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R Ducatelle

Publications and source records attributed to R Ducatelle.

At least 73 records · Page 4Linked to original sources
PubMed2000

Identification of virulence associated markers in the cell wall of pigeon Streptococcus gallolyticus strains.

The cell wall protein profiles of 56 isolates of Streptococcus gallolyticus of differing virulence for pigeons were compared by SDS-PAGE. Additionally, Western blot analysis was performed on the cell wall proteins of 14 strains using sera of pigeons, experimentally infected with A(+)T1 or A(-)T2 strains of S. gallolyticus. The profile of silver stained gels exhibited a complex array of 20-50 bands ranging from less than 6.5-210kDa. A band with molecular mass of 114kDa was only observed in isolates that belonged to the highly virulent A(+)T1, A(+)T2, A(+)T3 and A(-)T1 culture supernatant groups. A band with a slightly higher molecular mass (115kDa) as well as a 207kDa band were only detected in isolates that belonged to the moderately A(-)T3 or low A(-)T2 virulent culture supernatant groups. The 114 and 115kDa band were recognised by all homologous and heterologous pigeon sera used whereas the 207kDa band was only recognised by sera of pigeons infected with a A(-)T2 strain. These findings may indicate that the 114, 115 and 207kDa bands are useful as additional virulence associated markers for pigeon S. gallolyticus strains.

Animals↗
PubMed2000

Optimal development of Chlamydophila psittaci in L929 fibroblast and BGM epithelial cells requires the participation of microfilaments and microtubule-motor proteins.

The cytoskeleton is involved in several cellular activities, including internalization and transport of foreign particles. Although particular functions to each cytoskeleton component have been described, interactions between those components seem to occur. The involvement of the different host cell cytoskeletal components in uptake and development of Chlamydophila psittaci is incompletely understood. In this study, the participation of the microfilament network along with the kinesin and dynein microtubule motor proteins in the internalization and further development of Chlamydophila psittaci were investigated in L929 fibroblast and BGM epithelial cells. Cytochalasin D disruption of actin filaments, and blockage of the motor proteins through the introduction of monoclonal antibodies into the host cells were carried out, either single or combined, at different moments around bacterial inoculation, and Chlamydophila infectivity determined 24 h post- inoculation by direct immunofluorescence. Our results show that, although Chlamydophila Ipsittaci can make use of both microfilament-dependent and independent entry pathways in both cell types, Chlamydophila internalization and development in the fibroblast cells mainly concerned processes mediated by microfilaments while in the epithelial cells mechanisms that require microtubule motor proteins were the ones predominantly involved. Evidence that mutual participation of the actin and tubulin networks in both host cells are required for optimal growth of Chlamydophila psittaci is also presented.

Actins↗
PubMed2000

Interaction between turkey monocytes and avian Chlamydia psittaci in the presence of Mycoplasma sp.: the importance of nitric oxide.

The interaction between Chlamydia psittaci and turkey monocytes was studied in vitro. Purified monocytes were inoculated with C. psittaci, in the presence or absence of Mycoplasma hyorhinis. Whereas turkey monocytes produced high amounts of nitric oxide (NO) following the inoculation with M. hyorhinis, inoculation with C. psittaci did not induce NO production in these phagocytes. The monocytes strongly supported chlamydial growth, as demonstrated by the presence of inclusion forming units, the positive direct immunofluorescence staining and transmission electron microscopy. In contrast, upon co-inoculation of the monocytes with C. psittaci and M. hyorhinis, a reduced replication rate of C. psittaci was observed. N(G)-monomethyl-L-Arginine, a competitive inhibitor for the enzyme NO-synthase, inhibited the NO production and reversed the antichlamydial activity of the M. hyorhinis co-inoculated turkey monocytes. These results imply two considerations. First, as chlamydiae are obligate intracellular bacteria, special care should be taken to guard chlamydial cultures from mycoplasmal contamination, in order to prevent false results when investigating the response of immunomodulating cells to chlamydial infection. Secondly, as a mycoplasmal co-infection in vitro has the capacity of inducing antichlamydial activity in turkey monocytes, through the action of NO, it could be suggested that a similar interaction might take place in vivo. Moreover, it was shown that avian M. gallisepticum strains were also able to induce NO in turkey monocytes. Considering the high prevalence of both C. psittaci and Mycoplasma sp. in turkeys, this interaction, through the pivotal role of NO, might influence the outcome of respiratory diseases in turkeys.

Animals↗
PubMed2000

Proliferation, DNA ploidy, p53 overexpression and nuclear DNA fragmentation in six equine melanocytic tumours.

Melanocytic tumours are a well-known clinical and pathological entity in horses, but further phenotypic characterization of these tumours is lacking. Six melanocytic tumours from five horses (two metastatic and four benign) were examined by Ki67, PCNA and p53 immunostaining, DNA nick end labelling (Tunel) and Feulgen staining. The stainings were evaluated using quantitative image analysis. The resulting parameters of growth fraction (Ki67), S-phase index (PCNA), p53 index, apoptotic index, DNA index, nuclear diameter, ploidy balance, proliferation index (Feulgen) and hyperploidy were analysed. The metastatic melanomas showed overexpression of p53 in a large portion of the cells. Apoptosis was also found in the metastatic melanomas. No differences were found in growth fraction, S-phase index (PCNA) nor in DNA configuration between the metastatic and the benign tumours. No immunohistochemical evidence of mutant p53 could be found in the tumours. In conclusion, melanocytic tumours in horses seem to have different phenotypic characteristics in comparison with melanocytic tumours in dogs, cats and humans, especially with respect to proliferative activity of the benign tumours. Therefore, markers put forward in these other species for predicting the clinical behaviour of the melanomas seem to be of no value in the horse. Moreover, quantitative DNA changes or p53 mutations do not seem to be involved in tumourogenesis in these cases.

Animals↗
PubMed2000

Dynamics of the development of Chlamydophila psittaci inclusions in epithelial and fibroblast host cells.

The development of Chlamydophila psittaci (formerly Chlamydia psittaci, avian strains) inclusions in fibroblast L-929 and epithelial BGM cell lines was studied along the bacterial growth cycle using a BGM cell-adapted strain in the presence or absence of cycloheximide and cycloheximide + polyethylene glycol. Evolution of the inclusions was determined in terms of their number and size at 24, 30, 36, 48 and 54 h after infection. Significant differences in the chlamydial growth were found between both host cells, throughout the study. Higher numbers of inclusions (P < 0.05) were observed in L cells while larger inclusions (P < 0.01) were found in BGM cells. In both fibroblast and epithelial cells, inclusions showed a significant (P < 0.001) increase in size at the later times studied. Free extracellular chlamydial particles were noticed at 48 and 54 h post-infection (p.i.) in infected L cells, and at 54 h p.i. in BGM cells. Addition of cycloheximide or cycloheximide + polyethylene glycol had no significant effect on the number of inclusions or their size. The results suggest that host cell characteristics and innate compatibility between Chlamydophila strain and host cell are more important than host cell adaptation for the development of the microorganism.

Animals↗
PubMed2000

Histopathological characteristics of five clinical types of equine sarcoid.

The purpose of this study was to determine the characteristics of occult, verrucous, fibroblastic, nodular and mixed equine sarcoids. Ten tumours of each type were examined histologically and analysed for the presence of bovine papilloma virus (BPV)- DNA. All tumours were positive for BPV - DNA and showed an increased density of dermal fibroblasts. Epidermal hyperplasia, hyperkeratosis, rete peg and 'picket fence' formation were only found consistently in the verrucous and mixed types and were often not present in occult and nodular sarcoids. Immunohistochemical staining for Keratins 10 and 16, Ki67 and p53 showed no important differences between the clinical types. It can be concluded that the presence of BPV - DNA and the increased density of dermal fibroblasts were the only common characteristics for all sarcoids of the different clinical types. The presence of other microscopic alterations was variable but could not be used in the differentiation of the clinical types based on histology.

Animals↗
PubMed2000

Detection of "Candidatus Helicobacter suis" in gastric samples of pigs by PCR: comparison with other invasive diagnostic techniques.

Recently, a new 16S ribosomal DNA-based PCR assay was developed for the specific detection of "Candidatus Helicobacter suis" (former "Gastrospirillum suis") in porcine gastric samples. In the present study, this PCR assay was compared to three other invasive diagnostic methods (rapid urease test, immunohistochemistry, histologic analysis by Giemsa staining). Antral stomach samples from 200 slaughterhouse pigs from Belgium and The Netherlands were examined. Bacterial presence was determined in 77% (154 of 200) of the samples by PCR in combination with Southern blot hybridization, 56% (111 of 200) of the samples by immunohistochemistry, 61% (122 of 200) of the samples by urease testing (20 h postinoculation [p.i.]), 36% (71 of 200) of the samples by urease testing (3 h p.i.), and 33% (65 of 200) of the samples by Giemsa staining. The intrinsic specificity of the PCR assay was assessed by Southern blot analysis with an "Candidatus H. suis"-specific probe and sequencing of PCR products. Interassay sensitivity and specificity values were assessed for each test by pairwise comparisons between tests. Agreement between tests was evaluated by calculating Cohen's kappa coefficient. From that analysis, the PCR assay was considered the most reliable benchmark. Microscopic detection of immunohistochemically labeled or Giemsa-stained "Candidatus H. suis" cells in stomach sections proved to be highly specific (100%) but relatively insensitive (72 and 42%, respectively) compared to the PCR assay. A longer incubation time of the urease test improved its sensitivity considerably (74 versus 55%) but was accompanied by a loss of specificity (72 versus 93%). In conclusion, we found the "Candidatus H. suis"-specific PCR assay to be a sensitive and reliable diagnostic method for the detection of "Candidatus H. suis" in the stomachs of pigs and could prove to be a valuable tool for further epidemiological studies both for "Candidatus H. suis"- and for "Helicobacter heilmannii" type 1-related research.

Animals↗
PubMed1999

Early in vivo interactions of Actinobacillus pleuropneumoniae with tonsils of pigs.

Twenty gnotobiotic piglets were inoculated with 5 x 10(8) colony forming units of an Actinobacillus pleuropneumoniae biotype 1-serotype 9 strain onto their tonsils. Five other piglets (controls) were inoculated with phosphate-buffered saline solution. Pigs were euthanized at 30 min, 90 min, 180 min, 6 h, 9 h, 12 h or 24 h after inoculation. At necropsy, samples were taken from the tonsils for bacteriological, histological, immuno-histochemical and electron microscopical examination. A. pleuropneumoniae was isolated from tonsils of all the infected pigs, but not from tonsils of the control pigs. Early after inoculation bacteria were mainly associated with the stratified squamous epithelium and detached epithelial cells. Vacuolization and desquamation of the epithelium was observed and many transmigrating neutrophils were present. At later times after inoculation, bacteria were found closely associated with the crypt-walls and with detached cells present in the crypts. A strong neutrophil migration was observed mainly in the deeper parts of the crypts. It is concluded that attachment of A. pleuropneumoniae to tonsillar epithelial cells probably constitutes a first step in establishing bacteria at this body site.

Actinobacillus Infections↗
PubMed1999

Persistent vitelline vein in a foal.

A three-day-old foal died from intestinal strangulation due to a remnant of vitelline vein which extended between the umbilicus and the portal vein. The strangulating vein was identified on the basis of its morphological and histological structure. This finding, which is the first reported case of a persistent vitelline vein in a horse, is discussed in relation to the normal development and involution of the vitelline circulation.

Animals↗
PubMed1999

The association of Flavobacterium columnare strains of high and low virulence with gill tissue of black mollies (Poecilia sphenops).

The ability of a high virulence strain (AJS 1) and a low virulence strain (AJS 4) of Flavobacterium columnare (Flexibacter columnaris) to attach to the gills of black mollies (Poecilia sphenops) was investigated. For that purpose, two groups of 25 black mollies each were immersed in a bath containing 10(6) CFU/ml of F. columnare AJS 1 or AJS 4. At regular intervals from 1 to 12 h after the contact infection, fish were sacrificed and gills, skin, spleen and heart were sampled for bacteriology. Samples of the gills were taken for immunohistochemical and electron microscopic examination. Bacteriological examination proved that the number of gill-associated F. columnare was higher for AJS 1 than for AJS 4. Strain AJS 1 was isolated from the heart and spleen of 6 and 1 of the 16 examined animals, respectively. Strain AJS 4 was not isolated from the internal organs of any fish. When examined immunohistochemically, strain AJS 1 was found closely associated with gill epithelium whereas this was not the case for strain AJS 4. The adherence of bacteria to the gill tissue challenged with the virulent strain AJS 1 was also clearly demonstrated using scanning and transmission electron microscopy. These results indicate that adhesion of F. columnare to the gill tissue constitutes an important step in pathogenesis.

Animals↗
PubMed1999

Oxidative activity of turkey monocytes, following the inoculation with Chlamydia psittaci.

Chemiluminescence (CL) was used to investigate the competence of turkey monocytes to mount a respiratory burst response upon interaction with Chlamydia psittaci. The oxidative activity of purified turkey monocytes, following inoculation with the avian C. psittaci serovar D strain 92/1293, was studied using luminol- and lucigenin-enhanced CL. Purified turkey monocytes were inoculated with C. psittaci at multiplicity of infection (MOI) of approximately 100, 10 and 1. In the presence of luminol, no detectable CL or only a weak CL response was obtained, and if present it increased with increasing MOI. Either sham inoculated monocytes, or monocyte-free control assays supplemented with C. psittaci, gave no detectable luminol-enhanced CL responses. In the lucigenin-enhanced assays, monocytes inoculated with C. psittaci demonstrated an immediate CL peak, the height of which was proportional to the MOI used. Following inoculations at a MOI 1, a faint second peak was observed, when applying high concentrations of lucigenin. Sham inoculated monocytes gave no detectable lucigenin-enhanced CL responses. However, in the presence of lucigenin, the addition of C psittaci to monocyte-free controls also resulted in an immediate CL peak, though no second peak was detected. This immediate lucigenin-dependent CL peak induced by C. psittaci was similar to the one observed in the presence of monocytes, and was not inhibited by superoxide dismutase. We demonstrated that this avian C. psittaci strain induces only a very weak respiratory burst response in turkey monocytes. In contrast, C. psittaci itself elicited an intense non-superoxide mediated lucigenin-dependent CL, indicating that in chlamydial research the detection of superoxide, using lucigenin, should be confirmed with a specific superoxide inhibitor.

Acridines↗
PubMed1999

PCNA and Ki67 proliferation markers as criteria for prediction of clinical behaviour of melanocytic tumours in cats and dogs.

Melanocytic tumours in domestic animals vary from benign to highly malignant. Diagnosis and prognosis are mainly based on the somewhat uncertain interpretation of cytological signs of malignancy in histological sections. The purpose of the present retrospective study was to compare the accuracy of prognosis based on the classical morphological criteria with that provided by quantitative computerized analysis of proliferation-associated antigens. Twenty-seven melanocytic tumours (20 canine and seven feline) from 24 animals (20 dogs and four cats) were examined. These comprised eight tumours histologically classified as benign melanoma (BM) (seven canine, one feline), 16 classified as primary malignant melanoma (PMM) (13 canine, three feline) and three classified as metastatic melanoma (MMM) (three feline). Tumour size, predominant histological cell type, invasive growth and clinical outcome were recorded for each case. In addition, the proliferation (phase) index and growth fraction were measured, after bleaching, by means of quantitative image analysis of tissue sections immunolabelled for proliferating cell nuclear antigen (PCNA) and MIB-1 (Ki67). Lesions classified histologically as benign or malignant, differed significantly (Copyright P<0.001) in respect of Ki67 and PCNA positivity. No such difference could be shown between PMM and MMM. High growth fraction (measured by the Ki67 positive cells) and macroscopic invasive growth were associated with decreased survival time (P=0.027 and P=0.024, respectively). Moreover, the established cytological classification also proved to be associated with the survival time (P<0.001). The results suggest that Ki67 is a potentially important prognostic factor in melanomas of the cat and dog. Other criteria, including tumour size, predominant cell type and intensity of PCNA expression, were not of significant prognostic value (P>0.05).

Animals↗
PubMed1999

Phylogenetic characterization of 'Candidatus Helicobacter bovis', a new gastric helicobacter in cattle.

Recently helicobacter-like organisms have been reported in the pyloric part of the abomasum of calves and adult cattle. Cultivation of these spiral bacteria has not been successful to date. In the present study, comparative 16S rDNA sequence analysis was used to determine the taxonomic position of these bacteria. Seven abomasal biopsies of adult cattle were sampled from different Belgian and Dutch farms. In all samples the presence of helicobacter-like organisms was demonstrated by biochemical, immunohistochemical and electron microscopical data. Bacterial 16S rDNA was amplified by PCR and sequences were determined either by direct or indirect sequence analysis. Pairwise comparisons revealed all sequences to be more than 99% homologous. Phylogenetic analysis placed the organism, corresponding to the reference sequence R2XA, within the genus Helicobacter. A diagnostic PCR assay was designed, differentiating all of the bovine 16S rDNA sequences from Helicobacter and Wolinella species. The low similarity level towards Helicobacter bilis (92.8%), its closest validly named neighbour, indicates that this novel taxon is indeed a novel Helicobacter species. An in situ hybridization procedure associated the bovine sequences to the helicobacter-like organisms in the abomasum. The name 'Candidatus Helicobacter bovis' is proposed for this new abomasal helicobacter from cattle.

Abomasum↗
PubMed1999

'Candidatus Helicobacter suis', a gastric helicobacter from pigs, and its phylogenetic relatedness to other gastrospirilla.

'Gastrospirillum suis' is an uncultured, tightly spiral micro-organism that has been associated with ulcer disease in the stomachs of pigs. It was the purpose of this study to determine the phylogenetic position of 'G. suis'. Stomachs of five slaughterhouse pigs, originating from different Belgian and Dutch farms, were selected on the basis of the presence of 'G. suis'-like bacteria, as demonstrated by biochemical, immunohistochemical and electron microscopical data. Bacterial 16S rDNA was amplified by PCR using broad-range primers and five helicobacter-like sequences were determined either by direct or indirect sequence analysis. An inter-sequence homology of 99.7% was observed, suggesting that the sequences originated from strains belonging to a single species. Phylogenetic analysis of the consensus sequence placed the organism within the genus Helicobacter, where it formed a distinct sub-group together with other gastrospirillum-like bacteria (Helicobacter felis, Helicobacter bizzozeronii, Helicobacter salomonis and 'Helicobacter heilmannii' types 1 and 2). Diagnostic PCR primers and a probe were developed that differentiated the porcine sequences from all known helicobacters. These results indicate that the porcine sequences represent a single taxon within the genus Helicobacter. The low similarity level towards H. salomonis (96.6%), its closest validly named neighbour, strongly suggests that this taxon is a novel Helicobacter species. In situ hybridization experiments linked the reference sequence to the 'G. suis'-like bacteria. On the basis of these results, we propose the name 'Candidatus Helicobacter suis' for this gastric helicobacter from pigs.

Animals↗