Preface

Despite novel human pathogens emerging worldwide, such as COVID-19, which is responsible for the severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2) development, *Helicobacter pylori* remains one of the principal human infections. *H. pylori* is a condition with a relative risk of developing various clinical disorders of the upper gastrointestinal tract, such as chronic gastritis, peptic ulcer disease, mucosa-associated lymphoid tissue (MALT lymphoma), and gastric adenocarcinoma.

The infection has also been associated with the development of some extradigestive diseases, such as hepatobiliary, cardiovascular and pancreatic diseases, and iron deficiency anemia, among others.

All individuals with *H. pylori* infection have histological gastritis, which corresponds to classical chronic gastritis and is characterized by the infiltration of neutrophils and other inflammatory cells. However, most patients are asymptomatic for life, while only some will come to develop a digestive disease. Studies have been demonstrating that different disease developments are probably due to the bacterial pathogenicity and due to the host susceptibility factors that include the role of bacterial genetic diversity in host colonization and persistence, outer membrane proteins, and modulation of adhesin expression and virulence factors (VacA, CagA, and BabA, among others).

The routes of transmission of *H. pylori* are not completely clarified, but infection is usually acquired during childhood and is characterized as being chronic, with greater prevalence in developing countries in all ages. Guides for the management of *H. pylori* have been developed in various countries in order to identify which cases are indicated to eradicate the bacterium. Therefore, various guidelines for the management of *H. pylori* infection are available. Nevertheless, there are discussions concerning the eradication treatment in asymptomatic individuals that receive a positive diagnosis for *H. pylori* in routine examinations.

Various aspects of this important microorganism are explored in this book, which is divided into two sections: the first one "*Helicobacter pylori* - A Very Old Human Microorganism" with two chapters and the second one, with chapters concerning the diseases associated with *H. pylori* infection and their new approaches.

Dr. Maldonado describes the bacterium in important aspects, considering that the interaction of the strain's characteristics, the host's characteristics, and the environment is responsible for several diseases that can be developed due to this infection, which affects more than half of the world population.

Prof. Cheng An-Lii attempts to provide evidence that early-stage gastric diffuse large B-cell lymphoma with (DLBCL[MALT]) and without ("pure" DLBCL) histological features of MALT origin is closely related to *H. pylori* infection.

Dr. Zhenguo reports and discusses the relationship between *H. pylori* infection and extradigestive diseases, especially cardiovascular diseases, like hypertension, and

atherosclerosis. He also reports the possible interactions between this infection and endothelial dysfunction and the role of exosomes in mediating the effect of the microorganism's presence on the endothelial function.

Dr. Rendón-Huerta discusses the principal mechanisms by which *H. pylori* is able to disrupt the tight junctions and invade the gastric epithelial mucosa.

Dr. Vasilievna attempts to study and analyze the MALT gastric lymphomas and the chapter is divided into two principal sections: the morphological aspects of the diagnosis of MALT gastric lymphomas and the clinical aspects of MALT gastric lymphomas.

Dr. Mascellino reports the principal virulence factors that have been studied in this important microorganism, which has accompanied human physiology in its complex migration history. Besides, the genotypic resistance related to phenotypes, antibiotics, and updated treatment strategies are also described and discussed.

Dr. Oti attempts to evaluate and study the antibody *H. pylori* seromarkers in students from Nasarawa State University, Nasarawa State, Nigeria.

Finally, the editor expresses her sincere thanks for the excellent work of the contributing authors. It was really a real challenge to prepare our book in the midst of a pandemic situation that hit humanity as a whole! The editor thanks Ms. Sara Debeuc, Author Service Manager at IntechOpen, for her excellent work and help in all aspects. In addition, the editor is especially thankful for the essential support given by Ms. Lucija Tomicic-Dromgool during the book's development, as well as the entire IntechOpen publishing team. It was a great pleasure working with you again!

> **Dr. Bruna Maria Roesler** State University of Campinas, Brazil
