Biomedical subjects

B Poutrel

Publications and source records attributed to B Poutrel.

At least 55 records · Page 3Linked to original sources

PubMed1990

Phagocytosis of mastitis isolates of Staphylococcus aureus and expression of type 5 capsular polysaccharide are influenced by growth in the presence of milk.

Phagocytosis by bovine polymorphonuclear granulocytes of seven capsular polysaccharide type 5 Staphylococcus aureus strains isolated from mastitis [corrected] was investigated by means of luminol-dependent chemiluminescence. Bacteria were grown on four different agar media (brain heart infusion, Columbia broth, modified staphylococcus medium 110, and skim milk) and were opsonized by normal bovine serum. When compared to growth on brain heart infusion agar, Columbia agar, and modified staphylococcus medium 110 agar, growth on skim milk agar rendered five of the strains more resistant to opsonization. The other two strains were resistant in all culture media used. Short periods of incubation in milk after growth on brain heart infusion agar did not augment resistance to phagocytosis, indicating that mere adsorption of milk components on bacteria was not responsible. The variability of the chemiluminescence response of polymorphonuclear leukocytes was pronounced among strains with each growth medium except milk. Growth on modified staphylococcus medium 110 and on milk agar favored the masking of teichoic acid, as shown by inagglutinability with rabbit antiserum. Interestingly, agglutination by a monoclonal antibody to capsular polysaccharide type 5 was optimal when bacteria were grown on skim milk agar. This suggests that capsular polysaccharide participated in the masking effect. These findings indicate that masking of the bacterial target of most of the naturally acquired opsonins present in normal bovine serum occurred when bacteria grew in the presence of milk, resulting in an increased resistance to phagocytosis by polymorphonuclear leukocytes.

Animals↗

PubMed1990

Reactivity of coagulase-negative staphylococci isolated from cow and goat milk with monoclonal antibodies to Staphylococcus aureus capsular polysaccharide types 5 and 8.

Monoclonal antibodies to Staphylococcus aureus capsular polysaccharide types 5 and 8 were used in an enzyme-linked immunosorbent assay to serotype 74 and 42 coagulase-negative isolates from cow and goat milk, respectively. Eighteen (15.5%) isolates were typable: 13 Staphylococcus haemolyticus, 1 S. hyicus, 1 S. simulans, and 1 S. warneri from bovine origin and 2 S. lentus from caprine origin. Type 5 was predominant, accounting for about 89% of typable isolates. Reactivity with monoclonal antibodies varied considerably according to isolates. The significance and the potential importance of these findings are discussed.

Animals↗

PubMed1990

Encapsulation of Staphylococcus aureus isolates from mastitic milk: relationship between capsular polysaccharide types 5 and 8 and colony morphology in serum-soft agar, clumping factor, teichoic acid, and protein A.

A total of 193 Staphylococcus aureus isolates from bovine, caprine, and ovine mastitis producing type 5 or 8 capsular polysaccharides were investigated for colony morphology in serum-soft agar and agglutinability by an anti-teichoic acid serum, after cultivation in modified staphylococcus medium no. 110. Also, 40 of these strains were cultivated in brain heart infusion and submitted to clumping factor and protein A detection tests. Considering capsular serotyping as a reference method, diffuse growth in serum-soft agar and inagglutinability by anti-teichoic acid serum identified, respectively, 57.5 and 45% of encapsulated strains cultivated in brain heart infusion and 85.5 and 77.2% of those cultivated in modified staphylococcus medium 110. Consequently, these indirect techniques underestimated encapsulation and were greatly influenced by culture conditions. Whatever the medium used, diffuse colony morphology in serum-soft agar was generally characterized by a masking of teichoic acid and protein A. By contrast, these surface antigens were detected in association with compact morphology; the presence of a thin or discontinuous capsular material could explain this result. Moreover, the masking of teichoic acid and the removal of capsular polysaccharide by washing in saline suggest that type 8 capsular polysaccharide is more abundant and labile than type 5.

Agglutination↗

PubMed1990

Detection of capsular polysaccharide in milk of cows with natural intramammary infection caused by Staphylococcus aureus.

Detection of capsular polysaccharide (CP) in milk of cows with natural intramammary infection caused by Staphylococcus aureus was attempted. Five quarters of 5 cows harboring S aureus strains that produce type-8 CP were selected. Using an ELISA with a monoclonal antibody, type-8 CP was not detected in extracts prepared from fresh milk collected aseptically. By contrast, CP was easily detectable after incubation of infected milk at 38 C for 20 hours. Quantitation of CP in extracts from incubated milk samples by use of ELISA indicated a great variation of CP expression by strains. Although an incubation step was necessary to detect CP, results of the study indicate that CP may be expressed in vivo during intramammary infection caused by S aureus.

Animals↗

PubMed1988

Ingestion and killing of Streptococcus agalactiae by bovine granulocytes in the presence of natural opsonins.

An enzyme-linked immunosorbent assay (ELISA) demonstrated the presence of naturally acquired antibodies against Streptococcus agalactiae in normal bovine serum (NBS). In milk wheys, ELISA values were much lower than in sera. Pre-colostral calf serum (PCS) was shown to lack antibodies to type II and III S. agalactiae. The opsonic requirements of 10 human and 10 bovine strains were investigated by evaluating the phagocytosis-induced reduction of the incorporation of radiolabeled thymidine by streptococci. Antibodies present in NBS were required for the efficient ingestion of both human and bovine isolates type II by bovine granulocytes. Three out of five type III bovine isolates were opsonized in the absence of specific antibodies (opsonization by PCS) and type II and III bovine isolates did not require complement opsonization. By contrast, inactivation of complement reduced phagocytosis of human isolates and only one type III strain of human origin was opsonized by PCS. These findings suggest that human isolates had higher opsonic requirements. The phagocytic killing of 6 type III strains (5 mastitis isolates and the reference typing strain) was investigated. Opsonization by normal serum enabled bovine blood granulocytes to ingest and kill S. agalactiae. Nevertheless, greater than or equal to 35% of bacteria remained viable at the end of the phagocytosis incubation in 10% NBS. Heat treatment of serum decreased the efficacy of killing for only 3 of the 6 tested strains. An IgG2 fraction of normal adult bovine serum promoted active ingestion, which was still increased in the presence of PCS. Normal wheys displayed large variations in their ability to promote ingestion of S. agalactiae by blood granulocytes. The promoting effect was systematically less than that of serum from the same cow, and this can be related to the lower ELISA values found in wheys.

Animals↗

PubMed1988

Prevalence of capsular polysaccharide types 5 and 8 among Staphylococcus aureus isolates from cow, goat, and ewe milk.

Monoclonal antibodies to Staphylococcus aureus capsular polysaccharide types 5 and 8 were used to serotype by enzyme-linked immunosorbent assay 212, 54, and 33 isolates from cow, goat, and ewe milk, respectively. Capsular types 5 and 8 accounted for 69.4% of bovine isolates and 71.5 and 78.8% of goat and ewe isolates, respectively. Type 5 was predominant in strains from bovine sources (51.4%), whereas type 8 was prevalent in strains from caprine (68.5%) and ovine (75.8%) sources.

Animals↗

PubMed1988

Physiological and pathological factors influencing bovine immunoglobulin G2 concentration in milk.

Bovine IgG2 concentration was determined by radial immunodiffusion in 355 milk samples of uninfected quarters, 101 milk samples of infected quarters, and 118 blood serum samples from 42 Holstein-Friesian cows taken at 30, 150, and 270 d. Concentration of IgG2 in blood serum (11.3 mg/ml) was highest at the beginning of lactation (30 d). Immunoglobulin G2 concentration in milk (16.81 micrograms/ml) from cows with uninfected quarters was not affected by quarter location but was correlated with IgG2 concentration in blood serum (.30; P less than .001). The IgG2 concentration in milk was lower in midlactation (150 d: 14.81 micrograms/ml) and in the two first lactations. Immunoglobulin G2 concentration in milk was correlated with SCC. Quarter infection by Corynebacterium bovis or major pathogens increased IgG2 concentration up to 47.9 micrograms/ml for Staphylococcus aureus. Only S. aureus influenced IgG2 concentration in blood serum. Correlation between IgG2 content and SCC in milk decreased when quarters were infected, regardless of bacterial species.

Animals↗

PubMed1988

Effect of naturally occurring intramammary infections by minor pathogens on new infections by major pathogens in cattle.

New mammary infections were recorded in 3 dairy herds during a lactation period by bacteriologic examination of milk samples at 3-week intervals. Influences of the infection status of quarters at the time of new infection and of microorganisms responsible for bacterial invasion were analyzed. The new infection rate in uninfected quarters was about 3 times the rate in quarters already harboring bacterial considered minor pathogens (coagulase-negative staphylococci and Corynebacterium bovis) or major pathogens (Staphylococcus aureus, streptococci). The frequency of new infections with major pathogens was almost halved by preexisting infections with minor pathogens (P = 0.05), mainly because of coagulase-negative staphylococci (P = 0.05) and, to a lesser extent, C bovis (P = 0.19). New infections by minor pathogens also were less frequent in quarters harboring a major pathogen (P less than 0.05), indicating that the competition or antagonism between mammary infections was a general phenomenon.

Animals↗

PubMed1986

Hemolytic and bactericidal activities of bovine complement in mammary secretions of cows during the early nonlactating (dry) period.

Hemolytic and bactericidal complement-dependent activities were measured in quarter mammary secretions obtained during the first 21 days of the nonlactating (dry) period from 8 Holstein-Friesian cows. We demonstrated an inhibition of hemolytic activity and bactericidal activity against a serum-sensitive Escherichia coli strain. Both hemolytic and inhibitory titers increased markedly during active involution. The bactericidal activity of dry secretions required a minimal threshold of complement and an inhibitory titer lower than the hemolytic titer.

Animals↗

PubMed1985

Virulence of human and bovine isolates of group B streptococci (types Ia and III) in experimental pregnant mouse models.

Two experimental mouse models were tested for their suitability in measuring virulence of two human and two bovine isolates (types Ia and III) of group B streptococci. In the first model, the kinetics of the number of bacteria in the spleen, liver, and placenta of mice inoculated intravenously on day 16 of pregnancy were monitored for 48 h after infection. In the second model, lethality and abortion were recorded for mice inoculated on day 13 of pregnancy. Levels of colonization in spleens or livers and lethality were significantly greater (P less than 0.001) for human isolates than for bovine isolates. In contrast, no statistically significant differences in the ability to colonize placentas and to induce abortions were noted between human and bovine isolates. The results showed that pregnant mice were more sensitive than nonpregnant mice to a challenge with group B streptococci. The results also suggest that placental colonization and abortion could be a suitable mouse model in evaluating the virulence of human and bovine isolates of group B streptococci.

Animals↗

PubMed1985

Physiological and pathological factors influencing bovine alpha-lactalbumin and beta-lactoglobulin concentrations in milk.

Bovine alpha-lactalbumin and beta-lactoglobulin concentrations were determined by radial immunodiffusion in 354 milk samples from uninfected and 98 samples from infected quarters from 42 Holstein-Friesian cows taken at 30, 150, and 270 days of lactation. alpha-Lactalbumin and beta-lactoglobulin concentrations were not affected by quarter location. The alpha-lactalbumin decreased at the end of lactation and in samples collected beyond second lactation. The beta-lactoglobulin concentration increased with stage of lactation. There was a positive correlation between alpha-lactalbumin and beta lactoglobulin (r = .12). Milk from uninfected quarters had mean alpha-lactalbumin and beta-lactoglobulin concentrations of 1.47 and 4.6 mg/ml, respectively. Milk from quarters infected by major pathogens or Corynebacterium bovis had less alpha-lactalbumin. Milk from quarters infected by minor pathogens had less beta-lactoglobulin. There was a negative correlation between alpha-lactalbumin concentration and somatic cell count (r = .31), which was amplified by infection status of quarters. No correlation was noted between somatic cell count and beta-lactoglobulin concentration when considered over the whole sampling period, but the correlation became negative in quarters infected by major pathogens.

Animals↗

PubMed1984

Udder infection of goats by coagulase-negative staphylococci.

Infection of udder halves by coagulase-negative staphylococci in seven commercial goat herds was studied in conjunction with the California Mastitis Test (CMT). Nine different species were identified and only 10% of strains belonged to groups which could not be identified with any of the known Staphylococcus species. The most prevalent species were Staphylococcus epidermidis (47.7%) and Staphylococcus caprae (19.7%). About half of the coagulase-negative staphylococcal infections gave negative CMT scores. The score was independent of the species of staphylococci involved and the stage of lactation. About 60% of the coagulase-negative staphylococcal species isolated were reisolated in the identical half udder during the following lactation.

Animals↗

PubMed1984

Evaluation of the API 20 Strep system for species identification of streptococci isolated from bovine mastitis.

A new commercial system (API 20 Strep) for the species identification of streptococci associated with bovine mastitis was compared with the conventional biochemical methods. A total of 84 strains, including Streptococcus agalactiae (13), S. dysgalactiae (16), S. uberis (24), S. faecalis (12), S. faecium (5), and S. bovis (14) were tested. Using profile index and table data issued by the manufacturer, we identified 71.4% of strains by the API 20 Strep system. Our results indicate that improvement of the identification key is needed for accurate identification of streptococci isolated from bovine mastitis.

Animals↗

PubMed1984

Assessment of hemolytic and bactericidal complement activities in normal and mastitic bovine milk.

Bactericidal and hemolytic complement activities were investigated in 51 quarter milk samples of 13 cows in late lactation. Hemolytic activity was in all of the samples but one, after accounting for whey inhibitory activity. Mean hemolytic activity and inhibitory activities were .18 and .34 complement hemolytic units. Inflammation, in relation to infection status, increased hemolytic titers and heat-labile bactericidal activities of milk. Correlation coefficient was .76 between albumin content of milk serum and hemolytic titer of samples from infected quarters. Normal milk decreased bactericidal titer of bovine serum against a serum-sensitive Escherichia coli strain. When compared to veronal buffer saline solution, milk did not accelerate decay of hemolytic activity over 7-h incubation at 39 degrees C. Taken together, these results suggest that the adverse effect of milk on both hemolytic and bactericidal activities of complement is limited and might be of significance essentially before full establishment of the inflammatory reaction to bacterial invaders.

Animals↗

PubMed1984

Characteristics of non-clinical mammary infections of goats.

This study, carried out on 1217 milk goats (2428 milk samples), sampled at two different periods of lactation, showed that non-clinical mammary infections of the goat were due to major pathogens (7.5%) and coagulase-negative staphylococci (24.1%). Among major pathogens, Staphylococcus aureus was the most frequently isolated species (75.2%). However, great variations were observed between herds, in levels of infection by major pathogens. The intensity of the inflammatory response, measured by the cell count, depended on the pathogen present in the mammary gland. Evidence was found that 75% of infections persisted throughout the lactation and 61% during the dry-period. The arithmetic mean cell counts for milk samples from halves infected with major pathogens was 6.77 X 10(6) cells/ml, determined by Coulter Counter. It was 1.78 and 1.54 X 10(6) cells/ml respectively for halves infected with coagulase-negative staphylococci and non-infected halves. The arithmetic mean cell counts were higher at drying-off than in lactation. The threshold of 1 X 10(6) cells/ml was reliable for diagnosis in mid-lactation and permitted to diagnose 72% of major pathogen infections.

Animals↗

PubMed1984

Staphylococcus sciuri subsp lentus associated with goat mastitis.

An organism recovered from mastitic milks of goats was identified as Staphylococcus sciuri subsp lentus. Isolation of this organism in pure cultures from individual half-udder samples of 5 goats of 18 affected, confirms that it possesses pathogenic potential.

Animals↗

PubMed1984

Non-random distribution of udder infections among cows. Evaluation of some contributing factors.

Bovine udder infections were recorded in three herds throughout a lactation period with bacteriological examinations at 3 week intervals. For analysis, each cow was taken into account at the time when the greatest number of its quarters were infected. Distributions of cows having 0, 1, 2, 3, or 4 infected quarters, either by major or minor pathogens, differed significantly (P less than 0.01) from the random binomial distribution: the number of cows with 3 or 4 infected quarters was much higher than expected. As the two types of pathogens behave similarly, they were not distinguished and data were pooled. Distributions of infections among cows within each of the three herds were not random. Cross-infections (from a quarter to another of the same cow) could have given rise to less than one-third of the new infections. A greater proportion of cows became multi-infected with increasing age. This process was delayed in the herd with the lowest new infection rate. In the three most highly represented lactation ages (1, 2, and 4), differences between actual and theoretical distributions were all significant (P less than 0.01). Results suggested that together with the major contribution of concentration of infections in the older cows and the less important contribution of cross-infections, individual susceptibility played a part in the non-random distribution. Nevertheless the resistance of the less susceptible cows seemed to have been easily overcome when measures for control of new infections were not used.

Age Factors↗

PubMed1983

A sensitive microassay for the determination of hemolytic complement activity in bovine milk.

A 51Cr release microhemolytic complement assay is described to detect hemolytic complement activity in bovine milk. 51Cr-labeled guinea-pig erythrocytes (GPRBC), which have been sensitized with a subagglutinating amount of rabbit anti-GPRBC, are placed in microtiter plates. Pooled bovine sera as source of complement to achieve about 50% of 51Cr release were added to each well prior to the addition of the samples on the test. Determination of CH100 titer was obtained by difference of counting between heated and unheated diluted whey samples from a standard linear regression. Comparative hemolytic values throughout lactation were established for the first time and confirmed the improved sensitivity of the assay.

Animals↗