be over 50 kDa. The current study shows for the first time that H. pullorum causes mitotic catastrophe resulting in primary necrosis in mouse hepatocytes.

Journal of Medical Microbiology, 2007

Campylobacter jejuni is one of the leading causes of food-borne gastroenteritis. Because of the h... more Campylobacter jejuni is one of the leading causes of food-borne gastroenteritis. Because of the high prevalence of C. jejuni in poultry, poultry meat is considered a major source of C. jejuni infections for humans. However, it is not known whether all poultry-associated C. jejuni strains are capable of causing disease in humans. Four different virulence properties of C. jejuni strains were compared between 20 poultry isolates and 24 human isolates. Strains were chosen based on their PFGE pattern to represent a heterogeneous population. The isolates were compared for their ability to invade and induce interleukin-8 (IL-8) production in T84 cells, their production of functional cytolethal distending toxin (CDT) using HEp-2 cells, and their sodium deoxycholate resistance. All four virulence factors were present among strains of human and poultry origin, with strong differences observed among strains. For invasion and IL-8 induction, no difference was observed between the two population...

International Journal of Systematic and Evolutionary Microbiology, 2007

Gram-negative, curved, motile bacteria (strains EqF1T and EqF2) were isolated from faecal samples... more Gram-negative, curved, motile bacteria (strains EqF1T and EqF2) were isolated from faecal samples from two clinically healthy horses. Both strains possessed a single, monopolar, sheathed flagellum and were urease-negative. The novel strains grew at 37 °C under microaerobic conditions and were positive for oxidase, catalase and alkaline phosphatase activities. The isolates reduced nitrate to nitrite, but γ-glutamyl transpeptidase activity was not detected. The novel isolates did not grow at 42 °C or on media containing 1 % glycine. They were resistant to cephalotin and nalidixic acid and susceptible to metronidazole. Analysis of the 16S and 23S rRNA gene sequences of the two novel strains identified them as representing a single species within the genus Helicobacter. In terms of 16S rRNA gene sequence similarity, Helicobacter pullorum and Helicobacter canadensis were the most closely related species (98 % similarity). 23S rRNA gene sequence analysis also classified strains EqF1T and ...

Equine Veterinary Journal, 2007

Reasons for performing study: A novel urease-negative Helicobacter species has been isolated from... more Reasons for performing study: A novel urease-negative Helicobacter species has been isolated from faecal samples of clinically healthy horses, but no information is available about the main sites of colonisation in the equine gastrointestinal tract nor is the pathogenic potential of this microorganism known. An experimental infection in horses was therefore carried out. Methods: Four horses were infected with H. equorum strain CCUG 52199T and subjected to euthanasia at 10 (n = 2) and 30 days (n = 2) post inoculation. A fifth animal was inoculated with phosphate buffered saline and used as control. Gastrointestinal samples were examined histologically and bacteriologically. These samples, as well as faecal material collected at regular intervals, were also subjected to PCR analysis. Results: All horses remained clinically healthy and no specific macroscopic lesions were identified, nor were there any microscopic changes. H. equorum-DNA was detected in the faeces during the whole experiment in all infected animals but not in the negative control. Sites of colonisation were caecum, colon and rectum. Conclusions: H. equorum is able to colonise the equine lower bowel and is excreted in faeces without apparent pathology. No association between the presence of the organism and gastrointestinal disease was demonstrated.

Emerging Infectious Diseases, 2006

A total of 110 broilers from 11 flocks were tested for Helicobacter pullorum by polymerase chain ... more A total of 110 broilers from 11 flocks were tested for Helicobacter pullorum by polymerase chain reaction; positive samples were reexamined with a conventional isolation method. H. pullorum isolates were examined by amplified fragment length polymorphism (AFLP) fingerprinting for interstrain genetic diversity and relatedness. Sixteen isolates from cecal samples from 2 different flocks were obtained. AFLP analysis showed that these isolates and 4 additional isolates from a different flock clustered according to their origin, which indicates that H. pullorum colonization may occur with a single strain that disseminates throughout the flock. Strains isolated from different hosts or geographic sources displayed a distinctive pattern. H. pullorum is present in approximately one third of live chickens in Belgium and may represent a risk to human health.

Clinical Chemistry, 2013

BACKGROUND The HepaRG cell line is widely used as an alternative for primary human hepatocytes fo... more BACKGROUND The HepaRG cell line is widely used as an alternative for primary human hepatocytes for numerous applications, including drug screening, and is progressively gaining importance as a human-relevant cell source. Consequently, increasing numbers of experiments are being performed with this cell line, including real-time quantitative PCR (RT-qPCR) experiments for gene expression studies. CONTENT When RT-qPCR experiments are performed, results are reliable only when attention is paid to several critical aspects, including a proper normalization strategy. Therefore, in 2011 we determined the most optimal reference genes for gene expression studies in the HepaRG cell system, according to the MIQE (Minimum Information for Publication of Quantitative Real-Time PCR Experiments) guidelines. This study additionally provided clear evidence that the use of a single reference gene [glyceraldehyde-3-phosphate dehydrogenase (GAPDH), ribosomal protein S18 (RPS18), or actin, beta (ACTB)] wa...

The EU FP6 project carcinoGENOMICS explored the combination of toxicogenomics and in vitro cell c... more The EU FP6 project carcinoGENOMICS explored the combination of toxicogenomics and in vitro cell culture models for identifying organotypical genotoxic- and non-genotoxic carcinogen-specific gene signatures. Here the performance of its gene classifier, derived from exposure of metabolically competent human HepaRG cells to prototypical non-carcinogens (10 compounds) and hepatocarcinogens (20 compounds), is reported. Analysis of the data at the gene and the pathway level by using independent biostatistical approaches showed a distinct separation of genotoxic from non-genotoxic hepatocarcinogens and non-carcinogens (up to 88 % correct prediction). The most characteristic pathway responding to genotoxic exposure was DNA damage. Interlaboratory reproducibility was assessed by blindly testing of three compounds, from the set of 30 compounds, by three independent laboratories. Subsequent classification of these compounds resulted in correct prediction of the genotoxicants. As expected, resu...

the presence of Campylobacter dna was studied by means of Pcr in fecal samples from 37 dogs suffe... more the presence of Campylobacter dna was studied by means of Pcr in fecal samples from 37 dogs suffering from acute or chronic diarrhea and 50 dogs without clinical signs. in total, 47% of the fecal samples were positive for Campylobacter dna, with C. upsaliensis being the predominant species, followed by C. coli, C. jejuni and C. mucosalis. C. helveticus, C. lari, C. hyointestinalis, C. sputorum, C. fetus and C. lanienae DNA was not detected in any of the samples. No significant difference was noted between the healthy dogs and the diarrheic dogs. Dogs younger than 12 months old were significantly more often infected with Campylobacter species than older dogs. although a pathogenic role cannot be excluded, the detection of these organisms in fecal samples is not diagnostic for Campylobacter-associated disease in dogs. however, because of their frequent presence in dog feces, Campylobacter species may constitute a public health

To date, 13 en te ro he pa tic He li co bac ter spe cies have been de tec ted in la bo ra to ry r... more To date, 13 en te ro he pa tic He li co bac ter spe cies have been de tec ted in la bo ra to ry ro dents. Some of the se spe cies, in par ti cu lar He li co bac ter he pa ti cus and He li co bac ter bi lis, cau se dis e a se in im mu no com pro mi sed and im mu no com pe tent la bo ra to ry mice, rats and/or ham sters. In ad di ti on, sub cli ni cal in fec ti ons with the se bac te ria may in ter fe re with re sults ob tai ned from ex pe ri men tal re search in the se ani mals and thus may lead to faul ty in ter pre ta ti on of the data. Some la bo ra to ry ro dent-as so ci a ted He li co bac ter spe cies may also be con si de red zoono tic agents. Apart from He li co bac ter he pa ti cus, the pa tho ge ne sis of He li co bac ter in fec ti ons has not been stu died ex ten si ve ly, a fact which me ans the re are sub stan ti al gaps in the com pre hen si on of the vi ru len ce mecha nisms of en te ro he pa tic He li co bac ter spe cies as so ci a ted with la bo ra to ry ro dents. For...

Stem cell reports, Jan 12, 2016

Induced pluripotent stem cells (iPSCs) hold great potential not only for human but also for veter... more Induced pluripotent stem cells (iPSCs) hold great potential not only for human but also for veterinary purposes. The equine industry must often deal with health issues concerning muscle and cartilage, where comprehensive regenerative strategies are still missing. In this regard, a still open question is whether equine iPSCs differentiate toward muscle and cartilage, and whether donor cell type influences their differentiation potential. We addressed these questions through an isogenic system of equine iPSCs obtained from myogenic mesoangioblasts (MAB-iPSCs) and chondrogenic mesenchymal stem cells (MSC-iPSCs). Despite similar levels of pluripotency characteristics, the myogenic differentiation appeared enhanced in MAB-iPSCs. Conversely, the chondrogenic differentiation was augmented in MSC-iPSCs through both teratoma and in vitro differentiation assays. Thus, our data suggest that equine iPSCs can differentiate toward the myogenic and chondrogenic lineages, and can present a skewed d...

Archives of Toxicology, 2015

analysis protocols. We have conducted an inter-laboratory study for testing chemical carcinogenic... more analysis protocols. We have conducted an inter-laboratory study for testing chemical carcinogenicity evaluating two human in vitro assays: hepatoma-derived cells and hTERTimmortalized renal proximal tubule epithelial cells, representing liver and kidney as major target organs. Cellular systems were initially challenged with thirty compounds, genome-wide gene expression was measured with microarrays, and hazard classifiers were built from this training set. Subsequently, each system was independently established in three different laboratories, and gene expression measurements were conducted using anonymized compounds. Data analysis was performed independently by two separate groups applying different protocols for the assessment of inter-laboratory reproducibility and for the prediction of carcinogenic hazard. As a result, both workflows came to very similar conclusions with respect to (1) identification Abstract The assessment of the carcinogenic potential of chemicals with alternative, human-based in vitro systems has become a major goal of toxicogenomics. The central read-out of these assays is the transcriptome, and while many studies exist that explored the gene expression responses of such systems, reports on robustness and reproducibility, when testing them independently in different laboratories, are still uncommon. Furthermore, there is limited knowledge about variability induced by the data

Hepatology International, 2013

Veterinary Surgery, 2005

Objective-To determine radiocarpal (RC) joint synovial fluid and plasma ceftiofur concentrations ... more Objective-To determine radiocarpal (RC) joint synovial fluid and plasma ceftiofur concentrations after regional intravenous perfusion (RIP) and systemic intravenous (IV) administration. Study Design-Experimental cross-over study. Animals-Five normal adult horses. Methods-One RC joint was randomly selected for RIP and the contralateral RC joint was sampled to determine intrasynovial ceftiofur concentrations after IV administration. Wash-out between IV and RIP was ! 14 days. After surgical introduction of an intraarticular catheter, ceftiofur (2 g) was administered under general anesthesia either IV or by RIP after tourniquet application. Plasma and synovial fluid were collected over 24 hours. Samples were analyzed using high-performance liquid chromatography with ultraviolet detection and the results were statistically analyzed using a linear mixed effect model. Results-Mean synovial fluid ceftiofur concentrations were consistently higher after RIP than after IV administration and were 4 1 mg/mL (minimal inhibitory concentration [MIC] for common pathogens) for 424 hours. Mean synovial fluid peak concentration of ceftiofur after RIP and IV administration was 392.7 AE 103.29 mg/mL at 0.5 hours postinjection (HPI) and 2.72 AE 0.31 mg/mL at 1 HPI, respectively. Large variations in synovial fluid and plasma ceftiofur concentrations were observed between horses regardless of administration technique. RIP did not cause adverse effects. Conclusions-Under the present experimental conditions RIP with ceftiofur (2 g) induced significantly higher intraarticular antibiotic concentrations in the RC joint in comparison with IV administration. Moreover, after RIP, synovial fluid ceftiofur concentrations remain above the MIC for common pathogens (1 mg/mL) for 4 24 hours. No adverse effects from the technique or the antibiotic were observed. Clinical relevance-RIP with high doses of ceftiofur may be a beneficial adjunctive therapy when treating equine synovial infections which are caused by cephalosporin susceptible microorganisms.

Nature Methods, 2013

The need for transparency and good practices in the qPCR literature Two surveys of over 1,700 pub... more The need for transparency and good practices in the qPCR literature Two surveys of over 1,700 publications whose authors use quantitative real-time PCR (qPCR) reveal a lack of transparent and comprehensive reporting of essential technical information. Reporting standards are significantly improved in publications that cite the Minimum Information for Publication of Quantitative Real-Time PCR Experiments (MIQE) guidelines, although such publications are still vastly outnumbered by those that do not.

Microbiological Research, 2006

Cytolethal distending toxin (CDT) is a bacterial protein that is widely distributed among Gram-ne... more Cytolethal distending toxin (CDT) is a bacterial protein that is widely distributed among Gram-negative bacteria including Escherichia coli, Campylobacter spp., enterohepatic Helicobacter spp., Actinobacillus actinomycetemcomitans and Haemophilus ducreyi. In vitro studies demonstrated that it is able to stop proliferation of various cell lines. The toxin is composed of three subunits designated CDTs A, B and C. The B subunit targets the eukaryotic DNA and triggers a signalling pathway involving different protein kinases which results in a cell block before entering into mitosis. To date, the individual role of the A and C subunits has not been totally elucidated. There are indications that the CDT is also produced in vivo. Its exact role in pathogenesis is not yet clear, but possible actions include inhibition of epithelial cell proliferation, apoptosis of immune cells and inhibition of a fibrotic response.

Journal of Morphology, 2009

Helicobacter pullorum infections have been associated with several enterohepatic diseases, but th... more Helicobacter pullorum infections have been associated with several enterohepatic diseases, but the mechanism of action is currently undefined. The present study was therefore set up to investigate possible cytotoxic effects of this pathogen on liver cells. A mouse hepatic cell line was exposed to H. pullorum sonicate and cytotoxicity was observed for all isolates after incubation for 72 h. Features characteristic for mitotic catastrophe characterized by chromatin condensation, formation of multinuclear distended cells and micronucleation, were recorded. In addition, intranuclear pseudoinclusions were seen in sonicate-treated cells. Finally, cells exposed to sonicate eventually underwent cell death with the morphological features of necrosis, which occurred without activation of caspase-3. The toxic factor involved in the cytotoxic activity proved to be soluble, trypsin-sensitive and stable at 56 degrees C and at -70 degrees C with a molecular weight to be over 50 kDa. The current study shows for the first time that H. pullorum causes mitotic catastrophe resulting in primary necrosis in mouse hepatocytes.

Journal of Medical Microbiology, 2007

Campylobacter jejuni is one of the leading causes of food-borne gastroenteritis. Because of the h... more Campylobacter jejuni is one of the leading causes of food-borne gastroenteritis. Because of the high prevalence of C. jejuni in poultry, poultry meat is considered a major source of C. jejuni infections for humans. However, it is not known whether all poultry-associated C. jejuni strains are capable of causing disease in humans. Four different virulence properties of C. jejuni strains were compared between 20 poultry isolates and 24 human isolates. Strains were chosen based on their PFGE pattern to represent a heterogeneous population. The isolates were compared for their ability to invade and induce interleukin-8 (IL-8) production in T84 cells, their production of functional cytolethal distending toxin (CDT) using HEp-2 cells, and their sodium deoxycholate resistance. All four virulence factors were present among strains of human and poultry origin, with strong differences observed among strains. For invasion and IL-8 induction, no difference was observed between the two population...

International Journal of Systematic and Evolutionary Microbiology, 2007

Gram-negative, curved, motile bacteria (strains EqF1T and EqF2) were isolated from faecal samples... more Gram-negative, curved, motile bacteria (strains EqF1T and EqF2) were isolated from faecal samples from two clinically healthy horses. Both strains possessed a single, monopolar, sheathed flagellum and were urease-negative. The novel strains grew at 37 °C under microaerobic conditions and were positive for oxidase, catalase and alkaline phosphatase activities. The isolates reduced nitrate to nitrite, but γ-glutamyl transpeptidase activity was not detected. The novel isolates did not grow at 42 °C or on media containing 1 % glycine. They were resistant to cephalotin and nalidixic acid and susceptible to metronidazole. Analysis of the 16S and 23S rRNA gene sequences of the two novel strains identified them as representing a single species within the genus Helicobacter. In terms of 16S rRNA gene sequence similarity, Helicobacter pullorum and Helicobacter canadensis were the most closely related species (98 % similarity). 23S rRNA gene sequence analysis also classified strains EqF1T and ...

Equine Veterinary Journal, 2007

Reasons for performing study: A novel urease-negative Helicobacter species has been isolated from... more Reasons for performing study: A novel urease-negative Helicobacter species has been isolated from faecal samples of clinically healthy horses, but no information is available about the main sites of colonisation in the equine gastrointestinal tract nor is the pathogenic potential of this microorganism known. An experimental infection in horses was therefore carried out. Methods: Four horses were infected with H. equorum strain CCUG 52199T and subjected to euthanasia at 10 (n = 2) and 30 days (n = 2) post inoculation. A fifth animal was inoculated with phosphate buffered saline and used as control. Gastrointestinal samples were examined histologically and bacteriologically. These samples, as well as faecal material collected at regular intervals, were also subjected to PCR analysis. Results: All horses remained clinically healthy and no specific macroscopic lesions were identified, nor were there any microscopic changes. H. equorum-DNA was detected in the faeces during the whole experiment in all infected animals but not in the negative control. Sites of colonisation were caecum, colon and rectum. Conclusions: H. equorum is able to colonise the equine lower bowel and is excreted in faeces without apparent pathology. No association between the presence of the organism and gastrointestinal disease was demonstrated.

Emerging Infectious Diseases, 2006

A total of 110 broilers from 11 flocks were tested for Helicobacter pullorum by polymerase chain ... more A total of 110 broilers from 11 flocks were tested for Helicobacter pullorum by polymerase chain reaction; positive samples were reexamined with a conventional isolation method. H. pullorum isolates were examined by amplified fragment length polymorphism (AFLP) fingerprinting for interstrain genetic diversity and relatedness. Sixteen isolates from cecal samples from 2 different flocks were obtained. AFLP analysis showed that these isolates and 4 additional isolates from a different flock clustered according to their origin, which indicates that H. pullorum colonization may occur with a single strain that disseminates throughout the flock. Strains isolated from different hosts or geographic sources displayed a distinctive pattern. H. pullorum is present in approximately one third of live chickens in Belgium and may represent a risk to human health.

Clinical Chemistry, 2013

BACKGROUND The HepaRG cell line is widely used as an alternative for primary human hepatocytes fo... more BACKGROUND The HepaRG cell line is widely used as an alternative for primary human hepatocytes for numerous applications, including drug screening, and is progressively gaining importance as a human-relevant cell source. Consequently, increasing numbers of experiments are being performed with this cell line, including real-time quantitative PCR (RT-qPCR) experiments for gene expression studies. CONTENT When RT-qPCR experiments are performed, results are reliable only when attention is paid to several critical aspects, including a proper normalization strategy. Therefore, in 2011 we determined the most optimal reference genes for gene expression studies in the HepaRG cell system, according to the MIQE (Minimum Information for Publication of Quantitative Real-Time PCR Experiments) guidelines. This study additionally provided clear evidence that the use of a single reference gene [glyceraldehyde-3-phosphate dehydrogenase (GAPDH), ribosomal protein S18 (RPS18), or actin, beta (ACTB)] wa...