Biomedical subjects
Publications and source records attributed to L M Wallace.
Five virulent strains of Fusobacterium necrophorum resembled a single strain examined earlier by possessing little or no immunogenicity: severe subcutaneous infections cured with metronidazole failed to increase the resistance of mice to subcutaneous challenge 22 days after the cessation of treatment.
It had already been shown with a single virulent strain (A42) of Fusobacterium necrophorum that suspension of the fusobacteria in sub-lethal doses of broth cultures of other bacteria reduced the minimum infective dose (greater than 10(6) organisms) for mice by subcutaneous inoculation, sometimes to less than 10 organisms. The present study extended the known range of bacteria with strong infectivity-enhancing properties to include Bacillus cereus, Klebsiella oxytoca and Staphylococcus aureus; and those with weaker effect to include Bacillus subtilis, 'Bacteroides melaninogenicus', Clostridium sporogenes, Pasteurella haemolytica, and Proteus mirabilis. The study also showed that five further virulent strains of F. necrophorum closely resembled A42 in respect of striking susceptibility to infectivity enhancement by Escherichia coli. Actinomyces (Corynebacterium) pyogenes and S. aureus. One further strain (A6) of F. necrophorum resembled A42 in respect of strong infectivity enhancement by A. pyogenes, S. aureus, B. cereus and K. oxytoca but differed from it and the other five strains in being only slightly affected by E. coli. This work was a necessary prelude to the development of a method, based on infectivity enhancement, for the detection and isolation of F. necrophorum present in small numbers in heavily contaminated material such as faeces.
The isolation of Fusobacterium necrophorum present in small numbers in heavily contaminated material such as faeces or soil is hampered by the lack of an efficient selective medium and by the high minimum infective dose of the organism. A sensitive method for the detection and isolation of faecal strains of F. necrophorum type A was based on the subcutaneous injection of faeces, suspended (5% w/v) in broth culture of Actinomyces (Corynebacterium) pyogenes or Staphylococcus aureus to increase fusobacterial infectivity, into mice pretreated with clostridial antitoxins. When necrobacillosis developed F. necrophorum was identified microscopically in tissue from the advancing edge of the lesion and isolated on a partly selective medium. The enhancement of fusobacterial infectivity produced by A. pyogenes and by S. aureus was high, but the latter was slightly the more efficient, enabling as few as 80 F. necrophorum organisms/g of faeces to be detected. Use of the method showed that 3 of 16 wallabies had F. necrophorum in their faeces at the time of examination. Numerous epidemiological applications are suggested.
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Earlier studies showed that the minimum infective dose (greater than 10(6) organisms) of a virulent strain of Fusobacterium necrophorum could be greatly reduced by suspending the fusobacteria in sub-lethal doses of cultures of other bacteria such as Escherichia coli before inoculating mice subcutaneously. In the present study the infective dose of the same strain of F. necrophorum was reduced by a factor of greater than 10(3) by suspending the fusobacteria in sub-lethal doses of 5% homogenate of gaur or wallaby faeces. Sterile faecal filtrate had no such effect. The sites of low grade infection produced by the prior subcutaneous injection of E. coli culture or gaur faecal suspension were susceptible to superinfection by doses of F. necrophorum far below those required to infect normal tissue. This work helps to explain the production of necrobacillosis by the faecal contamination of small wounds. It proved impossible, however, to produce necrobacillosis in mice by the subcutaneous injection of faecal suspensions from 33 farm cattle. This suggests that the proportion of cattle with virulent F. necrophorum in their faeces is low.
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Necrobacillosis is caused by Fusobacterium necrophorum (FN), but other organisms are often present in the lesions. Their possible role was studied in experiments made with a virulent FN strain which, by itself, produced fatal necrobacillosis in mice provided that large doses (greater than 10(6) organisms, subcutaneously) were given. Mice were inoculated subcutaneously with FN suspended in sub-lethal doses (0.1 ml) of undiluted or diluted broth cultures of other bacteria. Undiluted culture of a strain of Escherichia coli reduced the infective dose of FN to less than 10 organisms; in the necrobacillosis lesions that developed, fusobacteria greatly outnumbered E. coli. A heat-killed preparation or sterile filtrate of E. coli culture had little if any effect on FN. Citrobacter freundii and comparatively small numbers of Corynebacterium (Actinomyces) pyogenes produced effects similar to that of E. coli. An alpha-haemolytic streptococcus, Pseudomonas aeruginosa, Bacteroides fragilis and Fusobacterium nucleatum also enhanced the infectivity of FN, though less strikingly than E. coli. FN increased the persistence in vivo of the alpha-haemolytic streptococcus and B. fragilis, and enabled the latter to multiply profusely.
The study arose from the recent finding that sub-lethal numbers of certain bacterial species greatly enhanced the infectivity of Fusobacterium necrophorum. A severe F. necrophorum infection in mice, cured with metronidazole, produced significant though slight resistance, which was demonstrable by challenge with a minute dose of F. necrophorum (less than 20 organisms) suspended in a sub-lethal dose of Escherichia coli (300 x 10(6) organisms) to enhance fusobacterial infectivity. In an earlier comparable experiment, challenge with F. necrophorum alone, in necessarily large doses (greater than or equal to 3 x 10(6) organisms), failed to demonstrate that a single cured fusobacterial infection gave rise to resistance; such an infection neither protected against the fatal necrobacillosis produced by challenge nor prolonged survival. A sub-lethal E. coli infection was also shown by challenge with a minute dose of F. necrophorum (less than 10 organisms), suspended in a sub-lethal dose of E. coli (152 x 10(6) organisms), to produce significant though slight protection against necrobacillosis. The degrees of resistance demonstrated were too slight to give any encouragement to the prospect of an effective necrobacillosis vaccine.
An investigation of the psychological sequelae of two samples of burns patients is presented. Both samples are a nearly complete consecutive series of adult patients treated at a British Regional Burns Unit. Sixteen patients were interviewed at their first discharge from the ward and 6 months later. A further 15 patients were assessed 2 years after their first discharge. Systematic assessment included psychological questionnaires giving estimates of the severity of psychological disturbance. Thirty-one per cent of adults at discharge, 38 per cent at 6 months and 40 per cent at 2 years were sufficiently disturbed to require specialist referral. The type of help received and preferred by patients is also discussed and conclusions drawn about how burns unit staff can improve the adjustment of burns-injured adults.
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Trait anxiety was found to predict elevations in state anxiety not only on the morning of surgery but six to eight weeks before hospitalization, in 118 women undergoing laparoscopic surgery. Trait anxiety was not a strong predictor of state anxiety on the evening of surgery and a very weak predictor of pain, symptoms and behavioural recovery.
The prospect of surgery represents a threatening and often fear-provoking event even to adult patients. Medical practitioners are responsible for obtaining informed consent for elective surgery, which includes an explanation of the reasons for surgery and its likely and possible effects. In practice a dilemma exists between the principle of respect for autonomy of the patient, and between the wish to do the patient no harm. The extent to which patients have been shown to benefit or to be harmed by information about elective surgery is examined by reference to existing studies of surgical patients and to the author's data gathered for interviews and observations on two samples of 131 and 80 women undergoing minor gynaecological surgery. The evidence suggests that most adult patients wish to be informed in detail about their surgery. Information about the likely serious complications is upsetting to some patients, but accurate information about the likely effects of surgery is welcomed, and may even promote faster recovery after the operation. However, much information presented to patients is not understood or is rapidly forgotten. Greater involvement by patients in discussions about their medical care may redress some of these problems and shift some of the responsibility towards the patient.
An experimental study of the design and implementation of a special preparatory booklet designed to reduce stress in surgical patients is reported. Patients in this study were 63 women undergoing minor gynaecological surgery. They were allocated sequentially to three groups: routine care only (control group), routine care plus a minimally informative booklet (placebo group) and routine care plus a maximally informative booklet (experimental group). Changes in cognitive variables were assessed prospectively over the course of hospitalization and surgery. As expected, the intervention had direct effects on patients' knowledge, reported information and worries about surgery. It also had indirect beneficial effects on the amount of reported information and support from staff and families. Finally, patients in the placebo group were found to have more misconceptions about surgery and to more often report anxiety in communication with staff and in association with reading materials. Partial correlation analyses showed that patients who have more knowledge about surgery have fewer worries and recover faster. The implications for cognitive theories of the process of stress reduction for surgical patients by psychological preparation are discussed.
Psychological theories of stress suggest competing hypotheses for the predictive relationship between pre-operative anxiety and post-operative adjustment and recovery. Evidence is presented to assess whether linear or curvilinear (quadratic) relationships account for the association between pre-operative anxiety and post-operative variables. These two hypotheses are tested on two samples of patients undergoing elective minor gynaecological surgery. Multiple regression analyses provided weak support for a linear, but not a curvilinear, relationship between pre-operative anxiety and post-operative anxiety but not with post-operative outcomes other than anxiety such as pain or speed of returning to normal activities. Qualitative data are also presented which examine whether patients who show either low or high levels of pre-operative anxiety differ in the nature of their fears of surgery or their preferred methods of coping with fear and with post-operative pain. No evidence was found to suggest that patients with either high or low levels of pre-operative anxiety differed in appraisal or coping strategies. There was little evidence that the beneficial effects of a special preparatory booklet on post-operative adjustment and recovery were mediated by its influence on state anxiety.
One hundred and thirty-one patients undergoing elective laparoscopic surgery for sterilization or infertility investigations were examined in a prospective study. Firstly, the contributions of the reason for undergoing the operation to the patients' psychological adjustment and recovery, is examined. Measures were taken of personality, mood, physical symptoms, vital signs and the patients' speed of returning to normal activities. The reason for laparoscopy does not appear to influence the amount of fear immediately before and after the operation, post-operative physical symptoms, nor the majority of mood states at follow up. There were significant differences between infertility and sterilization patients on state anxiety on the morning of surgery, vital signs, post-operative intramuscular analgesia, and the speed of returning to normal activities. In particular, sterilization patients did not report greater pain but received more analgesia, and returned to their normal activities more rapidly than infertility patients. Secondary infertility patients showed the slowest rate of return to normal activities, and reported more adverse mood states at 1 week follow up. The investigation of patients' attitudes to the operation revealed that patients undergoing sterilization and infertility investigation are concerned about the costs and benefits of the operation which include not only influencing fertility, but influencing menstruation and sexual activity. Patients misunderstood information about surgery, and the majority of patients welcomed additional psychological preparation. Suggestions concerning the management of patients undergoing laparoscopy for different fertility reasons are discussed.
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