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Biomedical subjects

J R Walton

Publications and source records attributed to J R Walton.

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

Plasmid and chromosomal related toxin polymorphism of Escherichia coli serogroup O 138; plasmid transfer and co-integration with pRP4.

DNA-DNA hybridisation was used to examine 89 isolates of Escherichia coli serogroup O138 for toxin gene content and location. Sixty-six isolates encoded toxin genes; 29 were STpa STpb VT2, 24 were VT2, four were STpa STpb, three were STpb VT2, three were STpb VT2LT and one was STpa. None were K88-, K99- or F41-positive. The VT toxin gene was chromosomally located in all VT+ isolates tested whereas STpa, STpb and LT were plasmid borne. In co-transfer experiments with pRP4 as the mobilising plasmid, VT2 genes were not transferred to recipient E. coli K12 whereas STpa, STpb and LT genes were. Two VT2-positive isolates inhibited pRP4 transfer to K12 by a factor of 10(6) and rare transconjugants harboured a co-integrate plasmid comprising pRP4 (54kb) and a cryptic host plasmid (145 kb). In a K12 background, the co-integrate had transfer and incompatibility properties of pRP4 whereas in both progenitor E. coli O138 backgrounds the co-integrate was transfer inhibited and in one case resolved to give original plasmids.

Animals↗
PubMed1988

Antibiotic resistance: an overview.

The results of large scale surveys have indicated that in general terms antibiotic resistance in bacteria has not increased, especially in Europe and North America. When the prevalence of resistance in specific bacteria has increased the increase has usually been associated with the introduction of a novel antimicrobial agent, whether in human or veterinary clinical practice, but the prevalence of resistance that is recognised may be very small. It would appear that the use of antibiotics in livestock farming during the past 20 years has not compromised public health. Any problems in human medicine which are due to bacterial resistance have resulted from the use of antibiotics in man and not from their use in agriculture. Similarly, any problems in veterinary medicine which are due to bacterial resistance have resulted from the use of antibiotics in animals and not from their use in man.

Animals↗
PubMed1987

Zygote viability in gene transfer experiments.

To learn why some zygotes remain viable after gene transfer while others lyse, we injected DNA into fertilized eggs and compared those that lysed within 1 h of injection with others that retained a normal appearance. Using scanning electron microscopy, we found open holes on the surface of lysed eggs, indicating failure of the plasma membrane to reseal after microinjection. No holes were seen in unlysed eggs, but many of them had membrane alterations suggestive of healed punctures. We also examined aspects of the gene transfer procedure that might influence survival such as the size of injection pipettes and their taper relative to zygote diameter, possible toxicity of the injection medium, the timing of injection, and immediate vs. delayed pipette withdrawal. The only factors that significantly affected cell viability were pipette size and taper, and timing of injection in relation to first cleavage. This suggests that zygote viability correlates inversely with the size of the hole produced by the injection pipette and that damage to the membrane is less successfully repaired as the fertilized egg readies itself for division.

Animals↗
PubMed1986

A new controversy in respiratory equipment management: reusables versus disposed disposables versus reused disposables.

On the topic of respiratory equipment management, few quantitative studies have been conducted to investigate the alternatives of reusables, disposed disposables, and reused disposables. The controversy involving disposed disposables versus reusables is based on four principal issues: quality of construction, safety in handling, infection control, and total cost. Because disposable devices have improved in quality and durability, the importance of the first two issues has dissipated. The infection control issue argues in favor of disposed disposables. The total cost issue is difficult to resolve, as many of the expense components are specific to each particular institution. Nevertheless, it appears that in high-usage situations, reusable equipment is more cost-effective than disposables and that at lower volume disposables are less costly than their reusable counterparts. The controversy over reusing disposables has an added legal dimension. The patient care provider can be held directly liable if a device meant to be disposable was reused and caused patient injury. Evidence is lacking in the respiratory care literature to support the contention that reusing disposables is less costly than the other options. Further, there are many patient safety issues that are currently unresolved. When care providers choose to reuse equipment intended to be disposable, they must be prepared to accept the same responsibilities as manufacturers. For life-support equipment, the potential risks associated with reusing disposables appear to outweigh the unproven benefits.

Costs and Cost Analysis↗
PubMed1983

Mastitis in a large, zero-grazed dairy herd.

A zero-grazed herd of approximately 400 cows had a significant mastitis problem associated with Escherichia coli and Streptococcus uberis during a study over three and a half years. Dry cow therapy and post-milk teat dipping effectively controlled staphylococci and the bulk milk cell count averaged less than 400 X 10(3) cells/ml, but over 1800 clinical cases of mastitis occurred over this period, 32 per cent of which were associated with E coli and 25 per cent with Str uberis. Only 8 per cent of the cases associated with E coli showed obvious systemic disturbance and 75 per cent were cured following penicillin and streptomycin treatment. The incidence was highest during spring and summer when the housed cows were dirtiest. Gross teat-end contamination came mainly from sources other than cubicle bedding, and changing the bedding from sawdust to sand did not alter the incidence of clinical mastitis. It was not possible to maintain adequate cleanliness either inside or outside the parlour, nor maintain a trouble-free milking apparatus. The costs of mastitis in this herd during one year are calculated.

Animals↗