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Biomedical subjects

C Wray

Publications and source records attributed to C Wray.

At least 55 records · Page 3Linked to original sources
PubMed1995

Observations on disinfection regimens used on Salmonella enteritidis infected poultry units.

Studies carried out at the laboratory and in the field identified many potential problems during disinfection of poultry units naturally contaminated with Salmonella enteritidis. There appeared to be variations in the efficiency of commonly used disinfectants within a disinfectant group when used in a contaminated house. It was possible for Salmonella and other coliforms to be amplified during the pressure washing or steam cleaning process. If an effective terminal disinfectant was not used after this, then high levels of Salmonella were likely to persist. The efficiency of the disinfection regimen was not directly dependent on the standard of physical cleaning if this was carried out to a reasonable standard, as a high level of elimination of Salmonella could be achieved even in the presence of substantial quantities of residual organic matter. Disinfection regimens involving formaldehyde, either as part of a terminal compound disinfectant spray or as a final fogging agent, were found to be the most effective in the field.

Animals↗
PubMed1994

Observations on a broiler breeder flock naturally infected with Salmonella enteritidis phage type 4.

Bacteriological and serological studies in a broiler breeder flock naturally infected with Salmonella enteritidis indicated that the infection had become established by about 20 to 22 weeks of age. By 35 weeks, 70 per cent of the birds were positive by ELISA and at 39 weeks, 39 per cent were estimated to be carrying the infection as judged by culture post mortem. By 50 weeks, post mortem culture showed 17 per cent to be infected and 85 per cent reacted to the ELISA. Over the period of observation at the laboratory, combined cloacal swabbing and post mortem culture showed that at least 12.5 per cent of the birds were carrying the infection and 95.7 per cent reacted serologically. As the level of infection apparently declined with age it may have been present at too low a level to detect in the unincubated eggs and newly hatched chicks which were cultured. However, maternal antibody was present in 81 per cent of the eggs and 23 per cent of the chicks and it may have affected the colonisation of the organism and the ability to isolate S enteritidis.

Animals↗
PubMed1994

Computational problems in molecular systematics.

The development of extremely powerful computer programs and the ready availability of microcomputers has revealed several computational problems with data analysis. These problems occur in the handling of systematic data in general and molecular systematic data in particular. This paper examines three areas of controversy in molecular systematics resulting from increased computer power. We start by examining the first step in DNA sequence analysis, the establishment of homology via sequence alignment. Next we examine several problems in phylogenetic analysis that have arisen in the last few years due to use of the PAUP (Swofford, 1991), HENNIG86 (Farris, 1988), and PHYLIP programs. These problems include limitations on the number of taxa examined in a given analysis and the accuracy of the parsimony trees in such analyses. The final subject is an examination of programs used for assessing tree robustness. We concentrate on certain programs (such as MALIGN (Wheeler and Gladstein, 1993), PAUP (Swofford, 1991), HENNIG86 (Farris, 1988), PHYLIP (Felsenstein, 1990), CLADOS (Nixon, 1993), MacClade (Maddison and Maddison, 1993), etc.), but similar comments about other programs could also be made.

Animals↗
PubMed1994

An approach to reduction of Salmonella infection in broiler chicken flocks through intensive sampling and identification of cross-contamination hazards in commercial hatcheries.

A comparative study of salmonella contamination in eleven commercial hatcheries in the UK was carried out during 1992/93. The sampling protocol involved individual swabbing and culture from surfaces and items of equipment within each premises. This allowed the identification of many areas where salmonella control measures were not successful resulting in a cross-contamination hazard for eggs and chicks. Egg sanitisation and handling methods, design of incubator and whole building ventilation systems, control of dust, fluff and aerosol production, disinfection of surfaces and equipment and handling of waste were areas where improvements could be made. There were examples of successful reduction of salmonella in all key areas and these could be extended to provide general practical protocols for salmonella control. The sampling and culture techniques used in this study required less labour and were more rapid and sensitive than traditional methods so could be used in comparative investigations of other complex high throughput livestock and food processing operations.

Animal Husbandry↗
PubMed1994

Evaluation of a rapid cultural method for identification of salmonellas in naturally contaminated veterinary samples.

Three thousand and forty-two samples of post-mortem tissues, environmental swabs, animal feed ingredients and eggs were examined by conventional methods and by a simple rapid culture method. The rapid method gave reliable presumptive identification of salmonella contamination within 48 h of the start of culture. The rapid method also showed enhanced sensitivity for detection of salmonellas, in most types of sample, particularly those taken in poultry houses and hatcheries where high levels of competitive faecal bacteria are present.

Animal Feed↗
PubMed1993

Escherichia coli isolated from farm animals in England and Wales between 1986 and 1991.

Escherichia coli isolated from farm animals in England and Wales between 1986 and 1991 were examined for their serogroup, fimbrial adhesin and toxin production, and resistance to antimicrobial drugs. Among the 3595 porcine isolates the more common serogroups were O149, O8, O138, O147 and O157. The F4(K88) adhesin was detected in 21 per cent of the cultures, whereas the other adhesins were never present in more than 3 per cent during any year, although there was an upward trend in the prevalence of the F6(987P) antigen. The heat labile enterotoxin was produced by more than 17 per cent of the cultures usually in association with the F4 antigen. The other toxins, heat stable (STa), verocytotoxin (VT) and cytotoxic necrotising factor (CNF) were produced by 5.3, 4.7 and 6.8 per cent of the cultures, respectively. Among the 1383 bovine cultures the more common serogroups were O8, O101 and O17. The F5(K99) adhesin was detected in 9.1 per cent of the cultures, usually in association with STa production. The toxins STa, VT and CNF were produced by 4.4, 2.8 and 8.3 per cent of the cultures, respectively. Among the 407 ovine isolates the more common serogroups were O8, O101 and O78, and 11 per cent of the cultures produced the F5(K99) antigen. The toxins STa, VT and CNF were produced by 1.5, 6.1 and 9.1 per cent of the cultures, respectively. In the case of the 402 poultry isolates the more common serogroups were O78, O2 and O8, which are usually associated with colisepticaemia. Resistance to antibiotics was common, particularly among the bovine isolates.

Animals↗
PubMed1993

PCR jumping in clones of 30-million-year-old DNA fragments from amber preserved termites (Mastotermes electrodominicus).

DNA from 30-million-year-old amber preserved termites (Mastotermes electrodominicus) was PCR amplified with nuclear ribosomal RNA small subunit primers and cloned into the TA vector (INVITROGEN). We obtained several classes of recombinant clones as a result. Authentic Mastotermes electrodominicus clones were identified. The source of other classes of clones was identified as contaminants of the ancient DNA template. Several of the clones appeared to be chimeric in structure with half of the clone identical to the termite sequence and the other half identical to contaminant sequences. The phenomenon of PCR jumping was identified as a possible source for the chimeric clones.

Animals↗
PubMed1993

Experimental infection of neonatal pigs with CNF toxin-producing strains of Escherichia coli.

To examine and compare the pathogenicity of cytotoxic necrotising factor (CNF)-producing Escherichia coli, two litters of piglets were infected orally with 10(10) E coli O88 or 10(10) E coli O32 strains. Of the six piglets infected with E coli O88, two died within 24 hours and three developed blood-stained diarrhoea. The other piglets were killed one, five, six and eight days after infection, when bacterial cultures indicated an overwhelming bacteraemic infection with E coli O88 in the early stages followed by clearance through the large intestine. The pathological changes consisted of an early enteritis, progressing to enterocolitis and a bacteraemic spread to the lungs. The histopathological changes were characteristic of toxaemic effects in brain, heart, liver and kidney, and characterised by congestion, oedema and exudation. Infection with E coli O32 produced a milder but similar enterocolitis, also with bacterial colonisation in the lungs. The histopathological findings again reflected a toxaemia. The enteritis was more persistent after E coli O32 infection and the strain persisted in large numbers in the intestine. No evidence of bacterial adherence to the intestinal mucosa was found with either strain. Enteroinvasion was only evident in one E coli O88-infected piglet, but the consistent occurrence of interstitial pneumonia showed the predilection of these organisms for the lung. The results confirm the toxigenic properties of CNF+ E coli and suggest an important role for this organism in enteric infection of young pigs.

Animals↗
PubMed1993

Bacterial resistance monitoring of salmonellas isolated from animals, national experience of surveillance schemes in the United Kingdom.

Antimicrobial resistance has been monitored in salmonellas isolated from animals in England and Wales since 1970. The current trends are indicated by comparing the results for the years 1981, 1989 and 1990. Seventy-six per cent of all salmonella isolations are still sensitive to all 16 antimicrobials used for testing. Most antimicrobial resistance is encountered in bovine isolations of Salmonella typhimurium especially phage type DT204C. This phage type, which was initially resistant to at least seven antimicrobials, has however become more susceptible in recent years. Ninety-eight per cent of S. dublin strains from cattle are still sensitive to all the antimicrobials used for testing. Although the number of porcine salmonella isolations is small, many show antimicrobial resistance especially to tetracyclines. A large increase in the number of salmonellas isolated from poultry has occurred in recent years and 75% of these strains are sensitive to all the antibiotics used for testing. Although there has been a slight decrease in the percentage of S. enteritidis strains showing susceptibility 87% of isolations are still sensitive. The emergence of resistance to the newer antimicrobials trimethoprim, apramycin and fluorquinolones has been studied and data presented. The results are discussed with regards to the choice of techniques, bacteria monitored and future surveillance programmes in relation to the veterinary use of antimicrobials.

Animals↗
PubMed1993

On choosing a baby's sex: what the future generation thinks, a preliminary survey.

The new biomedical techniques of reproduction, such as predetermination of a baby's sex, are gradually being initiated into formal practice in some countries such as Britain. This paper surveyed the attitudes of 60 academic and 60 nonacademic men and women between 18 and 20 years on whether they supported the idea of choosing a baby's sex. More than 75% of all participants rejected the idea of choosing a baby's sex, whilst only 20% agreed with the latter issue and a negligible number (4%) offered no opinion. Neither sex differences nor differences between academic/nonacademic population were significant. The results are discussed in relation to recent work on differences in attitudes between genders in academic and nonacademic settings.

Adolescent↗
PubMed1992

An interlaboratory trial of a latex agglutination kit for rapid identification of Salmonella enteritidis.

An interlaboratory trial was conducted of a latex agglutination kit for the rapid identification of Salmonella enteritidis, to assess the stability of the components and its performance with respect to a panel of three coded salmonellas and 243 field isolates. Two of the components of the kit deteriorated with time. All 62 isolates of S enteritidis were correctly identified by the kit; only two false positives were recorded and no false negatives.

Animals↗
PubMed1992

Detection of entero- and verocyto-toxin genes in Escherichia coli from diarrhoeal disease in animals using the polymerase chain reaction.

Oligonucleotide primers were designed for the specific polymerase chain reaction (PCR) amplification of the enterotoxins STIa and LTI and of the verocytotoxins VT1 and VT2. All of 184 E. coli isolates from cases of diarrhoea from pigs, cattle and sheep gave identical toxin profiles by PCR and gene probe. Differentiation between VT2 and VT2v was achieved using two oligonucleotide primers pairs in PCR and showed that all of 34 VT2+ porcine isolates, of which 23 were 0138:K1, harboured VT2v whereas 20 VT2+ bovine and ovine isolates harboured VT2. No isolate harboured both VT2 polymorphs. Simplified methods for sample preparation for PCR were examined and showed that PCR was not inhibited by direct addition of broth culture to the reaction mixture.

Animals↗
PubMed1992

A disc ELISA for the detection of Salmonella group D antibodies in poultry.

An ELISA using lipopolysaccharide antigens prepared from Salmonella gallinarum and S enteritidis was developed for the serological diagnosis of fowl typhoid and S enteritidis infection in poultry. There was good agreement between the results of the ELISA and conventional serological tests when samples from naturally infected birds and S enteritidis immunised birds were tested. Some cross reactions were observed when serum samples from S typhimurium infected birds were tested by ELISA. Subsequently a disc ELISA, using filter paper discs, was developed to facilitate sampling and testing of poultry. There was good correlation between the results of the disc and serum ELISAs and the test is recommended for the field testing of birds.

Agglutination Tests↗
PubMed1992

Serum, disc and egg ELISA for the serodiagnosis of Salmonella gallinarum and S. enteritidis infections in chickens.

An ELISA was evaluated for the serodiagnosis of fowl typhoid and paratyphoid due to Salmonella enteritidis in chickens. The hot phenol: water lipopolysaccharide (LPS) extract of Salmonella was used as the antigen. Chicken serum, eggs and discs impregnated with chicken blood were tested for the presence of antibodies against Salmonella factor 'O' 9 antigen. The substrate and chromogen used were hydrogen peroxide and orthophenylenediamine respectively. Serological results from the experimentally and naturally infected chickens showed close agreement between the conventional Serum Tube Agglutination Test (SAT) and serum ELISA while serum ELISA results were in close agreement with the egg and disc ELISA results. It was noted that ELISA was highly sensitive, convenient and versatile. It is concluded that ELISA, especially disc ELISA, ought to replace SAT for seroscreening chickens against S. gallinarum and other Salmonella Group D infections.

Agglutination Tests↗
PubMed1991

Differentiation of Salmonella senftenberg into biogroups.

Ninety-six strains of Salmonella senftenberg, isolated between 1984 and 1986 from different parts of England and Wales, were tested for their biochemical reactions and biotyped according to the method of Duguid and others (1975). Nine biogroups were identified on the basis of their metabolism of L-tartrate, D-tartrate, Bitter's xylose and Stern's glycerol. In addition, fumaric, oxalic, succinic, glutaric, malonic, maleic, L-malic, L-aspartic, lactic and formic acids were used but did not increase the discrimination. Three biogroups (7, 2 and 5) accounted for 79 per cent of the cultures examined.

Bacterial Typing Techniques↗
PubMed1991

Epidemiology of Salmonella typhimurium infection in calves: persistence of salmonellae on calf units.

Salmonella typhimurium DT204C infection is the commonest cause of salmonellosis in calves. On five calf rearing farms a distinct strain, as indicated by plasmid profile analysis, was found to have persisted on the premises for periods ranging from four months to two years, the average being 14 months. The persistence of salmonellae in the environment appears to be an important factor in the epidemiology of calf salmonellosis and clearly indicates the inadequacy of many cleaning and disinfection routines.

Animal Husbandry↗
PubMed1991

Transmission of salmonellae among calves penned individually.

An analysis of the spatial and temporal patterns of excretion of salmonellae by calves penned individually showed that non-contagious routes were more important than contagious routes in disease spread. The avoidance of aerosol production, and the effective cleaning and disinfection of utensils between feeds and of buildings between batches, are likely to be more important than pen design in the control and prevention of calf salmonellosis.

Aerosols↗