Helicobacter pylori—Associated Dyspepsia in Paediatrics
Dyspepsia - Advances in Understanding and Management
Prevalence of infection H. pylori is one of the most common gastrointestinal bacterial infections among humans, affecting more than 50% of the world's population [1, 20] . Infection is usually acquired during the first years of life in both developing and industrialized countries, with intra-familial spread playing a central role in transmission of the infection [21, 22] . The prevalence of H. pylori is markedly variable between developing and developed countries, and even among individuals
... ong individuals living in the same country, varying according to ethnicity, place of birth and socioeconomic factors. Besides geographic area, age is also significantly and independently associated with an increase in H. pylori prevalence, a phenomenon known as birth cohort effect, which is a progressive reduction of the infection rate in successive birth cohorts, due to the improvements in general living conditions (reviewed in  ). In less developed countries the infection rate reaches almost 50% in very young children and more than 90% in adults, whereas in industrialized countries H. pylori infects 20-50% of adults and less than 10% of children, and has been declining over time [23, 24] . Indeed, the prevalence of H. pylori infection is showing a decreased trend worldwide that is directly associated with an improvement in the socioeconomic status and hygienic conditions of the populations. Accordingly, in Europe and North America, the epidemiology of H. pylori infection in children has changed in recent decades. Nowadays, low incidence rates are found in the northern and western European countries, resulting in prevalence far below 10% in children and adolescents. In contrast, the infection is still common in certain geographic areas such as southern or eastern Europe, Mexico, and certain immigrant populations from South America, Africa, most Asian countries, and first-nation (aboriginal) people in North America    . In Portugal with the worst scenario of Europe, the prevalence of H. pylori infection is closer to the situation observed in developing countries, reaching 80% among the adult population in their early nineties, and, more recently, varying from approximately 20% in young children (less than 5 years old) to 50% in children 10 to 15 years old [28, 29] . The absence of effective vaccines  and of efficient alternatives to antibiotics [31-34] renders difficult the worldwide prevention of H. pylori infection-associated diseases through massive eradication of the bacterium. The current antibiotic therapy against H. pylori infection fails in about 20% of the patients; depending on the therapeutic schema and strain resistance pattern, the failure rate may reach 70%. Antibiotic resistance, mainly to clarithromycin, is the major factor affecting the efficacy of standard triple therapy of H. pylori infection (co-administration of two antibiotics and a proton pump inhibitor or ranitidine bismuth for seven to ten days). In fact, the resistance rates to this and other second line antibiotics, such as the fluoroquinolones, are increasing in many geographical areas    . Several studies reveal a similar or higher resistance rate to clarithromycin among paediatric isolates as compared to those obtained from adults, especially in southern European countries, reflecting the recognized overuse of macrolides in children in these countries [31, 34, 37, 38] . As an example, Portugal displays one of the highest rates of H. pylori primary resistance to clarithromycin in Europe, similarly high in children as among adults (≈33%)  . Moreover, resistance to second line antibiotics has rapidly increased over the last decade and is a matter of concern [31-34]. This places the research on disease-specific bacterial biomarkers and their Dyspepsia -Advances in Understanding and Management Helicobacter pylori-Associated Dyspepsia in Paediatrics http://dx.