Microbiomes are defined as complex microbial communities, which are mainly composed of bacteria, fungi, and viruses residing in diverse regions of the human body. The human stomach consists of a unique and heterogeneous habitat of microbial communities owing to its anatomical and functional characteristics, that allow the optimal growth of characteristic bacteria in this environment. Gastric dysbiosis, which is defined as compositional and functional alterations of the gastric microbiota, can be induced by multiple environmental factors, such as age, diet, multiple antibiotic therapies, proton pump inhibitor abuse, H. pylori status, among others. Although H. pylori colonization has been reported across the world, chronic H. pylori infection may lead to serious consequences; therefore, the infection must be treated. Multiple antibiotic therapy improvements are not always successful because of the lack of adherence to the prescribed antibiotic treatment. However, the abuse of eradication treatments can generate gastric dysbiotic states. Dysbiosis of the gastric microenvironment induces microbial resilience, due to the loss of relevant commensal bacteria and simultaneous colonization by other pathobiont bacteria, which can generate metabolic and physiological changes or even initiate and develop other gastric disorders by non-H. pylori bacteria. This systematic review opens a discussion on the effects of multiple environmental factors on gastric microbial communities.

Ganglioneuromas are histologically benign neoplasms derived from the sympathetic nervous system, whose occurrence in the gastrointestinal tract is rare and often syndromic. According to the injury pattern and extension, lesions are divided into polypoid ganglioneuroma, ganglioneuromatous polyposis, and diffuse ganglioneuromatosis. This work aimed to present the incidental post mortem finding of diffuse ganglioneuromatosis of the gastrointestinal tract in a patient without syndromic involvement. We describe the case of a two-year-old female patient with surgically corrected type III tracheoesophageal atresia and fistulous recanalization, multiple episodes of aspiration pneumonia, and septic shock. During the last admission, she developed massive pulmonary hemorrhage and multi-organ failure. Post mortem histopathological study identified hypertrophy of the pylorus and enlarged enteric nerve trunks and plexuses with intermingled mature ganglion cells. We identified ganglioneuromatosis affecting all gastrointestinal tract segments with the predominance of the myenteric plexuses. Intestinal ganglioneuromatosis is a rare disease with a spectrum of lesions ranging from isolated to syndromic with high morbidity and mortality. Therefore, it is necessary to know the condition, investigate systematically when it is suspected, and rely on genetic studies to confirm or rule out any syndromic association.

Dysbiosis plays an important role in the development of bacterial infections in the gastric mucosa, particularly Helicobacter pylori. The international guidelines for the treatment of H. pylori infections suggest standard triple therapy (STT). Nevertheless, because of the increasing resistance rates to clarithromycin, metronidazole has been widely considered in several countries. Unfortunately, the non-justified administration of antibiotics induces dysbiosis in the target organ. We characterized the gastric microbiota of patients diagnosed with follicular gastropathy and pangastropathy attributed to H. pylori infection, before and after the administration of STT with metronidazole. Dominant relative abundances of Cutibacterium were observed in pre-treatment patients, whereas H. pylori was observed at <11%, suggesting the multifactor property of the disease. The correlation of Cutibacterium acnes and H. pylori with gastric infectious diseases was also evaluated using quantitative real-time polymerase chain reaction. The dominance of C. acnes over H. pylori was observed in gastritis, gastropathies, and non-significant histological alterations. None of the microorganisms were detected in the intestinal metaplasia. Post-treatment alterations revealed an increase in the relative abundances of Staphylococcus, Pseudomonas, and Klebsiella. Non-H. pylori gastrointestinal bacteria can be associated with the initiation and development of gastric diseases, such as pathobiont C. acnes.