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F Ashton

Publications and source records attributed to F Ashton.

At least 19 recordsLinked to original sources
PubMed1991

Restriction enzyme analysis of Listeria monocytogenes strains associated with food-borne epidemics.

Listeria monocytogenes (serotype 4b) has caused four major food-borne epidemics in North America. In this study, L. monocytogenes isolates from the Nova Scotia (Canada), Boston (Mass.), and Los Angeles (Calif.) outbreaks were examined by restriction enzyme analysis with the endonuclease HhaI. Human isolates (n = 32) from the 1981 Canadian outbreak were compared with a strain recovered from coleslaw, which was epidemiologically incriminated as the vehicle of infection. After HhaI digestion, 29 of 32 isolates exhibited the restriction enzyme pattern of the reference coleslaw isolate. The restriction enzyme patterns of the nine clinical isolates from the 1983 Massachusetts outbreak were identical to each other but differed from those of raw milk isolates recovered from sources supplying the pasteurizer. Isolates (n = 48) from the 1985 California outbreak were evaluated. The restriction enzyme patterns of the L. monocytogenes isolates from humans and from the suspect cheese samples were identical to those of four of five cheese factory environmental isolates. Isolates from each of these outbreaks exhibited a restriction enzyme pattern that was characteristic of that outbreak. The case with which restriction enzyme analysis can be applied to all serotypes of L. monocytogenes argues for its use in the epidemiology of L. monocytogenes.

DNA, Bacterial↗
PubMed1991

Variability in growth of Neisseria polysaccharea on colistin-containing selective media for Neisseria spp.

In a prospective survey of 773 healthy schoolchildren in southern Alberta, Canada, Neisseria polysaccharea was isolated from the pharynxes of only 4 (0.5%) subjects, whereas Neisseria lactamica and Neisseria meningitidis were isolated from 110 (14%) and 15 (2%) children, respectively. These strains of N. polysaccharea, together with three other sporadic isolates from Alberta, Canada, were compared with the type strain from France and strains from Spain and Germany. All strains were phenotypically identical, except that the Canadian and German strains, for which the colistin MICs were 1 mg/liter, failed to grow on Thayer-Martin medium (TMM), whereas the type strain and the Spanish strains, for which the colistin MICs were greater than 7.5 mg/liter, were not inhibited. Multilocus enzyme electrophoresis indicated that six distinct electrophoretic types were present among the seven Canadian strains. Our results show that growth on gonococcal selective media which contain colistin is a variable feature of this taxon.

Adolescent↗
PubMed1990

Hepatocidal toxicity of Listeria species.

A novel rat hepatocidal test, based on morphological changes in monolayer culture and the percentage of lactate dehydrogenase (LDH) released into the medium after exposure to culture filtrates of Listeria spp. was used to determine listerial toxicity and pathogenicity. Primary cultures of rat hepatocytes exposed to brain heart infusion (BHI) culture filtrates from ATCC strains of Listeria monocytogenes and L. ivanovii, released 91-92% and 95% of LDH after 3 h and 18.5 h, respectively. Cultured monolayers changed from normal hepatocytes into nonviable round forms. Brain heart infusion broth and BHI culture filtrates of other Listeria spp. were nontoxic to hepatocytes. The rat hepatocidal test is a quantitative and rapid system for studying listerial toxicity and pathogenicity.

Animals↗
PubMed1986

Atherosclerosis in vascular grafts for peripheral vascular disease. Part 2. Synthetic arterial prostheses.

Thirty-nine synthetic (32 Dacron and 7 Teflon) arterial prostheses (from 38 patients with peripheral arterial disease) removed after periods between 2 months and 18 years, were examined by histology and immuno-histology. The grafts were initially permeated by thrombus containing platelet antigens and this became organised and converted to granulation, and then to fibrous, tissue. The newly-formed tissue contained 'foreign-body' giant-cells in contact with the plastic prosthesis and showed evidence of permeation by plasma proteins. In grafts of over 2 years duration, this reactive tissue no longer contained platelet antigens but invariably revealed bound lipid, identifiable as apolipoprotein-B-containing lipoproteins (LpB), and fibrinogen-related antigens (FRA), in a distribution resembling that seen in atherosclerotic arteries. LpB and FRA were also seen in organised, or partially organised, mural thrombi in older grafts. The oldest grafts additionally showed stenosis, calcification or aneurysm formation. Lipid deposition increases with the age of grafts; is independent of the nature of the plastic fibre used or its mode of fabrication; and sometimes contributes to graft failure. Immuno-histology indicates that this is an insudative process indistinguishable from 'true' atherosclerosis which occurs in graft-linings of prostheses of long duration and in old mural thrombi in grafts and that the lipid in these lesions derives from plasma LpB rather than from platelets. This source for the lipid suggests that the insudative and thrombogenic theories of atherogenesis can be reconciled.

Adult↗
PubMed1986

Perioperative complications of in-situ vein bypass.

Experience with 146 in-situ vein bypass procedures for obliterative arterial disease are reviewed to determine the specific complication of the technique. Vein wall injury with the Hall valvulotome occurred in 6 patients (4%) and vein patching of a stenosed femoral vein was required in 2 patients. Residual arteriovenous fistulae occurred in 24 patients (16.5%) of whom 9 had an associated graft thrombosis distal to the fistula of which 6 were corrected by thrombectomy and fistula ligation. Perioperative thrombosis occurred in 29 grafts (20%) and was more common in the femoropopliteal group (23/80) than in the femorocrural group (6/66) (P less than 0.01, X2 = 7.55). Fourteen of the femoropopliteal and two of the femorocrural thromboses were corrected resulting in an immediate patency of 89% and 94% respectively with the cumulative patency at one year being 77.5% and 79%. Complications of the in-situ bypass technique remain despite having largely overcome the problems of valve disruption. However, until a standard method emerges careful note must be made of technique and complications when considering reports of in-situ bypass patency.

Adult↗
PubMed1985

Significance of positive bacterial cultures from aortic aneurysm contents.

Aneurysm contents were cultured in 275 patients out of a series of 546 cases undergoing infrarenal aortic aneurysm repair between 1961 and 1981. The incidence of positive cultures was 8 per cent. Cultures were more likely to be positive if taken from ruptured (16.7 per cent) and acute (9.1 per cent) aneurysms than from elective (4.2 per cent) cases (X2 = 6.69, P less than 0.01). Gram-positive organisms predominated with Micrococcus being the commonest isolate. Positive cultures were seen at an annual rate of 1-3 cases up to 1976 since which time all have been negative and we believe this may be due to prophylactic antibiotics being given preoperatively rather than postoperatively. The incidence of subsequent graft sepsis was greater in patients with positive aneurysm contents cultures (7 out of 22) than in those with negative cultures (6 out of 253) (X2 = 32.7, P less than 0.001). We recommend the routine culture of aneurysm contents to identify patients who are at high risk of developing graft sepsis and suggest that those cases with positive cultures receive prolonged organism-specific antibiotic therapy. In addition, there is evidence that pre-operative antibiotics may eliminate organisms from aneurysms, thus reducing the subsequent risk of graft sepsis.

Adult↗
PubMed1985

Atherosclerosis in vascular grafts for peripheral vascular disease. Part 1. Autogenous vein grafts.

29 autogenous vein grafts, from 26 patients with peripheral arterial disease, were studied. 4 grafts of Group I (less than 3 months duration) were patent and removed for reasons other than graft failure. These showed 'arterialisation' only; 4 grafts of Group II (duration 5-18 months) showed thrombotic occlusion; 21 grafts of Group III (duration greater than 2 years) showed impaired graft patency and lipid identifiable as apolipoprotein B-containing-lipoproteins (LpB), and fibrinogen-related antigens (FRA) were seen as intramural deposits in the thickened grafts. LpB was also seen in a perifibrous distribution on the collagen of organised thrombi. Complicated lesions in some Group III grafts showed stenosis or occlusion, ulceration, calcification or aneurysm formation. These features suggest that a process indistinguishable from 'true' atherosclerosis affects vein grafts of long duration. The ways in which such changes may: contribute to graft failure; and improve our understanding of the basic processes involved in atherogenesis, are discussed.

Adult↗
PubMed1985

Protection against infection with Neisseria meningitidis group B serotype 2b by passive immunization with serotype-specific monoclonal antibody.

Hybridomas derived from mice immunized with Neisseria meningitidis serogroup B serotype 2b (B,2b) outer membrane preparations produced monoclonal antibodies (MAbs) specific for major outer membrane proteins of classes 1, 2, and 5. The MAbs were examined by enzyme-linked immunosorbent assay against a selected panel of seven strains of N. meningitidis (B,2b) of different sodium dodecyl sulfate-polyacrylamide gel electrophoresis patterns, a serotype 2a, and a nontypable strain. The five MAbs selected were all bactericidal and of different immunoglobulin subclasses. None of the MAbs reacted with other bacterial strains in a dot-enzyme immunoassay. The corresponding antigenic determinant for each MAb was localized on a specific outer membrane protein by immunoblotting of sodium dodecyl sulfate-polyacrylamide gel electrophoresis patterns of major outer membrane proteins. MAbs M5-11 and M5-30 bound to the class 2 protein and were serotype 2b specific. MAb M2-20 bound to the class 1 protein, and MAbs M5-16 and M5-19 bound to the class 5 protein. A mouse model of infection was established whereby a local infection progressed to lethal bacteremia over 3 days, and 50% of the animals were killed with an intraperitoneal injection of 10 meningococci plus 4% mucin and 1.6% hemoglobin. The ability of the MAbs to provide passive protection against experimental infection with N. meningitidis (B,2b) was examined. Both serotype-specific MAbs M5-11 and M5-30 were highly protective even though they were of different immunoglobulin subclasses. The class 5-specific MAb offered no protection, while the class 1-specific MAb gave limited protection. It may therefore be possible to provide protection against serotype 2b infection by using as vaccine the class 2 serotype-specific surface-exposed outer membrane protein epitopes defined by MAb M5-11 or M5-30.

Animals↗
PubMed1985

Problems in diagnosis of popliteal aneurysms.

Clinical features and errors in diagnosis have been assessed in a retrospective study of 62 popliteal aneurysms in 40 patients, 22 of whom had bilateral aneurysms. Only 29% of patients complained of pain or swelling behind the knee, while 31% of aneurysms had produced distal ischaemia presenting as intermittent claudication, 9 aneurysms had thrombosed producing ischaemic rest pain in 6 legs, and 4 aneurysms had ruptured. Although 94% of aneurysms were suspected or confidently diagnosed by palpation alone, only 43% of patients had had the correct diagnosis made at the time of initial referral. Treatment was delayed in 12 patients, 8 of whom subsequently required amputation. Popliteal aneurysm should be suspected in patients with a prominent popliteal pulse who present with intermittent claudication, and in patients with acute ischaemia of the leg who may have a thrombosed aneurysm requiring surgical exploration.

Adult↗
PubMed1979

Long term results of autogenous vein bypass grafts in femoropopliteal arterial occlusion.

The results of 329 consecutive autogenous vein grafts carried out between January 1962 and June 1973 have been reviewed. The 5- and 10-year mortality rates were 14.6 per cent and 18.7 per cent respectively. The corresponding patency rates were 70 per cent at 5 years and 34 per cent at 10 years, the lowest patency (27.8 per cent) occurring in below-knee anastomoses with grafts of 5 mm or less in diameter. As other have noted, the state of the popliteal--tibial run-off vessels had a considerable influence on long term patency rates. In severely ischaemic limbs, the limb salvage rate following this operation was 77 per cent. An analysis of symptoms, associated disease and complications is presented and discussed. No valid conclusions could be made regarding the effect of lumbar sympathectomy and postoperative anticoagulants on long term patency. This review has confirmed the findings of earlier studies that a satisfactory 5-year patency rate and a gratifying limb salvage rate can be achieved with an extremely low operative mortality rate of 0.37 per cent. Despite the presence of widespread atherosclerotic arterial disease, the 5-year mortality rate is 14.6 per cent, indicating that an attempt at reconstructive surgery is usually well worth while.

Adult↗
PubMed1975

Studies on gonococcal infection. I. Electron microscopic studies on phagocytosis of Neisseria gonorrhoeae by macrophages.

Macrophages from mice were infected with Neisseria gonorrhoeae type 1 cells, and their ultrastructure was studied by electron microscopy. The macrophages showed various stages of engulfment and digestion of gonococci 2 hr after infection. Infected macrophages seemed to develop pseudopodia for phagocytosis, and could engulf more than 30 gonococcal cells. Some engulfed bacteria appeared morphologically intact, while others appeared lysed and some structures resembling the L form of N. gonorrhoeae were also seen. These observations suggest that gonococcal cells may be able to survive intracellularly with normal or altered forms of morphology, and that macrophages containing these bacteria may disseminate gonococcal infection in man.

Animals↗
PubMedDate not supplied

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Creativity↗
PubMedDate not supplied

Abdominal aortic aneurysms complicated by spontaneous iliocaval or duodenal fistulae.

Seven hundred and twenty one abdominal aortic aneurysms were treated between 1960 and 1985. Twenty one of these (2.9%) were complicated by the development of a spontaneous primary fistula, 16 (2.2%) into the vena cava or iliac veins and 5 (0.7%) into the duodenum. A correct preoperative diagnosis was made in only four instances, two aorto-caval and two aorto-duodenal fistulae. Hospital mortality was 44% for aorto-caval and 60% for aorto-duodenal fistulae. Despite the lack of a precise preoperative diagnosis in the majority of cases, the prognosis for aorto-caval fistula remained comparable to that for patients undergoing emergency surgery for uncomplicated ruptured aortic aneurysms. The mortality of spontaneous aorto-duodenal fistulae was appreciably higher and the aneurysmal contents of 4 out of these 5 cases had positive bacterial cultures.

Aged↗
PubMedDate not supplied

Peripheral arterial embolism. A 20 year review.

Two hundred and forty eight peripheral arterial emboli occurring in 221 patients during a period of 20 years have been retrospectively reviewed. Best results are seen following early surgery with the balloon catheter but, in the clinical absence of tissue necrosis, late embolectomy is worthwhile. Atrial fibrillation and post-myocardial thrombus are the major sources of emboli, but tumour and septic emboli do occur and histological and bacteriological examination of retrieved material is essential. Patients who have sustained myocardial infarction have an increased risk of embolism in the first two weeks and despite modern therapy its incidence remains unchanged. Distinguishing true embolism from acute arterial thrombosis is a continuing problem and different surgical regimes for the two conditions are discussed. Embolectomy following anticoagulation has a high limb salvage rate and a low mortality; anti-coagulation as an adjuvant to surgery also improves prognosis for these patients who have lower amputation rates than those not anticoagulated.

Adult↗