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Biomedical subjects

K A McKay

Publications and source records attributed to K A McKay.

18 recordsLinked to original sources
PubMed1978

Intraperitoneal immunization against necrobacillosis in experimental animals.

Experiments employing recently developed mouse models indicated that intraperitoneal immunization with the cytoplasm (intracellular fraction) of Fusobacterium necrophorum protected the animals from a lethal challenge of the pathogen. The critical immunization schedule needed to achieve complete protection involved six weekly intraperitoneal doses of the intracellular antigen. Livers of immunized mice were cleared of infecting fusobacterial within 24 hours whereas those of nonimmunized mice harboured increasing numbers of hte bacteria. Sera from both groups did not protect recipient mice form developing liver abscesses after challenge. Sheep immunized intraperitoneally with 20 mg of cytoplasmic protein given in three doseases were protected against the development of abscesses induced by F. necrophorum.

Administration, Intranasal↗
PubMed1977

Hepatic lesions and bacterial changes in mice during infection of Fusobacterium necrophorum.

Liver abscesses were induced in male albino mice within 1 week after intraperitoneal inoculation of viable Fusobacterium necrophorum LA19 culture. Fusobacteremia was transitory and reached a peak 2 h after inoculation then sharply declined until its disappearance 24 h post inoculation. By contrast, the number of fusobacteria in the liver increased rapidly during the first 4 h post inoculation and continued to do so less rapidly until the last sampling time (48 h post inoculation). There were small or large areas of necrosis, usually surrounded by inflammatory cells, small focal accumulations of lymphocytes, plasma cells, and macrophages in areas of parenchyma with no degenerations, generalized proliferation of Kupffer cells, and a few accumulations of fibrin and leukocytes on the surface. Ultrathin sections of infected liver tissues reveled both intact and partially degraded F. necrophorum cells enclosed in phagocytic and digestive vacuoles of mononuclear cells, The results indicate that macrophages play a key role in the pathogenesis of liver abscesses.

Animals↗
PubMed1975

Characterization of endotoxin from Fusobacterium necrophorun.

Endotoxic lipopolysachharide (LPS) was obtained from phenol-water extraction of cell walls prepared from mass-cultivated Fusobacterium necrophorum. The LPS was relatively free of nucleic acids and low in protein, and constituted about 4% of the cell walls. Upon acid hydrolysis, some of the components detected were hexosamines (7.0%), neutral and reducing sugars (50.5%), heptose (6.4%), 2-keto-3-deoxyoctonate (0.8%), lipid A (21.0%), and phosphorus (1.7%). Under electron microscopy the LPS appeared mainly as ribbon-like trilaminar structures, and upon chemical treatment it displayed a behavior resembling that reported in certain enterobacterial LPS. The LPS was lethal to mice, 11-day-old chicken embryos, and rabbits. Endotoxicity in mice was enhanced at least 1,380-fold by the addition of 12.5 mug of actinomycin D. Induced tolerance to lethal effect of the endotoxin and rapidly acquired resistance to infection by F. necrophrum viable cells were also demonstrated in mice. The endotoxin produced both localized and generalized Shwartzman reactions as well as biphasic pyrogenic responses in rabbits. These results firmly establish the presence of a classical endotoxin in F. necrophorum, thus providing strong support to our recent suggestion that cell wall-associated components may contribute significantly to the pathogenicity of F. necrophorum.

Animals↗
PubMed1975

Biological characterization of Fusobacterium necrophorum. Cell fractions in preparation for toxin and immunization studies.

Fusobacterium necrophorum isolated from bovine liver abscesses was grown in bulk at 37 C for 24 h under a strict anaerobic atmosphere. Harvested washed cells were disrupted ultrasonically and fractionated by differential centrifugation into the intracellular (cytoplasm) and cell wall fractions. Both intact cells and cell fractions induced generalized cytopathic effect on primary pig kidney cultures and caused a variety of signs of illness and/or death of intraperitoneally injected mice. The intact cells, disrupted cells, and cell walls produced necrotic lesions and erythema on intradermally injected guinea pigs and rabbits, whereas the cytoplasm mainly erythema. By contrast, the used culture medium (culture filtrate) of F. necrophorum did not show any detectable toxicity. The toxic component of the cytoplasm appears to be associated with nondialyzable, hemolytic, high-molecular-weight proteins and its toxicity is reduced by trypsin and pronase. Heating at 60 C for 10 min decreased markedly its erythemal and cytotoxic ability, wheras the toxicity of the cell walls appeared to be only slightly affected even when heated at 100 C for 1 h. These results suggest that at leasttwo distinct cell-bound toxic factors are present in F. necrophorum cells.

Amino Acids↗
PubMed1974

Results of a preliminary trial with Sphaerophorus necrophorus toxoids to control liver abscesses in feedlot cattle.

A preliminary field experiment was undertaken to evaluate the efficacy of alum precipitated toxoids of Sphaerophorus necrophorus prepared from sonicated whole cells and cell fractions to reduce the incidence of bovine abscesses. A total of 108 calves were divided into five groups and treated as follows: I. uninoculated control, II. adjuvant inoculated control, III. 15.5 mg protein of sonicated (fragmented cells) toxoid, IV. 10.5 mg protein of cytoplasmic toxoid. V. 15.5 mg protein of cytoplasmic toxoid. All animals were maintained under similar conditions to those prevailing in feedlots in Alberta. Livers were examined at slaughter. The most promising result was achieved with the injection of 15.5 mg protein of cytoplasmic toxoid. In this treatment group, no scars (healed lesions) were found in the liver and the incidence of liver abscesses was reduced to 10% from the average 35% liver abscesses and scars found in the uninoculated and adjuvant inoculated groups. The toxoid from sonicated whole cells did not reduce liver abscess incidence. These data suggest that the incidence of liver abscesses in cattle fattened in feedlots may be reduced by immunization.

Adjuvants, Immunologic↗
PubMed1971

Application of immunofluorescence to studies on the ecology of Sphaerophorus necrophorus.

Sphaerophorus necrophorus (bovine liver abscess isolates) antiserum was fractionated and labeled with fluorescein isothiocyanate. The fluorescent-antibody (FA) conjugate proved to be species-specific and facilitated the detection of S. necrophorus cells in liver abscesses, viscera, and ruminal contents of cattle. Brightly fluorescing S. necrophorus cells were observed in experimentally inoculated soil incubated anaerobically at 37 and 4 C for 8 and 10 months, respectively. When incubated under moist conditions (80% water holding capacity) at 37 C, the test organism survived in both sterile and unsterile soil for as long as 8 weeks. Results strongly support the feasibility of using FA techniques concurrent with cultural methods for rapid detection of S. necrophorus infections.

Animals↗
PubMed1970

Pathogenic microorganisms in soil: an old problem in a new perspective.

Early investigations on the survival of pathogenic bacteria in soil have been directed mainly to changes in the numbers of viable populations. More reliable techniques to assess the physiological, biochemical and pathogenic capabilities of such organisms are necessary to gain a better understanding of the nature of the diseases they cause and ultimately of the means to control them.

Actinomyces↗
PubMed1970

A stable L-form of Haemophilus pleuropneumoniae.

A stable L-form of Haemophilus pleuropneumoniae (Shope) was isolated from primary pig kidney cell tissue cultures which had been inoculated 28 days previously with glycine induced spheroplasts of this organism.H. pleuropneumoniae was definitely cytopathic in primary pig kidney cell cultures, producing cell rounding, cytoplasmic vacuolation and nuclear enlargement with peripheral condensation of nuclear DNA. By contrast, the effect of spheroplasts was much less distinct, producing only loss of cytoplasmic granularity coincident with apparent loss of some cytoplasmic RNA, and slight nuclear enlargement. Both the organism and its L-form were shown to be related by cultural methods, antibiotic sensitivity tests, immunofluorescence and immunodiffusion. The L-form remained stable after 90 serial passages on agar and 45 in broth, each medium being capable of supporting the growth of both forms of the organism.

Animals↗
PubMed1969

Glasser's disease of swine produced by the intracheal inoculation of haemophilus suis.

The intracheal inoculation of pigs with Haemophilus suis led to the production of Glasser's disease at every attempt without significant pulmonary involvement. Isolation of this organism from the experimental animals was possible only in the acute phase of the disease. The indirect fluorescent antibody technique when applied to frozen sections of tissues obtained from the experimentally infected pigs at autopsy, revealed a few rod forms but mostly "round bodies" of H. suis in animals from which the organism was isolated, and "round bodies" only in the pigs from which the organism was not isolated. Attention is drawn to the similarities between the lesions caused by H. suis and Mycoplasma hyorhinis, and to the confusion which may result therefrom. It is stressed that the laboratory diagnosis of these two diseases is complicated by the fact that both agents may not be isolated on the media commonly used in diagnostic laboratories. Both organisms necessitate the use of special media where the clinical and autopsy results indicate polyserositis and arthritis.

Animals↗
PubMed1969

The incidence and significance of clostridia isolated from ready-to-eat meats and rendered products.

Approximately 26% of rendered and 10% of ready-to-eat products contained species of the genus Clostridium. Eleven species of clostridia were isolated from a total of 524 products tested. Some products harboured more than one species.C. sporogenes, one of the most heat resistant organisms, was the most common type isolated.C. sordellii produced a transient illness in guinea pigs while all other species were innocuous.

Animals↗