- Volume 48, Issue 10, 1999
Volume 48, Issue 10, 1999
- Editorial
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- Case Report
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Aureobacterium masquerading as ‘Corynebacterium aquaticum’ infection: case report and review of the literature
More LessSummaryA gram-positive bacillus was isolated repeatedly from blood taken through the lumina of a central venous catheter of a patient with multiple myeloma who developed febrile neutropenia following chemotherapy. The bacterium was identified by the API CORYNE system as ‘Corynebacterium aquaticum’. Gene analysis targeting the 16S rRNA indicated that the organism had a 99.5% identity with Aureobacterium liquefaciens although there were two phenotypic characteristics at variance with the description of this species. Problems remain with the routine identification of ‘C. aquaticum’ and Aureobacterium species. The few clinical reports on patients infected with ‘C aquaticum’ and A. liquefaciens indicate that these are rare infections often associated with immunocom-promise.
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- Correspondence
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- Bacterial Pathogenicity
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Intestinal colonisation of gnotobiotic pigs by Salmonella organisms: interaction between isogenic and unrelated strains
More LessSummaryThe effect of intestinal colonisation by a Salmonella strain on the establishment in the gut of an isogenic mutant administered orally 24 h after the first strain was studied in gnotobiotic pigs. Irrespective of the clinical outcome of the infection, the extensive colonisation of one Salmonella strain prevented a similar degree of colonisation by an otherwise isogenic antibiotic resistant strain; in some cases the second strain was hardly detectable. The poor colonisation of the challenge Salmonella strains was generally reflected in very low counts of organisms in the tissues. Colonisation by a strain of Escherichia coli reduced the rate of establishment of an isogenic E. coli, strain but did not prevent colonisation by an S. Typhimurium strain. S. Typhimurium with mutations in the tsr (serine chemotaxis receptor protein) or oxrA (transcriptional regulator of anaerobic metabolism) genes did not inhibit colonisation. Mutations in cya (adenylate cyclase), tar and trg (chemotaxis receptor proteins for aspartate and ribose respectively) genes were less inhibitory, while motB (non-motile) and cheR (impaired motility) mutants were fully inhibitory.
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Colostral proteins from cows immunised with Streptococcus mutans/S. sobrinus support the phagocytosis and killing of mutans streptococci by human leucocytes
More LessSummaryPassive immunisation, based on bovine colostral preparations, is an area of active research. Specific bovine antibodies inhibit the virulence factors of target pathogens but the interactions between whey preparations and human immune defence cells are not well known. Bovine colostrum inhibits the phagocytic activity of bovine leucocytes and this may reflect the biological activity of immunoglobulins in it. Therefore, this study aimed to examine the effects of bovine whey protein preparations from the colostrum of Streptococcus mutans/S. sobrinus-immunised and sham-immunised cows on binding, ingestion and killing of these bacteria by human leucocytes. Binding and ingestion of FITC-labelled bacteria were estimated by flow cytometry and leukocyte activation was measured as chemiluminescence. Killing rate was estimated by plate counting and by measuring bioluminescence from S. mutans- containing the insect luciferase gene. Colostral whey protein preparation from hyperimmunised cows activated human leucocytes by opsonising specific bacteria. Neutrophils, eosinophils and monocytes weakly phagocytosed non-opsonised bacteria and bacteria opsonised with control product. On the contrary, binding and ingestion were efficient in the presence of the preparation from immunised cows. Thus, these results show that bovine colostral whey proteins are able to support the activation of human phagocytes against pathogenic microbes and that this property is related to specific antibodies in whey preparations. These whey proteins may also be clinically useful, especially in preventing the colonisation of newly erupted teeth by mutans streptococci.
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Induction of secretion of interleukin-8 from human gastric epithelial cells by heat-shock protein 60 homologue of Helicobacter pylori
SummaryEscherichia coli cells expressing fusion proteins consisting of β-galactosidase and bacterial heat-shock protein (HSP) 60 of E. coli, Yersinia enterocolitica or Helicobacter pylori were constructed, and designated as HY1, HY2 or HY3, respectively. Fusion proteins prepared from HY2 and HY3 induced secretion of interleukin-8 (IL-8) from human gastric epithelial KATO III cell cultures. On the other hand, the parent strain (E. coli pop2136), PEX (pop2136 transformed by vector) and fusion protein prepared from HY1 did not induce IL-8 secretion from KATO III cells. Other human gastric (MKN45) and non-gastric cell lines (Int 407 and A549) did not secrete IL-8 following treatment with these proteins. These results indicate that H. pylori HSP60 induces IL-8 secretion from human gastric cells and the levels of IL-8 differ among the various gastric cell lines, suggesting that HSP60 might be an important virulence factor associated with chronic gastric inflammation following H. pylori infection in man.
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Growth inhibition of multiresistant enterococci by interferon-γ-activated human uro-epithelial cells
SummaryNosocomial infections with enterococci are an increasing problem in modern medical practice due to the development of resistance to a wide range of antibiotics, including the glycopeptides vancomycin and teicoplanin. An increasing number of vancomycin-resistant enterococci (VRE) have been cultured from clinical specimens - especially from patients undergoing immunosuppressive therapy - and bacteraemia caused by these VRE, subsequent to colonisation of epithelial surfaces, is a significant cause of mortality in such patients. Recent evidence showed that the induction of indoleamine 2,3 dioxygenase (IDO) by interferon-γ (IFN-γ) inhibited growth of group B streptococci by depleting the essential amino acid L-tryptophan. This study describes the IFN-γ-induced expression of IDO - shown at a transcriptional level by Northern blot analysis, at translational level by Western blot and also at a functional level by L-tryptophan degradation to L-kynurenine - in the uro-epithelial cell line RT4. The depletion of L-tryptophan resulted in growth inhibition of enterococci, and this was confirmed by abrogation of the inhibitory effect by re-supplementation with excess L-tryptophan. Multiresistant enterococci, including vancomycin-resistant strains resistant to all commercially available antibiotics, were inhibited by the IFN-γ-induced expression of IDO and subsequent L-tryptophan degradation. This may be an important mechanism in the local restriction of colonisation of the urinary tract by endogenous enterococci and in inhibiting the spread of the bacteria beyond the epithelial barrier.
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Upper respiratory tract infection, heterologous immunisation and meningococcal disease
More LessSummaryTo test the hypothesis that an episode of upper respiratory tract infection or heterologous immunisation is a predisposing factor for the occurrence of meningococcal disease, data from 377 cases of meningococcal disease and their household contacts (n = 1124) were analysed by conditional logistic regression analysis with stratification for household. The odds ratio for a recent upper respiratory tract infection for patients versus household contacts, adjusted for age and the presence of an underlying predisposing disease, was 2.8 and that for recent heterologous immunisation 1.0. These results support previous observations regarding the association between a preceding upper respiratory tract infection and the occurrence of meningococcal disease; however, no association was found between preceding heterologous immunisation and meningococcal disease. Therefore, increased alertness after heterologous immunisation does not seem warranted.
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- Molecular Diagnosis And Epidemiology
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An improved method for detecting faecal Vibrio cholerae by PCR of the toxin A gene
SummaryA method for removing inhibitor(s) of the PCR assay for the direct detection of cholera toxin A gene (ctxA) in human faeces is described. Inhibitors of the PCR were removed by centrifugation and the activity of the remaining inhibitors by dilution. Based on these data, a protocol was developed for pre-treatment of stool specimens for PCR assay, and a simple and rapid protocol was constructed for the diagnostic detection of the ctxA genes in stool specimens in combination with single band detection on gel electrophoresis, dot-blot hybridisation and enrichment culture. This protocol was applied to clinical specimens and showed that the PCR method gave 100% agreement with established culture methods for the detection of cholera toxin-producing Vibrio cholerae O1. This protocol was considered to be useful because of its simplicity and the rapidity of diagnosis.
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Molecular characterisation of verocytotoxin-producing Escherichia coli of serogroup O111 from different countries
SummaryA collection of epidemiologically unrelated verocytotoxin (VT)-producing Escherichia coli (VTEC) strains of serogroup O111 isolated from human patients and cattle with diarrhoeal disease in five different countries were characterised by determination of their VT genotypes, the presence of other virulence factors such as the intimin-coding eae gene and the enterohaemorrhagic E. coli (EHEC) plasmid, and their antibiotic susceptibility patterns. The genetic relatedness among isolates was evaluated by genomic DNA fingerprinting techniques such as restriction fragment length polymorphism analysis of ribosomal RNA genes (ribotyping) and pulsed-field gel electrophoresis. The results indicated that the VTEC O111 examined belong to two distinct clonal lineages. The first group was constituted mainly of non-motile, eae-positive, EHEC plasmid-positive isolates from both man and cattle. The second lineage was represented by an 0111:H2 epidemic strain, isolated during an outbreak of haemolytic uraemic syndrome in France and exhibiting an unusual combination of virulence factors: VT production and aggregative adhesion to HEp-2 cells associated with an enteroaggregative E. coli (EAEC) plasmid.
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Oropharyngeal samples for genotyping and monitoring response to treatment in AIDS patients with Pneumocystis carinii pneumonia
More LessSummaryA nested PCR, amplifying a portion of the gene encoding the mitochondrial large subunit ribosomal RNA (mt LSU rRNA) of Pneumocystis carinii sp. f. hominis was applied to oropharyngeal samples obtained on repeated occasions from 12 HIV-infected patients with P. carinii pneumonia (PCP) to monitor response to anti-P. carinii treatment. Genotyping of P. carinii sp. f. hominis was also performed on paired samples of oropharyngeal and broncho-alveolar lavage samples before the start of treatment, and on oropharyngeal samples during the course of treatment, by analysis of sequence variation at the internal transcribed spacer (ITS) regions of the nuclear rRNA operon. When a simple dilutional method was used, a reduction in the amount of amplification product was observed in samples from all patients during the course of treatment. In eight of the 12 patients, a single ITS sequence type was found in the oropharyngeal samples and also in the paired broncho-alveolar lavage sample. A mixed infection was identified in the samples from three patients. In eight patients, the ITS sequence types identified in the oropharyngeal sample were the same as in the broncho-alveolar lavage sample. Nested PCR amplifying the mt LSU rRNA on oropharyngeal samples provides a non-invasive method of monitoring response to treatment of PCP. ITS sequence typing of P. carinii sp. f. hominis from oropharyngeal samples appears to be a reliable alternative to broncho-alveolar lavage samples and provides a non-invasive tool for further epidemiological studies.
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- Mycology
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Comparison of four methods for DNA typing of clinical isolates of Candida glabrata
SummaryA series of 35 isolates of Candida glabrata from 29 subjects (five AIDS patients and 24 HIV-seronegative individuals) was typed by electrophoretic karyotyping (EK), restriction fragment length polymorphism (RFLP) analysis, random amplification of polymorphic DNA (RAPD) and inter-repeat PCR (IR-PCR). The rank order of discriminatory ability among the four methods was as follows: EK (25 DNA types) > RAPD (19 DNA types) > IR-PCR (14 DNA types) > RFLP (4 DNA types). A composite DNA type was defined for each of the strains as the combination of types obtained by the four molecular methods. A total of 32 DNA types was obtained by this procedure; each individual harboured their own specific isolate (DNA type). Neither source of isolation nor HIV status was associated with a given DNA type. In three of five cases, initial and relapse isolates from individual patients were assigned to the same DNA type. These findings indicate that EK is the most useful method for the investigation of inter-strain variations within this Candida species.
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- Virology
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Functional antibody response to human cytomegalovirus in immunocompetent and HIV-1 infected individuals with antibodies that inhibit virus penetration into cells and intercellular transmission of viral infection
More LessSummaryAntibodies mediating post-attachment virus neutralisation (PN), inhibition of human cytomegalovirus (HCMV)-induced cell fusion in the glioblastoma cell line U373 (IF) and global neutralising activity (NA) were quantified in sera from healthy immunocompetent individuals, asymptomatic HIV-1-infected subjects and AIDS patients to further characterise the neutralising antibody response to HCMV in these population groups and to assess whether HIV-1-infected individuals exhibited an abnormal functional antibody profile. PN and IF antibodies accounted for a minor fraction of the NA activity of sera from all population groups. Sera from HIV-1-infected individuals (particularly AIDS patients) displayed higher levels of PN and IF antibodies than those from the healthy control group; however, the relative contribution of these antibodies to the global serum NA activity appeared to be lower in the former individuals than in immunocompetent controls. Serum antibodies preventing HCMV cell-to-cell spread (IP) were then measured to determine whether a specific deficiency could be detected in the HIV-1-infected group population. Serum IP antibody titres were significantly higher in HIV-1-infected individuals (particularly in AIDS patients) than in controls. The potential implications of the data for explaining the pathogenesis of HCMV infection are discussed.
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- Book Reviews
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Volumes and issues
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Volume 73 (2024)
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