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Volume 51,
Issue 4,
2002
Volume 51, Issue 4, 2002
- Editorial
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- Diagnostic Microbiology
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Gastric mucosal density of Helicobacter pylori estimated by real-time PCR compared with results of urea breath test and histological grading
The accuracy of the urea breath test (UBT) and histological grading for estimation of the density of Helicobacter pylori in gastric mucosa is not known. Real-time (TaqMan) PCR was used to estimate the total number of H. pylori genomes in biopsy samples. These values were compared with those obtained by the UBT and the histological grade obtained by the Sydney system. The UBT and endoscopy with antral and corporal biopsies were performed in 88 consecutive untreated patients with dyspepsia. Bacterial culture and the rapid urease test were done with fresh biopsy materials. TaqMan PCR and histological examination were done on serial paraffin sections of the biopsy samples. Of the five methods tested, TaqMan PCR had the highest sensitivity and specificity (both 100%) in the diagnosis of H. pylori infection. The mean density of H. pylori genomes for pairs of biopsy samples from individual patients was compared with the individual values obtained by the UBT; correlation between the results was significant. The density of H. pylori genomes was higher in histological grades 1, 2 and 3 than in grade 0, without significant differences between adjacent grades from 1 to 3. These results suggest that the severity of H. pylori infection of the stomach can be estimated by the UBT and that histopathologists might state whether the organism is present or absent, rather than making a quantitative statement as recommended in the Sydney system.
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- Antimicrobial Agents
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Mixed species biofilms of Candida albicans and Staphylococcus epidermidis
More LessA simple catheter disk model system was used to study the development in vitro of mixed species biofilms of Candida albicans and Staphylococcus epidermidis, two organisms commonly found in catheter-associated infections. Two strains of S. epidermidis were used: a slime-producing wild type (strain RP62A) and a slime-negative mutant (strain M7). In mixed fungal-bacterial biofilms, both staphylococcal strains showed extensive interactions with C. albicans. The susceptibility of 48-h biofilms to fluconazole, vancomycin and mixtures of the drugs was determined colorimetrically. The results indicated that the extracellular polymer produced by S. epidermidis RP62A could inhibit fluconazole penetration in mixed fungal-bacterial biofilms. Conversely, the presence of C. albicans in a biofilm appeared to protect the slime-negative staphylococcus against vancomycin. Overall, the findings suggest that fungal cells can modulate the action of antibiotics, and that bacteria can affect antifungal activity in mixed fungal-bacterial biofilms.
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- Epidemiology
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Prevalence of Helicobacter pylori at oral and gastrointestinal sites in children: evidence for possible oral-to-oral transmission
More LessAcquisition of Helicobacter pylori occurs mainly in childhood. However, the mode of transmission remains unclear. To help elucidate this, 100 children attending for upper gastrointestinal endoscopy were investigated for the presence of H. pylori at various sites. H. pylori was detected in antral gastric biopsies by the rapid urease test (13 patients), culture (13 patients), histology (15 patients) and PCR (20 patients). Gastric juice was positive for H. pylori in 3 patients by culture and 11 patients by PCR. The dental plaque from 68% of gastric biopsy-positive patients (as determined by culture or PCR) and 24% of gastric biopsy-negative patients was positive for H. pylori by PCR. The presence of H. pylori in dental plaque was significantly associated with the presence of this organism in the stomach. H. pylori was detected by PCR in the faeces of 25% of gastric biopsy-positive children sampled. H. pylori was not cultured on any occasion from the oral cavity or faeces. The evidence from this study suggests that oral-to-oral transmission may be a possible mode of spread of H. pylori in children.
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Genetic analysis of the outer surface protein C gene of Lyme disease spirochaetes (Borrelia burgdorferi sensu lato) isolated from rodents in Taiwan
More LessThe outer surface protein C gene (ospC) of Lyme disease spirochaetes (Borrelia burgdorferi sensu lato) was analysed for the first time in Taiwan. The genetic identities of these Taiwan isolates (TWKM1–7) were determined by restriction fragment length polymorphism (RFLP) analysis and sequence similarities of the PCR-amplified ospC gene amplicons. After cleavage by nuclease DraI, differential fragment patterns of PCR-amplified ospC DNA in relation to different genospecies of Lyme disease spirochaetes were observed and all of these Taiwan isolates were genetically affiliated to the genospecies of B. burgdorferi sensu stricto. The phylogenetic analysis on the sequence similarity of these Taiwan isolates revealed a highly homogeneous genotype, ranging from 99.3% to 100%, within the genospecies of B. burgdorferi sensu stricto and was distinguished from other genospecies of Borrelia isolates. The sequence similarity analysis also revealed the high sequence variability of the ospC gene among Borrelia strains that belong to the same genospecies but were isolated from different biological and geographical sources. Thus, these results provide the first investigation on the genetic identity of the ospC gene of these Taiwan isolates and show that these Taiwan isolates were closely related genetically to the genospecies of B. burgdorferi sensu stricto.
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Antibodies to granulocytic ehrlichiae in cattle from Connecticut
Enzyme-linked immunosorbent assays (ELISA) with a purified recombinant 44-kDa protein and indirect fluorescent antibody (IFA) staining methods incorporating whole-cell antigens of the human granulocytic ehrlichiosis (HGE) agent were used to detect antibodies to Ehrlichia phagocytophila genogroup organisms in cattle sera. The cattle lived in tick-infested areas of Connecticut, USA and were healthy at the times blood samples were collected in 1990, 1999 and 2000. Of the 339 serum samples analysed, 40 (12%) and 15 (4%) were positive by ELISA and IFA, respectively. Western immunoblots of a subset of sera verified antibody reactivity of six serum samples, positive by ELISA with titres of 640–2560, to a protein with a molecular mass of c. 44 kDa. Although seroprevalence rates were low, cattle were exposed to the HGE agent at different sites and should be monitored for anaemia, leukopenia or thrombocytopenia, especially if there is evidence of unexplained decreased milk production. Different serological testing methods should be used to detect immunoglobulins.
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Isolation and characterisation of Shiga toxigenic Escherichia coli strains from northern Palestine
K. ADWAN, N. ABU-HASAN, T. ESSAWI and M. BDIRShiga toxigenic Escherichia coli (STEC) isolates from symptomatic and asymptomatic patients in northern Palestine in 1999 were screened for serotype O157 and characterised for virulence genes by multiplex PCR assay. Of the 176 STEC isolates, 124 (70.5%) were of serotype O157. All these isolates carried the gene for Shiga toxin type 1 (stx 1) and 112 (90.3%) carried stx 2. The intimin encoding gene locus eae was detected in 16 isolates (12.9%) and the enterohaemolysin encoding gene, hlyA, in 18 (14.5%). Statistical analysis showed a significant association between the presence of eaeA and hlyA, either alone or combined with stx 1 and stx 2 genes in O157 isolates from symptomatic infection. ERIC-PCR analysis of DNA from 80 serotype O157 isolates revealed three major clonal populations.
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- Models Of Infection
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Experimental infection of germ-free mice with hyper-toxigenic enterohaemorrhagic Escherichia coli O157:H7, strain 6
A mouse enterohaemorrhagic Escherichia coli (EHEC) infection model was developed with a combination of germ-free (GF) mice and hyper-toxigenic EHEC (HT-EHEC) O157:H7 strain 6. The HT-EHEC strain 6 produced both Shiga-like toxin (SLT)-1 1.0 μg/ml and SLT-2 8.2 μg/ml in vitro. Eight-week-old germ-free mice were inoculated intragastrically with 5.0×107 cfu of HT-EHEC strain 6. All GF mice challenged with the HT-EHEC developed ruffled fur and convulsion of limbs or hindleg weakness within 3 days after the challenge, culminating in death within 5 days. The HT-EHEC colonised well at a level of 108−−109 cfu/g of faeces 5 days after the challenge. Both SLT-1 and SLT-2 were demonstrated in the faeces of the mice for 5 days after challenge. Histological examination of the colons of the infected mice showed congestion of the lamina propria mucosa, mild inflammatory cell infiltration and goblet cell depletion. In proximal tubules of the renal cortex, epithelial swelling with scattered necrotic cells was recognised. Endothelial swelling and mononuclear cell infiltration were also observed in the glomeruli. The brain showed acute neuronal necrosis in the cerebrum and slight loss of Purkinje cells in the cerebellum. Passive immunisation with anti-SLT antisera prolonged the life of the mice without any neural symptoms. Microscopically, all tissue specimens from the passively immunised mice were not remarkable. These results indicate that the infection of GF mice with HT-EHEC is a useful animal model to study the pathogenicity of SLT-producing E. coli and the toxins.
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- Microbial Pathogenicity
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Characterisation of monoclonal antibodies against haemagglutinin associated with Clostridium botulinum type C neurotoxin
Of 11 monoclonal antibodies (MAbs) prepared against the non-toxic component of type C Clostridium botulinum 16S toxin to clarify the function of the non-toxic component, seven recognised HA1, three recognised HA3b and one recognised HA2. Results of epitope mapping indicated that three of the seven anti-HA1 MAbs recognised the region between amino acid residues 121 and 140 and four recognised the three-dimensional structure of HA1. Three anti-HA3b MAbs recognised different regions between (approximately) amino acids 405–430, 180–270 and 275–297. The ability of these MAbs to interfere with binding of 16S toxin or non-toxic component, HA1 or HA3b to erythrocytes and to intestine tissue sections of guinea-pig was observed. MAbs against HA3b and HA2 did not inhibit 16S toxin binding to either erythrocytes or epithelial cells, whereas some MAbs against HA1 did inhibit binding. The seven anti-HA1 MAbs can be classified into four groups based on their binding inhibition activities. The anti-HA1 MAbs that inhibited the binding of 16S toxin to the epithelial cells also neutralised or reduced the oral toxicity in mice, indicating that HA may play an important role in the absorption of the 16S toxin from the small intestine.
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Interleukin-8 induction and adhesion of the coccoid form of Helicobacter pylori
To determine the pathological significance of the coccoid form of Helicobacter pylori, its adhesion to and induction of secretion of interleukin-8 (IL-8) by gastric epithelial (MKN45) cells were studied. By flow cytometry, the adhesion of the coccoid form to MKN45 cells was significantly lower than that of the helical form. The monoclonal antibody A20 recognising lipopolysaccharide of H. pylori inhibited the adhesion of the coccoid form to MKN45 cells as much as that of the helical form. There was significantly lower induction of IL-8 secretion by MKN45 cells exposed to the coccoid form (two of four strains) as compared with the helical form.
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Prevalence of serum antibodies to Helicobacter pylori VacA and CagA and gastric diseases in Chile
More LessThe objective of this study was to evaluate the prevalence of antibodies to Helicobacter pylori CagA and VacA proteins and correlate this prevalence with gastric diseases in colonised Chileans. The study was performed in 418 adults colonised with H. pylori: 316 with gastroduodenal pathology (152 duodenal ulcer, 14 gastric cancer and 150 gastritis patients) and 102 asymptomatic subjects. Serum IgG antibodies to H. pylori were determined by enzyme immunoassay (EIA). Antibodies to VacA and CagA proteins were detected by Western blotting. In a subgroup of the patients, the vacuolating activity was determined by HeLa cell assay and the CagA product was confirmed by PCR assay. IgG antibodies to both VacA and CagA proteins of H. pylori were found in 270 (85%) of 316 colonised gastric patients and in 72 (71%) of 102 asymptomatic subjects. Colonisation with virulent strains was significantly higher among duodenal ulcer and gastric cancer patients than in gastritis patients or asymptomatic subjects. Infections with VacA+/CagA+ H. pylori strains is common in Chile but, in contrast to some Asian countries, this phenotype was more prevalent in isolates from patients with more severe gastric pathologies.
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- Virology
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Protective immunity against lethal HSV-1 challenge in mice by nucleic acid-based immunisation with herpes simplex virus type-1 genes specifying glycoproteins gB and gD
DNA-based vaccines were employed to assess protective immunity against herpes simplex virus in experimental infections of hairless (strain SKH1) and BALB/c mice. Mice were vaccinated with plasmids containing the herpes simplex virus type-1 (HSV-1) glycoprotein B (gB) or D (gD) genes under the human cytomegalovirus immediate-early promoter control. Vaccines were injected intramuscularly (i.m.) or intraperitoneally (i.p.) as purified DNA alone or as formulations supplemented with different non-ionic block copolymers. Antibody responses were assessed by immunofluorescence and radio-immunoprecipitation assays. Mice inoculated with either gB or gD plasmid, alone or with non-ionic block copolymers CRL 1029 and CRL 1190, produced high levels of antibodies specific for gB or gD. Three weeks after the last vaccination, mice were challenged with a clinical HSV-1 isolate (ABGK-1) by inoculation of a shaved and subsequently scarified area between the third and fourth lumbar vertebrae. Mice immunised with either gD or gB plasmid alone or mixed with copolymers were protected against lethal HSV-1 challenge when immunisation was performed via the i.m. route. Immunisations given via the i.p. route induced humoral responses in some mice and protected the animals against lethal HSV-1 challenge only when the formulations contained copolymers. The BALB/c mouse model was shown to be as good a model as the hairless mouse model.
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- Book Reviews
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Volumes and issues
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Volume 74 (2025)
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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 51 (2002)
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Volume 35 (1991)
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Volume 6 (1973)
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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)
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