- Volume 35, Issue 1, 1991
Volume 35, Issue 1, 1991
- Articles
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Clinical and diagnostic findings in 20 patients with toxoplasmosis and the Acquired Immune Deficiency Syndrome
More LessSummaryThe clinical and diagnostic findings in 20 cases of toxoplasmosis associated with the Acquired Immune Deficiency Syndrome (AIDS) were investigated in a prospective study of patients in south-east England. Individual details were recorded by a standardised questionnaire incorporating an evaluation of initial presentation, radiological findings, therapy and clinical progression. Toxoplasma serology was performed by reference assays and the presence of the parasite in tissue was sought by culture, histological examination and specific DNA detection. Clinical findings at presentation and results of radiological investigation were comparable with previously published experience from the USA. In contrast, sampling of the cerebrospinal fluid was rarely performed and was found to be of little clinical value. Examination of tissue samples was diagnostic when available, but was not performed routinely. Sulphonamide plus pyrimethamine was the treatment of choice in most cases and response to therapy was satisfactory, although a high incidence of toxicity was recorded.
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Age-related microbiological changes in the salivary and plaque microflora of healthy adults
More LessSummaryThe effect of age on quantitative or qualitative differences in selected bacteria of dental significance and on the carriage of opportunistic pathogens and transient oral species was determined in 79 healthy, non-denture wearing individuals divided into four age groups: 20-39 years (group A), 40-59 years (group B), 60-79 years (group C) and ≥ 80 years (group D). Samples of dental plaque and whole saliva were cultured on appropriate selective and non-selective bacteriological media. The total numbers of viable bacteria in saliva, and the prevalence of mutans streptococci in plaque and saliva were similar in all age groups. Similarly, there was no correlation between the numbers of spirochaetes in plaque and age. In contrast, statistically significantly higher mean proportions (p = 0.004), mean log10 viable counts (p = 0.001) and isolation frequencies (p < 0.01) of lactobacilli were found in the saliva of those aged ≥ 70 years compared to subjects in group A. The isolation frequency (p < 0.05) and proportions (p = 0.056) of staphylococci in saliva were also higher in those aged ≥ 70 years. Yeasts were isolated most often and in higher numbers from saliva in those aged ≥ 80 years and the proportion of yeasts was higher after 60 years of age, but these differences were not significant in comparison with results from individuals in group A. Actinomyces spp. were commonly isolated from plaque, but there was a change, with age, in the ratio of the proportions of A. viscosus and A. naeslundii so that A. viscosus predominated in elderly subjects (groups C and D). The results suggest that genuine age-related changes in the oral microflora can be detected, particularly after the age of 70 years, which are not related to denture-wearing or disease.
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Pre-opsonisation of Escherichia coli induces resistance to neutrophil killing in serum and urine: relationship to growth phase
More LessSummaryTests of phagocytosis and killing by polymorphonuclear neutrophil leucocytes (PMNL) are usually done with pre-opsonised organisms. Phagocytosis of 11 strains of Escherichia coli, pre-opsonised, and in the stationary phase, resulted in the killing of only one strain although all the organisms were phagocytosed. However, when the same strains were added unopsonised to a PMNL-serum mixture, eight were killed after phagocytosis. With two of these strains, the amount of killing was inversely proportional to the time of preopsonisation. E. coli incubated for 30 min in dilute peptone water in Hanks’s Balanced Salts Solution before phagocytosis also became resistant to killing; bacterial division did not occur during this period. Experiments with bacteria in urine confirmed these findings and showed that E. coli exposed to serum or urine before phagocytosis became resistant to killing by PMNL. E. coli rapidly changes its sensitivity to phagolysosome killing during transition from stationary to lag phase in a nutrient medium. This resistance is retained through the exponential phase but is lost during the stationary phase. The killing of Pseudomonas, Enterobacter, and Acinetobacter by PMNL was unaffected by varying the method of opsonisation or the phase of growth. If this phenomenon occurs in vivo it may affect the outcome of infections caused by strains of E. coli that survive killing by PMNL.
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Early events after intra-abdominal infection with Bacteroides fragilis and Escherichia coli
More LessSummaryGrowth of Bacteroides fragilis and Escherichia coli was monitored during early stages of single (mono-) and mixed intra-abdominal infection in a rat fibrin clot model. When B. fragilis and E. coli were together involved in the infection, B. fragilis numbers increased about 6h after an initial decline. This increase was not found with B. fragilis mono-infections. The numbers of E. coli increased rapidly in both mono- and mixed infections and stayed high for several days, but only mixed infection resulted in abscesses that persisted for more than 7 days. Macrophages, the main component of the peritoneal cellular defence mechanism, were outnumbered by polymorphonuclear leucocytes during the first 6 h of infection. Further characterisation of the macrophage population by means of monoclonal antibodies showed a shift from resident to exudate macrophages as the result of influx of the latter.
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Isoation and characterisation of an extracellular alkaline protease of Aspergillus fumigatus
M. Monod, G. Togni, L. Rahalison and E. FrenkSummaryAspergillus fumigatus secreted an inducible alkaline protease (AIPase) when cultivated in the presence of collagen (200 μg/ml) as sole nitrogen and carbon source. Proteolytic activity was maximum at pH 9.0 with azocollagen as substrate. The enzyme, which was the major protein found in the supernate of a liquid culture, was purified by ammonium sulphate precipitation and gel filtration. The Mr was determined to be 33 Kda by gel filtration and sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The isoelectric point was estimated to be pH 8.2. Divalent cations strongly inhibited enzyme activity, whereas non-ionic detergents and reducing agents had no effect. A. fumigatus AlPase was totally inhibited by phenylmethanesulphonyl fluoride, antipain, chymostatin and α-2-macroglobulin. A. fumigatus AlPase is closely related to the A. oryzae AlPase, a serine protease of the subtilisin family, as attested by the antigen pattern seen by immunoblotting. The high collagenic activity and the ability of A. fumigatus AlPase to digest elastin could play a role in the invasion of the tissues by the fungus.
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Killing of Histoplasma capsulatum by γ-interferon-activated human monocyte-derived macrophages: evidence for a superoxide anion-dependent mechanism
More LessSummaryThe interaction of human macrophages with the yeast form of the thermally dimorphic fungal pathogen, Histoplasma capsulatum, was studied. Macrophages derived from monocytes by culture in vitro for 3 days ingested H. capsulatum, but were neither fungicidal or fungistatic. In contrast, when monocytes were exposed to human recombinant gamma-interferon (γ-IFN) during their differentiation into macrophages, those macrophages were able to reduce the number of ingested or adherent cfu of H. capsulatum by 44-75% in 2 h. Activation of macrophages for fungicidal activity by γ-IFN was dose dependent and 500-1000 units ml were optimal. Antibody to γ-IFN abrogated the γ-IFN activation process. Killing of H. capsulatum by activated macrophages in 2-h assays could be inhibited by superoxide dismutase but not by sodium azide.
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SDS-PAGE and immunological analysis of different axenic Blastocystis hominis strains
More LessSummaryConsistent major differences were detected by SDS-PAGE, Western blotting and Ouchterlony immunodiffusion in four axenic and microscopically indistinguishable strains of the anaerobic human parasite Blastocystis hominis from different sources. It is concluded that at least two variants with different polypeptide patterns and antigens exist and the biological significance of these findings is discussed.
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Purification and characterisation of toxin B from a strain of Clostridium difficile that does not produce toxin A
More LessSummaryMost toxigenic strains of Clostridium difficile produce both toxin A and toxin B. The toxin produced by C. difficile strain 8864 was characterised and compared with those produced by C. difficile strain 10463. Toxin A was not detected by immunoassay in cultures from strain 8864 and all the cytotoxic activity produced by this strain was neutralised by antiserum to toxin B. Toxin B from strain 8864 was purified and compared with toxin B from strain 10463. The size of the purified subunits of toxin B from strain 8864 differed slightly from those of strain 10463 and there were small immunological differences. The effect on fibroblast cells was more like that of C. sordellii cytotoxin than of toxin B from strain 10463. These results suggest that C. difficile strain 8864 produces a modified toxin B and does not produce toxin A.
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Susceptibility to desferrioxamine: a new test for the identification of Staphylococcus epidermidis
More LessSummaryThe ability to identify Staphylococcus epidermidis quickly and accurately has become increasingly important in clinical microbiology. Susceptibility to desferrioxamine, an iron-chelating agent, was investigated as a new test for the identification of S. epidermidis. All strains of S. epidermidis and S. hominis tested were susceptible to a 1000-μg disk of desferrioxamine when grown on brain heart infusion agar. All other strains of coagulase-negative staphylococci, S. aureus and micrococci were resistant. As a single test, susceptibility to desferrioxamine was 96.4% efficient in identifying S. epidermidis; when combined with additional tests such as alkaline phosphatase production and fermentation of trehalose, the efficiency improved to 100%. Desferrioxamine disks were easy to prepare, stable and inexpensive. The test was simple to perform and interpret and should readily find application in clinical microbiology laboratories.
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Provisional identification of Haemophilus influenzae from sputum cultures within 1 h by rapid enzyme tests
More LessSummaryPossible Haemophilus influenzae colonies in cultures of sputum samples are currently identified by tests for dependence on X and V factors. This method requires further overnight culture and may give a relatively high number of false negative results. Identification of suspected H. influenzae colonies by a 5-min test for production of indole and β-galactosidase followed by a 1-h porphyrin test was compared with tests for dependence on X and V factors. A commercially produced form of the rapid tests (Haemstrip®, Lab M, Bury, Lancs) was used to test 252 potential haemophilus colonies from cultures of sputum samples on heated blood agar. Colonies that were β-galactosidase-positive after 5 min were considered to be non-H. influenzae and those that were β-galactosidase-negative but indolepositive were considered to be H. influenzae. At this stage the test had a sensitivity of 99.4% and a specificity of 90.9%. After 1 h, only colonies that were β-galactosidase-and porphyrinnegative were considered to be H. influenzae, the sensitivity was then 99.5% and the specificity 100%. Similar results were found with colonies from sputum cultures on selective heated blood agar containing bacitracin. The X and V dependence and Haemstrip results were in 97.6% agreement in a double blind test. Of 100 non-haemophilus colonies tested by Haemstrip, two pseudomonads could have been identified as H. influenzae by this method. The high positive predictive value of Haemstrip results depends partly on the initial recognition of potential haemophilus colonies.
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Passive secretory immunity against Salmonella typhimurium demonstrated with foster mouse pups
More LessSummaryMice immunised by drinking water containing an Aro mutant strain of Salmonella typhimurium produced intestinal IgA antibodies after a memory response which was demonstrated by measuring copro-antibodies. After oral challenge with a virulent strain of S. typhimurium, foster mouse pups placed with immunised mothers survived longer than control pups held with non-immunised mothers.
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Detection of nephritis strain-associated streptokinase by monoclonal antibodies
SummaryMonoclonal antibodies (MAbs) N-59 and RU-1 were produced by immunisation of mice with streptokinase secreted by Streptococcus group A, type 12, strain A374 isolated from a patient with post-streptococcal glomerulonephritis (PSGN) and were characterised by Western blot analysis. MAb N-59 recognised antigenic determinants shared by both nephritis strain-associated streptokinase (NSA-SKase) and streptokinase of Streptococcus group C (C-SKase); MAb RU-1 reacted only with NSA-SKase. All nephritis-associated group A streptococcal strains tested reacted with MAb N-59; 87.5% of these strains reacted with MAb RU-1. MAb N-59 reacted with SKase produced by group G streptococcal strains isolated from patients with PSGN, and MAb RU-1 recognised SKase in two out of three of these strains.
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