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Biomedical subjects

N Banatvala

Publications and source records attributed to N Banatvala.

At least 37 records · Page 2Linked to original sources
PubMed1996

Shiga-like toxin-producing Escherichia coli O111 and associated hemolytic-uremic syndrome: a family outbreak.

OBJECTIVE: To describe a family cluster of Shiga toxin-producing Escherichia coli O111ac:NM infection. STUDY DESIGN: The index case was identified as part of a United States prospective study of hemolytic-uremic syndrome. Epidemiologic investigation was conducted through interviews. E. coli O111:NM infection was characterized through culture and serology. Shiga toxin 1 and 2 gene sequences were determined with oligonucleotide DNA probes. RESULTS: All three children and both parents had nonbloody diarrhea, vomiting and abdominal cramps, and one child developed hemolytic-uremic syndrome. Shiga toxin 1- and 2-producing E. coli O111ac:NM was isolated from two children. IgG antibodies to E. coli O111 were detected in all three children. CONCLUSIONS: To our knowledge this is the first reported cluster of O111 infection and only the second caused by non-O157 Shiga toxin-producing E. coli in North America.

Bacterial Toxins↗
PubMed1995

Migration and Helicobacter pylori seroprevalence: Bangladeshi migrants in the U.K.

Helicobacter pylori, an infectious agent of worldwide public health importance, has higher seroprevalence in developing countries than in developed countries. We investigated whether Bangladeshi women, born in Bangladesh, have a greater H. pylori seroprevalence than Bangladeshi women born in the U.K. and, in addition, whether there is an association between H. pylori seropositivity and age of migration to the U.K. amongst Bangladeshi women. Women attending antenatal clinics at the Royal London Hospital were screened using ELISA for anti-H. pylori IgG. In Bangladeshi individuals born in the U.K., 13/16 (81%, 95% confidence interval (CI) 54%-96%) and, in Bangladeshi individuals born in Bangladesh 91/137 (66%, 95% CI 59%-74%) had antibodies to H. pylori. No significant association was found between H. pylori seropositivity and country of birth, or age at migration to the U.K. Public health strategies concerning H. pylori should consider migrant populations with high seroprevalence of H. pylori.

Adolescent↗
PubMed1995

Helicobacter pylori infection in dentists--a case-control study.

To test the null hypothesis that frequent and multiple salivary exposure is not a risk factor for developing H. pylori infection, serum anti-H. pylori IgG from 179 dentists and dental students and 179 age-, sex- and socioeconomic-matched controls were assayed using an ELISA. Seroprevalence in dentists was 16% (11/70); clinical dental students 6% (3/47); and pre-clinical dental students 10% (6/62). There were no differences in H. pylori seropositivity between cases and controls. There was an increase in H. pylori seropositivity with age (chi (trend)2 9.04, p = 0.003). These data provide evidence that adults are not at high risk of developing H. pylori infection as a result of exposures to saliva from multiple sources.

Adolescent↗
PubMed1994

The frequency of culturing stools from adults with diarrhoea in Great Britain.

Utilizing the Office of Population Censuses and Surveys (OPCS) Omnibus Survey, it was possible to measure the frequency with which a stool culture was obtained following episodes of diarrhoea in adults. Interviewing over 8000 adults, over a 4-month period between October 1992 and January 1993, 633 persons (7.9%) reported one episode of diarrhoea in the previous month, and 5.4% of these individuals with diarrhoea reported that a stool had been requested for examination. No significant regional differences were observed with the sample size available. The estimate of the rate of diarrhoea in adults was just under one episode per person per year.

Adolescent↗
PubMed1994

Conservation of the cytotoxin-associated (cagA) gene of Helicobacter pylori and investigation of association with vacuolating-cytotoxin activity and gastroduodenal disease.

Polymerase chain reaction (PCR) amplification and DNA hybridization analyses were used to test for the presence of the cytotoxin-associated (cagA) gene in 108 strains of Helicobacter pylori. Fifty-two geographically diverse strains of known vacuolating cytotoxin activity, and 56 recent UK clinical isolates from patients with duodenal ulceration (n = 28) and from healthy individuals who were endoscopically normal (n = 28) were studied. Overall, cagA was detected by PCR in 74 (69%) strains and DNA hybridization provided evidence of gene homologues in a further eight strains. For 96% of the cytotoxin-producing strains and 46% of the non-cytotoxin producing strains, there was a close association either with presence or absence of cagA. At the genomic level, Southern blot DNA hybridization showed that cagA was probably present in a single copy in most of the H. pylori tested, and that HaeIII restriction site variation within and around the gene provided additional markers of diversity for the species. As 40% of the cagA containing strains did not produce an active cytotoxin, and no significant association between cagA presence and DU-disease was observed, we concluded that the presence of the cagA gene in H. pylori could not be used as a single reliable predictor of higher risk patients.

Antigens, Bacterial↗
PubMed1994

Hypogammaglobulinaemia associated with normal or increased IgM (the hyper IgM syndrome): a case series review.

The clinical and immunological aspects of 16 children with the syndrome of hypogammaglobulinaemia associated with normal or increased IgM (the hyper IgM syndrome) and their responses to treatment are reviewed. Increased concentrations of IgM, neutropenia, and recurrent infections could usually be controlled by antimicrobial and intravenous immunoglobulin treatment. Together with the bacterial infections characteristic of hypogammaglobulinaemia, these patients often developed opportunistic infections, including Pneumocystis carinii pneumonia, often presenting in the first year of life. The occurrence of sclerosing cholangitis, neurological complications, and neutropenia may be a result of an underlying cell mediated immune deficiency, autoimmunity, or infection. Despite a high incidence of opportunistic infections, immunological investigations did not show any abnormality of T cell function. These findings are discussed in the light of the recent demonstration that the lack of expression of a T lymphocyte activation antigen is the molecular basis of the X linked form of the disorder.

Agammaglobulinemia↗
PubMed1994

High prevalence of Helicobacter pylori metronidazole resistance in migrants to east London: relation with previous nitroimidazole exposure and gastroduodenal disease.

A high prevalence of metronidazole resistance in Helicobacter pylori is reported in developing countries. This study examined whether migrants referred for diagnostic gastroscopy at a United Kingdom centre (n = 54), had a higher prevalence of metronidazole resistance than subjects born in the United Kingdom attending endoscopy (n = 46). Records of nitroimidazole treatment prescribed in the United Kingdom was obtained in 83 patients to find out if there was an association between H pylori metronidazole resistance and previous ingestion of either metronidazole or tinidazole. The prevalence of metronidazole resistant isolates varied according to country of birth: Bangladesh (90%, 27 of 30), other countries (67%, 16 of 24), and United Kingdom (37%, 17 of 46) (p < 0.001). Among those born in the United Kingdom, women were more likely to harbour resistant H pylori than men (54% v 18% respectively, p = 0.01) and more likely to have a history of previous nitroimidazole ingestion (41% v 11% respectively, p = 0.02). Patients previously exposed to either metronidazole or tinidazole were more likely to harbour resistant strains (84% (27 of 32) v 41% (21 or 51), p < 0.0001). The distribution of gastroduodenal disease, assessed endoscopically, was not affected by metronidazole resistance status.

Adult↗
PubMed1994

Helicobacter pylori stimulates antral mucosal reactive oxygen metabolite production in vivo.

To determine if reactive oxygen metabolites have a pathogenic role in Helicobacter pylori (H pylori) related gastroduodenal disease, this study measured their production in antral mucosal biopsy specimens. Two related chemiluminescence techniques were used comparing H pylori positive (n = 105) and negative patients (n = 64) with a similar spectrum of macroscopic disease. After chemiluminescence assays, biopsy specimens were graded histologically. Increased luminol dependent chemiluminescence (detecting reactive oxygen metabolites through peroxidase catalysed reactions) was found in H pylori positive patients (median photon emission = 6.4 x 10(3)/min/mg wet weight (95% confidence intervals 3.6 to 9.9)) but not H pylori negative cases (-0.9 (-1.3 to -0.6)) (p = 0.0001). Similar results were found using lucigenin (which reacts directly with oxygen metabolites, particularly superoxide): (H pylori positive 0.9 (0.1 to 3.2); H pylori negative -1.2 (-3.4 to -0.6)) (p = 0.0003). Chemiluminescence was greater in H pylori positive compared with negative tissue when samples were grouped by equivalent macroscopic or microscopic damage. This difference was in part accounted for by a greater neutrophil infiltration in the H pylori positive mucosa, but when biopsy specimens with equivalent neutrophil infiltration could be compared directly, positive specimens gave greater chemiluminescence than negative. Smoking, drugs, and alcohol consumption had no independent effect. It is concluded that excess mucosal reactive oxygen metabolite production is associated with H pylori gastric antral infection and may be an important pathogenic mechanism. There is no evidence for reactive oxygen metabolite participation in the pathogenesis of gastric mucosal injury in cases unrelated to H pylori infection.

Antioxidants↗
PubMed1994

Relationship between infective load of Helicobacter pylori and reactive oxygen metabolite production in antral mucosa.

Helicobacter pylori infection has been associated with stimulation of gastric mucosal reactive oxygen metabolite production. To provide further evidence of a causal relationship we looked for a dose-response relationship. We studied antral biopsy material from 110 patients. Quantitative H. pylori assessments were made using histologic and microbiologic methods. Reactive oxygen metabolite production was measured by luminol-dependent chemiluminescence. The usefulness of timed urease test colour changes as a guide to infective load was assessed. There was a positive association between mucosal reactive oxygen metabolite production and histologic (p = 0.002, n = 69) and microbiologic (Spearman's R = +0.6, p = 0.05, n = 18) quantitative H. pylori assessments. H. pylori infective load varied markedly over small areas (coefficient of repeatability of paired cultures (in colony-forming units/mg) = 1.9 x 10(6). Urease test timing correlated with histologic (p = 0.01) and microbiologic (p = 0.03) H. pylori quantitation. Histologically assessed mucosal damage was related to quantitative H. pylori assessment and to mucosal reactive oxygen metabolite production (p = 0.0001). These results support the hypothesis that H. pylori stimulates gastric mucosal reactive oxygen metabolite production and that this phenomenon is of pathogenic importance.

Adolescent↗
PubMed1993

The epidemiology of Helicobacter pylori: missing pieces in a jigsaw.

Gastric colonisation with Helicobacter pylori is common throughout the world. Although most infected individuals remain well, H. pylori is involved in the pathogenesis of type B gastritis and peptic ulcer disease. There is also an epidemiological association with gastric cancer. Person-to-person spread is the most likely form of transmission but it is not clear whether this is faecal-oral or oral-oral. The risk factors for developing disease following infection are poorly understood. The development of diagnostic techniques suited to epidemiological studies, as well as microbiological typing methods, should help to resolve these uncertainties.

Adolescent↗
PubMed1993

Comparison of urease gene primer sequences for PCR-based amplification assays in identifying the gastric pathogen Helicobacter pylori.

Different genomic DNA samples and primer sequences were evaluated in urease (ure) gene-based PCR assays for rapid identification of Helicobacter pylori. Purified DNA and heated (boiled) cell lysates of bacterial cultures from gastric biopsies were tested with three primer sets for unique internal ureA, ureA+B and ureC sequences. The heated-lysates of H. pylori were quick to prepare but more frequently gave unexpected variable or negative PCR results than assays performed on purified DNA, which were highly specific and reproducible for all three primer sets. Results indicated that sensitivity of the assay was linked to the size of the amplified target region rather than any particular strain feature, with the small 294 bp ureC product providing more accurate assays with heated-lysates of H. pylori. We strongly recommend that negative results in any PCR assay should be checked on purified DNA to exclude the possibility of a false-negative result.

Bacterial Proteins↗
PubMed1993

The cohort effect and Helicobacter pylori.

A total of 631 serum samples collected in 1969, 1979, and 1989 from adults and children were screened for Helicobacter pylori by Western blot analysis. Results showed that H. pylori seroprevalence has become less frequent over the 20-year period. By studying seropositivity by year of birth, the magnitude of a cohort effect of H. pylori seropositivity was estimated. The odds of being seropositive decreased by 26% per decade, P = .008 (95% confidence interval, 8%-41%). Estimates of seroprevalence adjusted for both age-specific variation and the cohort effect suggest that most seropositivity in adults occurs by the age of 15 years. The implication of these findings is that H. pylori infection is becoming less frequent and is predominantly acquired in childhood.

Adolescent↗
PubMed1990

Secretor status, smoking and carriage of Neisseria meningitidis.

A survey of ABO blood groups, secretor status and smoking habits among 389 students and staff of a school in which there was an outbreak of meningococcal disease found no difference in the distribution of the ABO blood groups but a significantly higher proportion of non-secretors (37.6%) in the population examined compared with that reported for previous surveys of the neighbouring population in Glasgow (26.2%) (P less than 0.0005). There was also a significantly higher proportion of non-secretors among carriers of meningococci (47%) compared with non-carriers (32%). Increased carriage of meningococci among non-secretors might contribute to the increased susceptibility of individuals with this genetic characteristic to meningococcal disease observed in previous studies. Although passive exposure to cigarette smoke has been associated with meningococcal disease, there was no association between passive smoking and carriage. There was, however, a significant association between active smoking and carriage.

ABO Blood-Group System↗