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Biomedical subjects

F Haesebrouck

Publications and source records attributed to F Haesebrouck.

At least 163 records · Page 9Linked to original sources
PubMed1996

Detection of antibodies to Salmonella enteritidis in sera and yolks from experimentally and naturally infected chickens.

An indirect enzyme-linked immunosorbent assay (ELISA) based on the lipopolysaccharide (LPS) of Salmonella enteritidis phage type 4, was developed for the detection of antibodies to salmonella. Sera and yolks from chickens infected experimentally with S enteritidis showed strong positive reactions. Cross-reactions occurred with sera from chickens inoculated with S typhimurium or S gallinarum. Cross-reactions were weak with sera from chickens infected with five strains of other Enterobacteriaceae. The ELISA was tested with sera and yolks from commercial poultry flocks which were bacteriologically negative for salmonella or infected with salmonella serotypes belonging to serogroup D or to other serogroups. The serological reactions were strong in most flocks infected with S enteritidis and were weaker in flocks infected with S typhimurium. In some flocks infected with these serotypes no antibodies were detected. The correct setting of the cut-off value of the optical density in the ELISA makes it possible to discriminate between chickens which are infected with S enteritidis and chickens which are not infected with S enteritidis.

Animals↗
PubMed1996

Oxygenation activity of chicken blood phagocytes as measured by luminol- and lucigenin-dependent chemiluminescence.

Luminol- and lucigenin-dependent chemiluminescence (CL) was used to compare activation of the respiratory burst of chicken peripheral blood monocytes and heterophils after stimulation with various agents. Monocytes and heterophils were obtained from the blood of three specific-pathogen-free chickens at 14 months of age and purified by a two-step discontinuous Percoll gradient. All cells responded to phorbol 12-myristate 13-acetate (PMA), zymosan A and calcium ionophore A23187 producing CL. The time course of luminol- and lucigenin-dependent CL was similar for both monocytes and heterophils after stimulation with PMA or zymosan A. Heterophils at lower cell number than monocytes responded with similar or higher peak maximum (PM) values. At the concentrations of stimuli used, the order of mean PM values was: zymosan A > PMA > A23187. Addition of 4 x 10(-6) M N-formyl-1-L-methionyl-L-leucyl-L-phenylalanine (fMLP) showed weak but significant CL activity at 1 x 10(6) monocytes per tube with luminol and at 5 x 10(6) monocytes per tube with lucigenin. No significant response to fMLP was observed with heterophils. The results indicate that the respiratory burst of chicken monocytes and heterophils can be measured by CL.

Acridines↗
PubMed1996

Secreted antigens as virulence associated markers in Streptococcus bovis strains from pigeons.

SDS-PAGE and Western blot analysis were performed on the culture supernatant of 7 pigeon S. bovis reference strains belonging to the serotypes 1, 2, 3 and 5. The culture supernatant of highly virulent serotype 1, 2 and 5 strains contained four antigens that were absent in low virulent serotype 3 strains, notably a 185 kDa minor protein band (A) and a triplet (T1) of 70 kDa. The less virulent serotype 3 strains on the other hand contained protein triplets, that had a molecular mass of either 68 kDa (T2) or 74 kDa (T3). The prevalence of A, T1, T2 and T3 was examined in 68 S. bovis strains isolated from healthy pigeons and in 68 S. bovis strains isolated from pigeons that died of S. bovis septicaemia. Six supernatant phenotypes were identified: A-T1 (32 strains), A- T2 (10 strains), A- T3 (7 strains), A+ T1 (84 strains), A+ T2 (1 strain) and A+ T3 (2 strains). Ninety-four percent of the strains lacking the A and T1 proteins were isolated from healthy pigeons, and only 6% were isolated from septicaemia. Strains expressing A and/or T1, however, were isolated form septicaemia in 57% of the cases. These observations may indicate that the A and/or T1 proteins are associated with virulence.

Animals↗
PubMed1996

Pharmacokinetics and bioavailability of doxycycline in turkeys.

The pharmacokinetic parameters of doxycycline (DOX) were determined in 3 day, 3-, 6- and 12-week-old fasted turkeys, after a single intravenous (i.v.) dose of 25 mg doxycycline. HCl/kg body weight. Doxycycline disposition fitted an open two-compartment model. The mean (+/-SD) elimination half-life was 10.6 +/- 0.7, 10.8 +/- 1.5, 7.9 +/- 1.4 and 10.0 +/- 0.9 h in 3 day, 3-, 6- and 12-week-old turkeys, respectively. Mean (+/- SD) total body clearance was 0.19 (+/-0.01), 0.27 (+/-0.03), 0.11 (+/-0.03) and 0.06 (+/-0.01) L/h.kg in 3 day, 3-, 6- and 12-week-old turkeys, respectively. The steady-state volume of distribution was 1.77 (+/-0.2), 2.1 (+/-0.2), 0.7 (+/-0.4) and 0.5 (+/-0.2) L/kg in turkeys of the above mentioned ages, respectively. The AUC value significantly increased with the age of the turkeys. An oral doxycycline solution at a single dose of 25 mg/kg of body weight was administered to 3 day. 3-, 6- and 12-week-old turkeys. The maximal plasma concentrations in fasted turkeys were 3.8, 5.6, 7.4 and 5.7 micrograms/mL. with tmax values of 4.7, 1.5, 2.8 and 5.4 h, for the different ages, respectively. In fed turkeys the Cmax values were 2.5, 6.1, 4.8 and 3.0 micrograms/mL. with tmax values of 4.2, 5.3, 4.5 and 7.5 h, respectively. The absolute bioavailability in fasted turkeys varied between 25.0 +/- 9.0% (for 12-week-old birds) and 63.5 +/- 7.1% (for 3-week-old birds). The relative bioavailability varied between 40.0 +/- 13.0% (for 12-week-old birds) and 83.7 +/- 14.3% (for 3-week-old birds).

Administration, Oral↗
PubMed1996

A new pathogenic Staphylococcus aureus type in commercial rabbits.

Heavy losses in commercial rabbitries with mainly cutaneous infections were found to be caused by a special Staphylococcus aureus type. This type differs from the previously known rabbit and hare pathogenic strains causing similar infections, mainly in its unique phage type.

Abscess↗
PubMed1996

Presence of vancomycin-resistant enterococci in farm and pet animals.

Enterococcus faecium strains with vanA-mediated glycopeptide resistance were isolated by enrichment culture from the intestines and feces of several animal species, mainly horses and dogs (8% positive), chickens (7% positive), and pigs (6% positive). Other vanA-positive enterococcal strains were identified as E. durans in gallinaceous birds, E. faecalis in a horse, and E. gallinarum in a pheasant. Samples from pigeons, cage birds, and ruminants were negative. It was concluded that vancomycin resistance is widespread among isolates from farm and pet animals.

Animals↗
PubMed1996

Ultrastructural changes in avian Chlamydia psittaci serovar A-, B-, and D-infected Buffalo Green Monkey cells.

In order to find an explanation for the observed differences in levels of pathogenicity in turkeys of Chlamydia psittaci 84/55 (avian serovar A), 89/1326 (avian serovar B), 92/1293 (avian serovar D), and the Texas Turkey strain (avian serovar D) (P.B. Wyrick, J. Choong, S.T. Knight, D. Goyeau, E.S. Stuart, and A.B. MacDonald, Immunol. Infect. Dis. 4:131-141, 1994), the reproductive cycles of organisms of the four strains were studied in Buffalo Green Monkey cells by transmission electron microscopy, immunoelectron microscopy, and flow cytometry. Organisms of strains most pathogenic in turkeys, namely, the serovar A strain and the 92/1293 serovar D strain, (i) replicated faster, since at 50 h postinoculation significantly larger inclusions with more numerous infectious organisms were observed than with the less pathogenic strains; (ii) were often found devoid of inclusion membranes scattered throughout the cytoplasms; and (iii) induced severe degenerative changes in Buffalo Green Monkey cells. By immunoelectron microscopy and flow cytometry, chlamydial antigens could not be detected in the plasma membranes of infected host cells. However, the presence of chlamydial antigens in inclusion membranes was demonstrated by immunoelectron microscopy.

Animals↗
PubMed1996

Influence of Actinobacillus pleuropneumoniae and its metabolites on porcine alveolar epithelial cells.

The effect of Actinobacillus pleuropneumoniae and its metabolites on the viability of porcine alveolar epithelial cells was studied by using a neutral-red uptake test. Alveolar epithelial cells were obtained from 5-week-old colostrum-deprived pigs. The purity of these cells as assessed by the modified Papanicolaou stain was 90 to 95%. Incubation of these cells with 10(6) CFU of a biotype 1 serotype 1 strain resulted in death of the alveolar epithelial cells within 1.5 h. A cytotoxic effect was also seen when alveolar epithelial cells were incubated with sterile culture supernatants of biotype 1 serotype 1, biotype 1 serotype 10, and biotype 2 serotype 2 strains or with ApxI, ApxII, or ApxIII produced by recombinant Escherichia coli. Incubation of alveolar epithelial cells with a knockout mutant of the biotype 1 serotype 1 parent strain which is unable to secrete Apx toxins or with its supernatant did not result in death of these cells. These results indicate that cytotoxicity is at least in part due to production of Apx toxins.

Actinobacillus pleuropneumoniae↗
PubMed1996

Acidification of methyl-alpha-D-glucopyranoside: a useful test to differentiate Enterococcus casseliflavus and Enterococcus gallinarum from Enterococcus faecium species group and from Enterococcus faecalis.

Enterococcus gallinarum and E. casseliflavus are difficult to differentiate from other enterococci, particularly E.faecium. The former two species were found to produce acid from methyl-alpha-D-glucopyranoside in phenol red broth, while E.faecalis strains and strains of the E.faecium species group, including E.faecium, E.durans, E. hirae, and E.mundtii, failed to produce acid from this substrate.

Bacterial Typing Techniques↗
PubMed1995

Identification of Enterococcus species isolated from foods of animal origin.

Enterococci isolated from a large variety of fresh and prepared foods of animal origin during routine microbiologic control tests in a distribution firm, were identified to species level using API 20 STREP galleries supplemented with conventional tests, rapid ID32 STREP galleries and SDS-PAGE analysis. API 20 STREP tests correctly identified 77% of the strains, mainly Enterococcus faecium and E. faecalis. A simple presumptive identification scheme based on pigmentation, tetrazolium reduction and acid production from mannitol and raffinose identified 90% of the strains. More complex procedures were necessary to identify the remaining strains. Nearly all strains isolated from hard cheeses and prepared cheese-meat combinations were identified as E. faecium while E. faecalis was the most frequent species in crustaceans. In meat and in prepared meat products E. faecium, E. faecalis and less frequently E. hirae/E. durans were found. Three of four E. gallinarum strains were isolated from products containing turkey meat.

Animals↗
PubMed1995

Chlamydia psittaci infections: a review with emphasis on avian chlamydiosis.

In the first part of this article the general characteristics of Chlamydia psittaci namely the history, taxonomy, morphology, reproductive cycle, metabolism and genetics are reviewed. For the taxonomy in particular, a considerable amount of new information has become available in recent years, following the application of monoclonal antibodies and restriction enzymes. Using these techniques isolates of Chlamydia psittaci from birds have been subdivided in different serovars, a number of isolates have been classified in a new species (Chlamydia pecorum) and isolates from animals have been classified as Chlamydia trachomatis. In the second part of the article, the current knowledge on avian chlamydiosis is summarized. Emphasis is put on clinical signs, lesions, pathogenesis, epizootiology, immunity, diagnosis, prevention and treatment. Also the public health considerations are reviewed. It is concluded that the diagnosis of avian chlamydiosis is laborious and that there is still a need for more accurate, simple and rapid diagnostic tools, both for antigen and antibody detection in various species of birds.

Animals↗
PubMed1995

Intracellular survival and multiplication of virulent and less virulent strains of Streptococcus bovis in pigeon macrophages.

The intracellular fate of pigeon S. bovis strains ingested by macrophages was studied in vivo and in vitro. During in vivo experiments, histological and electron microscopical examinations demonstrated numerous cocci, which appeared to be actively multiplying, within splenic macrophages of pigeons experimentally inoculated with a highly virulent S. bovis serotype 1 strain. In pigeons inoculated with a low virulence serotype 3 strain, intracellular cocci were only occasionally observed. For in vitro experiments, pigeon peritoneal macrophages were inoculated with a S. bovis serotype 1 or serotype 3 strain and incubated. Following an initial decrease, an increase in the number of intracellular bacteria was observed in tests performed with the S. bovis serotype 1 strain, demonstrating intracellular multiplication. Macrophages in these experiments had all died after 7 h of incubation, possibly indicating that the intracellular replication of S. bovis resulted in the release of substances toxic for macrophages. In experiments performed with the S. bovis serotype 3 strain, the number of intracellular bacteria continuously decreased, reflecting killing of organisms. Significant changes in the number of adhering macrophages in S. bovis serotype 3 inoculated cultures were not observed. These results indicate S. bovis in pigeons is a facultative intracellular bacterium and intracellular multiplication may be involved in virulence.

Ampicillin↗
PubMed1995

Chlamydia psittaci in turkeys: pathogenesis of infections in avian serovars A, B and D.

At 7 days of age, 4 groups, each of twenty specific pathogen free turkeys kept in isolation units were inoculated by aerosol with the Texas Turkey strain (avian Chlamydia psittaci serovar D), strain 92/1293 (avian Chlamydia psittaci serovar D), strain 84/55 (avian Chlamydia psittaci serovar A) or strain 89/1326 (avian Chlamydia psittaci serovar B). A fifth group of 4 specific pathogen free turkeys were sham inoculated controls. At daily intervals for 10 days and then twice weekly up to 34 days post infection, one bird in each group was killed and the target tissues and cells for replication and the sequence of events of serovar A, B and D infections was examined. In these turkeys, the primary site of replication was the respiratory tract. Chlamydial replication could be detected in the respiratory tract on day 1 post inoculation (p.i.) for group A, on day 3 p.i. for group B and on day 1 to 2 p.i. for groups D1 and D2. Subsequently, there was chlamydaemia and localisation in the digestive tract, in one or more parenchymatous organs, in the pericardium and in the conjunctivae. Specific immunoperoxidase staining revealed chamydiae in these organs in epithelial cells and in monomorphonuclear cells in all infected groups. The monomorphonuclear cells were identified as macrophages by double immunofluorescence staining. Chlamydiae were present in the same tissues for serovars A and D, but could not be demonstrated in proventriculus, duodenum, pancreas, ovaries and testes for serovar B. Furthermore, the intensity of replication was similar for all serovars. However, for serovar B in comparison with the other serovars, the bacteria appeared in most tissues 1 to 6 days later and the maximal replication in these tissues occurred 3 to 4 days later.

Aerosols↗
PubMed1995

Effects of Staphylococcus aureus mastitis after endotoxin application on milk yield and composition during subsequent lactation of guinea-pigs.

The effects of Staphylococcus aureus mastitis on milk yield and composition throughout subsequent lactation in lactating guinea-pigs and the role of endotoxin pretreatment on these phenomena were investigated. Primiparous lactating guinea-pigs were intramammarily inoculated with sterile saline (group 1), S. aureus strain UC 6097 (group 2), or with S. aureus UC 6097 after endotoxin pretreatment (group 3). Clinical signs and survival rate were monitored. During the second lactation, daily milk yield was measured and milk composition was determined. In primiparous inoculated guinea-pigs, moderate (group 3)-to-severe acute mastitis (group 2) was produced. During subsequent lactation, milk yield in the control group peaked on day 5 and then decreased. Concentrations of Na+ and Cl- in milk, and concentrations of fat, gradually increased, but lactose and K+ decreased. After an early decrease, NAGase in milk increased towards the end of lactation. Except for higher NAGase concentrations in group 3, milk yield and composition during the second lactation did not differ significantly between the mastitis and the control groups. Endotoxin pretreatment only plays a role in the determination of the severity of the infection.

Animals↗
PubMed1995

Knockout mutants of Actinobacillus pleuropneumoniae serotype 1 that are devoid of RTX toxins do not activate or kill porcine neutrophils.

The Actinobacillus pleuropneumoniae RTX-toxins ApxI, ApxII, and ApxIII are important virulence factors of this swine pathogen. It is hypothesized that the Apx toxins are deleterious to defense cells of the host, enabling the bacterium to infect the host. To confirm this, we studied the effect on porcine polymorphonuclear neutrophils of mutant strains of A. pleuropneumoniae that were devoid of Apx toxins. For this purpose, we developed a system for targeted mutagenesis of A. pleuropneumoniae based on the conditionally replicating plasmid pVE6063 and insertional mutagenesis by homologous recombination. Employing this system on the reference strain of serotype 1, a strain that secretes ApxI and ApxII, we generated mutant strains that were devoid of ApxI and/or ApxII. We compared the ability of the parent strain and the mutant strains to provoke an oxidative burst in porcine neutrophils and to kill these cells. The parent strain and mutants that secreted either ApxI or ApxII provoked an oxidative burst and killed the neutrophils, whereas mutant strains that were devoid of ApxI and ApxII did not. These experiments indicate the importance of ApxI and ApxII to these profound effects on neutrophils and emphasize the importance of ApxI and ApxII in pathogenesis.

Actinobacillus pleuropneumoniae↗
PubMed1994

Streptococcus bovis infections in pigeons: virulence of different serotypes.

In a first experiment, the relative virulence for pigeons of 5 strains of S. bovis was assessed by experimental inoculations. Two S. bovis serotype 1 strains, one serotype 2 strain and two serotype 3 strains were examined. One of the serotype 1 strains and the serotype 2 strain were isolated from pigeons that died from septicaemia. The other strains were isolated from cloaca samples of healthy pigeons. For each strain, 10-20 pigeons were intravenously inoculated with 1 x 10(9) CFU. Morbidity after infection with the serotype 1 and 2 strains varied between 75% and 90%. Disease signs included inability to fly, lameness, emaciation, production of slimy, green droppings, polyuria and sudden death. In groups of pigeons inoculated with the serotype 3 strains, morbidity was 0% and 6%, respectively. Results demonstrate that serotype 3 strains are less virulent for pigeons than serotype 1 and 2 strains. In a second experiment, bacteriological and histological examinations were performed on organs of pigeons serially killed between 1 and 10 days after experimental inoculation with an S. bovis serotype 3 strain of low virulence. Results were compared with results of studies carried out with a highly virulent serotype 1 strain. Notwithstanding bacterial spread and replication in various organs of inoculated pigeons, clinical disease was not observed and histological lesions were scarce and of limited extent.

Animals↗