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Biomedical subjects

C Wray

Publications and source records attributed to C Wray.

At least 73 records · Page 4Linked to original sources
PubMed1991

The epidemiology of Salmonella in calves: the role of markets and vehicles.

Environmental contamination has been shown to be an important aspect of the epidemiology of salmonellosis in calves. Markets and transport vehicles are important links in the calf marketing chain and these were investigated to determine the level of salmonella contamination. Salmonellas were isolated from 7 of the 14 markets surveyed, with 31 of 838 samples (3.7%) being positive. Nine different salmonella serotypes, of which the commonest was Salmonella typhimurium, were isolated. Four different phage types of S. typhimurium were detected, the commonest being DT204C. Salmonellas were isolated from 22 of the 107 vehicles (20.6%) examined before washing and from 4 of the 62 vehicles (6.5%) examined after cleaning. Twelve different salmonella serotypes were isolated, of which the most frequent was S. typhimurium. The commonest of the six different S. typhimurium phage types was DT204C. These results indicate that improved cleaning and disinfection routines both for vehicles and markets are necessary to control salmonellosis in calves.

Animals↗
PubMed1990

Nine DNA probes for detection of toxin and adhesin genes in Escherichia coli isolated from diarrhoeal disease in animals.

DNA gene probes specific for genes encoding heat labile enterotoxin (LTI), heat stable enterotoxins (STIa, STII), vero cytotoxins (VT1, VT2), and adhesins K88 (F4), K99(F5), F41 and 987P(F6) were used to examine 873 isolates of E. coli from cases of diarrhoea (680 from pigs, 187 from cattle and six from sheep). A total of 188 were toxin gene positive and of these 84 belonged to the classical ETEC serogroups. Of the other 104 toxin gene positive strains, 80 hybridized with the VT2 probe of which 34 were from cases of porcine post-weaning diarrhoea belonging to serogroup 0138:K81 and 22 were untypable strains from cattle.

Adhesins, Escherichia coli↗
PubMed1990

DNA probes for the detection of toxin genes in Escherichia coli isolated from diarrhoeal disease in cattle and pigs.

DNA gene probes specific for genes coding for heat labile toxin (LT), heat stable toxins (STpa, STpb) and Vero-cell toxins (VT1, VT2) were used to examine 1031 diarrhoeal disease isolates of E. coli (345 from cattle and 686 from pigs). Of the bovine strains, 60 hybridized with the STpa probe and most possessed the K99 (F5) or F41 adhesin. Five bovine strains possessed STpb genes and five either VT1 or VT2 genes. Of the porcine strains, 245 hybridized with one or more gene probes. Of 160 K88 (F4) positive strains, 133 possessed both LT and STpb genes, whilst 17 possessed LT or STpb or STpa alone or in combination. Ten K88 strains did not possess toxin genes. Isolates bearing the K99 (F5) adhesion possessed either STpa, STpb and VT2 genes alone or in combination; in one isolate only the LT gene was detected. Isolates belonging to serogroup 0138:K81 were more heterogeneous as to their toxin genes; of the 60 strains, fourteen carried only VT2 genes, thirty-two carried VT2, STpa and STpb genes, one carried LT, VT2, STpa and STpb genes, two carried STpb gene, four carried STpa and STpb genes, one carried LT and VT2 genes, two carried LT and STpa genes, whilst four carried none. Twenty-four percent of all toxigenic strains apparently did not possess adhesins.

Animals↗
PubMed1990

The epidemiology of Salmonella infection of calves: the role of dealers.

Salmonellas were detected in the environment of 10 of the 12 calf dealers' premises studied. The cleaning and disinfection routines were often ineffective and salmonellas were isolated from 7.6% and 5.3% of the wall and floor samples before disinfection and 6.8% and 7.6% afterwards. Eight different salmonella serotypes were detected, of which the commonest were Salmonella typhimurium, predominantly phage type DT204C, and S. dublin. Plasmid profiles were used to fingerprint S. typhimurium DT204C and the results indicated that with the exception of one of the premises, prolonged salmonella-persistence in the environment was not occurring. Three separate epidemics of salmonellosis in calves were studied by use of plasmid profile analysis. The results illustrated the role of delers, and their subcontractors, in the dissemination of salmonellas. The study concludes with suggestions for methods to reduce the spread of salmonellas in the calf marketing chain.

Animals↗
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↗
PubMed1990

Biotechnology and veterinary science: production of veterinary vaccines.

The fundamental principles of genetic manipulation are explained, as are the methods of production of vaccines of veterinary importance. Specific attenuation of micro-organisms may result from genetically-engineered mutations which produce metabolic blocks, from the development of effective bacterial toxoids and from viral gene segment reassortment. Recombinant DNA techniques have been used to produce multi-component vaccines by the insertion of genes into carrier organisms, such as pox viruses and attenuated salmonella, and also to produce subunit vaccines. The use of synthetic peptide vaccines and anti-idiotype vaccines, together with problems of parasite vaccines, are described. Biotechnology would appear to have a major role to play in the future prevention of many animal diseases.

Adjuvants, Immunologic↗
PubMed1989

Occurrence of 'attaching and effacing' lesions in the small intestine of calves experimentally infected with bovine isolates of verocytotoxic E coli.

Nine calves (five colostrum-fed, four colostrum-deprived) were challenged with two field strains of Escherichia coli which produced either verocytotoxin 1 (VT1) or verocytotoxin 2 (VT2). Although three colostrum-fed calves had blood and mucus in their faeces, no diarrhoea was observed. Three of the four colostrum-deprived calves had diarrhoea and in two of them severe lesions were detected in the small intestine. Focal changes were detected in the colon of three calves. E coli were associated with the lesions in the small and large intestine and were shown by transmission electron microscopy to be intimately attached to the enterocyte surface with effacement of microvilli (attaching and effacing lesions). This is the first report of E coli which produce VT2 being associated with disease in calves.

Animals↗
PubMed1989

A three-year study of Salmonella dublin infection in a closed dairy herd.

Over a period of three years, Salmonella dublin was isolated occasionally from the faeces of nine adult cattle in a closed dairy herd. The organism was also isolated from 12 of the samples collected after parturition; isolations were made from newborn calves on 11 occasions, from a vaginal swab once and from a milk sample once. Nine of the isolations from the calves were made from swabs obtained within 24 hours of birth. Throughout the investigation isolations were made from heifers, steers and older calves and 11 infected animals were detected. S. dublin was widespread in the farm environment and it was concluded that environmental contamination was an important source of infection for animals of all ages, some of which may have become latent carriers. The family history of one cow, seven of whose offspring were infected with S dublin, suggested the possibility of vertical transmission. Without reliable tests to detect latent carriers, it is suggested that control of this infection must be based on improved hygiene and the use of vaccination to improve the immunity of the herd.

Animals↗
PubMed1989

The detection of Salmonella infection in calves by the fluorescent antibody test.

The fluorescent antibody test (FAT) was used for the direct detection of salmonellas in 182 lymph nodes from adult cattle and from calves submitted for autopsy or used for experimental purposes. Salmonellas were detected in 22 samples by the FAT and in 18 by culture examination. The predictive value of the FAT was 68% and it was concluded that the test could be used for the rapid presumptive diagnosis of bovine salmonellosis.

Animals↗
PubMed1989

Persistence of S. typhimurium in a large dairy herd.

Salmonella typhimurium 49a infection in a large dairy herd persisted for 3.5 years. Illness initially occurred in cows and calves but latterly although there were fewer clinical cases milk filters were culturally positive on 26 out of 73 samplings. Three associated human disease incidents occurred. Individual milk samples identified one cow as an excreter and the organism was recovered from the mammary gland of this animal at slaughter. Correlation between calving pattern, the times of calving and the occurrence of positive milk filters suggest that the cow may have been excreting the organism intermittently from the udder for 2.5 years.

Animals↗
PubMed1989

Distribution of virulence plasmids within Salmonellae.

The virulence region of the Salmonella dublin 50 MDa plasmid shared homology with 678 of 1021 salmonellae tested in colony hybridization experiments. The majority of S. dublin, S. typhimurium and S. enteritidis isolates tested hybridized with the region whereas, with the exception of S. hessarek, S. pullorum and S. gallinarum, other serotypes did not. Homologous virulence regions were plasmid encoded. In S. typhimurium a common 60 MDa plasmid was present in all phage types tested but not in DT4, DT37 and DT170. Smaller plasmids showing partial homology were found in DT12, DT18, DT193 and DT204C. In S. enteritidis a distinct plasmid profile for each of eight phage types was observed. Hybridizing plasmids were found in DT3, DT4, DT8, DT9 and DT11 whereas DT7, which was plasmid free, and DT10 and DT14, which harboured plasmids, did not hybridize. The extent of homology shared between S. dublin, S. typhimurium and S. enteritidis virulence plasmids was about 10 MDa and appeared conserved. Virulence plasmids from S. typhimurium and S. enteritidis did not show homology with a region of the S. dublin 50 MDa plasmid which was not associated with virulence functions whereas plasmids of about 24 MDa and 38 MDa in some S. typhimurium phage types did. The association of conserved virulence regions upon differing plasmids within salmonellae is discussed with reference to possible mechanisms of distribution and evolution of virulence genes.

DNA, Bacterial↗
PubMed1989

Genetic evidence for a chromosomally integrated multiresistance plasmid in Salmonella dublin.

Of 1099 isolates of Salmonella dublin during 1985-86, 11 (1%) were resistant to three or more antibiotics. Strain S4659/85, a multiresistant isolate, lacked autonomous R plasmids but showed incompatibility with incH2 plasmids and donated resistance determinants in matings. Transconjugants acquired incomplete R plasmids which integrated stably into a specific chromosomal site. These data provide an insight into the behaviour of R plasmids in S. dublin.

Animals↗