Helicobacter pylori Infection and Risk Factors in Relation to Allergy in Children

Helicobacter pylori Infection Does Not Protect Against Allergic Diseases: Evidence From a Pediatric Cohort From Northern Sardinia, Italy

BACKGROUND

The "hygiene hypothesis" states that reduced exposure to microbial antigens due to an excessively hygienic environment can increase the risk of developing autoimmune diseases, including atopic disorders and asthma. In recent decades, there has been a progressive decline in the prevalence of numerous microorganisms following improved hygienic-sanitary conditions. More specifically, several studies reported an inverse association between the reduction in Helicobacter pylori infection and the rise of asthma and allergic disorders.

AIM

To evaluate the prevalence of atopic disorders in a pediatric population in relation to seropositivity against H. pylori.

METHODS

Children from Northern Sardinia, Italy, referred to the local Children's Hospital for any reason, were investigated to identify risk factors, especially H. pylori infection, associated with atopic disorders. A validated questionnaire, including demographics, house size, history of breastfeeding, residence, school or daycare center attendance, exposure to animals, and a defined diagnosis of atopy-including asthma-was filled out by a trained pediatrician according to parents' answers and child records. A blood sample was collected from each participant and immunoglobulin G against H. pylori was assessed by a locally validated ELISA test.

RESULTS

The seroprevalence of H. pylori infection was 11.7% among 492 children (240 females). Thirty-two children had a confirmed diagnosis of asthma and 12 of allergy. No one child showed both conditions. Statistically significant differences in H. pylori seropositivity were not detected between children with or without atopy (8.4% vs. 12.6; p = 0.233). Although atopic disorders were more frequent in children exposed to traditional atopic risk factors, none of them showed to be significant after adjusting for all covariates.

CONCLUSIONS

Serologically assessed H. pylori infection was not significantly associated with a reduced risk of atopic diseases in children.

Population- and Gender-Based Investigation for Prevalence of Helicobacter pylori in Dhamar, Yemen

Among 35 species of genus Helicobacter, H. pylori is the most common causative agent of human gastritis, peptic ulcer, and gastric cancer. The infection can spread through direct human-to-human contact, fecal-oral route, and contaminated water. The study was designed to investigate the rate of prevalence of H. pylori in the population of Dhamar, Yemen. In this one-year study, 460 including 250 male and 210 female stool specimens were collected between January to December 2020 in Dhamar Governorate, Yemen. Of the total 460, 215 rural (male: n = 120 and female: n = 95) and 245 urban (male: n = 130 and female: n = 115) specimens were investigated for identification of H. pylori by serological test using Helicobacter pylori stool antigen (HpSA) test. In addition, for comparing an improved recovery of H. pylori, conventional culture-based isolation was also carried out using three selective media. Modified Campy-blood Agar (MCA), Belo Horizonte Agar (BHA), and Egg yolk Emulsion (EYE) medium supplemented with antimicrobial agents including vancomycin (10 mg/L), cefsulodin (5 mg/L), trimethoprim (5 mg/L), and amphotericin B (5 mg/L) and isolates were phenotypically characterized. The HpSA test results revealed that of the total 460 specimens, 89 (19.3%) were positive for H. pylori with relatively low in male (n = 43; 17.2%) as compared to the female (n = 46; 21.9%) specimens. After 3-10 days of incubation, H. pylori was recovered at a variable rate on each selective (MCA: 16.5%; BHA: 15.0%; EYE: 13.0%) media. However, culture-based assay results showed less recovery (n = 81; 17.6%) with no significant difference among all selective media tested and between genders (male: n = 39; 15.6%; female: n = 42; 20.0%). The infection rate was comparatively higher in rural (n = 45; 20.9%) as compared to urban (n = 36; 14.7%) population. Overall, the study data showed the prevalence of infection in both genders of all age groups. The present study showed a relatively high rate of infection of H. pylori in the Dhamar population. The serological identification and culture-based methods are important for rapid detection, aid in treatment, and developing policies for the control and eradication of H. pylori infection and to prevent the disease in different age groups in Yemen.

Helicobacter pylori Infection in Children and Adolescents

About one-third of all children worldwide is infected with H. pylori and its prevalence is low in developed and high in developing countries. H. pylori is mainly acquired during childhood and transmission of the bacterium commonly proceeds from person to person, especially among family members. The most frequent transmission route is from the mother to children. Various gastrointestinal and extra-gastrointestinal diseases are reported to be associated with H. pylori in children and adolescents, but the strongest recommendation for testing and treating is introduced only with children and adolescents having peptic ulcer disease. Iron deficiency anemia and chronic immune thrombocytopenic purpura are also considered for testing and treating, but the effectiveness is somewhat controversial. Invasive diagnosis is recommended, whereas none of the available diagnostic tests have 100% accuracy for reliable diagnosis, and therefore at least two or more tests should be performed. Urea breath test is the most reliable among the non-invasive tests. Because the number of antibiotics-resistant H. pylori strains is increasing, it is desirable to conduct a drug susceptibility test before treatment and to select the corresponding regime. H. pylori has been proven to be a major cause of gastric cancer and 'screen-and-treat' strategies are recommended in communities at high risk of gastric cancer. However, the application to children and adolescents is controversial. An effective vaccine is desirable, but not yet available. Screen-and-treat for adolescents has started in a few areas in Japan, where conditions are well established. New prevention strategies for gastric cancer are awaited worldwide.

Helicobacter pylori and some aspects of gut microbiota in children

Helicobacter pylori infection in children differs from infection in adults in many aspects. The rate of infection, epidemiology, clinical presentations and complications, the applicability of diagnostic tests, antibiotic resistance, treatment options, and success rates differ significantly. Due to all these differences, management guidelines for children and adults differ also substantially. In 2017, the Updated ESPGHAN and NASPGHAN Guidelines on the management of H. pylori infection in children were published, emphasizing the differences in clinical presentation and indications for treatment, stating that the primary goal of clinical investigation in children is to identify the cause of upper gastrointestinal symptoms rather than the presence of H. pylori infection. Therefore, the diagnosis should be based on upper endoscopy, and the "test and treat strategy" should not be used in children. Due to an increasing rate of antibiotic resistance worldwide, the updated guidelines recommend broader use of antimicrobial susceptibility testing for H. pylori strains in order to tailor eradication treatment accordingly. Moreover, treatment in children should be prescribed only when indicated and should be based on the rate of eradication in local populations aiming for treatment success above 90%. During the last two decades there has been a steady decrease in the rate of H. pylori infection in both children and adults in the Western world. Two recent publications studying the incidence of H. pylori infection confirmed that early childhood is a time for acquisition of infection both in industrialized and nonindustrialized countries. In addition, they showed that H. pylori could be acquired outside the family. In respect to the inverse association between H. pylori and allergy, a longitudinal study demonstrated that early exposure to H. pylori at any age was inversely associated with atopy and allergic conditions.