Innate immunity – the hallmark of Helicobacter pylori infection in pediatric chronic gastritis

The Most Recent Insights into the Roots of Gastric Cancer

Helicobacter pylori (H. pylori) is the most common bacterial infection worldwide, usually being acquired during childhood, and its persistence into adulthood represents one of the main contributors of gastric carcinogenesis. Based on these statements, it would be of great importance to know if the most early premalignant transformation occurs in children or later since, this would enable the development of effective anti-tumorigenesis strategies. The interplay between H. pylori virulence factors, the host's responses modified by this infection, and the gastric microecology are complex and eventually lead to the development of gastric cancer in susceptible individuals. Several biomarkers were identified as major contributors of this long-lasting process, such as pepsinogens, gastrin 17, lipid-, glucose- and iron-metabolism parameters, immunity players, aberrant bacterial DNA methylation, H. pylori virulence factors, and hallmarks of gastric dysbiosis. Several of these biomarkers were also identified in children with H. pylori infection, independently of the presence of premalignant lesions, which were also proven to be present in a subgroup of H. pylori-infected children, especially those carrying extremely virulent strains. Therefore, the most incipient premalignant gastric changes might indeed occur early during childhood, opening a promising research gate for further studies to delineate the border between infection and cancer.

Current Worldwide Trends in Pediatric Helicobacter pylori Antimicrobial Resistance

Helicobacter pylori (H. pylori) has acquired several resistance mechanisms in order to escape the currently used eradication regimens such as mutations that impair the replication, recombination, and transcription of DNA; the antibiotics capability to interact with protein synthesis and ribosomal activity; the adequate redox state of bacterial cells; or the penicillin-binding proteins. The aim of this review was to identify the differences in pediatric H. pylori antimicrobial-resistance trends between continents and countries of the same continent. In Asian pediatric patients, the greatest antimicrobial resistance was found to metronidazole (>50%), probably due to its wide use for parasitic infections. Aside from the increased resistance to metronidazole, the reports from different Asian countries indicated also high resistance rates to clarithromycin, suggesting that ciprofloxacin-based eradication therapy and bismuth-based quadruple therapy might be optimal choices for the eradication of H. pylori in Asian pediatric population. The scarce evidence for America revealed that H. pylori strains display an increased resistance to clarithromycin (up to 79.6%), but not all studies agreed on this statement. Pediatric patients from Africa also presented the greatest resistance rate to metronidazole (91%), but the results in terms of amoxicillin remain contradictory. Nevertheless, the lowest resistance rates in most of the African studies were found for quinolones. Among European children, the most frequent antimicrobial resistance was also noticed for metronidazole and clarithromycin (up to 59% and 45%) but with a predominance for clarithromycin as compared to other continents. The differences in antibiotic use among continents and countries worldwide is clearly responsible for the discrepancies regarding H. pylori antimicrobial-resistance patterns, emphasizing the crucial role of global judicious antibiotic use in order to control the increasing resistance rates worldwide.

Worldwide Prevalence and Risk Factors of Helicobacter pylori Infection in Children

Helicobacter pylori is usually acquired during childhood. The reports from the last two decades pointed out a decrease in H. pylori prevalence across geographical areas worldwide compared to previously reported data. Most of the studies performed in America found an overall H. pylori infection prevalence of approximately 50%. The most important risk factors in America include being male, poor adherence or difficult access to treatment, and the lack of in-home water service. Despite the descending trend in prevalence worldwide, the overall prevalence in Africa remains very high (70%). Nevertheless, the prevalence of H. pylori in children without gastrointestinal who underwent screening was reported to be only 14.2%. The main risk factors in Africa are having a traditional pit or no toilet, poverty, birth order, source of drinking water, or being a farmer. Asia seems to have the widest variations in terms of H. pylori prevalence. Several risk factors were reported in Asia to be associated with this infection, such as lower income and educational level, house crowding, rural residence, ethnicity, the use of tanks as water supplies, alcohol drinking, active smoking, eating spicy food or raw uncooked vegetables, poor living conditions and sanitation. The overall prevalence of H. pylori infection in European children is almost 25%. Portugal has the highest prevalence of all European countries at 66.2% in children 13 years of age. The risk factors in European individuals consist of living in rural areas, eating unwashed fruits and vegetables, not washing hands after school, low parental education and unemployment, and short education duration. Further studies are required to identify the precise mechanisms involved in the discrepancies of H. pylori prevalence worldwide.

Helicobacter pylori-Related Extraintestinal Manifestations—Myth or Reality

It is well documented that Helicobacter pylori (H. pylori) can cause both gastrointestinal and extraintestinal manifestations. The latter one represents a major burden in terms of diagnosis and treatment. H. pylori-associated systemic subclinical inflammation is mostly responsible for the development of extraintestinal manifestations, and its early eradication might result in preventing all adverse events related to their occurrence. Thus, it was suggested that H. pylori might be associated with iron deficiency anemia, thrombocytopenia (immune thrombocytopenic purpura), Schonlein Henoch purpura, failure to thrive, vitamin B12 deficiency, diabetes mellitus, body mass index, cardiovascular diseases, as well as certain neurological conditions. Nevertheless, studies showed both pros and cons in terms of the role of H. pylori in the development of previously mentioned clinical entity underlining the crucial need for further studies on these topics. Although most of these extraintestinal manifestations occur during adulthood, we must not forget that H. pylori infection is acquired mainly during childhood, and thus its early diagnosis and eradication might represent the cornerstone in the prevention of H. pylori-induced inflammatory status and consequently of all related extraintestinal conditions.

Old and New Aspects of H. pylori-Associated Inflammation and Gastric Cancer

H. pylori is involved in the development of 80% of gastric cancers and 5.5% of all malignant conditions worldwide. Its persistence within the host’s stomach causes chronic inflammation, which is a well-known hallmark of carcinogenesis. A wide range of cytokines was reported to be involved in the initiation and long-term persistence of this local and systemic inflammation. IL-8 was among the first cytokines described to be increased in patients with H. pylori infection. Although, this cytokine was initially identified to exert a chemoattracting effect that represents a trigger for the activation of inflammatory cells within H.-pylori-infected mucosa, more recent studies failed in encountering any association between IL-8 and H. pylori infection. IL-6 is a multifunctional, pleiotropic and multipotent cytokine involved in mediating the interaction between innate and adaptive immunity with a dichotomous role acting as both a proinflammatory and an anti-inflammatory cytokine depending on the signaling pathway. IL-1α functions as a promoter of angiogenesis and vascular endothelial cell proliferation in gastric carcinoma since it is closely related to H.-pylori-induced inflammation in children. IL-1β is an essential trigger and enhancer of inflammation. The association between a low IL-1β level and an increased TNF-α level might be considered a risk factor for peptic ulcer disease in the setting of H. pylori infection. IL-10 downregulates both cytotoxic inflammatory responses and cell-mediated immune responses. H. pylori uses the immunosuppressive role of IL-10 to favor its escape from the host’s immune system. TGFβ is a continuous inflammatory mediator that promotes the adherence of H. pylori to the host’s cells and their subsequent colonization. The role of H.-pylori-induced inflammatory responses in the onset of gastric carcinogenesis seems to represent the missing puzzle piece for designing effective preventive and therapeutic strategies in patients with H.-pylori-associated gastric cancer.

The Challenges of Eradicating Pediatric Helicobacter pylori Infection in the Era of Probiotics

Helicobacter pylori (H. pylori), the most common infection of childhood, results in life-threatening complications during adulthood if left untreated. Most of these complications are related to H. pylori-induced chronic inflammation. The dysbiosis caused by H. pylori is not limited to the gastric microenvironment, but it affects the entire gastrointestinal tract. Eradication of H. pylori has recently become a real challenge for clinicians due to both the persistent increase in antibiotic resistance worldwide and the wide spectrum of side effects associated with the eradication regimens resulting; therefore, there is an urgent need for more effective and less noxious treatment options. Thus, probiotics might be a promising choice in both adults and children with H. pylori infection since their role in improving the eradication rate of this infection has been proved in multiple studies. The positive effects of probiotics might be explained by their abilities to produce antimicrobial compounds and antioxidants, alter local gastric pH, and subsequently decrease H. pylori colonization and adherence to gastric epithelial cells. Nevertheless, if used alone probiotics do not considerably increase the eradication rate.