- Volume 47, Issue 1, 1998
Volume 47, Issue 1, 1998
- Editorial
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- Review Article
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Isolation, Identification and Increasing Importance of ‘Free-Living’ Amoebae Causing Human Disease
More LessAmphizoic small amoebic protozoa are capable of existing both in ‘free-living’ and in ‘parasitic’ form depending on the actual conditions. Two genera (Naegleria and Acanthamoeba) have become recognised as opportunist human parasites. Since the first description in 1965 of a lethal case of primary amoebic meningoencephalitis (PAM) caused by Naegleria, many more (mostly lethal) cases have been reported, while granulomatous amoebic encephalitis (GAE), as well as eye (keratinitis, conjunctivitis, etc.), ear, nose, skin and internal organ infections caused by Acanthamoeba have also occurred in rapidly increasing numbers. Both pathogenic and non-pathogenic species of Naegleria and Acanthamoeba are found worldwide in water, soil and dust, where they provide a potential source of infection. Successful differential diagnosis and appropriate (specific) therapy depends on precise laboratory identification of the ‘free-living’ amoebae. In most cases, isolation from the environment can be achieved, but identification and differentiation of the pathogenic and non-pathogenic strains is not easy. The methods presently available do not fulfil completely the requirements for specificity, sensitivity and reliability. Morphological criteria are inadequate, while thermophilic character, pH dependency and even virulence in infected mice, are not unambiguous features of pathogenicity of the different strains. More promising are molecular methods, such as restriction endonuclease digestion of whole-cell DNA or mitochondrial DNA, as well as iso-enzyme profile analysis after iso-electric focusing and staining for acid phosphatase and propionyl esterase activity. Use of appropriate monoclonal antibodies has also yielded promising results in the differentiation of human pathogenic and non-pathogenic strains. However, quicker, simpler, more specific and reliable methods are still highly desirable. The significance of endosymbiosis (especially with Legionella strains) is not well understood. The results of a systematic survey in Hungary for the isolation and identification of ‘free-living’ amoebae, including an investigation of the Hungarian amoebic fauna, the isolation of possibly pathogenic Naegleria strains and of some Acanthamoeba strains from eye diseases, as well as the finding of a case of endosymbiosis, are also reported here.
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- Diagnostic Microbiology
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Evaluation of a New Selective Medium for the Isolation of Corynebacterium Urealyticum
More LessA new selective medium (CBU agar) was compared with blood agar (BA) medium for primary isolation of Corynebacterium urealyticum from urine and skin samples of hospitalised patients. Overall, the CBU agar detected C. urealyticum in 14 (4.6%) of 302 urine samples and the BA medium detected the organism in four (1.3%), but most cultures which were positive only on CBU agar had < 104 cfu/ml. Six strains of C. urealyticum were isolated from 60 skin samples with CBU agar, whereas none was detected with BA. Although most skin samples had heavy inocula, the selective agar facilitated the recognition of low colony counts (≤ 10 cfu/plate) of C. urealyticum by reducing the growth of competing flora. Challenge of the selective medium with reference and clinical strains showed that CBU agar was inhibitory for gram-negative bacteria and reduced the gram-positive flora, allowing the growth of C. urealyticum strains. The new selective medium appears to be a useful epidemiological tool to study urinary and skin colonisation by C. urealyticum.
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- Antimicrobial Resistance
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Molecular Analysis of the Macrolide-Lincosamide Resistance Gene Region of a Novel Plasmid from Staphylococcus Hyicus
More LessResistance to macrolides and lincosamides in Staphylococcus hyicus has been shown to be encoded by a 4.0-kb plasmid designated pSES21. It differed distinctly in its restriction map from all other staphylococcal macrolide resistance plasmids reported so far. Southern blot hybridisation with gene probes specific for staphylococcal erm genes demonstrated that the macrolide resistance gene belonged to hybridisation class C. Analysis of the ermC gene revealed that the deduced amino-acid sequence of the pSES21-encoded ErmC methylase exhibited c. 93% identity with the ErmC methylase encoded by plasmid pE194. The ermC gene of pSES21 was expressed constitutively and sequence analysis of the regulatory region showed multiple base-pair insertions and substitutions in the translational attenuator. As a consequence of these mutations, the reading frame of the small regulatory peptide was destroyed and a novel pair of inverted repeated sequences was generated. Previous studies identified sequence deletions and sequence duplications in the ermC regulatory region as the basis for constitutive ermC gene expression. The multiple point mutations shown in the pSES21-encoded ermC translational attenuator represent a novel kind of structural alteration in this regulatory region and may explain constitutive ermC gene expression by pairing of the newly generated inverted repeated segments in the presence of a functionally deleted reading frame for the small regulatory peptide.
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- Epidemiology Of Infection
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Pneumococci Causing Invasive Disease in Britain 1982–1990
More LessA total of 5348 isolates of Streptococcus pneumoniae was serotyped and screened for insusceptibility to tetracycline, penicillin, erythromycin and chloramphenicol. Of these, 4238 (79%) were isolated from patients who had pneumonia or meningitis or were bacteraemic. Altogether, 3948 (74%) of the isolates belonged to one or other of the serotypes 1, 3, 4, 6, 8, 9, 14, 19 or 23 with serotypes 6, 14, 18, 19 and 23 being frequent causes of invasive disease in young children. Many isolates of type 1 were isolated from pneumonia and few from meningitis. Some 768 (14%) isolates were insusceptible to one or more antibiotic and 591 of these belonged to serotypes 6, 9, 14, 19 or 23. Representatives of type 14 resistant to erythromycin were prominent from 1986 onwards. There was an increase in the number of multi-resistant pneumococci from 1985. Among these were isolates of type 23 insusceptible to penicillin, chloramphenicol and tetracycline and cultures of type 6 resistant additionally to erythromycin.
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Lectin–Oral Streptococci Interactions
More LessLectins of various specificities were examined for interaction with strains of oral streptococci of various species. The lectins were capable of binding galactose, N-acetylgalactosamine, glucose, N-acetylglucosamine, mannose, fucose and sialic acid. Lectin reactivities were strain-dependent in that some members of a species, but not others, could be aggregated by certain lectins. Proteolysis and extraction with hot water, guanidine hydrochloride and sodium dodecyl sulphate tended to increase the reactivity of the streptococci with lectins but did not change the recognition patterns of the bacteria. Sonication, in contrast, tended to reduce the ability of streptococci to be agglutinated by lectins. Furthermore, lectin reactivities were dependent on the growth conditions, as evidenced by changes in lectin titres following streptococcal growth in sub-inhibitory concentrations of citrate, fluoride or antibiotics. It is likely that lectins could be useful tools for epidemiological studies and to probe strain-dependent and growth-dependent surface characteristics of viridans streptococci.
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- Model Of Infection
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Cryptosporidium Parvum Biliary Tract Infection in Adult Immunocompetent and Immunosuppressed Mice
More LessBiliary tract infection by Cryptosporidium parvum is a frequent complication of intestinal cryptosporidiosis in immunosuppressed patients. Although biliary tract infection can be produced in immunosuppressed models as a late complication of intestinal infection, there is no infection model in immunocompetent animals. A murine model of biliary tract cryptosporidiosis was developed by direct intra-gall bladder injection of C. parvum oocysts. In adult immunocompetent mice, intracellular parasitic stages were detected in the epithelium of the common bile duct in all animals on day 7 post-inoculation (p.i.). These findings were associated with a strong inflammatory reaction. Infection was cleared between days 14 and 21 p.i. All animals developed significant levels of specific serum and bile IgG, IgA and IgM. Dexamethasone treatment resulted in the inability of animals to eradicate the parasite and the establishment of ileal parasitism. This model can be used to study the immunological mechanisms imvolved in the control of biliary cryptosporidiosis.
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- Bacterial Characterisation
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Identification and Antibiotic Susceptibility of Nocardia Farcinica and N. Nova in the Uk
More LessNocardia asteroides has long been recognised as a heterogeneous group of organisms. The description and identification of two new subgroups, N. farcinica and N. nova, in other countries encouraged us to re-examine a collection of N. asteroides isolates from the UK. Of 73 clinical isolates identified as N. asteroides from different parts of England and Wales during 1991–1993, and now subjected to further differentiation tests by the Mycobacterial/Nocardial Reference Laboratory, 15 (20.5%) were identified as N. farcinica based on three out of four characteristics: growth property, acetamide production, rhamnose assimilation and a distinct antibiogram. No isolates were identified as N. nova. A revised identification and susceptibility system has significant clinical and taxonomic implications. Its introduction will improve speciation, identify antibiotic resistance and influence the choice of safer alternative therapy for patients infected with Nocardia spp. in the UK.
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- Immune Response To Infection
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Evaluation Of Immunogenicity and Protective Activity in Balb/C Mice of the 25-kDa Major Outer-Membrane Protein Of Brucella Melitensis (Omp25) Expressed in Escherichia Coli
More LessThe antibody response specific to the 25-kDa major outer-membrane protein (Omp25) of Brucella melitensis expressed in Escherichia coli was assessed in BALB/c mice. Groups of mice were immunised and boosted either with sonicated E. coli carrying plasmid pAC2533 – E. coli (pAC2533) – expressing the gene coding for Omp25 (omp25 gene) of B. melitensis, or with E. coli carrying plasmid pUC19 – E. coli (pUC19). One control group received saline. The evolution of antibody responses was investigated by indirect ELISA with whole rough (R) B. melitensis H38 cells as antigen. Serum antibody titres of mice immunised with E. coli (pAC2533) were appreciably higher than those of mice immunised with E. coli (pUC19). The specificity to Omp25 of murine antibodies induced by E. coli (pAC2533) was demonstrated by SDS-PAGE and immunoblotting of five B. melitensis strains. Binding of antibody in E. coli (pAC2533) immune sera to the surface of B. melitensis strains differing in their smooth lipopolysaccharide (S-LPS) expression was also studied by whole-cell ELISA and by flow cytometry. Antibody reactivity to R and smooth-rough (S-R) was much stronger than that to smooth (S) B. melitensis strains, indicating a much better accessibility of Omp25 to antibody on strains lacking or expressing less O-polysaccharide on their surface. The antibodies to Omp25 were predominantly of IgG2a isotype. The capacity of E. coli (pAC2533) to induce protective immune responses against four challenge strains of B. melitensis was further evaluated in mice. Significant reductions in splenic infections, in comparison with mice immunised with E. coli (pUC19) and unimmunised (saline injection) mice, were observed in R B. melitensis B115, S-R B. melitensis EP and S B. melitensis H38 infected mice. Protection against S B. melitensis 16M was not significant. The data from the present study, together with previous results, suggest that humoral immunity against probably conformational, well-exposed epitopes of the Omp25 could contribute to protective mechanisms against B. melitensis infection in mice.
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Anti-Phosphatidylcholine Antibodies in Patients with Brucellosis
M. A. Casao, J. Leiva, R. Diaz and C. GamazoAn indirect ELISA was adapted to measure individual classes of anti-phosphatidylcholine (PC) antibodies in patients with brucellosis; a comparison was made with patients with other infectious diseases and healthy human controls. Immunoconjugates of α, γ or μ chain specificity were used. The results were compared with those of conventional tests for brucella antibodies, Rose Bengal, microagglutination (MAT) and Coombs tests, as well as with VDRL. The results indicated that although all sera from patients with brucellosis were VDRL negative, 97% of them (30 of 31) had higher levels of IgA or IgG anti-PC antibodies than the healthy control group. The IgM anti-PC antibodies isotype was not discriminatory between both groups. Seven sera (19%) from patients with other infections had values of IgG anti-PC higher than those of the healthy group; three of them were VDRL positive. The mean ELISA values of IgG and IgA anti-PC (serum diluted 1 in 1600) in the brucellosis and healthy groups were: IgG, 0.80 SEM 0.17 versus 0.23 SEM 0.10; and IgA, 0.86 SEM 0.26 versus 0.35 SEM 0.15. The sensitivity and specificity for the ELISA-PC were: IgG, 96.8% and 96.5%, respectively; IgA, 90.3% and 89.7%, respectively. Only one of 14 individuals clinically cured from brucellosis had significant IgG anti-PC antibodies. In contrast, all of these patients gave positive values in the conventional test for brucellosis. No correlation was found between the serum levels of IgA, IgG anti-PC by ELISA-PC and the results of the MAT or Coombs tests.
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Interleukin-8 Release from Human Neutrophils after Phagocytosis of Listeria Monocytogenes and Yersinia Enterocolitica
More LessThe release of interleukin-8 (IL-8) from human neutrophils was investigated after their internalisation of the invasive bacteria Listeria monocytogenes and Yersinia enterocolitica. Three pairs of bacterial strains were used to study the influence of listeriolysin O, invasiveness and Yersinia virulence plasmid (pYV)-encoded proteins on neutrophil cytokine synthesis. The neutrophils secreted IL-8 into the culture supernate after exposure to all strains tested. With L. monocytogenes, the virulence factor listeriolysin O had no effect on IL-8 secretion, whereas a non-invasive mutant induced greater IL-8 release than the corresponding invasive strain. With Y. enterocolitica, expression of virulence plasmid-encoded proteins appeared to be responsible for diminished IL-8 release. Northern blot analysis showed that the induced IL-8 release was always accompanied by an enhanced level of cytoplasmic IL-8 mRNA. Cytokine priming of neutrophils with granulocyte macrophage colony-stimulating growth factor (GM-CSF), unlike granulocyte colony-stimulating factor (G-CSF), led to further enhancement of IL-8 secretion induced after internalisation of the bacteria. Again, the increased IL-8 release, from GM-CSF primed neutrophils, was accompanied by an increased level of cytoplasmic IL-8 mRNA. The results emphasise the role of IL-8 in neutrophil-mediated host defence mechanisms during the acute phase of L. monocytogenes and Y. enterocolitica infection.
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- Virology
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An Outbreak of Epidemic Keratoconjunctivitis Caused by Adenovirus Type 37
More LessAn outbreak of acute keratoconjunctivitis in an ophthalmology department affected 15 patients and seven members of staff and necessitated temporary closure of the unit. Adenovirus (Ad) was isolated from eye swabs taken during the outbreak, but typing of the isolates by virus neutralisation assay proved unsatisfactory, wrongly assigning the isolate to serotype 10. A robust and rapid method for preparing microgram amounts of Ad DNA from infected cells was devised and used as the basis of a non-radioactive method for routine genotyping of adenovirus clinical isolates. All isolates associated with the outbreak, and one from a patient presenting at a nearby hospital during the outbreak, were found to have restriction endonuclease digestion patterns characteristic of Ad 37.
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- Announcements
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Volumes and issues
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Volume 73 (2024)
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Volume 72 (2023 - 2024)
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Volume 71 (2022)
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Volume 70 (2021)
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Volume 69 (2020)
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Volume 68 (2019)
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Volume 67 (2018)
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Volume 66 (2017)
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Volume 65 (2016)
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Volume 64 (2015)
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Volume 63 (2014)
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Volume 48 (1999)
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Volume 47 (1998)
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Volume 46 (1997)
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Volume 45 (1996)
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Volume 43 (1995)
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Volume 41 (1994)
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Volume 39 (1993)
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Volume 35 (1991)
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Volume 34 (1991)
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Volume 27 (1988)
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Volume 25 (1988)
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Volume 22 (1986)
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Volume 17 (1984)
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Volume 16 (1983)
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Volume 15 (1982)
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Volume 14 (1981)
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Volume 12 (1979)
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Volume 10 (1977)
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Volume 9 (1976)
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Volume 8 (1975)
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Volume 7 (1974)
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Volume 6 (1973)
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Volume 5 (1972)
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Volume 4 (1971)
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Volume 3 (1970)
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Volume 2 (1969)
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Volume 1 (1968)