- Volume 49, Issue 4, 2000
Volume 49, Issue 4, 2000
- Short Article
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Identification and characterisation of Escherichia coli strains of O157 and non-O157 serogroups containing three distinct Shiga toxin genes
More LessThree Shiga toxin (Stx)-producing Escherichia coli (STEC) strains from patients with diarrhoea were identified, each of which contained three distinct stx genes (stx 1 , stx 2 and stx 2c ). The strains belonged to the serotypes O52:H19, O75:H− and O157:H− and harboured eae and EHEC-hly sequences. Colony-blot immunoassay was used to demonstrate that both major types of Stx were expressed. The association of stx genes with either phage or phage DNA was demonstrated in all three strains. Isolated phage DNA from all strains contained stx 1 sequences, but stx 2 sequences were found only in phage DNA of two of these strains. The presence of three distinct stx genes may enhance the virulence of STEC strains and should be monitored. The observations demonstrate not only the potential of stx genes to spread within different serotypes, but also their capacity to accumulate within a single strain.
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A method of decontaminating Strongyloides venezuelensis larvae for the study of strongyloidiasis in germ-free and conventional mice
To study the possible influence of intestinal micro-organisms on the course of strongyloidiasis in mice, a method was developed to obtain axenic infective larvae of Strongyloides venezuelensis. Cultured larvae from conventional mice were treated with sodium hypochlorite 0.25% for 10 min, washed in distilled water and then exposed to various combinations of antibiotics for 30 or 60 min. Success was achieved with a combination of penicillin 1805mumg/L and ceftazidime 15mumg/ml. Decontamination of the larvae was determined by aerobic and anaerobic culture and by inoculation into gnotobiotic mice. Viability was established by subcutaneous inoculation of larvae into germ-free and conventional mice. Preliminary results showed that gnotobiotic mice were more susceptible than conventional mice to infection with axenic S. venezuelensis larvae as judged by faecal egg excretion, recovery of worms in the small intestine and histopathological examination of the duodenal mucosa. These results suggest that the normal intestinal flora protects the host against experimental infection with S. venezuelensis.
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- Editorial
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- Review Article
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HLA molecules, bacteria and autoimmunity
A. EBRINGER and C. WILSONIt has been well established that many diseases are linked to HLA antigens. Two of the most interesting HLA associations may provide some insight into the pathogenesis of rheumatic inflammatory conditions. In ankylosing spondylitis (AS), 96% of patients possess HLA-B27, whilst the frequency of this marker in the general population is c. 8%. In rheumatoid arthritis (RA), >90% of patients possess either HLA-DR1 or some subtypes of HLA-DR4, whilst the frequency of this marker in the general population is c. 35%. The association between HLA-B27 and reactive arthritis (ReA) has also been well established. Furthermore, it has been shown that ReA is triggered by infection via the gastrointestinal tract due to Yersinia, Salmonella or Campylobacter spp. and in the genitourinary tract due to chlamydia. In a similar way, microbiological and immunological studies have revealed an association between Klebsiella pneumoniae in AS and Proteus mirabilis in RA. This article reviews the possible pathological implications of the associations between HLA-B27, K. pneumoniae and AS, as well as HLA-DR1/DR4, P. mirabilis and RA.
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- Clinical Microbiology
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Origins of Staphylococcus epidermidis and Streptococcus oralis causing bacteraemia in a bone marrow transplant patient
Coagulase-negative staphylococcal bacteraemia in immunocompromised patients is often associated with the use of central venous catheters, while the proposed origin of viridans streptococci causing bacteraemia in this patient group is the oral cavity. This report describes an episode of polymicrobial bacteraemia caused by Staphylococcus epidermidis and Streptococcus oralis followed by several further episodes of S. epidermidis bacteraemia in a 15-year-old boy after bone marrow transplantation. Pulsed-field gel electrophoresis (PFGE) of SmaI chromosomal DNA digests was used to compare blood culture and oral isolates of S. epidermidis and Str. oralis. The results indicated that the mouth was the source of both S. epidermidis and Str. oralis causing the first episode of bacteraemia. PFGE further demonstrated that the central venous catheter was the origin of a second strain of S. epidermidis responsible for subsequent episodes of staphylococcal bacteraemia. Both the oral mucosa and central venous lines should be considered as potential sources of organisms, including coagulase-negative staphylococci, associated with bacteraemia in immunocompromised patients.
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An outbreak of skin sepsis in abattoir workers caused by an ‘unusual’ strain of Streptococcus pyogenes
More LessAn outbreak of indolent skin infections due to an ‘unusual’ serological type of Streptococcus pyogenes that lasted for 3 months and affected eight workers in an abattoir is described. The group A streptococcal (GAS) isolates were serotyped as M-type 59; however, they possessed a T-protein pattern (T5/27/44) that is not commonly associated with M-type 59. Further genotypic characterisation studies revealed that all eight isolates were indistinguishable by pulsed-field gel electrophoresis (PFGE) and possessed the emm gene encoding for the M-type 59. Once identified, and after a combination of penicillin treatment, exclusion of workers with lesions and reinforcement of standard hygiene precautions, no further cases developed. Although common in the 1970s and 1980s, streptococcal infections in this situation are now reported infrequently. This report serves to highlight the issues surrounding working practices in abattoirs.
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- Correspondence
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- Bacterial Pathogenesis
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Enhancement of hepatocyte growth factor (scatter factor) production by human gingival fibroblasts in culture stimulated with Porphyromonas gingivalis fimbriae
More LessHepatocyte growth factor (HGF), also known as scatter factor (SF), is a motogen, mitogen and morphogen produced by mesenchymal cells that mainly acts on epithelial cells and is involved in osteoclast stimulation. This study examined the possible enhanced production of HGF/SF by human gingival fibroblasts upon stimulation with killed cells of Porphyromonas gingivalis strain 381 and its representative bioactive cellular components, fimbriae and lipopolysaccharide (LPS). P. gingivalis whole cells enhanced the production of HGF/SF detected by ELISA in culture supernates of the fibroblasts. Fimbriae prepared from P. gingivalis exhibited powerful HGF/SF-inducing activity in a concentration-dependent manner, with peak activity observed at 100–200 μg/ml. The fimbriae-induced HGF/SF mRNA expression by the cells was also detected by reverse transcription-PCR. P. gingivalis LPS exhibited weak HGF/SF-inducing activity. The study also examined the HGF/SF-inducing activity of seven synthetic peptides corresponding to the segments of P. gingivalis fimbrial subunit protein. The peptides of residues 282–301 and 302–321, which exhibited antagonistic effects against P. gingivalis fimbriae-binding to human gingival fibroblasts in a previous study, showed weak activity, whereas other non-antagonistic peptides showed no significant activity. These findings indicated that P. gingivalis fimbriae enhanced production of HGF/SF by human gingival fibroblasts, whereas synthetic peptide segments of fimbrial subunit protein were not sufficient to exert the activity.
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The role of fimbriae and flagella in the adherence of avian strains of Escherichia coli O78:K80 to tissue culture cells and tracheal and gut explants
More LessTo investigate the role of fimbriae and flagella in the pathogenesis of avian colibacillosis, isogenic insertionally inactivated mutant strains of Escherichia coli O78:K80 strain EC34195 defective in the elaboration of type-1 and curli fimbriae and flagella were constructed by allelic exchange. Single and multiple non-fimbriate and non-flagellate mutant strains were compared to the wild-type in vitro in adherence assays with a HEp-2 cell line, a mucus-secreting cell line HT2916E, a non-mucus-secreting cell line HT2919A, tracheal explant and proximal gut explant. Mutant strains defective in the elaboration of type-1 fimbriae were significantly less adherent – in the order of 90% reduction – than the wild-type strain in all assays. Mutant strains defective in the elaboration of flagella were generally as adherent as the wild-type strain except when assayed with the mucus-secreting cell line HT2916E, for which a significant reduction of adherence – of the order of 90% – compared with the wild-type strain was observed. Mutant strains defective for the elaboration of curli fimbriae adhered as well as the wild-type strain in all assays, except when assayed in tests with gut explant tissue for which a significant reduction of adherence – of the order of 80% – compared with the wild-type strain was observed. Adherence to explants was to epithelial, not serous, surfaces and was 10-fold greater to tracheal than to gut explants. Together, these data support the hypothesis that type-1 fimbriae are significant factors in adherence, aided by flagella for penetration of mucus and curli fimbriae for adherence to the gut.
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Regulation by protein kinase of phagocytosis of Mycobacterium leprae by macrophages
More LessMycobacterium leprae multiplies within host macrophages. The mechanism of internalisation of the bacteria by the phagocytic cells is unknown. In this study, M. leprae was purified from the foot pads of experimentally infected nu/nu mice. Peritoneal macrophages were harvested from BALB/c mice or C57 beige (bg/bg) mice. The effect of protein kinase inhibitors (erbstatin, genistein or staurosporine for BALB/c and bg/bg mice, plus herbimycin for bg/bg mice) on phagocytosis of the mycobacteria by the macrophage monolayers was tested. The untreated (control) macrophages phagocytosed M. leprae. Phagocytosis by BALB/c macrophages was inhibited by erbstatin and staurosporine but not by genistein; all the protein kinase inhibitors prevented uptake of M. leprae by bg/bg cells. The results demonstrate that protein kinase regulates phagocytosis of M. leprae by macrophages. The mechanism might prove to be a rational drug target for mycobacteria that multiply intracellularly.
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- Clinical And Molecular Epidemiology
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Quantitative culture of Helicobacter pylori from gastric juice: the potential for transmission
More LessThe transmission of Helicobacter pylori may occur by spread of organisms from gastric juice which has been introduced into the mouth by gastro-oesophageal reflux. The aim of this study was to quantify the load of H. pylori present in gastric juice available for transmission. Gastric antral biopsy and gastric juice samples were collected from 108 adult dyspeptic patients undergoing routine upper gastroscopy and the presence of H. pylori was determined. In all, 54 (50%) of 108 patients gave positive results in the gastric antral biopsy rapid urease test and for H. pylori histology. The gastric juice of 40 (37%) of patients gave positive results for the urease A gene by PCR assay; 34 (31%) of patients were positive by these three tests and H. pylori was cultured from the gastric juice of 13 (38%) of these patients. The median count of H. pylori in gastric juice was 1.75×101 cfu/ml. Viable organisms in gastric juice may lead to transmission of H. pylori when refluxed or vomited into the mouth.
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Characteristic distribution pattern of Helicobacter pylori in dental plaque and saliva detected with nested PCR
More LessThe precise mode of transmission and the natural reservoir for Helicobacter pylori are unknown. PCR assays have proved to be highly sensitive and specific and are regarded as the method of choice for detecting H. pylori DNA in the oral cavity. The aim of this study was to investigate the prevalence and distribution of H. pylori in the oral cavity. Forty-two patients undergoing gastroscopy were investigated for the presence of H. pylori in dental plaque and saliva by nested PCR, and in the stomach by the 13C-urea breath test. Samples tested comprised dental plaque from molars, premolars and incisors and saliva. Two sets of primers homologous to the 860-bp fragment of H. pylori DNA, which have been shown previously to be highly sensitive and specific, were used for nested PCR. Eleven patients (26.2%) were infected with H. pylori in the stomach. H. pylori DNA was identified in dental plaque samples from 41 patients (97%) and in 23 saliva samples (55%). The prevalence in dental plaque from molars, premolars and incisors was 82%, 64% and 59%, with an odds ratio of 3.18, 1.24 and 1 (reference), respectively. In conclusion, H. pylori was present in the oral cavity of 97% of tested patients, with a characteristic distribution that was independent of the infection status of the stomach. Thus H. pylori may belong to the normal oral microflora.
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Molecular analysis of Shigella sonnei isolated from three well-documented outbreaks in school children
Fifty-eight isolates of Shigella sonnei from three outbreaks in school children and eight control isolates from epidemiologically unrelated sporadic clinical infections in Taiwan were compared by antibiotic susceptibility testing and molecular typing. Antibiotic susceptibility testing showed that all strains except one sporadic isolate were multi-resistant. Ribotyping after restriction endonuclease digestion with SalI, PvuII and HindII generated the same ribosomal pattern in 65 of the 66 isolates. Plasmid profile analysis and pulsed-field gel electrophoresis (PFGE) produced eight and nine distinct patterns, respectively, and were in agreement with the epidemiological relationship of the outbreak strains. Nevertheless, some of the sporadic isolates could be discriminated only by a combination of these two methods. This study showed that plasmid profiling in combination with PFGE may be superior to ribotyping in molecular epidemiological investigations of S. sonnei.
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Clinical and microbiological epidemiology of Streptococcus pneumoniae bacteraemia
More LessA survey of Streptococcus pneumoniae bacteraemia in the Grampian region of Scotland was carried out over a 2-year period. One hundred and four bacteraemic episodes were identified in 103 patients, an incidence of 9.8/100 000 population/year, and the mortality was 24%. Clinical information was abstracted from 92 sets of patient notes and 98 isolates of S. pneumoniae were available for further study. The incidence of S. pneumoniae bacteraemia was highest at the extremes of age and peaked at 78 cases/100 000 population/year in those over 80 years old. Many patients had predisposing conditions, of which chronic lung disease (23%), chronic alcohol abuse (10%) and malignant disease (10%) were the commonest. Age was the highest risk factor for mortality, with 20 of the 22 deaths in those over 65 years old. The commonest serotype of S. pneumoniae isolated was serotype 14 (23.5%). Only one isolate (serotype 6A) showed intermediate resistance to penicillin, but 12 isolates (12.2%) were resistant to erythromycin. Nine of these 12 isolates were of serotype 14 and had MICs clustered in the range 12−−245mumg/L. Examination of all serotype 14 isolates by pulsed-field gel electrophoresis (PFGE) showed the presence of two distinct genetic clusters, with all the erythromycin-resistant isolates in the same cluster. These isolates had similar PFGE profiles to erythromycin-resistant serotype 14 strains isolated elsewhere in the UK and they were positive for the mefE gene by PCR, confirming that resistance was of the M phenotype. The recent increase in erythromycin resistance in S. pneumoniae may be due, at least in part, to the spread of a serotype 14 clone of the M phenotype which appears to be an important cause of invasive disease.
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- Mycology
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Multilocus enzyme electrophoresis analysis of Aspergillus fumigatus strains isolated from the first clinical sample from patients with invasive aspergillosis
The genotypes of 50 isolates of Aspergillus fumigatus from 11 patients with invasive aspergillosis, obtained from three hospitals in different geographical areas, were determined by multilocus enzyme electrophoresis (MLEE). The study analysed the genetic polymorphism of multiple isolates from the first sample. Seven of the 14 enzymic loci studied were polymorphic, giving rise to eight different electrophoretic types. For nine of 11 patients studied, no polymorphism was observed in isolates within the first clinical sample. Analysis of genetic distance between electrophoretic types demonstrated a genetic heterogeneity within each geographical site. Moreover, some genotypes were preferentially found in a given area and this revealed a population structure within these geographical sites. Therefore, the epidemiology of A. fumigatus should be considered separately for each of these areas. The multiple discriminatory markers of MLEE seem to provide a powerful tool for increasing the understanding of the biology of this fungus.
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- Virology
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Weak bases affect late stages of Mayaro virus replication cycle in vertebrate cells
More LessThis paper describes the effect of two weak bases (ammonium chloride and chloroquine) on the morphogenesis of Mayaro virus. When Mayaro virus-infected TC7 (monkey kidney) cells were treated with these agents it was observed that weak bases caused a significant reduction in virus yield. Also, cellular protein synthesis, which is inhibited by Mayaro virus infection, recovered to nearly normal levels. However, the synthesis of Mayaro virus proteins was affected. These phenomena were dose-dependent. The process of Mayaro virus infection in vertebrate cells is very rapid. Virus precursors are not observed in cell cytoplasm and budding through the plasma membrane seems to be the only way of virus release. Electron microscopy of cells infected with Mayaro virus and treated with weak bases revealed an accumulation of virus structures in cell cytoplasm. The study also noted an inhibition of budding through the plasma membrane and the appearance of virus particles inside intracytoplasmic vacuoles. These observations indicate an impairment at the final stages of the virus replication cycle.
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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 65 (2016)
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Volume 49 (2000)
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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 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)