No description available.

No description available.

The objective of the first part of this study was to observe and describe the profile of test-day somatic cell counts throughout a lactation in individual cows, and to examine the correspondence between such profiles and various lactation measures of cell count presently available. The objective of the second part of the study was to obtain estimates of the genetic and phenotypic parameters of lactation measures of cell count in different lactations, possibly for use in a breeding program. / In the first part of the study, the lactation cell count profiles of eighteen Holstein heifers of the Macdonald College Herd were individually examined. Weekly cell counts were expressed as deviations from the herd test-day average and plotted against week of test. A labile cell activity was found for most of the plotted lactations. The cellular responsiveness of cows facing external challenges seemed a trait peculiar to each individual. Lactation measures of cell count were unable to give good descriptions of cell count profiles of individual cows. However, they were better expressions of the lactation cell count performance than single test-day observations. / In the second part of the study, monthly cell count observations were obtained between February, 1977, and February, 1982, for the Holstein cows in herds enrolled on the official option of the Quebec Dairy Herd Analysis Service. Maximum likelihood, I-MINQUE (iterative Minimum Norm Quadratic Unbiased Estimation), and multivariate REML (Restricted Maximum Likelihood) procedures were used for the estimation of genetic and phenotypic parameters. / Repeatabilities of log test-day cell counts and log of test-day cell counts corrected for milk yield varied between 0.36 and 0.42 in first, second, third, fourth, and fifth and later lactations. Repeatabilities of test-day cell counts (cells/ml) in the five lactation groups varied between 0.17 and 0.25. Repeatabilities of lactation expressions for cell count between lactations ranged from 0.13 to 0.44. / Heritabilities of lactation expressions of cell count were low and varied from 0.06 to 0.14 in the five lactation groups examined; however, the genetic correlations between lactations were very close to unity, 0.90 to 0.97.

No description available.

No description available.

Thesis (MSc)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The effect of the bacteriocin-like peptide AS-48, produced by Enterococcus faecalis FAIRE 92, was tested against a mastitis isolate of Staphylococcus aureus in an in vivo and in vitro study. During initial tests peptide AS-48 showed no significant activity towards S. aureus, even with a ten-fold concentrated cell-free supernatant. Activity was obtained only after purification with Triton X-114 phase partitioning, followed by cation exchange chromatography. Titers for the purified peptide varied between 3200 and 12800 AU/ml. The purified peptide also exhibited activity towards Streptococcus agalactiae and Streptococcus dysgalactiae, but not against Escherichia coli. The size of peptide AS-48 was determined at 7150 Da, based on electronspray mass spectrometry and SDS-PAGE. Complete inhibition of cell growth was obtained by adding 1ml of the purified peptide (3200 AU/ml) to 100 ml of cells of S. aureus in the lag growth phase. When the same concentration of peptide AS-48 was added to a culture of S. aureus in mid-exponential growth, a slight decrease in viable cell numbers was recorded, which lasted for only 30 min. Cell growth commenced thereafter. In situ experiments in cows were done with purified peptide AS-48, encapsulated in liposomes. These in vivo studies were conducted by administering peptide AS-48 (6400 AU/ml) to different udder quarters. In a prevention trial, i.e. where quarters were pretreated with peptide AS-48, a reduction close to 90% in the viable cell numbers of S. aureus was recorded relative to the control quarters, which were not treated with the peptide. A 50% reduction in somatic cell count (SCC) was recorded. In the treatment trial, i.e. infected quarters treated with peptide AS-48, a reduction of up to 94% in viable cell numbers of S. aureus was recorded. In the same quarters, a reduction in SCC amounted to almost 80%. A recombinant strain was constructed by conjugating plasmid 92 (p92), encoding peptide AS-48, from Enterococcus faecalis FAIRE 92 to E. faecalis FA2/Ent, which produces enterocins 1071A and 1071B. Southern blot hybridization experiments revealed thepresence of plasmid p92 in the recipient strain without the loss of plasmid pEF1071, which encodes enterocins 1071A and 1071B. All three antimicrobial peptides, i.e. enterocin 1071A, enterocin 1071B and peptide AS-48, were produced in transconjugant FA2/Ent/AS-48. The spectrum of antimicrobial activity of the transconjugant was greater than that recorded for strains FA2/Ent and FAIRE 92, respectively and included E. faecalis, Bacillus cereus, Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus curvatus, Lactobacillus fermentum, Lactobacillus plantarum, Lactobacillus reuteri, Lactobacillus sakei, Leuconostoc cremoris, Leuconostoc pentosaceus, Staphylococcus carnosus and S. aureus. These organisms are not inhibited by strain FA2/Ent. However, low levels of peptide AS-48 was produced by strain FA2/Ent/AS-48. Further research in fermentation and gene expression will be needed before the transconjugant E. faecalis FA2/Ent/AS-48 may be used in the treatment of mastitis. / AFRIKAANSE OPSOMMING: Die effek van die bakteriosien-agtige, peptied AS-48, geproduseer deur Enterococcus faecalis FAIRE 92, is gedurende ‘n in vivo en in vitro studie teen ‘n mastitiese Staphylococcus aureus-isolaat getoets. Aanvanklike toetse met peptied AS-48, selfs tienvoudig gekonsentreerde selvrye supernatant, het geen beduidende aktiwiteit teen S. aureus getoon nie. Aktiwiteit is eers verkry na suiwering met Triton X-114 fase-skeiding gevolg deur katioon uitruilingschromatografie. Titers vir die gesuiwerde peptied het tussen 3200 en 12800 AE/ml gewissel. Die gesuiwerde peptied het ook aktiwiteit teen Streptococcus agalactiae en Streptococcus dysgalctiae getoon, maar nie teen Escherichia coli nie. Peptied AS-48 het ‘n molekulêre massa van 7150 Da, soos bepaal met elektronsproeimassa spektrometrie en SDS-PAGE. Totale inhibisie van selgroei is verkry deur 1 ml gesuiwerde peptied AS-48 (3200 AE/ml) by ‘n 100 ml kultuur van S. aureus in die sloerfase te voeg. Dieselfe konsentrasie peptied AS-48, toegevoeg tydens die mideksponensiële groeifase, het egter slegs ‘n klein vermindering in die aantal lewende selle teweeg gebring en het ook vir slegs ‘n 30 min geduur. Selgroei het hierna weer normaal voort gegaan. In situ eksperimente op koeie is uitgevoer met gesuiwerde peptied AS-48, geenkapsuleerd in liposome. Hierdie In vivo studies is onderneem deur peptied AS-48 (6400 AE/ml) in verskillende kwarte van die uier, kunsmatig of reeds geïnfekteerd met S. aureus, toe te dien. In ‘n voorkomings-eksperiment waar kwarte vooraf met peptied AS- 48 behandel is, is ‘n verlaging van byna 90% in die lewende seltelling van S. aureus relatief tot die kontrole kwarte, sonder behandeling met peptied AS-48, verkry. ‘n 50% verlaging in die somatiese seltelling (SST) is verkry. In die behandelings-eksperiment, waar geïnfekteerde kwarte met peptied AS-48 behandel is, is ‘n verlaging van byna 90% in lewende S. aureus selle gevind. In dieselfde kwarte is ‘n verlaging van byna 80% in die SST genoteer.‘n Rekombinante ras is gekonstrueer deur plasmied 92 (p92), wat kodeer vir peptied AS- 48, vanaf Enterococcus faecalis FAIRE 92 na E. faecalis FA2/Ent, wat enterosien 1071A en 1071B produseer, te konjugeer. Southern-klad hibridisasie het die teenwoordigheid van plasmied p92 in die ontvanger ras, sonder die verlies van plasmied pEF1071 wat enterosien 1071A en 1071B kodeer, getoon. Al drie antimikrobiese peptiede, nl. enterosien 1071A, enterosien 1071B en peptied AS-48, is deur die transkonjugant FA2/Ent/AS-48 geproduseer. Die spektum van antimikrobiese aktiwiteit van die transkonjugant vand die transkonjugant is breër as dié van rasse FA2/Ent en FAIRE 92, onderskeidelik en het ook E. faecalis, Bacillus cereus, Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus curvatus, Lactobacillus fermentum, Lactobacillus plantarum, Lactobacillus reuteri, Lactobacillus sakei, Leuconostoc cremoris, Leuconostoc pentosaceus, Staphylococcus carnosus en S. aureus ingesluit. Hierdie organismes word nie deur ras FA2/Ent geïnhibeer nie. Lae vlakke van peptied AS-48 is egter deur ras FA2/Ent/AS-48 geproduseer. Verdere navorsing in fermentasie en geenuitdrukking is nodig voordat E. faecalis FA2/Ent/AS-48 in die behandeling van mastitis gebruik kan word.

Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) are the most prevalent pathogens to induce mastitis. The pathogenesis of infections induced by E. coli is sophisticatedly modulated by lipopolysaccharide (LPS), LPS binding protein, membrane CD14 (mCD14), and soluble CD14 (sCD14). In the first study, administration of recombinant bovine sCD14 (rbosCDl4) significantly reduced the fatality of LPS challenged mice and the severity of mouse mastitis in terms of clinical signs, bacterial load, and TNF-alpha production. Before investigating the potential of this strategy in dairy cows, endogenous sCD14 in milk was characterized. Based on the data of 396 quarters, the milk concentration of sCD14 was 6.67 +/- 0.44 mug/ml. The stages of lactation affected the concentration of sCD14 in milk, which was higher in transitional milk (0--4 days postpartum). Milk sCD14 also increased during an intramammary LPS challenge, which paralleled with SCC increase. The protective effect of sCD14 on bovine E. coli mastitis was then investigated. It was shown that rbosCDl4 sensitized the mammary gland to recruit leukocytes in response to LPS. To prove that the early recruitment of leukocytes plays a role in preventing intramammary E. coli infections, E. coli mastitis was induced in 9 dairy cows with or without 100 mug rbosCD14. Quarters challenged with E. coli plus rbosCD14 had a more rapid recruitment of neutrophils, a faster clearance of bacteria, reduced concentrations of TNF-alpha and IL-8 in milk, and reduced clinical symptoms than quarters injected with saline. / For S. aureus mastitis, a newly designed trivalent whole-cell vaccine being composed of the most dominant serotypes (T5, T8, and T336) was evaluated. The vaccine was immunized with or without either one of the two adjuvants, aluminum hydroxide (ALUM) and Freund's incomplete adjuvant (FICA). The vaccine, with or without the presence of adjuvants, increased antigen-specific IgG1, IgG2, but not IgM, in serum. However, all formulations only had limited effects on lymphocyte subsets, interferon (IFN)-gamma mRNA expression, and neutrophil phagocytosis in comparison with the control. / Taken together, the results indicated that increasing the concentration of sCD14 in milk might be a potential strategy to prevent or reduce severity of E. coli mastitis. On the other hand, both ALUM and FICA did not augment the immune responses when formulated with trivalent vaccine. A more immunostimulatory adjuvant will be required to improve the efficacy of the novel trivalent vaccine against S. aureus mastitis.

No description available.

Thesis (MSc (Microbiology))--Stellenbosch University, 2008. / Mastitis is considered to be the most costly disease affecting the dairy industry. Management strategies involve the extensive use of antibiotics to treat and prevent this disease. Prophylactic dosages of antibiotics used in mastitis control programmes could select for strains with resistance to antibiotics. In addition, a strong drive towards reducing antibiotic residues in animal food products has lead to research in finding alternative antimicrobial agents. Streptococcus macedonicus ST91KM, isolated from bulgarian goat yoghurt, produces the bacteriocin macedocin ST91KM with a narrow spectrum of activity against Grampositive bacteria. These include mastitis pathogens Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis, Staphylococcus aureus and Staphylococcus epidermidis as well as Lactobacillus sakei and Micrococcus varians. Macedocin ST91KM is, according to tricine-SDS PAGE, between 2.0 and 2.5 kDa in size. The activity of macedocin ST91KM remained unchanged after 2 h of incubation at pH 2.0 to 10.0 and 100 min at 100 °C. The peptide was inactivated after 20 min at 121 °C and when treated with pronase, pepsin and trypsin. Treatment with α-amylase had no effect on activity, suggesting that the mode of action does not depend on glycosylation. Precipitation with 60 % saturated ammonium sulphate, followed by Sep-Pak C18 separation recovered 43 % of macedocin ST91KM. Amplification of the genome of strain ST91KM with primers designed from the sequence of the macedocin prescursor gene (mcdA) produced two fragments (approximately 375 and 220 bp) instead of one fragment of 150 bp recorded for macedocin produced by S. macedonicus ACA-DC 198. Strain ACA-DC 198 was not available. However, the DNA fragment amplified from strain LMG 18488 (ACA-DC 206), genetically closely related to strain ACADC 198, revealed 99 % homology to the mcdA of S. macedonicus ACA-DC 198 (accession number DQ835394). Macedocin ST91KM may thus be a related bacteriocin described for S. macedonicus. The peptide adsorbed equally well (66 %) to L. sakei LMG13558 and insensitive cells, e.g. Enterococcus faecalis BFE 1071 and FAIR E92, and Streptococcus caprinus ATCC 700066. Optimal adsorption of macedocin ST91KM was recorded at 37 °C and 45 °C and at pH of 8 - 10. Addition of solvents decreased adsorption by 50%, suggesting that the receptors to which the bacteriocin binds have lipid moieties. The addition of MgCl2, KI and Na2CO3 completely prevented adsorption of macedocin ST91KM to the target cells, possibly due to competitive ion adsorption on the bacterial cell surface. The peptide has a bacteriocidal mode of action, resulting in lysis and the release of DNA and β-galactosidase. Atomic force microscopy of sensitive cells treated with macedocin ST91KM have shown deformation of the cell structure and developing of irregular surface areas. Antimicrobial susceptibility patterns were evaluated against eighteen mastitis pathogens. All isolates tested were resistant to methicillin and oxacillin, but had minimum inhibitory concentrations (MICs) falling in the intermediate and susceptible range against erythromycin. S. agalactiae and S. epidermidis had the highest sensitivity to macedocin ST91KM. A teat seal preparation containing macedocin ST91KM effectively released bacteriocin inhibiting the growth of the bacterial pathogen. Macedocin ST91KM could form the basis for an alternative dry cow therapy to prevent mastitis infections in dairy cows, as it is effective against pathogens that display resistance to conventional antibiotic therapy.

O sistema de análise de perigos e pontos críticos de controle (APPCC) possui como principal objetivo a prevenção de riscos à saúde humana, bem como evitar alterações nos alimentos através da aplicação de práticas de controle em etapas da produção nas quais existe maior probabilidade de ocorrência de perigos ou situações críticas, sendo aplicado em todas as etapas de produção, desde a obtenção da matéria-prima até a elaboração do produto final. Desta maneira, o sistema APPCC é considerado como importante técnica para prevenção e controle de qualidade dos alimentos, já utilizado em fazendas leiteiras para controle de patógenos e resíduos de medicamentos. A contagem de células somáticas (CCS) e a contaminação bacteriana do Leite são fatores essenciais para manutenção da qualidade do leite em propriedades leiteiras, representando grandes prejuízos para a produção leiteira. Assim, os objetivos gerais da pesquisa foram: avaliação da eficiência, possíveis diferenças e principais problemas relacionados a aplicação do sistema APPCC em duas propriedades leiteiras (A e B) com vistas ao controle dos níveis de células somáticas e parâmetros higiênico-sanitários no leite do rebanho e ocorrência de mastite nos animais. Preliminarmente à implantação do sistema, realizou-se o treinamento em Boas Práticas de Produção e Manipulação para possibilitar a aplicação dos princípios do sistema APPCC. Os resultados mostraram que a aplicação do sistema foi eficaz para melhoria da qualidade do leite em uma das propriedades, resultado demonstrado pela melhoria da qualidade com referência ao controle da mastite e parâmetros higiênicos. Observou-se uma redução da CCS média dos animais, número de quartos afetados e escore de mastite. Quanto aos parâmetros higiênicos do leite, observou-se redução das contagens de mesófilos e coliformes fecais. Aspectos relacionados ao comprometimento dos funcionários e proprietário foram considerados essenciais para o sucesso do sistema APPCC, cuja implementação em propriedades leiteiras apresentou peculiaridades e diferenças pronunciadas em relação às indústrias alimentícias. / The Hazard Analysis Critical Control Point (HACCP) has, as the main objective the prevention of human’s health risks, as to avoid changes in the food due to use of the application of control practices in the steps of production, where the possibility of hazards or critical situations is bigger. The system is used in all steps of the production, since the ran material until the manufactured product. Regarding to this, the HACCP is considered as an important technique to prevent and to control the quality of the food that has been used in dainy forms to control pathogens and medical residues. The somatic cells count and the bacterial contamination of milk are essential factors to maintain the milk quality in the right condition, what represent big damages for the milk production. The objective of this research was to evaluate the efficiency, possible mistakes and the main problems related to the application of HACCP process in two dairy properties (A and B), based on the control of somatic cells level and hygienic conditions of the milk among the herd, besides the occurrence of the mastitis in animals. Before the application of the system, training in good manufacture practices and manipulation was accomplished to allow the use of the HACCP system. The results showed that the application of this method was efficient in order to improve the milk quality in one of the properties, what was shown in a better result of the mastitis’s control it was observed a reduction in the average counting of affected animals and mastitis’s cases. Related to the hygienic conditions of the milk, it was noticed a reduction in the numbers of mesophills and faecals coliforms. Aspects regarding the commitment of the workers and the owner were considered as essential for the success of the HACCP program, as the implementation in dairy forms showed particularities and differences related to the to the food industry.