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Biomedical subjects

Freddy Haesebrouck

Publications and source records attributed to Freddy Haesebrouck.

At least 37 records · Page 2Linked to original sources
PubMed2005

Helicobacter felis and Helicobacter bizzozeronii induce gastric parietal cell loss in Mongolian gerbils.

Non-pylori helicobacter infections are associated with gastritis, gastric ulcers and MALT lymphomas in man. Approximately 50% of these are caused by helicobacters commonly found in dogs and cats, including Helicobacter felis, Helicobacter bizzozeronii and H. salomonis. In contrast to Helicobacter pylori, the virulence mechanisms of these species are unknown. In this study the virulence of H. felis, H. bizzozeronii and H. salomonis was investigated in Mongolian gerbils. Female SPF gerbils were inoculated intragastrically with H. felis, H. bizzozeronii or H. salomonis and sacrificed 3 weeks later. Fundus and antrum samples were taken for bacterial detection by PCR. A longitudinal strip covering all stomach regions was taken for histology. Gastric colonization, inflammation, apoptosis, loss of parietal cells and cell proliferation were assessed. Controls and H. salomonis inoculated gerbils were negative in PCR. H. felis and H. bizzozeronii inoculated animals were positive. H. felis inoculated animals showed loss of parietal cells extending from the limiting ridge into the fundus. A high cell proliferation rate was noticed in the mucosal area devoid of parietal cells. A dense band of apoptotic cells and large numbers of Helicobacter bacteria were seen at the transition zone between affected and normal parietal cells. In H. bizzozeronii infected gerbils, this was less pronounced. Focal apoptotic loss of gastric epithelial cells was spatially associated with the presence of bacteria especially in H. felis and to a lesser extent in H. bizzozeronii infected gerbils. This loss of cells may lead to intestinal metaplasia.

Animals↗
PubMed2005

The diversity of Mycoplasma hyopneumoniae within and between herds using pulsed-field gel electrophoresis.

Over the years, pulsed-field gel electrophoresis (PFGE) has been proven a robust technique to type isolates with a high resolution and a good reproducibility. In this study, a PFGE protocol is described for the typing of Mycoplasma hyopneumoniae isolates. The potential of this technique was demonstrated by comparing M. hyopneumoniae isolates obtained from the same as well as from different herds. The use of two different restriction enzymes, SalI and ApaI, was evaluated. For each enzyme, the resulting restriction profiles were clustered using the unweighted pair group method with arithmetic means (UPGMA). For both obtained dendrograms, the included isolates of the related M. flocculare species clustered separately from all M. hyopneumoniae isolates, forming the root of the dendrograms. The PFGE patterns of the M. hyopneumoniae isolates of different herds were highly diverse and clustered differently in both dendrograms, illustrated by a Pearson's correlation coefficient of only 0.33. A much higher similarity was observed with isolates originating from different pigs of a same herd. The PFGE patterns of these isolates always clustered according to their herd and this for both dendrograms. In conclusion, the results indicate a closer relationship of M. hyopneumoniae isolates within a herd compared to isolates from different herds and this for both restriction enzymes used. Since the described PFGE technique was shown to be highly discriminative and reproducible, it will be a helpful tool to further elucidate the epidemiology of M. hyopneumoniae.

Animals↗
PubMed2005

tet(L)-mediated tetracycline resistance in bovine Mannheimia and Pasteurella isolates.

OBJECTIVES: Tetracycline-resistant Mannheimia and Pasteurella isolates, which were negative for the tetracycline resistance genes (tet) commonly detected among these bacteria, were investigated for other tet genes present and their location. METHODS: Mannheimia and Pasteurella isolates were investigated for their MICs of tetracycline and their plasmid content. Identification of tet genes was achieved by PCR. Plasmids mediating tetracycline resistance were identified by transformation and hybridization experiments. Plasmid pCCK3259 from Mannheimia haemolytica was sequenced completely and analysed for its structure and organization. RESULTS: All tetracycline-resistant isolates carried the gene tet(L) either on plasmids or on the chromosome. Two M. haemolytica isolates and one Mannheimia glucosida isolate harboured a common 5.3 kb tet(L) plasmid, designated pCCK3259. This plasmid was similar to the tet(B)-carrying tetracycline resistance plasmid pHS-Tet from Haemophilus parasuis and the streptomycin/spectinomycin resistance plasmid pCCK647 from Pasteurella multocida in the parts coding for mobilization functions. The tet(L) gene was closely related to that of the Geobacillus stearothermophilus plasmid pTB19. However, the translational attenuator responsible for the tetracycline-inducible expression of tet(L) was missing in plasmid pCCK3259. A recombination site was identified downstream of tet(L), which might explain the integration of the tet(L) gene region into a basic pCCK3259 replicon. CONCLUSION: A tet(L) gene was shown for the first time to be responsible for tetracycline resistance in Mannheimia and Pasteurella isolates. This report demonstrates a lateral transfer of a tetracycline efflux gene in Gram-negative bovine respiratory tract pathogens, probably originating from Gram-positive bacteria.

Animals↗
PubMed2005

Evaluation of amplified rDNA restriction analysis (ARDRA) for the identification of Mycoplasma species.

BACKGROUND: Mycoplasmas are present worldwide in a large number of animal hosts. Due to their small genome and parasitic lifestyle, Mycoplasma spp. require complex isolation media. Nevertheless, already over 100 different species have been identified and characterized and their number increases as more hosts are sampled. We studied the applicability of amplified rDNA restriction analysis (ARDRA) for the identification of all 116 acknowledged Mycoplasma species and subspecies. METHODS: Based upon available 16S rDNA sequences, we calculated and compared theoretical ARDRA profiles. To check the validity of these theoretically calculated profiles, we performed ARDRA on 60 strains of 27 different species and subspecies of the genus Mycoplasma. RESULTS: In silico digestion with the restriction endonuclease AluI (AG--CT) was found to be most discriminative and generated from 3 to 13 fragments depending on the Mycoplasma species. Although 73 Mycoplasma species could be differentiated using AluI, other species gave undistinguishable patterns. For these, an additional restriction digestion, typically with BfaI (C--TAG) or HpyF10VI (GCNNNNN--NNGC), was needed for a final identification. All in vitro obtained restriction profiles were in accordance with the calculated fragments based on only one 16S rDNA sequence, except for two isolates of M. columbinum and two isolates of the M. mycoides cluster, for which correct ARDRA profiles were only obtained if the sequences of both rrn operons were taken into account. CONCLUSION: Theoretically, restriction digestion of the amplified rDNA was found to enable differentiation of all described Mycoplasma species and this could be confirmed by application of ARDRA on a total of 27 species and subspecies.

Animals↗
PubMed2005

Cytolethal distending toxin generates cell death by inducing a bottleneck in the cell cycle.

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.

Bacterial Toxins↗
PubMed2005

Early interactions of Flavobacterium psychrophilum with macrophages of rainbow trout Oncorhynchus mykiss.

The early interactions of a low and a highly virulent Flavobacterium psychrophilum strain with head kidney and spleen macrophages of rainbow trout Oncorhynchus mykiss were characterized. The highly virulent strain was killed 5.8 to 11 times less frequently than the low virulent strain. The head kidney macrophages showed a microbicidal activity approximately twice as high as that of the spleen macrophages. A 2- to 3-fold higher production of reactive oxygen species (ROS) was induced by the highly virulent strain than by the low virulent one. The head kidney macrophages produced approximately twice as much ROS as the spleen macrophages. The low virulent strain was killed approximately 10 times more frequently by H2O2 than was the highly virulent strain. In spleen macrophages, the highly virulent strain caused twice as much cytotoxic effects compared to the low virulent strain. In conclusion, virulence in F. psychrophilum appears to be correlated with higher O. mykiss macrophage cytotoxicity and resistance to ROS and, therefore, with enhanced resistance to bacterial killing. Moreover, due to lower ROS production, spleen macrophages have a lower antimicrobial action against F. psychrophilum, compared to head kidney macrophages and, thus, might form a 'safe site' in which bacteria can reside.

Animals↗
PubMed2005

A comparative evaluation of phenotypic and molecular methods in the identification of members of the Staphylococcus sciuri group.

Members of the Staphylococcus sciuri group (S. sciuri, S. lentus, and S. vitulinus) are coagulase-negative, novobiocin-resistant staphylococci that could be distinguished from other staphylococci on the basis of positive oxidase activity. In the present study, a scheme based on conventional methods and utilization of various carbohydrates was evaluated for the identification of oxidase-positive staphylococci, and validated using two molecular techniques. Of the 173 oxidase-positive staphylococcal tested strains, 161 were identified as S. sciuri, 9 as S. lentus, 2 as S. vitulinus, and one as S. fleurettii by our scheme. The level of agreement with tRNA intergenic length polymorphism analysis (tDNA-PCR) was high (97.5-100% correlation). The accuracy and ease of use of this protocol suggest that it may be useful and valuable in microbiological laboratories for the identification of members of this group.

Bacterial Typing Techniques↗
PubMed2005

In vitro susceptibility of Helicobacter pullorum strains to different antimicrobial agents.

The in vitro activity of 13 antimicrobial agents against 23 Helicobacter pullorum strains from poultry (21) and human (two) origin, and one human H. canadensis strain was tested by the agar dilution method. With the H. pullorum strains, monomodal distributions of Minimum Inhibitory Concentrations (MICs) were seen with lincomycin, doxycycline, gentamicin, tobramycin, erythromycin, tylosin, metronidazole, and enrofloxacin in concentration ranges considered as indicating susceptibility in other bacteria. The normal susceptibility level for nalidixic acid was situated at or slightly above the MIC breakpoints proposed for Campylobacteriaceae. Ampicillin, ceftriaxone, and sulphamethoxazole-trimethoprim showed poor activity against H. pullorum. For the H. canadensis strain, a similar susceptibility pattern was seen, except for nalidixic acid and enrofloxacin, whose MIC of >512 and 8 microg/ml, respectively, indicated resistance of this agent. With spectinomycin, a bimodal distribution of the MICs was noted for the tested strains; eight H. pullorum isolates originating from one flock showed acquired resistance (MIC>512 microg/ml).

Anti-Infective Agents↗
PubMed2005

Characterization of In Vivo acquired resistance of Mycoplasma hyopneumoniae to macrolides and lincosamides.

Macrolides and related antibiotics are used to control mycoplasma infections in the pig industry worldwide. Some porcine mycoplasmas, however, survive these treatments by acquiring resistance. The mechanism of acquired resistance to macrolides and lincosamides was studied in more detail for Mycoplasma hyopneumoniae by comparing both the phenotype and genotype of a resistant field isolate to five susceptible isolates. The MICs were significantly higher for the resistant strain for all antibiotics tested. The MICs for the 16-membered macrolide tylosin ranged from 8 to 16 microg for the resistant strain and from 0.03 to 0.125 microg/ml for the five susceptible strains. The MICs for the 15-membered macrolides and lincosamides were higher than 64 microg/ml for the resistant strain while only 0.06 to 0.5 microg/ml for the susceptible strains. Mycoplasma hyopneumoniae strains are intrinsically resistant to the 14-membered macrolides due to a G 2057 A transition (E. coli numbering) in their 23S rDNA. Therefore, high MICs were observed for all strains, although the MICs for the resistant strain were clearly increased. An additional, acquired A 2058 G point mutation was found in the 23S rRNA gene of the resistant strain. No differences linked to resistance were found in the ribosomal proteins L4 and L22. The present study showed that 23S rRNA mutations resulting in resistance to macrolides and lincosamides as described in other Mycoplasma spp. also occur under field conditions in M. hyopneumoniae.

Drug Resistance, Multiple, Bacterial↗
PubMed2005

Variability in acquired resistance of Pasteurella and Mannheimia isolates from the nasopharynx of calves, with particular reference to different herd types.

To measure the level of antimicrobial resistance in potential bovine respiratory pathogens at different production types, nasal swabs were collected from 57 calves of 13 dairy herds, 150 calves of 9 beef cattle herds, and 289 calves of 5 high-density veal calf herds and investigated for the presence of Pasteurellaceae. All calves were less than 6 months old. Susceptibilities of the Pasteurella and Mannheimia isolates to eight antimicrobials were determined using an agar dilution method. P. multocida (37.3%) and hemolytic Mannheimia organisms (M. haemolytica sensu lato) (6.3%) were the most frequently detected organisms. The overall prevalence of isolates resistant to at least one antimicrobial from the dairy, beef, and veal calves were 17.6% (6/34), 21.9% (14/64), and 71.9% (64/89), respectively. In isolates obtained on the veal calf herds, acquired resistance to ampicillin, oxytetracycline, potentiated sulfonamides, gentamicin, tilmicosin, and enrofloxacin was frequently present, and 32.6% of these isolates were resistant to more than two of the tested antimicrobials. Resistance to ceftiofur and florfenicol was not detected. A substantial within-herd variability of species diversity and resistance profiles among isolates belonging to the genera Pasteurella and Mannheimia was found among the isolates of the veal calf farms.

Animals↗
PubMed2005

Presence and mechanism of antimicrobial resistance among enterococci from cats and dogs.

The presence and mechanism of acquired resistance to erythromycin, tylosin, lincomycin, quinupristin/dalfopristin, tetracycline, chloramphenicol, gentamicin, kanamycin, and vancomycin were determined in 97 and 104 enterococci isolated from rectal swabs of cats and dogs, respectively. Eleven feline and three canine enterococcal isolates contained the aac(6')-Ie-aph(2'')-Ia gene encoding high-level resistance to gentamicin, an antibiotic often used for treating enterococcal infections in humans. The combination of erm(B) and vat(E) genes encoding resistance to streptogramins was detected in one canine quinupristin/dalfopristin-resistant Enterococcus faecium isolate. Four quinupristin/dalfopristin-resistant enterococci only contained the erm(B) gene. Cross resistance against macrolides and lincosamides (30%) and resistance against tetracyclines (55%) was found to be widely distributed among enterococci from pets. In all of the feline and in 93% of the canine macrolide and lincosamide-resistant isolates, this resistance was encoded by the erm(B) gene. tet(M) was the most prevalent tetracycline resistance gene. It was detected in 91% of the feline and 86% of the canine tetracycline- resistant enterococci. A high occurrence of the Tn916/Tn1545 transposon family was found among these tet(M)-positive isolates. Enterococci from pet animals with resistance against vancomycin were not found. This study shows that enterococci from the intestinal microbiota of cats and dogs may act as a reservoir of resistance genes for animal or human pathogens.

Animals↗
PubMed2005

Staphylococcus pseudintermedius sp. nov., a coagulase-positive species from animals.

Four staphylococcal isolates from clinical and necropsy specimens from a cat, a dog, a horse and a parrot (Psittacus erithacus timneh) were found to constitute a distinct taxon. 16S rRNA gene sequence analysis revealed that its closest phylogenetic relatives are Staphylococcus intermedius and Staphylococcus delphini. Growth characteristics, biochemical features and DNA-DNA hybridizations demonstrated that the strains differ from these and other known species and that they represent a single, novel Staphylococcus species for which the name Staphylococcus pseudintermedius sp. nov. is proposed. The novel species is commonly confused with S. intermedius in routine diagnostic veterinary bacteriology. Although the strains described were isolated from lesions and show several characteristics typical of pathogenic staphylococci, such as coagulase, DNase and beta-haemolysin production, the pathogenic significance of the novel species remains unclear. The type strain, LMG 22219(T) (=ON 86(T)=CCUG 49543(T)), was isolated from lung tissue of a cat.

Animals↗
PubMed2005

Enterococcus canintestini sp. nov., from faecal samples of healthy dogs.

The taxonomic position of strain LMG 13590(T), originally isolated from dog faeces and classified as Enterococcus dispar in the BCCM/LMG Bacteria Catalogue, was reinvestigated. This strain and 12 recent isolates from faecal samples of healthy dogs occupied a clearly separate position when investigated with multilocus sequence analysis (MLSA) of the genes encoding the alpha subunit of ATP synthase (atpA), RNA polymerase alpha subunit (rpoA) and phenylalanyl-tRNA synthase alpha subunit (pheS). The 16S rRNA gene sequence of one representative strain showed highest similarities of 98-99% with E. dispar LMG 13521(T), Enterococcus canis LMG 12316(T) and Enterococcus asini LMG 18727(T). A further polyphasic taxonomic study based on whole-cell protein fingerprinting, DNA-DNA hybridization and biochemical features demonstrated that the 13 enterococcal dog faecal strains represent a single, novel Enterococcus species for which the name Enterococcus canintestini sp. nov. is proposed. The type strain is LMG 13590(T) (=CCM 7285(T)).

Animals↗
PubMed2005

Detection of non-pylori Helicobacter species in "Helicobacter heilmannii"-infected humans.

BACKGROUND: A small proportion of patients suffering from chronic active gastritis are diagnosed with gastric Helicobacter species other than Helicobacter pylori. Circumstantial evidence has suggested that these bacteria, also referred to as "Helicobacter heilmannii"-like organisms (HHLO), may be transmitted through animals. The isolation of a Helicobacter bizzozeronii strain from a human patient confirmed this hypothesis. It was the aim of the present study to assess the presence of animal Helicobacter species and H. pylori in humans infected with HHLO, as diagnosed by histology. METHODS: Paraffin-embedded gastric biopsy specimens of 108 HHLO-infected patients (42 women and 66 men) from three clinical centers were screened for the presence of animal gastric Helicobacter species by polymerase chain reaction (PCR), using assays targeting the 16S rDNA region of the three known canine and feline helicobacters (H. bizzozeronii, H. salomonis and H. felis), "Candidatus H. suis", and "Candidatus H. bovis". In addition, the presence of H. pylori was evaluated by multiplex PCR analysis. RESULTS: In 63.4% of the stomachs (64/101) classification of the Helicobacter infection into the above mentioned groups was achieved. Non-pylori Helicobacter species commonly colonizing the stomachs of cats and dogs were found in 48.5% (49/101) of the patients. Fourteen (13.9%) samples tested positive for "Candidatus H. suis", and "Candidatus H. bovis" was demonstrated in 1 (0.9%) patient. The presence of H. pylori was established in 13 patients (12.9%). Eleven stomachs (10.9%) were infected with at least two different Helicobacter species. CONCLUSIONS: This study identifies animal Helicobacter species in the stomach of a large series of HHLO-infected patients, which may have clinical implications in a subset of patients with gastric disease.

Adolescent↗
PubMed2005

Novel spectinomycin/streptomycin resistance gene, aadA14, from Pasteurella multocida.

A novel spectinomycin/streptomycin resistance gene, designated aadA14, was detected on the mobilizable 5,198-bp plasmid pCCK647 from Pasteurella multocida. The aadA14 gene encodes an aminoglycoside adenylyltransferase of 261 amino acids. Sequence comparisons revealed that the AadA14 protein showed less than 60% identity to the AadA proteins known so far.

Animals↗
PubMed2005

Identification of non-Helicobacter pylori spiral organisms in gastric samples from humans, dogs, and cats.

Tightly coiled bacteria are a rare cause of gastric pathology in humans and represent a mixture of species for which a zoonotic origin is suspected. Similar organisms are common inhabitants of the gastric mucosae of carnivores and pigs. It was the goal of the present study to determine the actual occurrence of each individual Helicobacter species in human, canine, and feline stomachs in order to better understand the possible zoonotic significance. Gastric biopsy samples from humans with histological evidence of non-Helicobacter pylori spiral bacteria (n = 123) and samples from the gastric antrum, corpus, and cardia from dogs (n = 110) and cats (n = 43) were subjected to a multiplex PCR, enabling the identification of Helicobacter felis, Helicobacter bizzozeronii, Helicobacter salomonis, and "Candidatus Helicobacter suis." A PCR for detecting H. pylori was applied to all human samples. Single infections with "Candidatus Helicobacter suis," H. felis, H. bizzozeronii, H. salomonis, a hitherto unknown genotype of a non-H. pylori spiral organism (Helicobacter-like organism 135 [HLO135]), and H. pylori were identified in 30.9%, 8.9%, 2.4%, 11.4%, 7.3%, and 8.9% of the human biopsy samples, respectively. Mixed infections (16.3%) with two or even three of these were also found. In the canine stomach, H. bizzozeronii (70.0%) was encountered as the main spiral organism, while H. felis (62.7%) and HLO135 (67.4%) were the predominant Helicobacter species found in the feline gastric mucosa. Although the majority of human non-H. pylori organisms are Helicobacter species naturally occurring in the stomachs of pigs, cats, and dogs, the frequent identification of H. salomonis in human gastric biopsy samples is in contrast to its rare identification in pet carnivore samples, urging us to suspect other sources of infection.

Animals↗
PubMed2005

Prevalence of Helicobacter pullorum among patients with gastrointestinal disease and clinically healthy persons.

Feces from 531 patients with gastroenteritis and from 100 clinically healthy individuals were tested for Helicobacter pullorum by use of PCR. Samples positive by PCR were qualified for isolation. H. pullorum DNA was demonstrated to be present in feces from 4.3% of patients with gastrointestinal disease but also in feces from 4.0% of clinically healthy persons. One strain was isolated from one patient with gastrointestinal disease.

DNA, Bacterial↗