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Biomedical subjects

A J Bramley

Publications and source records attributed to A J Bramley.

At least 37 records · Page 2Linked to original sources
PubMed1990

The coagulase of Staphylococcus aureus 8325-4. Sequence analysis and virulence of site-specific coagulase-deficient mutants.

The sequence of the coagulase gene (coa) from Staphylococcus aureus strain 8325-4 is reported. The deduced amino acid sequence of the coagulase protein is compared with previously reported sequences of coagulases from strains 213 and BB. The secreted mature forms of coagulase proteins are composed of three distinct segments: (i) the N-terminal 150-270 residues, which are c. 50% identical, (ii) a central region with high (greater than 90%) residue identities, and (iii) a C-terminal region composed of repeated 27-amino-acid residue sequences. The variable N-terminal sequences are probably responsible for antigenic differences among coagulases of different serotype. The region of coagulase which binds to prothrombin and activates it to form staphylothrombin is also located in the N-terminal half of the protein. A site-specific substitution mutation in the coa gene, which abolished plasma clotting activity, was isolated by recombinational allele-replacement in strains 8325-4 and M60. The Coa- mutants did not show diminished virulence in subcutaneous and intramammary infections of mice. No evidence for a role for coagulase in virulence of toxigenic or nontoxigenic strains was obtained. This contradicts findings of several groups using Coa- mutants generated by chemical mutagenesis and suggests that the earlier results were obtained with strains that had suffered additional mutations in virulence-related genes.

Alleles↗
PubMed1990

Effects of lysostaphin on Staphylococcus aureus infections of the mouse mammary gland.

A 5 to 6 log10 reduction in the viable count of Staphylococcus aureus was produced in vitro with 10 micrograms lysostaphin ml-1 milk. Infusion of the lactating murine mammary gland with 10 micrograms lysostaphin, immediately following inoculation with 10(8) colony forming units of S aureus, resulted in a significant 2 to 3 log10 reduction in viable S aureus (P less than 0.02) within 30 minutes. Pre-infusion with 10 micrograms lysostaphin either immediately before or one hour before staphylococcal challenge reduced the recovery of S aureus by more than 6 log10 and greatly reduced pathological changes typical of S aureus mastitis. This clearly demonstrates that lysostaphin has considerable potential for the therapeutic or prophylactic control of staphylococcal mastitis.

Animals↗
PubMed1989

Effect of udder preparation on transmission of Staphylococcus aureus while milking with a multi-valved cluster.

With two groups of 12 cows, a procedure involving foremilking, teat washing and drying before milking was compared with no premilking preparation for its effects on mastitis and teat contamination. Half the cows in each group were deliberately infected in a single udder quarter with Staphylococcus aureus and milked alternately with uninfected cows for 9 weeks. To minimize transfer during milking all cows were milked with the use of a multi-valved claw. Five new staphylococcal infections developed in the 12 animals in the teat preparation group compared to one in the control group. A significantly higher incidence of teat orifice colonization developed in the prepared cows compared to the control cows (17 v. 7). Foremilking and teat preparation led to transfer of staphylococci between quarters (within cow) but this was effectively prevented by the multi-valve claw in the absence of teat preparation.

Animals↗
PubMed1989

Roles of alpha-toxin and beta-toxin in virulence of Staphylococcus aureus for the mouse mammary gland.

Mutants of Staphylococcus aureus which fail to express alpha-toxin (Hly), beta-toxin (Hlb), or both have been constructed by site-specific mutagenesis. The virulence of the mutants was compared with that of wild-type toxigenic strains by intramammary inoculation of lactating mice. A bovine strain, M60, and a laboratory strain, 8325-4, caused acute mastitis and death within 48 h for 60% of the mice inoculated. Animals inoculated with Hly mutants also developed acute mastitis, but no deaths occurred. Comparisons of Hly- or Hlb-positive strains with the double mutation Hly Hlb showed that both toxins led to a significantly higher recovery of S. aureus from the gland 48 h postinfection. Histopathological examination of mammary glands showed that phagocytosis of bacteria occurred irrespective of toxigenicity, but toxigenic strains, particularly those which were Hly+, continued to multiply, invaded the interalveolar tissues, and produced severe lesions. Stimulation of an inflammatory response by inoculation of the mammary gland with endotoxin prior to challenge with S. aureus reduced recovery of the bacteria 10- to 100-fold and, under these conditions, neither alpha-toxin nor beta-toxin contributed significantly to growth and survival.

Animals↗
PubMed1988

Histochemical localization and possible antibacterial role of xanthine oxidase in the bovine mammary gland.

Xanthine oxidase (XO) was demonstrated to be present in the teat canal and secretory tissue of the bovine mammary gland by histochemical techniques. Homogenates of these tissues were able to replace XO in an antibacterial assay with Streptococcus uberis. The action of XO on its substrate hypoxanthine was shown to provide an essential component for anti-streptococcal activity mediated by lactoperoxidase. A mechanism is proposed whereby the interaction of XO, lactoperoxidase and thiocyanate may provide antibacterial activity in the teat canal.

Animals↗
PubMed1988

An in-line sampling technique to measure the bacterial contamination of milk during milking.

The development of devices to sample milk at the clawpiece and at the end of the pipeline during milking are described. The results of tests to compare the bacteriological and compositional quality of milk collected from the sampling devices or from the recorder jar or milk cans were similar, demonstrating that the samples provided accurate and representative values. The use of the in-line sampling technique, whereby samples of the milk are taken at three points during its passage through the milking plant, to assess accurately the sources of bacterial contamination of bulk tank milk on farms is discussed.

Animals↗
PubMed1988

A multi-valved milking machine cluster to control intramammary infection in dairy cows.

A milking machine claw incorporating valves to prevent movement of milk between teats during milking, and its contribution to the prevention of udder infection under experimental and field conditions, is described. Under experimental conditions a suspension of Streptococcus agalactiae and Str. dysgalactiae was introduced into the milking cluster during milking; 11 of 40 quarters became infected using a conventional claw piece whereas none of 40 quarters milked with the multi-valve claw developed intramammary infection. In a 12-month experiment in ten commercial herds, each split into two equal susceptibility groups, the multi-valved cluster reduced the incidence of new infection with coliforms and Str. uberis by 17% (P less than 0.1). The incidence of all new infections and new clinical cases was 14 and 25% lower compared to conventional clusters but these reductions were not significant.

Animals↗
PubMed1986

Influence of the lactoperoxidase system on susceptibility of the udder to Streptococcus uberis infection.

Lactoperoxidase (LP), thiocyanate (SCN-), pH and somatic cell counts (SCC) were measured in mammary secretions from 20 cows collected 14 d before drying-off, 7 and 21 d after drying-off, and 3-18 d postcalving. The inhibitory activity of the secretions on Streptococcus uberis was determined and the susceptibility of the udder to infection by this organism was tested by intramammary infusion of 250 colony forming units at the above stages. LP, SCN-, pH and SCC increased during involution and fell postcalving. The secretions collected before drying-off, 7 d after drying-off and postcalving inhibited growth of Str. uberis.; those collected 21 d after drying-off did not. Inhibitory activity in pre-drying-off secretions was destroyed by heating and restored by addition of LP, glucose and glucose oxidase, but addition of these substances to secretion 21 d after drying-off did not provide a full inhibitory system. The growth of Str. uberis in the secretions was correlated with intramammary susceptibility, since challenges with Str. uberis at 14 d before drying-off, at 7 and 21 d after drying-off and postcalving led to 43.8, 25.0, 81.3 and 37.5% of quarters becoming infected. It is suggested that the LP/SCN-/H2O2 system plays a role in protecting the lactating mammary gland from infection with Str. uberis but becomes ineffective as involution progresses.

Animals↗
PubMed1985

The pathogenesis of a high-virulence and a low-virulence strain of Corynebacterium bovis in the mammary gland of the mouse.

A comparison was made of the pathogenesis of experimental mastitis in mice caused by a strain of Corynebacterium bovis (P3) isolated from clinical mastitis in the cow and a strain (NCDO 1930) isolated from the teat of a symptomless carrier cow. Strain NCDO 1930 elicited a neutrophil response which controlled the infection so that, after 6 to 8 days, 9 of 10 glands were sterile and one abscess was found. In contrast, the neutrophil response to strain P3 failed to control the infection and, by 6 to 8 days, 8 of 10 glands were infected and there were abscesses in 11 of 20 glands. The virulence of strain P3 was associated with its ability to colonize on and in milk fat globules, from which the organisms multiplied in the alveolar lumen irrespective of the neutrophil infiltration.

Animals↗
PubMed1985

Carriage of Corynebacterium pyogenes by the cattle nuisance flies Hydrotaea irritans (Fallén) and Musca autumnalis (De Geer).

Two species of cattle-visiting Muscidae were experimentally contaminated with C. pyogenes, a pathogen involved in the aetiology of summer mastitis. Surface contamination persisted for at least 4 days. Since M. autumnalis would not feed on media containing C. pyogenes the bacterium did not persist internally. All C. pyogenes were eliminated from the gut of H. irritans in 4 days. H. irritans is thus more likely to transmit C. pyogenes than is M. autumnalis but only by mechanical transfer, and is not a true vector.

Animals↗
PubMed1985

An examination of teat drying with disinfectant impregnated cloths on the bacteriological quality of milk and on the transfer of Streptococcus agalactiae before milking.

Total bacterial counts of the milk from individual cows were measured for three groups of ten winter housed cows at three milkings. The teats were either (i) left unwashed or (ii) washed with disinfected water (60 ppm available iodine) and dried with individual paper towels or (iii) washed with plain water and then dried with a single fabric cloth impregnated with a polymeric bisguanide and a quaternary ammonium compound. The mean total bacterial counts/ml for the groups were 5820, 2108 and 1116 respectively. Treatments (ii) and (iii) were also compared for their ability to prevent the inter-teat transfer of bacteria. Before teat washing and drying, one teat of each cow was deliberately contaminated with Streptococcus agalactiae. Significantly fewer teats (5/30) became contaminated with Str. agalactiae when treatment (iii) was used for teat washing and drying compared with treatment (ii) (20/30).

Animals↗
PubMed1985

Effect of reaming the papillary duct of cows' teats on keratin removal and penetrability of the duct to implanted Escherichia coli endotoxin.

Penetrability of the bovine teat duct to Escherichia coli endotoxin solution was measured before and after reaming the duct with a polypropylene tube, a steel twist drill bit, or a fluted drill point. There was some evidence of a transient increase in penetrability for one or two milkings following reaming but most ducts were not rendered penetrable to endotoxin. Histological examination of ducts after reaming showed that although the loosely packed superficial keratin was effectively removed a continuous smooth keratin layer remained covering the epithelium. These observations are discussed with respect to the possible mechanisms responsible for maintaining the defensive barrier of the duct to bacterial penetration.

Animals↗
PubMed1984

Summer mastitis.

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Animals↗
PubMed1984

Stimulation of Streptococcus thermophilus growth in mastitic milk.

Growth of Streptococcus thermophilus was faster in mastitic milk, aseptically collected following intramammary infusion of Escherichia coli endotoxin, than in normal aseptically collected milk. The contribution of polymorphonuclear leucocytes (PMN), of plasma and plasmin to this stimulation has been investigated. Addition of plasmin to low cell count milk stimulated growth of the streptococcus to the same degree as mastitic milk. However, addition of plasma or PMN from blood or from milk were less stimulatory. The part played by these components in providing casein breakdown products for the weakly proteolytic Str. thermophilus in mastitic milk is discussed.

Animals↗
PubMed1984

Observations on Corynebacterium bovis infection of the bovine mammary gland. II. Experimental infection.

Experiments are described in which lactating cows were exposed to Corynebacterium bovis either by dipping the teats in a suspension of the bacteria or by inoculating the bacteria into the teat duct or the teat sinus. All three methods readily led to 'infection' being established. The effect of these infections on somatic cell count was minor and no clinical mastitis resulted during the course of the experiments although some cases occurred subsequently. There was evidence that 44% of these infections were confined to the teat duct. Quarters excreting C. bovis in milk continued to do so during endotoxin-induced inflammation and showed a similar cellular response to that of uninfected quarters.

Animals↗