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B Poutrel

Publications and source records attributed to B Poutrel.

At least 37 records · Page 2Linked to original sources
PubMed1996

Bovine mastitis caused by Listeria monocytogenes: kinetics of antibody responses in serum and milk after experimental infection.

The kinetics of antibodies in serum and milk directed against proteins from Listeria monocytogenes were studied using 4 lactating cows after infection was experimentally induced in the udder with four strains of serotypes 4b or 1/2a. Antibodies (IgG and IgA) in samples of composite quarter milk and serum of the cow were measured by indirect ELISA. Microtiter plates were coated with proteins obtained from the culture supernatant of L. monocytogenes 4b. After challenge, an IgG response in serum and milk to listerial infections in the udder occurred for all cows, although the response varied among cows. In sera, the IgG titers reached a peak at 9 to 13 wk after challenge and remained elevated until 21 to 33 wk after challenge. In milk, the IgG titer increased significantly 3 wk after the challenge for all cows. A weak and nonpersistent increase in IgA antibodies also occurred. These results indicate that IMI by L. monocytogenes induced an increase of antibodies in milk, which could be detected with an ELISA test using our antigenic preparation. Therefore, this antigenic preparation could be used for the evaluation of a new method of diagnosis for bovine mastitis caused by L. monocytogenes.

Animals↗
PubMed1996

Field trial evaluation of two teat dips containing nisin or polyvinylpyrrolidone iodophor designed for use before and after milking.

In a first trial involving six commercial dairy herds and 291 cows for a period of eight months, pre-milking udder sanitation by dipping teats in a 0.25% polyvinylpyrrolidone (PVP) iodophor product followed by wiping with paper towels was compared in each herd with traditional teat washing and wiping with individual udder cloths. The incidence of new intramammary infections by Staphylococcus aureus, Streptococcus uberis and Corynebacterium bovis were significantly (P < 0.05) reduced, respectively by 48%, 60% and 47%. There were no significant differences in the two groups of cows for other intramammary infections, total bacterial counts, clostridia spore counts, iodine residues in milk or teat condition scores. In a second trial involving nine commercial dairy herds and 367 cows for a period of seven months, a teat dip containing nisin used before and after milking was compared in each herd with a classical 0.5% iodophor product used in the same way. There was no significant difference in the incidence of new intramammary infections, in spite of a higher rate of new Staphylococcus aureus infections in the group of cows teat-dipped with the nisin product (P = 0.06). It was concluded that pre-dipping with teat dips specifically designed to be safely used before milking can be more efficient than traditional pre-milking udder preparation. These teat dips, when used before and after milking, seem to be as efficient as products which should normally be restricted to post-milking use.

Animals↗
PubMed1995

Bovine mastitis caused by Listeria monocytogenes: characteristics of natural and experimental infections.

Experimental mastitis induced with a single intramammary injection of Listeria monocytogenes was compared with two naturally occurring cases. Four strains of L. monocytogenes, two of serotype 1/2a and two of serotype 4b were used for the experimental infections and two diametrically opposed quarters of four cows were inoculated with 300 cfu. Bacteriological examination and somatic cell counts of quarter foremilk samples were performed weekly for at least 6 months after challenge. All the inoculated quarters developed chronic subclinical mastitis with occasional clinical episodes. The results were similar to those observed in natural listeria mastitis. Four experimentally infected quarters were treated during lactation (gentamicin and cloxacillin) or at "drying-off" (cloxacillin), or at both times. Only one of four quarters was cured after treatment only at "drying-off". All experimental and naturally infected animals were slaughtered and bacteriological examination was performed on liver, spleen and supramammary, iliac and mesenteric lymph nodes. L. monocytogenes strains were isolated from the supramammary lymph nodes of two experimentally and two naturally infected cows and from an iliac lymph node from one of the naturally infected cows. The epidemiological data were supported by serotyping, lysotyping and DNA macro-restriction analysis. The experimental model of listeria mastitis mimics spontaneous cases and should be useful in further studies of listeria mastitis.

Animals↗
PubMed1995

Effects of culture conditions on production of type 5 capsular polysaccharide by human and bovine Staphylococcus aureus strains.

Two Staphylococcus aureus strains, the prototype human Reynolds strain and a bovine isolate, were grown in different complex media and in a synthetic medium (D. Taylor and K. T. Holland, J. Appl. Bacteriol. 66:319-329, 1989) and compared for their ability to produce type 5 capsular polysaccharide. Cell-bound and cell-free type 5 capsular polysaccharide were measured by a new one-step competition enzyme-linked immunosorbent assay. The total production and the proportion of cell-bound type 5 capsular polysaccharide were dependent on the nature of the medium, the duration of the culture, and the strain. Both strains produced more type 5 capsular polysaccharide when cultivated in the synthetic medium than when cultivated in complex media. The best yield of type 5 capsular polysaccharide, about 300 micrograms/ml of medium, was obtained with strain Reynolds grown for 48 h with shaking in the synthetic broth containing glucose as a carbon source.

Agar↗
PubMed1995

Capsular polysaccharide types 5 and 8 of Staphylococcus aureus bind specifically to human epithelial (KB) cells, endothelial cells, and monocytes and induce release of cytokines.

In order to examine the possible implication of capsular polysaccharide (CP) types 5 and 8 (CP5 and CP8) from Staphylococcus aureus in the pathological mechanism associated with staphylococcal infections, we tested the immunomodulatory effects of CP5 and CP8 on human epithelial KB cells, endothelial cells, and monocytes. Using biotinylated CP5 and CP8, we provide evidence that both CPs bind to KB cells, endothelial cells, and monocytes in a dose- and calcium-dependent manner through specific interactions. These results were confirmed by competition experiments using soluble cell extracts. Furthermore, we show that CPs bind to identical cell membrane receptors on all three types of human cells and that human normal serum contains a factor(s) which inhibits the binding of both CPs to human KB cells, endothelial cells, and monocytes. The ability of CP5 and CP8 to stimulate the production of cytokines by the human cells was then examined. CP5 and CP8 trigger KB cells to produce interleukin-8 (IL-8); endothelial cells to produce IL-8 and IL-6; and monocytes to produce IL-8, IL-6, IL-1 beta, and tumor necrosis factor alpha. The release of cytokines by all three types of cells is time dependent and dose dependent, and the tumor necrosis factor alpha production by monocytes is not affected by the addition of polymyxin B. We further confirm that human normal serum inhibits the immunomodulatory effects of both polysaccharides on each kind of cell. These results confirm that S. aureus CPs act as bacterial adhesins having immunomodulatory effects for human cells.

Bacterial Adhesion↗
PubMed1995

Deposition of complement components on Streptococcus agalactiae in bovine milk in the absence of inflammation.

Bovine milk is generally considered to be almost devoid of complement, on the basis of undetectable hemolytic activity, unless inflammation recruits plasma components. This study examines the deposition of complement components on a mastitis-causing isolate of Streptococcus agalactiae by enzyme-linked immunosorbent assay (ELISA). Neat milk from mid-lactating, uninflamed mammary glands (normal milk) effected marked C3 deposition on bacteria. Kinetic studies showed a protracted lag period (30 to 45 min) preceding C3 deposition, which required about 2 h to reach a maximum. Experiments with diluted serum suggested that this slow C3 deposition resulted mainly from the low concentration of certain components of complement in milk. Bacteria incubated in neat milk readily bound bovine conglutinin, indicating the presence of iC3b. Elution of covalently bound C3 fragments with hydroxylamine confirmed the deposition of C3b and iC3b on bacteria. Deposition of C4 on bacteria was not detected in neat milk, suggesting that C3 deposition did not result from the activation of the classical pathway. This was not the result of a lack of antibodies. However, C4 deposition could be obtained by adding purified bovine C1q to normal milk, and C3 deposition was accelerated, suggesting the participation of the classical pathway. The deposition of C1q on antibody-sensitized bacteria was impeded by milk compared with that of C1q diluted in phosphate-buffered saline. Concentrations of C1q in normal milk were very low, ranging from 150 to 250 ng/ml. Overall, these findings indicate that C1q was a limiting factor of the classical pathway in normal milk. The capacity of milk to deposit C3 fragments on mastitis-causing S. agalactiae prompts further studies to investigate its role in opsonophagocytosis.

Animals↗
PubMed1994

Phenotypic variability of X-protein expression by mastitis-causing Streptococcus agalactiae of serotype NT/X and opsonic activities of specific antibodies.

This study examined the role of antibodies against the X-protein, a surface-localized antigen frequently associated with streptococci causing mastitis in cattle, in the opsonization and phagocytosis of unencapsulated Streptococcus agalactiae. The analysis of various strains of serotype NT/X by flow cytometry, after labeling with a monoclonal antibody to X-protein, revealed that they consisted of a mixture of unstained and stained bacteria. Cloning of mother strains yielded clones of unstained bacteria but not homogeneous clones of stained bacteria. Analysis by ELISA of an unstained clone (4.1) derived from the reference NT/X strain 24/60 indicated that it expressed low amount of X-protein at its surface, about 25 times less than the stained clone 24/60 5.6. Colloidal gold immunolabeling showed the X-protein at the periphery of bacteria (of clone 5.6 and in lower amount of clone 4.1), at a distance from the cell wall. Bovine antibodies (essentially IgG) to X-protein behaved like the monoclonal antibody in the cytometric assay. They activated the classical pathway of complement as shown by the deposition of C1q and C4 on bacteria. Deposition of C4 also occurred on the low-surface-producing clone 4.1 in the presence of antibodies to X-protein, although less efficiently than on the high-surface-producing clone 5.6. When used alone, antibodies promoted the ingestion of bacteria and heat-inactivated immune serum promoted the chemiluminescence activity and the killing by polymorphonuclear cells. In conclusion, antibodies to X-protein induced the deposition of C3 by the classical pathway and were also able to stimulate opsonophagocytic killing of X-bearing S. agalactiae in the absence of deposited C3.

Animals↗
PubMed1994

Immunogenicity in cows of Staphylococcus aureus type 5 capsular polysaccharide-ovalbumin conjugate.

Six dairy cows were immunized subcutaneously with purified type 5 capsular polysaccharide (CP5) of Staphylococcus aureus or CP5-ovalbumin conjugate in Freund's incomplete adjuvant. The CP5 antibodies elicited were measured in sera and analysed with regard to isotypes by enzyme-linked immunosorbent assay. At the doses tested, the purified CP5 did not induce a humoral response in the cows. Immunization of two cows with the CP5-ovalbumin conjugate elicited a CP5 antibody response mainly of the IgG2 isotype, which culminated 4 weeks later. A second injection of conjugate, 3 months after the first one, resulted in a rapid and durable anti-CP5 response without exceeding the first antibody peak value. Intramammary infusion of purified CP5 failed to provoke an inflammatory response in the milk of the immunized cows. In contrast, a marked recruitment of cells was recorded in the milk of the sensitized cows after intramammary infusion of ovalbumin. These results demonstrate that injection of CP5-protein carrier conjugate in cows entails both antibody response against CP5 and carrier-specific recruitment of cells in milk of immunized animals.

Animals↗
PubMed1994

Virulence factors involved in the pathogenesis of bovine intramammary infections due to Staphylococcus aureus.

Staphylococcus aureus is a major causative agent of intramammary infections in dairy cows. In this report, the pathogenesis of these infections is described. The potential role in virulence of S. aureus surface components (adhesins, protein A and capsular polysaccharides), toxins, extracellular enzymes and coagulase, and perspectives for the development of an efficient vaccine are discussed.

Animals↗
PubMed1993

Type 5 and 8 capsular polysaccharides are expressed by Staphylococcus aureus isolates from rabbits, poultry, pigs, and horses.

A total of 103 Staphylococcus aureus isolates from rabbits (n = 37), poultry (n = 33), pigs (n = 27), and horses (n = 6) and 14 Staphylococcus intermedius isolates from wild animals were serotyped for capsular polysaccharide types 5 and 8 by an enzyme-linked immunosorbent assay using polyclonal rabbit antibodies. About 98% of the S. aureus isolates were typeable. Type 5 was predominant in the poultry (75.8%) and pig (66.7%) isolates, whereas type 8 was more frequent among the isolates from rabbits (59.5%) and horses (83.3%). By contrast, none of the 14 S. intermedius isolates was typeable.

Animals↗
PubMed1993

Risk factors associated with contamination of raw milk by Listeria monocytogenes in dairy farms.

A case-control study involving 128 selected dairy farms was conducted to assess the association of several suspected risk factors with the odds of contamination of raw milk by Listeria monocytogenes. Using logistic regression, we found that poor quality of silage (pH > 4.0), inadequate frequency of cleaning the exercise area, poor cow cleanliness, insufficient lighting of milking barns and parlors, and incorrect disinfection of towels between milkings were significantly associated with milk contamination by L. monocytogenes. More attention to preparing silage and good milking and barn hygiene are important for diminishing the risks of exogenous contamination of raw milk by L. monocytogenes.

Animals↗
PubMed1991

Purification of the protein X of Streptococcus agalactiae with a monoclonal antibody.

The protein X of Steptococcus agalactiae is a surface antigen included in the typing scheme of group B streptococci (GBS). We have developed a monoclonal antibody to the protein X and used it to purify this antigen by affinity chromatography. Electrophoresis in polyacrylamide, and immunoblotting using the monoclonal antibody or a rabbit antiserum raised with the affinity purified protein X, revealed a major band in the region of 200 kDa and a smaller one at 100 kDa. The isolated protein X will make possible investigations of its potential role in virulence and protection.

Animals↗
PubMed1991

The kinetics of inflammation and phagocytosis during bovine mastitis induced by Streptococcus agalactiae bearing the protein X.

The protein X of Streptococcus agalactiae is a surface antigen borne by a high proportion of strains isolated from bovine mastitis. We have tested the capacity of two strains of X-bearing Streptococcus agalactiae to induce mastitis in dairy cows. The reference X-strain (411.07) produced an intramammary infection with local clinical signs in the three inoculated quarters. Another X-bearing strain (443.31) of bovine origin produced infection in all 11 quarters inoculated with only 25 or 85 colony-forming units. In naive cows, strain 433.31 induced less exudation of plasma into the milk, shedding of bacteria, macroscopic alteration, and a lower somatic cell count (SCC) than did the reference strain. Only one quarter spontaneously eliminated the infection before antibiotic treatment 9 days after inoculation. The serum of all the cows contained naturally acquired or induced antibodies to the challenge strain (443.31) and possessed opsonic activity. Before inflammation occurred, the milk was almost devoid of antibody or opsonic activities. The early phase of infection was characterized by rapid multiplication of streptococci in the milk, followed by a sharp drop in bacterial counts concomitant with the onset of inflammation. Three cows immunized with protein X displayed higher SCC and bactericidal activity in milk from the inoculated quarter at the onset of inflammation than non-immunized cows. Two of the three immunized cows underwent an early and transient febrile episode and eliminated the infection.

Animals↗
PubMed1991

Pathogenicity of Listeria monocytogenes isolates in immunocompromised mice in relation to listeriolysin production.

The virulence of 74 Listeria monocytogenes isolates from clinical cases and food products and of 11 isolates of other Listeria species was tested in mice immunocompromised with carrageenan. Isolates of species other than L. monocytogenes were not lethal to such mice. All 29 clinical isolates of L. monocytogenes (serotypes 1/2a, 1/2b, 4b) and 33 of 42 isolates of various serotypes isolated mainly from dairy products killed all test mice (100% lethality) at an inoculum of 10(4) cfu/mouse. All lethal strains of L. monocytogenes were haemolytic and possessed the 58-Kda band specific for listeriolysin O as demonstrated by SDS-PAGE immunoblotting. The nine avirulent strains of L. monocytogenes had detectable haemolytic activity, but in six of them this activity was significantly weaker than in virulent strains and the 58-Kda band was not detected. The other three avirulent strains were highly haemolytic and possessed the 58-Kda band, which suggests that other factor(s) could be involved in the virulence of L. monocytogenes.

Animals↗
PubMed1991

Protein X of Streptococcus agalactiae induces opsonic antibodies in cows.

Protein X of Streptococcus agalactiae is a surface protein frequently associated with strains isolated from cases of mastitis of dairy cows. By immunizing cows with purified protein X, we obtained an antibody response which was restricted to X-bearing strains of S. agalactiae in a whole-cell enzyme-linked immunosorbent assay. This response resulted in an increase in the opsonic activity of serum for strains bearing protein X, as assessed through the augmentation of the chemiluminescence response of phagocytosing polymorphonuclear cells and through an increased ingestion of bacteria, although the proportion of ingested bacteria which were killed (about 60%) remained unchanged. Protein X behaved as a target of opsonins and, as such, could be a protective antigen worth incorporating in a vaccine against S. agalactiae mastitis.

Animals↗
PubMed1990

Efficacy of a germicidal post milking barrier-type teat dip in preventing intramammary infections.

Five commercial dairy herds with 269 lactating cows participated for 12 months in a field trial to determine the effectiveness of a barrier teat dip containing chlorous acid/chlorine dioxide germicide. The right quarters of the cows in two herds and the left quarters of the cows in three herds were dipped in the experimental teat dip after the removal of the milking machine. The other quarters were dipped in a conventional 0.5 per cent iodophor product. Compared with this control product, teat dipping with the experimental dip reduced the number of new intramammary infections by 18.8 per cent, infections with major pathogens by 13.6 per cent, infections with minor pathogens by 16.8 per cent and clinical mastitis by 33.3 per cent. Statistical analysis indicated a trend towards decreased intramammary infections with coliforms and coagulase-negative staphylococci when the experimental teat dip was used. It was concluded that under the conditions of this investigation it was effective in preventing new infections due to both contagious and some environmental pathogens. However, the data suggested that it could adversely affect the condition of the skin of the teat when it was used after incorrect preparation of the udder.

Animals↗
PubMed1990

The contribution of mammary infections by coagulase-negative staphylococci to the herd bulk milk somatic cell count.

Quarter foremilk samples were taken at 2-3 weekly intervals for several years in an experimental herd comprising about 45 cows. The samples were submitted to bacteriological analysis and somatic cell counting. The most prevalent quarter infections from 1982 to 1988 were by coagulase-negative staphylococci (15-20% of all the quarters sampled). Most of these (75.6%) persisted until drying-off. Dry cow therapy eliminated 86.5% of these infections. Comparison of udder quarters within cows, involving 775 samples from pairs of non-infected quarters and quarters infected by coagulase-negative staphylococci, yielded geometric means of somatic cell counts of 210,000 and 420,000 cells/ml, respectively. The correlation (r = 0.87) between the herd bulk milk somatic cell count (SCC) and its estimation from the quarter milk somatic cell count performed on the same day allowed us to evaluate the contribution of the different categories of quarters, according to their infection status, to the herd bulk milk SCC. Quarters infected by a major pathogen (8.5% of samples) gave rise to 46.6% of the total number of cells, while quarters infected by coagulase-negative staphylococci (17.8% of samples) gave rise to 18.1%. Although coagulase-negative staphylococci represented only a secondary source of somatic cells as compared to major pathogens, they were not a negligible source considering the threshold of 300,000 somatic cells advocated for herd milk of good quality.

Animals↗