Histological findings in amyloidosis of rabbits.
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Biomedical subjects
Publications and source records attributed to M Hinton.
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A total of 2973 Escherichia coli, isolated from six different groups of animals, were examined for their ability to ferment adonitol, dulcitol, raffinose, rhamnose and sorbose in solid media. Twenty-nine fermentation patterns were recorded although 2443 (82%) of the E. coli belonged to seven of the 32 possible biotypes. Ninety-six O-serotypes were identified within the 2973 E. coli. The number of O-serotypes represented in the 15 most common biotypes ranged from three to 15. Serotypes O8 and O9 were found most commonly in the different groups of animals and several biotypes amongst these two O-serotypes were identified in two or more groups of the animals. The ability of the E. coli to metabolize aesculin, ornithine, salicin and sucrose was also assessed. These test proved less reproducible and were not included in the primary biotyping scheme although their use allowed the enumeration of additional biotypes. The application of biotyping to the study of the ecology of drug-resistant strains of E. coli in five situations is briefly presented.
Salmonella typhimurium phage type DT 193 survived in small numbers, in stored static slurry derived from veal calves, for the 7-week period of observation. The viable coliform count fell by 1 1/2 logs during the first 2 weeks of storage, thereafter there were only relatively small fluctuations in the coliform population. In all 735 of 752 Escherichia coli isolates examined from eight samples of slurry were resistant to 3-6 antibacterial drugs. There was no dramatic change in the overall level of drug resistance amongst the E. coli with time. Chloramphenicol resistance was recorded in 400 (55%) of the E. coli. It was always associated with multiple resistance, with 96% of the strains being resistant to 5 or 6 drugs, although the proportion of isolates of each of the ten most prevalent O-serotypes resistant to chloramphenicol was variable and ranged between none and 97.5%. The use of biotyping together with O-serotyping indicated that the E. coli population was extremely complex, although certain components of the population remained relatively stable within the dominant flora with time since several of the more common O-serotype/biotype combinations were isolated from more than half of the eight slurry samples examined.
Antibacterial drugs (oxytetracycline, streptomycin and sulphonamides) were included in the drinking water of healthy broiler chicks from the sixth to the twentieth day of life to select a resistant gut flora. On the twenty-first day the birds were divided into three groups and reared in separate rooms until 100 days of age. One group was housed in cages with wire floors while the others were reared on litter. Faeces from adult hens were added regularly to the litter of one of these groups to determine its effect on the gut flora of the chicks. The ecology of Escherichia coli was studied using O-serotyping, biotyping and antibacterial drug resistogram typing. The proportion of E. coli in the dominant faecal flora resistant to two to four antibacterial drugs increased with time to reach a peak several days after the drugs were withdrawn. Thereafter, the level of drug resistance in the E. coli declined equally in all three groups. The majority of organisms with multiple resistance were derived from biotypes of O-serotypes initially resistant to only one drug and were identified before the drugs were administered. The decline in the level of resistance in the dominant faecal flora after the fourth week was due to the appearance of either new O-serotypes or new biotypes of O-serotypes previously shown to be multiply resistant, and which were either sensitive or resistant to only one drug. It is probably that these new strains were derived from the food since several O-serotypes appeared simultaneously in all three groups of birds.
Haematological data from 94 diseased rabbits and 23 healthy adult rabbits were analysed statistically using principal components analysis and multiple discriminant function analysis. The 1st principal component accounted for 32% of the variation and was interpreted as showing total blood cellularity. This was decreased in the majority of diseased rabbits, principally due to anaemia, although in a few it was slightly increased possibly as a result of dehydration. The 2nd principal component (22% of the variation) had high positive loadings on monocyte and heterophil counts and weak negative loadings on the red cell characters. This component was interpreted as the response of the white blood cells to disease. When classification analysis was used to decide whether or not an animal was 'normal' the heterophil and lymphocyte counts alone provided almost as accurate an assessment as when all the blood parameters were taken into account. The role of these analyses in the diagnosis of disease is discussed.
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The in vitro resistance of 40 strains of Staphylococcus aureus isolated from dogs to trimethoprim, sulphamethoxazole and co-trimoxazole (SXT) was assessed using the disc diffusion technique on Diagnostic Sensitivity Test Agar (DSTA), DSTA with 5% lysed horse blood (DSTA + B), IsoSensitest Agar (ISTA) and Wellcotest Sensitivity Test Agar (WSTA). When sensitivity was based on a zone width of greater than or equal to 4 mm all 40 strains were sensitive to SXT on DSTA + B and ISTA, 39 were sensitive on WSTA while only 31 (77.5%) were sensitive on DSTA. A comparison of the results obtained for each strain for trimethoprim and sulphamethoxazole with those obtained with the Oxford strain of S. aureus and using a scheme for interpretation recommended by Garrod & O'Grady (1971) indicated that the proportion of strains classed as sensitive for therapeutic purposes was 5%, 55%, 47.5% and 15% respectively on DSTA, DSTA + B, ISTA and WSTA.
Histological lesions were observed in the kidneys of 77 (32.5%) of 237 rabbits which were either found dead or were killed because they were unwell, and in 19 (25%) of 75 apparently healthy adult rabbits. Lesions associated with an infectious process such as renal abscesses, staphylococcal nephritis, pyelonephritis and pyelitis were the principal finding in rabbits up to 5 months of age, while renal fibrosis, with or without dystrophic calcification, was the most common lesion observed in rabbits aged over 10 months. Spontaneous amyloidosis was seen in 2 rabbits.
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Over 25 conditions were identified in 417 rabbits dying within the first six months of life. Conditions affecting the gastrointestinal tract and respiratory tract were the most common and involved 124 (29.7 per cent) and 81 (19.4 per cent) cases. No obvious gross lesions were identified in 161 (38.7 per cent) of the animals.
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