Biomedical subjects
H E Larson
Publications and source records attributed to H E Larson.
Multiple episodes of bacterial endocarditis occurring over 9 years.
We present a patient who was treated for bacterial endocarditis on 10 occasions in 9 years. In all but one of these episodes blood cultures were positive and the last two recurrences occurred on an aortic valve homograft. The pathogenesis of recurrent infective endocarditis in non-intravenous drug abusers is unclear and prevention of recurrences poses a difficult problem.
Quantitative study of antibiotic-induced susceptibility to Clostridium difficile enterocecitis in hamsters.
Commonly used antibiotics were compared for their ability to induce Clostridium difficile enterocecitis and death in hamsters. Susceptibility to infection with C. difficile was measured by calculating 50% lethal doses (in CFU) for hamsters for various intervals after antibiotic treatment. Infection occurred after very small doses of C. difficile were given to hamsters treated with clindamycin, ampicillin, flucloxacillin, and cefuroxime; there was little difference between the antibiotics in the degree of susceptibility that they induced. A large difference in the duration of susceptibility was observed, however, with susceptibility being temporary following ampicillin, flucloxacillin, and cefuroxime administration but long-lived following clindamycin administration. A larger dose of ampicillin, multiple doses of ampicillin, and a combination of antibiotics had comparatively small effects on the duration of susceptibility. C. difficile growth and toxin production in in vitro suspensions of cecal contents were found to correlate closely with in vivo hamster infectivity. A persisting loss of colonization resistance following antibiotic treatment may be a type of postantibiotic effect. Although these results cannot be applied directly to humans, they suggest lines of further investigation into how antibiotics may differ in producing risks of C. difficile infection and pseudomembranous colitis in patients.
Hydatid disease and cholestasis.
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IgG1 subclass deficiency in patients with chronic fatigue syndrome.
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Neonatal necrotizing enterocolitis: a neonatal infection?
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Infectious diarrhea due to Clostridium perfringens.
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Antitoxin activity of human polymorphonuclear leucocytes.
Human polymorphonuclear leucocytes (PMNL) inactivate Clostridium difficile cytotoxin and C. perfringens phospholipase C, but not C. perfringens enterotoxin. Both whole cells and sonicated suspensions possess activity, but mononuclear cell fractions of peripheral blood do not. Antitoxin activity closely correlates with cell concentration. The highest cell concentrations tested completely inactivated C. difficile cytotoxin by 2 min. Sucrose density gradient fractionation of PMNL showed antitoxin activity to be associated with myeloperoxidase, locating it in the primary or azurophil granules. Toxin inactivation was prevented by protease inhibitors suggesting that it is due to one of the neutral proteases present in these granules. PMNL are more active against C. difficile cytotoxin than purified chymotrypsin. PMNL may be a primary defence against certain bacterial exotoxins.
Pseudomembranous colitis.
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Morphology of experimental antibiotic-associated enterocolitis in the hamster: a model for human pseudomembranous colitis and antibiotic-associated diarrhoea.
The morphology of antibiotic-associated enterocolitis in the hamster is described and compared with human antibiotic-associated pseudomembranous colitis. It is shown to be a caecal disease with proliferative mucosal changes and in this respect unlike the human counterpart. The bacteriology and toxicology, however, are identical. In addition, mucosal changes are described in animals on antibiotics but without established enterocolitis. As a result we suggest that there may be a spectrum of human disease ranging from mild antibiotic-associated diarrhoea to established pseudomembranous colitis. Therefore, despite the morphological variation, the hamster remains a good model for investigating the pathogenesis of pseudomembranous colitis and antibiotic-associated enteropathy in general.
Vancomycin for pseudomembranous colitis.
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Clostridium difficile and the aetiology of pseudomembranous colitis.
Bacterial isolates from 5 patients with pseudomembranous colitis (P.M.C.) were screened for toxin production. Strains of Clostridium from 4 patients produced in vitro a toxin similar to that found in P.M.C. faecal suspension. These were identified as C. difficile. Use of the strains from 2 patients induced a fatal enterocolitis when inoculated orally into hamsters pretreated with vancomycin. The C. difficile that produced the toxin in vitro was then re-isolated from hamster caecal contents. These findings suggest that P.M.C. results from infection with C. difficile and that previous antibiotic therapy produces susceptibility to infection.
Viruses and diarrhoea in West Africa and London: A collaborative study.
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Immunity to challenge in volunteers vaccinated with an inactivated current or earlier strain of influenza A(H3N2).
Volunteers were inoculated with vaccine made from the 30c mutant, A/Port Chalmers/73 or B/Hong Kong/8/73. Preliminary experiments showed that the 30 c strain was antigenically quite close to A/HK/8/68. Volunteers given 30c developed haemagglutination inhibiting antibodies against the 'current' 1973 serotypes (as well as to the vaccine virus) but the titres were less than those after the A/PC/73 vaccine. Volunteers were then challenged with a live attenuated virus, WRL 105, with A/Finland/4/74 antigens, by intranasal inoculation. The rates of infection were 43% after B/Hong Kong/8/73, 20% after 30c and 5% after A/PC/73. This indicated that the 30c gave some protection but that the vaccine prepared from the current strain gave more.
An isolation unit in a district general hospital.
The working of a 19-bed isolation unit in a general hospital was studied from August 1975 to July 1976. A few patients received the highest degree of isolation, but infections in all categories were contained and patients at risk in the same unit were protected from infection.
Undescribed toxin in pseudomembranous colitis.
A girl aged 12 developed pseudomembranous colitis after a short course of oral penicillin. She had no history of adverse reaction to penicillin before or after the illness. No pathogenic bacteria, mycoplasmas, or viruses were found in her faeces, but they did contain a toxin. Toxin was also found in four of five other patients with pseudomembranous colitis but not in six specimens obtained from patients with diarrhoea caused by other disorders. Further studies may show that pseudomembranous colitis is caused by a bacterial toxin.
Arthritis after meningococcal meningitis.
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Influenza viruses and staphylococci in vitro: some interactions with polymorphonuclear leucocytes and epithelial cells.
Bacterial infection contributes substantially to the morbidity and mortality of human influenza. In vitro experiments were performed to test two hypotheses regarding a possible relationship between the virus and bacterial infection. Firstly, maintenance media from tissue and organ cultures infected with influenza virus were tested for the presence of staphylococcal growth-promoting factors; no evidence for these was found. Secondly, we looked for a virus effect on polymorphonuclear leucocyte function. We found that human leucocytes purified from venous blood and exposed to influenza virus responded normally to stimulation of hexose monophosphate shunt activity and chemiluminescence. However, their responses in tests of phagocytic function and of chemotaxis were inhibited. By various criteria this effect was specific to the virus and could be obtained even when only a few virus particles were present per leucocyte. We propose that this is a mechanism by which influenza virus could enhance susceptibility to bacterial infection in the lung.