Population genetic analyses of Helicobacter pylori isolates from Gambian adults and children.

The gastric pathogen Helicobacter pylori is one of the most genetically diverse of bacterial species. Much of its diversity stems from frequent mutation and recombination, preferential transmission within families and local communities, and selection during persistent gastric mucosal infection. MLST of seven housekeeping genes had identified multiple distinct H. pylori populations, including three from Africa: hpNEAfrica, hpAfrica1 and hpAfrica2, which consists of three subpopulations (hspWAfrica, hspCAfrica and hspSAfrica). Most detailed H. pylori population analyses have used strains from non-African countries, despite Africa's high importance in the emergence and evolution of humans and their pathogens. Our concatenated sequences from seven H. pylori housekeeping genes from 44 Gambian patients (MLST) identified 42 distinct sequence types (or haplotypes), and no clustering with age or disease. STRUCTURE analysis of the sequence data indicated that Gambian H. pylori strains belong to the hspWAfrica subpopulation of hpAfrica1, in accord with Gambia's West African location. Despite Gambia's history of invasion and colonisation by Europeans and North Africans during the last millennium, no traces of Ancestral Europe1 (AE1) population carried by those people were found. Instead, admixture of 17% from Ancestral Europe2 (AE2) was detected in Gambian strains; this population predominates in Nilo-Saharan speakers of North-East Africa, and might have been derived from admixture of hpNEAfrica strains these people carried when they migrated across the Sahara during the Holocene humid period 6,000-9,000 years ago. Alternatively, shared AE2 ancestry might have resulted from shared ancestral polymorphisms already present in the common ancestor of sister populations hpAfrica1 and hpNEAfrica.

Deprivation, timing of preschool infections and H. pylori seropositivity at age 49-51 years: the Newcastle Thousand Families birth cohort.

BACKGROUND: Helicobacter pylori infection is acquired in early childhood and persists for life (or until eradication treatment is taken). Seropositivity of H. pylori at age 49-51 years was assessed in relation to socio-economic deprivation in early life and the timing of other childhood infections common at that time. METHODS: Prospectively collected socio-economic and morbidity data from the Newcastle Thousand Families study, a birth cohort established in 1947. H. pylori IgG seropositivity was assessed at 49-51 years and examined in relation to both whether the individual had been diagnosed with one of measles, mumps or chicken pox, and, if so, the age at first infection. This was done in logistic regression models, allowing adjustment for socio-economic status and housing quality in childhood. RESULTS: Adult H. pylori status was strongly linked to disadvantaged socio-economic status in early life (p ≤ 0.002), unlike measles, mumps and chicken pox which showed no associations. Early measles infection was independently associated with H. pylori seropositivity (p = 0.01). CONCLUSIONS: Of the four infectious diseases that we have studied, it appears that H. pylori differs from the others by the strength of association with socio economic deprivation in early childhood. Our findings further highlight the complex interaction between measles, childhood infections and other non-microbiological factors that occur within a whole population. These data suggest a strong association between H. pylori and deprivation and raise the possibility of an interaction between early measles exposure and increased risk of exposure to H. pylori infection.

Childhood infectious disease and premature death from cancer: a prospective cohort study.

Studies of the association between early life infections and cancer have produced inconsistent findings, possibly due to limited adjustment for confounding and retrospective designs. This study utilised data from the Newcastle Thousand Families Study, a prospective cohort of 1,142 individuals born in Newcastle-upon-Tyne in 1947, to assess the impact of various childhood infectious diseases on cancer mortality during ages 15-60 years. Detailed information was collected prospectively on a number of early life factors. Deaths from cancer during ages 15-60 years were analysed in relation to childhood infections, adjusting for potential early-life confounders, using Cox proportional-hazards regression. In a subsample who returned questionnaires at aged 49-51 years, additional adjustment was made for adult factors to predict death from cancer during ages 50-60 years. Childhood history of measles and influenza, were both independently associated with lower cancer mortality during ages 15-60 years (adjusted hazard ratios = 0.39, 95% CI 0.17-0.88 and 0.49, 95% CI 0.24-0.98 respectively). In contrast, childhood pertussis was associated with higher cancer mortality during ages 15-60 years (adjusted hazard ratio = 4.88, 95% CI 2.29-10.38). In the subsample with additional adjustment for adult variables, measles and pertussis remained significantly associated with cancer mortality during ages 50-60 years. In this pre-vaccination cohort, childhood infection with measles and influenza were associated with a reduced risk of death from cancer in adulthood, while pertussis was associated with an increased risk. While these results suggest some disease-specific associations between early-life infections and cancer, further studies are required to confirm the specific associations identified.

Antimicrobial susceptibility and resistance patterns among Helicobacter pylori strains from The Gambia, West Africa.

Helicobacter pylori is a globally important and genetically diverse gastric pathogen that infects most people in developing countries. Eradication efforts are complicated by antibiotic resistance, which varies in frequency geographically. There are very few data on resistance in African strains. Sixty-four Gambian H. pylori strains were tested for antibiotic susceptibility. The role of rdxA in metronidazole (Mtz) susceptibility was tested by DNA transformation and sequencing; RdxA protein variants were interpreted in terms of RdxA structure. Forty-four strains (69%) were resistant to at least 8 µg of Mtz/ml. All six strains from infants, but only 24% of strains from adults, were sensitive (P = 0.0031). Representative Mtz-resistant (Mtz(r)) strains were rendered Mtz susceptible (Mtz(s)) by transformation with a functional rdxA gene; conversely, Mtz(s) strains were rendered Mtz(r) by rdxA inactivation. Many mutations were found by Gambian H. pylori rdxA sequencing; mutations that probably inactivated rdxA in Mtz(r) strains were identified and explained using RdxA protein's structure. All of the strains were sensitive to clarithromycin and erythromycin. Amoxicillin and tetracycline resistance was rare. Sequence analysis indicated that most tetracycline resistance, when found, was not due to 16S rRNA gene mutations. These data suggest caution in the use of Mtz-based therapies in The Gambia. The increasing use of macrolides against respiratory infections in The Gambia calls for continued antibiotic susceptibility monitoring. The rich variety of rdxA mutations that we found will be useful in further structure-function studies of RdxA, the enzyme responsible for Mtz susceptibility in this important pathogen.

Mixed infection with cagA positive and cagA negative strains of Helicobacter pylori lowers disease burden in The Gambia.

BACKGROUND: The prevalence of Helicobacter pylori including strains with putatively virulent genotypes is high, whereas the H. pylori-associated disease burden is low, in Africa compared to developed countries. In this study, we investigated the prevalence of virulence-related H. pylori genotypes and their association with gastroduodenal diseases in The Gambia. METHODS AND FINDINGS: DNA extracted from biopsies and H. pylori cultures from 169 subjects with abdominal pain, dyspepsia or other gastroduodenal diseases were tested by PCR for H. pylori. The H. pylori positive samples were further tested for the cagA oncogene and vacA toxin gene. One hundred and twenty one subjects (71.6%) were H. pylori positive. The cagA gene and more toxigenic s1 and m1 alleles of the vacA gene were found in 61.2%, 76.9% and 45.5% respectively of Gambian patients harbouring H. pylori. There was a high prevalence of cagA positive strains in patients with overt gastric diseases than those with non-ulcerative dyspepsia (NUD) (p = 0.05); however, mixed infection by cagA positive and cagA negative strains was more common in patients with NUD compared to patients with gastric disease (24.5% versus 0%; p = 0.002). CONCLUSION: This study shows that the prevalence of H. pylori is high in dyspeptic patients in The Gambia and that many strains are of the putatively more virulent cagA+, vacAs1 and vacAm1 genotypes. This study has also shown significantly lower disease burden in Gambians infected with a mixture of cag-positive and cag-negative strains, relative to those containing only cag-positive or only cag-negative strains, which suggests that harbouring both cag-positive and cag-negative strains is protective.

PCR-based genotyping of Helicobacter pylori of Gambian children and adults directly from biopsy specimens and bacterial cultures.

BACKGROUND: Helicobacter pylori is an important agent of gastroduodenal disease in Africa and throughout the world. We sought to determine an optimum method for genotyping H. pylori strains from children and adults in The Gambia, West Africa. RESULTS: Virulence genes were amplified in 127 of 190 cases tested (121 adults and 6 children); each of 60 bacterial cultures, and 116 from DNA extracted directly from biopsies. The proportion of biopsies that were cagA+, the ratio of vacAs1/s2, and vacAm1/m2, and the proportion of mixed strain populations in individual subjects changed with age. Strains lacking virulence cagA and vacA genes and with apparently homogeneous (one predominant strain) infections were more common among infants than adults. CONCLUSIONS: In order to detect the range of bacterial genotypes harbored by individual patients, direct PCR proved slightly superior to isolation of H. pylori by biopsy culture, but the techniques were complementary, and the combination of both culture and direct PCR produced the most complete picture. The seemingly higher virulence of strains from adult than infant infections in The Gambia merits further analysis.

High-energy and -protein diet increases brain and corticospinal tract growth in term and preterm infants after perinatal brain injury.

OBJECTIVE: Our hypothesis was that infants with perinatal brain injury fail to thrive in the first postnatal year because of increased energy and protein requirements from deficits that accumulated during neonatal intensive care. Our aim was to assess whether dietary energy and protein input was a rate-limiting factor in brain and body growth in the first year after birth. METHODS: We conducted a prospective, double-blind and randomized, 2-stage group sequential study and controlled for gestation, gender, and brain lesion. Neonates with perinatal brain damage were randomly allocated to receive either a high- (120% recommended average intake) or average (100% recommended average intake) energy and protein diet. The study began at term and continued for 12 months. Three-day dietary diaries estimated energy and protein intake. The primary outcome measure was growth of occipitofrontal circumference. Other measures were growth of axonal diameters in the corticospinal tract, which were estimated by using transcranial magnetic stimulation, weight gain, and length. RESULTS: The study was terminated at the first analysis when the 16 subjects had completed the protocol, because the predetermined stopping criterion of >1 SD difference in occipitofrontal circumference at 12 months' corrected age in those receiving the higher-energy and -protein diet had been demonstrated. Axonal diameters in the corticospinal tract, length, and weight were also significantly increased. CONCLUSIONS: These data support our hypothesis that infants with significant perinatal brain damage have increased nutritional requirements in the first postnatal year and suggest that decreased postnatal brain growth may exacerbate their impairment. There are no measures of cognitive ability at 12 months of age, and whether there will be any improvement in the status of these children, therefore, remains to be shown.

Evaluation of 13C-urea breath test and fecal antigen immunoassay to detect Helicobacter pylori infection in Gambian infants.

Helicobacter pylori colonization was measured by [13C]-urea breath test in 198 Gambian infants and by fecal enzyme-linked immunosorbent assay in 52 of the 198 at ages 2, 5, and 12 months. By 12 months there was good concordance between tests; 33 of 44 (75%) test results were positive by enzyme-linked immunosorbent assay, and 29 of 44 (66%) test results were positive by urea breath test. H. pylori colonization is common among Gambian infants, and noninvasive tests can provide a reliable means of diagnosis.

Does increased duration of exclusive breastfeeding protect against Helicobacter pylori Infection? The Newcastle Thousand Families Cohort Study at age 49-51 years.

OBJECTIVE: Helicobacter pylori acquired in childhood is an important risk factor for gastric carcinoma. Once colonization is established, infection may be carried for life. This study used prospectively recorded, detailed information on infant feeding and investigated the potential link between duration of exclusive breastfeeding in infancy and seropositivity at age 50 years, as measured by enzyme-linked immunosorbent assay. METHODS: H. pylori seropositivity at age 50 years was investigated among 407 individuals born in Newcastle in May and June 1947 and related to the duration of exclusive breastfeeding after adjusting for measures of socioeconomic status and adverse housing conditions at birth. RESULTS: Duration of exclusive breastfeeding in infancy was significantly associated with H. pylori seropositivity (odds ratio per 30 days, 0.88; 95% confidence interval, 0.78 to 0.98). The significant protective trend was only seen among men (odds ratio per 30 days, 0.78; 95% confidence interval, 0.65 to 0.95), with no significant effect seen among women. CONCLUSION: Increased duration of exclusive breastfeeding in infancy may have a long-term protective effect against chronic H. pylori infection and hence the risk of gastric carcinoma. Although further research is required, particularly as to why a significant effect was only seen among men, the results provide additional support for the concept that breastfeeding may have long-term influences on health and that human milk is the ideal complete first diet for human infants.

Tooth loss and Helicobacter pylori seropositivity: the Newcastle Thousand Families Cohort Study at age 49-51 years.

BACKGROUND: Helicobacter pylori, one of the commonest chronic bacterial infections of humankind, is an important risk factor for gastric carcinoma. It has also been suggested to be present in dental plaque. This study investigated the potential link between the number of teeth lost and H. pylori seropositivity at age 50 years. METHODS: H. pylori seropositivity at age 50 years was investigated among 334 individuals born in Newcastle upon Tyne, United Kingdom, in May and June 1947 and related to the number of teeth lost, after adjusting for socioeconomic status. RESULTS: The unadjusted risk of being seropositive for H. pylori increased with increasing number of teeth lost (odds ratio per tooth 1.03, 95% confidence interval 1.01-1.06, p = .019). However, after adjustment for socioeconomic status at birth and at age 50 years, the relationship was no longer significant (p = .36). CONCLUSIONS: Our results, obtained using prospectively collected data, suggest that any relationship between poor oral health and seropositivity to H. pylori may be due to both tooth loss and H. pylori colonization being associated with socioeconomic status and related factors.

Novel 180- and 480-base-pair insertions in African and African-American strains of Helicobacter pylori.

Helicobacter pylori is a genetically diverse bacterial species that chronically infects human stomachs and sometimes causes severe gastroduodenal disease. Studies of polymorphic DNA sequences can suggest geographic origins of individual strains. Here, we describe a 180-bp insertion (ins180), which is just after the translation stop of a gene of unknown function, near the promoter of jhp0152-jhp0151 two-component signal transduction genes in strain J99, and absent from this site in strain 26695. This ins180 insertion was found in 9 of 9 Gambian (West African), 9 of 20 (45%) South African, and 9 of 40 (23%) Spanish strains but in only 2 of 20 (10%) North American strains and none of 20 Lithuanian, 20 Indian, and 20 Japanese strains. Four South African isolates that lacked ins180 and that belonged to an unusual outlier group contained a 480-bp insertion at this site (ins480), whereas none of 181 other strains screened contained ins480. In further tests 56% (10 of 18) of strains from African Americans but only 17% (3 of 18) of strains from Caucasian Americans carried ins180 (P < 0.05). Thus, the H. pylori strains of modern African Americans seem to retain traces of African roots, despite the multiple generations since their ancestors were taken from West Africa. Fragmentary ins180-like sequences were found at numerous sites in H. pylori genomes, always between genes. Such sequences might affect regulation of transcription and could facilitate genome rearrangement by homologous recombination. Apparent differences between African-American and Caucasian-American H. pylori gene pools may bear on our understanding of H. pylori transmission and disease outcome.

Specific immunoglobulin A antibodies in maternal milk and delayed Helicobacter pylori colonization in Gambian infants.

BACKGROUND: Immunoglobulin A (IgA) in maternal milk may protect Gambian infants from early Helicobacter pylori colonization. This study sought evidence that this protection could be due to specific IgA antibodies. METHODS: Sixty-five infants were screened from 12 weeks of age with [13C]-urea breath tests. Antibodies in maternal milk were measured to determine total IgA content and to detect specific IgA antibodies against crude whole-cell and recombinant H. pylori urease antigen preparations. RESULTS: Ten children (15%) had no evidence of early H. pylori colonization, 10 (15%) had early H. pylori colonization, and 43 (66%) had mixed results. Levels of maternal circulating specific immunoglobulin G, total milk IgA, and IgA directed against crude whole-cell H. pylori antigen preparation were not significantly associated with the rate of infant H. pylori colonization. However, mothers of infants with no evidence of early colonization produced significantly higher levels of anti-recombinant urease IgA antibodies in milk than did control mothers, particularly at 8, 16, and 20 weeks postpartum (P<.01). CONCLUSIONS: These observations support the hypothesis that antibodies in mother's milk directed against H. pylori urease can protect against colonization in human infancy.

IgG subclass responses in childhood Helicobacter pylori duodenal ulcer: evidence of T-helper cell type 2 responses.

BACKGROUND: Duodenal ulcer in adults chronically infected with Helicobacter pylori is associated with a polarized T-helper cell type 1 (Th1) mucosal immune response, with a predominantly immunoglobulin G2 (IgG2) systemic specific response. It has been suggested that children colonized by H. pylori also produce a mucosal Th1 response, but there are few studies that have measured IgG subclass responses in children with duodenal ulcer. MATERIALS AND METHODS: Seven children with endoscopically proven duodenal ulcer and H. pylori infection and 18 children with biopsy proven H. pylori infection but no duodenal ulcer had relative concentrations of IgG subclass responses (IgGsc) against H. pylori antigens measured by ELISA. Eighteen IgG seropositive adults acted as controls. The range of antigens recognised by IgG1 and IgG2 subclass responses were investigated by Western blots. RESULTS: There were no differences in mean IgGsc responses between children with or without duodenal ulcer. Adults produced an IgG2 predominant response. Western blots showed no qualitative differences in antigens recognised by IgG1 or IgG2. CONCLUSION: Children with duodenal ulcer, in contrast to adults, produce an IgGsc response consistent with a mucosal Th2 response to H. pylori regardless of the presence of duodenal ulceration. This suggests that disease causation amongst children with H. pylori associated duodenal ulceration may not be dependant upon a mucosal Th1 biased response.

Placental acquisition of maternal specific IgG and Helicobacter pylori colonization in infancy.

BACKGROUND: Colonization with Helicobacter pylori generally occurs in infancy, and the microorganism is often acquired from close family members. Rate of infant colonization may be affected by maternal immune status. METHODS: To investigate the potential protective effect of anti-H. pylori immunoglobulin G (IgG) acquired via the placenta, 65 mothers and their infants were studied from the infant's birth for 1 year. Circulating IgG antibodies were measured by enzyme-linked immunosorbent assay (ELISA) in cord blood and every 8 weeks. Immunoblotting was performed on sera from infants with significant increases in IgG levels. Rate of infant H. pylori colonization was measured by 13C urea breath tests every 4 weeks from the age of 12 weeks. RESULTS: Maternal and infant cord blood specific IgG levels were correlated (R2 =.747, p <.001). Infant H. pylori specific IgG fell 5-fold compared to maternal levels over the first 6 months of life, and rose subsequently in many cases, with the development of novel immunoblot patterns. There were no significant associations between the age at first positive urea breath test and maternal or infant cord specific H. pylori IgG levels. CONCLUSIONS: Transplacentally acquired specific IgG antibody does not protect infants from colonization by H. pylori.

Current practice in the management of children with cerebral palsy: a national survey of paediatric dietitians.

BACKGROUND: Dietitians play a key role in the clinical management of children with cerebral palsy. This survey was conducted with the aim of establishing an overview of current dietetic practice in the management of these children. METHOD: A questionnaire which asked for information on aspects of dietetic practice relating to children with cerebral palsy was circulated to members of the British Dietetic Association during May to October 2000. RESULTS: Many respondents had a small caseload size. However, a larger caseload was linked to membership of a multi-disciplinary team, a greater proportion of severely disabled children and use of a wider range of anthropometric measurements. Dietitians who were members of a multi-disciplinary team were more likely to visit children at home. CONCLUSIONS: This survey provides an overview of current dietetic practice in the UK regarding the management of children with cerebral palsy. There is a potential shortfall in specialist dietitians and this survey highlights some of the gaps in service provision. Children with cerebral palsy benefit from dietetic input and there is an increasing need for specialist dietitians to be involved in their management. It will be necessary to continue to identify any gaps and find ways to overcome them.