Eosinophilic Gastrointestinal Disease.

This JAMA Insights Clinical Update discusses the symptoms, diagnosis, and management of eosinophilic gastrointestinal diseases.

A Community Waterborne Salmonella Bovismorbificans Outbreak in Greece.

BACKGROUND: In August 2022, the Hellenic National Public Health Organisation was notified about a gastroenteritis outbreak in town A in Southern Greece. Investigations aimed to identify the source and implement control measures. METHODS: Case definition categories were used in a 1:3 case-control study. Cases and controls were interviewed about various exposures. Cases' stool samples were cultured on agar plates and characterised by serotyping, antimicrobial susceptibility testing and Pulse Field Gel Electrophoresis (PFGE). Environmental investigations included tap water sampling for microbiological and chemical analysis in town A and inspection of the water supply system. RESULTS: We identified 33 cases (median age: 17 years). Tap water consumption was the only significant risk factor for gastroenteritis (OR = 5.46, 95% CI = 1.02-53.95). Salmonella (S.) Bovismorbificans isolated from eight stool and one tap water samples had identical PFGE profiles. No resistant isolates were identified. Residual chlorine levels were lower than the acceptable limits before and during the outbreak. We advised consumption of bottled water and adherence to strict hand hygiene rules until tap water was declared suitable for drinking. CONCLUSIONS: Epidemiological and molecular data revealed a waterborne S. Bovismorbificans outbreak in town A. We recommend local water safety authorities to ensure that residual chlorine levels comply with the legislation towards water safety planning, to mitigate risks.

From Foodborne Disease Outbreak (FBDO) to Investigation: The Plant Toxin Trap, Brittany, France, 2018.

On 6 July 2018, the Center for Epidemiology and Public Health of the French Armed Forces was informed of an outbreak of acute gastroenteritis among customers of a dining facility at a military base in Brittany, France. A total of 200 patients were reported out of a population of 1700 (attack rate: 12%). The symptoms were mainly lower digestive tract disorders and occurred rapidly after lunch on 5 July (median incubation period: 3.3 h), suggesting a toxin-like pathogenic process. A case-control survey was carried out (92 cases and 113 controls). Statistical analysis pointed to the chili con carne served at lunch on 5 July as the very likely source of poisoning. Phytohaemagglutinin, a plant lectin, was found in the chili con carne at a concentration above the potentially toxic dose (400 HAU/gram). The raw kidney beans incorporated in the chili con carne presented a high haemagglutination activity (66,667 HAU/gram). They were undercooked, and the phytohaemagglutinin was not completely destroyed. FBDOs due to PHA are poorly documented. This study highlights the need to develop methods for routine testing of plant toxins in food matrices. Improved diagnostic capabilities would likely lead to better documentation, epidemiology, and prevention of food-borne illnesses caused by plant toxins.

Norovirus and sapovirus infections after allogeneic hematopoietic stem cell transplantation: is it worth it to look for them?

Norovirus (NoV) and Sapovirus (SaV) are potential causative agents of diarrhea after allogeneic HSCT but little is known in this population. We performed a retrospective analysis by RT-PCR of calicivirus (NoV and SaV), Human adenovirus (HAdV), rotavirus (RV), Aichi virus (AiV), enterovirus (EV), human parechovirus (HPeV) and Human bocavirus (HBoV) in the diarrheal stools of patients after allogeneic HSCT. 49/162 patients had positive viral assays: HAdV (17%), EV (7%), NoV (4.3%), RV and HBoV (3.1% each), SaV (1.9%), AiV (1.2%), HPeV (0.6%). Seven patients were positive for NoV and 3 for SaV. Among viruses-positive samples, the frequency of caliciviruses cases was 7% in the 6 months post-HSCT compared to 40% after (p < 0.0001). The median duration of symptom was 0.7 months but 2 cases, occurring more than one year after HSCT, were chronic, undiagnosed and strongly contributed to morbidity. Systematic testing of caliciviruses appears especially useful in late chronic diarrhea.

Clinical manifestations and risk factors of campylobacter gastroenteritis in children in Taiwan.

BACKGROUND: Campylobacteriosis is a common cause of bacterial gastroenteritis worldwide. This study aimed to investigate the potential risk factors, clinical and laboratory manifestations of children with campylobacteriosis under five years old in Taiwan. METHODS: This retrospective case-control study was conducted in ten major hospitals in Taiwan from 2014 to 2017. Laboratory tests and stool specimen were collected and analyzed together with questionnaire survey. Multivariate stepwise logistic regression model was used for identification of risk factors. RESULTS: A total of 64 campylobacteriosis cases were included with a median age of 25 months. We observed a less prolonged vomiting (p = 0.047), more bloody (p < 0.001) and mucoid (p = 0.005) stools, and lower AST levels (p = 0.020) in patients with campylobacteriosis. Lower parental educational attainment (p < 0.001), direct contact with acute gastroenteritis patients (p < 0.001), as well as diarrhea in the mutually cared children (p = 0.007) were linked to campylobacteriosis. Consumption of municipal water (p < 0.001), milk (OR 0.34, 95% CI 0.118-0.979), and soft beverages (OR 0.41, 95% CI 0.192-0.888) were identified as protective factors, while consuming takeout food (p = 0.032) and seafood (p = 0.019) increased risk of campylobacteriosis. CONCLUSIONS: Shorter vomiting duration, bloody and mucoid stool, and less elevated AST levels are manifestations suggestive of campylobacteriosis. Risk factors of campylobacteriosis were low parental educational attainment, direct contact with acute gastroenteritis patients, diarrhea in mutually cared children, takeout food and seafood intake. Potential protective factors include municipal water, milk, and soft beverage intake.

Epidemiological Characteristics of Norovirus Outbreaks in Shenyang from 2017 to 2021.

Norovirus is one of the leading causes of acute gastroenteritis outbreaks worldwide. This study aimed to identify the epidemiological characteristics of norovirus outbreaks and to provide evidence for public health entities. Specimens and epidemiological survey data were collected to determine if there were differences in the attack rate of norovirus in terms of the year, season, transmission route, exposure setting, and region and to determine whether there were relationships between the reporting interval, the number of illnesses in a single outbreak and the duration of the outbreak. Norovirus outbreaks were reported throughout the year, with seasonal characteristics (i.e., high rates in spring and winter). Among all regions in Shenyang with the exception of Huanggu and Liaozhong, norovirus outbreaks had been reported, and the primary genotype was GII.2[P16]. Vomiting was the most common symptom. The main places of occurrence were childcare institutions and schools. The person-to-person route was the main transmission route. The median duration of norovirus was 3 days (IQR [interquartile range]: 2-6 days), the median reporting interval was 2 days (IQR: 1-4 days), the median number of illnesses in a single outbreak was 16 (IQR: 10-25); there was a positive correlation between these parameters. Norovirus surveillance and genotyping studies still need to be further strengthened to increase knowledge regarding the pathogens and their variant characteristics, to better characterize the patterns of norovirus outbreaks and to provide information for outbreak prevention. Norovirus outbreaks should be detected, reported and handled early. Public health entities and the government should develop corresponding measures for different seasons, transmission routes, exposure settings, and regions.

N-Glycosylation of Rotavirus NSP4 Protein Affects Viral Replication and Pathogenesis.

Rotavirus (RV), the most common cause of gastroenteritis in children, carries a high economic and health burden worldwide. RV encodes six structural proteins and six nonstructural proteins (NSPs) that play different roles in viral replication. NSP4, a multifunctional protein involved in various viral replication processes, has two conserved N-glycosylation sites; however, the role of glycans remains elusive. Here, we used recombinant viruses generated by a reverse genetics system to determine the role of NSP4 N-glycosylation during viral replication and pathogenesis. The growth rate of recombinant viruses that lost one glycosylation site was as high as that of the wild-type virus. However, a recombinant virus that lost both glycosylation sites (glycosylation-defective virus) showed attenuated replication in cultured cell lines. Specifically, replications of glycosylation-defective virus in MA104 and HT29 cells were 10- and 100,000-fold lower, respectively, than that of the wild-type, suggesting that N-glycosylation of NSP4 plays a critical role in RV replication. The glycosylation-defective virus showed NSP4 mislocalization, delay of cytosolic Ca2+ elevation, and less viroplasm formation in MA104 cells; however, these impairments were not observed in HT29 cells. Further analysis revealed that assembly of glycosylation-defective virus was severely impaired in HT29 cells but not in MA104 cells, suggesting that RV replication mechanism is highly cell type dependent. In vivo mouse experiments also showed that the glycosylation-defective virus was less pathogenic than the wild-type virus. Taken together, the data suggest that N-glycosylation of NSP4 plays a vital role in viral replication and pathogenicity. IMPORTANCE Rotavirus is the main cause of gastroenteritis in young children and infants worldwide, contributing to 128,500 deaths each year. Here, we used a reverse genetics approach to examine the role of NSP4 N-glycosylation. An N-glycosylation-defective virus showed attenuated and cell-type-dependent replication in vitro. In addition, mice infected with the N-glycosylation-defective virus had less severe diarrhea than mice infected with the wild type. These results suggest that N-glycosylation affects viral replication and pathogenesis. Considering the reduced pathogenicity in vivo and the high propagation rate in MA104 cells, this glycosylation-defective virus could be an ideal live attenuated vaccine candidate.

IL-17D affects the chemokines and chemokine receptors of intestinal epithelial cells under hyperoxia.

IL-17D is a new member of the IL-17 family. Currently, it is believed that IL-17D can directly act on immune cells or may indirectly modulate immune responses by regulating cytokine expression. Herein, we hypothesized that IL-17D regulates the expression of chemokines in intestinal epithelial cells, in turn modulating the immune response within intestinal mucosa under hyperoxia. To explore this notion, newborn rats were divided into a hyperoxia group (85 % O2) and control group (21 % O2). Small intestinal tissues were obtained from neonatal rats at 3, 7, 10, and 14 days. Similarly, intestinal epithelial cells were treated by hyperoxia (85 % O2) as the hyperoxia group or were incubated under normal oxygen (21 % O2) as the control group. Finally, intestinal epithelial cells subjected to hyperoxia were treated with recombinant IL-17D and IL-17D antibodies for 24, 48, and 72 h. Immunohistochemistry, western blot, and reverse transcription-quantitative polymerase chain reaction were used to detect the expression levels of chemokines and chemokine receptors in intestinal tissues of newborn rats and intestinal epithelial cells. We found that hyperoxia affected chemokine expression both in vivo and in vitro. Under hyperoxia, IL-17D promoted the expression of CCL2, CCL25, CCL28, and CCR9 in intestinal epithelial cells while downregulating CCR2, CCR5, CCL5, and CCL20. Our findings provide a basis for further study on the effects of hyperoxia-induced intestinal inflammation and intestinal injury.

Norovirus infections in the Czech Republic in 2008-2020.

INTRODUCTION: Noroviruses, together with rotaviruses, are the most common cause of viral gastroenteritis in the Czech Republic (CR). The aim of this study was to analyse data on the incidence of norovirus gastroenteritis in the CR and thus to add to the body of knowledge about its significance. MATERIAL AND METHODS: A descriptive analysis was performed of the basic characteristics of norovirus gastroenteritis reported under ICD-10 code A08.1 to the Epidat or ISIN electronic infectious diseases information system between 2008 and 2020. On the basis of reports from five microbiological laboratories, weekly data on confirmed cases of norovirus infection from 2010-2020 were analysed. Databases of microbiology laboratories from across the Czech Republic were searched to determine the number of the laboratories where norovirus infections were diagnosed and the methods used for this purpose in 2008-2020. RESULTS: From 2008 to 2020, 33,575 cases of norovirus gastroenteritis were reported to the infectious diseases information systems, which equates to an annual incidence of 24.5/100,000 population, varying between years from 8.2 to 77.1/100,000. Men accounted for 40.2% of cases with an incidence of 20.1/100,000 compared to 28.8/100,000 recorded in women. Of the total of reported cases, 14,282 patients (42.5%) required hospital admission. Over the whole study period, 7,431 cases of norovirus gastroenteritis were recorded in children under 5 years of age. This age category accounted for 13.7-38.9% of the annual totals of reported cases. The incidences were 101.8/100,000 in children under 5 years of age, 40.1/100,000 in 5-14-year-olds, 12.7/100,000 in 15-64-year-olds, and 38.2/100,000 in the age group 65 years and over. Twenty-four deaths (case fatality rate of 0.07%) were reported as associated with norovirus gastroenteritis at the ages 42-94. In the age categories 15-64 years and 65 years and over, the case fatality rates were 0.02% and 0.24%, respectively. Over the study period, 274 epidemics occurred, during which 16,893 (50.3%) of the total of 33,575 cases were reported. In the epidemic outbreaks, 1,694 (10.0%) patients required hospital admission. The largest outbreak with 5,248 reported cases in 2015 was associated with contamination of the Prague water supply system. Norovirus infections were laboratory diagnosed year-round, peaking in the autumn and winter months. They are currently diagnosed by 81 laboratories in the Czech Republic, 90.1% of which use immunochromatographic tests. CONCLUSION: The study confirmed the highest incidence of norovirus gastroenteritis among children under 5 years of age and the highest case fatality rate in the age group 65 years and over. Over half of the reported cases were outbreak associated. Most laboratories use immunochromatographic tests. The use of more sensitive laboratory methods would improve diagnosis.

[A case of eosinophilic gastroenteritis caused after the use of Seprafilm®].

Eosinophilic gastroenteritis is a fairly uncommon condition. It has been suggested that allergic reactions may have played a role in the development of this illness. The case of a 66-year-old woman who had a total hysterectomy due to a right ovarian tumor is described here. At this operation, a sodium hyaluronate carboxymethylcellulose bioresorbable membrane (Seprafilm®) was used. She was admitted to our hospital 47 days after the operation with abdominal pain. Laboratory data indicated elevated WBC (29450/µl) and eosinophilia (69.2%), and CT scan showed thickening of intestinal wall and ascites around there. Ascites cytology showed a significant increase of eosinophils (94.0%). She began taking oral steroids after being diagnosed with eosinophilic gastroenteritis, and her symptoms improved quickly. Despite the fact that Seprafilm® was thought to be a reliable and safe tool, it was suggested that a foreign body reaction to Seprafilm® could lead to eosinophilic gastroenteritis.

High-Fat Diet-Induced Obesity Aggravates Food Allergy by Intestinal Barrier Destruction and Inflammation.

INTRODUCTION: The increase in high-fat diet (HFD)-induced obesity and food allergy leads to an assumption that the 2 are related. This study aims to (1) systematic verification of HFD-induced obesity aggravates food allergy and (2) explore the correlation and molecular mechanisms of HFD-induced obesity promotes food allergy. METHODS: Female BALB/c mice are divided into the control group (control), the ovalbumin (OVA)-sensitized group (OVA), the HFD-induced obesity group (HFD), and HFD-induced allergic obesity group (HFD + OVA). RESULTS: In vivo data showed that HFD feed enhance clinical symptoms and intestinal mucosa villi shed on allergic mice. Moreover, we found that HFD and OVA irritation enhanced levels of mast cell degranulation and Th2 humoral response. Additionally, Western blot analysis showed the potentiation of peroxisome proliferator-activated receptor γ (PPAR γ) remarkably reduced on intestinal in HFD and OVA group, thereby inhibiting the expression of nuclear factor kappa B (NF-κB)/PPAR γ signal the phosphorylation of NF-κB P65. CONCLUSIONS: Overall, our results suggest that HFD-induced obesity is a potential risk factor for food allergy, which related to intestinal barrier destruction and inflammation through the PPAR γ/NF-κB signaling pathway.

Enteric Illness Outbreaks Reported Through the National Outbreak Reporting System-United States, 2009-2019.

BACKGROUND: The National Outbreak Reporting System (NORS) captures data on foodborne, waterborne, and enteric illness outbreaks in the United States. This study describes enteric illness outbreaks reported during 11 years of surveillance. METHODS: We extracted finalized reports from NORS for outbreaks occurring during 2009-2019. Outbreaks were included if caused by an enteric etiology or if any patients reported diarrhea, vomiting, bloody stools, or unspecified acute gastroenteritis. RESULTS: A total of 38 395 outbreaks met inclusion criteria, increasing from 1932 in 2009 to 3889 in 2019. Outbreaks were most commonly transmitted through person-to-person contact (n = 23 812; 62%) and contaminated food (n = 9234; 24%). Norovirus was the most commonly reported etiology, reported in 22 820 (59%) outbreaks, followed by Salmonella (n = 2449; 6%) and Shigella (n = 1171; 3%). Norovirus outbreaks were significantly larger, with a median of 22 illnesses per outbreak, than outbreaks caused by the other most common outbreak etiologies (P < .0001, all comparisons). Hospitalization rates were higher in outbreaks caused by Salmonella and Escherichia coli outbreaks (20.9% and 22.8%, respectively) than those caused by norovirus (2%). Case fatality rate was highest in E. coli outbreaks (0.5%) and lowest in Shigella and Campylobacter outbreaks (0.02%). CONCLUSIONS: Norovirus caused the most outbreaks and outbreak-associated illness, hospitalizations, and deaths. However, persons in E. coli and Salmonella outbreaks were more likely to be hospitalized or die. Outbreak surveillance through NORS provides the relative contributions of each mode of transmission and etiology for reported enteric illness outbreaks, which can guide targeted interventions.

Prevalence of Gastrointestinal Symptoms in Severe Acute Respiratory Syndrome Coronavirus 2 Infection: Results of the Prospective Controlled Multinational GI-COVID-19 Study.

INTRODUCTION: Gastrointestinal (GI) symptoms in coronavirus-19 disease (COVID-19) have been reported with great variability and without standardization. In hospitalized patients, we aimed to evaluate the prevalence of GI symptoms, factors associated with their occurrence, and variation at 1 month. METHODS: The GI-COVID-19 is a prospective, multicenter, controlled study. Patients with and without COVID-19 diagnosis were recruited at hospital admission and asked for GI symptoms at admission and after 1 month, using the validated Gastrointestinal Symptom Rating Scale questionnaire. RESULTS: The study included 2036 hospitalized patients. A total of 871 patients (575 COVID+ and 296 COVID-) were included for the primary analysis. GI symptoms occurred more frequently in patients with COVID-19 (59.7%; 343/575 patients) than in the control group (43.2%; 128/296 patients) (P < 0.001). Patients with COVID-19 complained of higher presence or intensity of nausea, diarrhea, loose stools, and urgency as compared with controls. At a 1-month follow-up, a reduction in the presence or intensity of GI symptoms was found in COVID-19 patients with GI symptoms at hospital admission. Nausea remained increased over controls. Factors significantly associated with nausea persistence in COVID-19 were female sex, high body mass index, the presence of dyspnea, and increased C-reactive protein levels. DISCUSSION: The prevalence of GI symptoms in hospitalized patients with COVID-19 is higher than previously reported. Systemic and respiratory symptoms are often associated with GI complaints. Nausea may persist after the resolution of COVID-19 infection.

Cytomegalovirus gastroenteritis in patients with acute graft-versus-host disease.

A preemptive strategy has successfully decreased cytomegalovirus (CMV) disease after allogeneic hematopoietic cell transplantation (HCT). However, some recipients still develop CMV gastroenteritis, especially after acute graft-versus-host disease (aGVHD), and its incidence, risk factors, and prognostic impact remain to be elucidated. We retrospectively analyzed 3759 consecutive adult patients who developed grade II-IV aGVHD using a Japanese registry database. The cumulative incidence of CMV gastroenteritis was 5.7% by day 365 from the development of grade II-IV aGVHD. Advanced age (hazard ratio [HR], 1.60; 95% confidence interval [CI], 1.16-2.22; P = .004), GVHD prophylaxis with mycophenolate mofetil and calcineurin inhibitor (HR, 1.73; 95% CI, 1.08-2.77; P = .024), lower-gut aGVHD (HR, 2.17; 95% CI, 1.58-2.98; P < .001), and the use of systemic steroids (HR, 1.78; 95% CI, 1.16-2.74; P = .008) were independent risk factors for CMV gastroenteritis. Development of CMV gastroenteritis was associated with an increased risk of nonrelapse mortality (HR, 1.89; 95% CI, 1.50-2.39; P < .001). Moreover, letermovir prophylaxis significantly reduced both the incidence of CMV gastroenteritis (HR, 0.50; 95% CI, 0.25-0.99; P = .047) and the risk of nonrelapse mortality (HR, 0.72; 95% CI, 0.52-0.99; P = .043). In summary, CMV gastroenteritis is a life-threatening complication that sets the need for preventive strategies with letermovir and targeted surveillance.

Detection of Enterotoxigenic Escherichia coli in Rotavirus-Infected Ghanaian Children Diagnosed with Acute Gastroenteritis.

Diarrhea is a notable global health problem in several developing countries, especially in children. Prior to the introduction of the rotavirus vaccination program in Ghana, a surveillance study was conducted to investigate the prevalence of the disease caused by rotavirus in children. In this report, we re-used archival stool samples from the pre-vaccine surveillance study to provide information on prevalence of enterotoxigenic Escherichia coli in Ghanaian children. Re-analysis of the stool samples revealed co-infection of enterotoxigenic E. coli and rotavirus in 2% of the children whose samples were selected for this study. As Ghana is approaching 10 years post-implementation of the rotavirus vaccination program, the preliminary data presented in this report are a vital reference for subsequent studies aimed at ascertaining the effect of the vaccine on both rotavirus and enterotoxigenic E. coli.

Plesiomonas: A Review on Food Safety, Fish-Borne Diseases, and Tilapia.

Fish and fish products are considered a fundamental part of the human diet due to their high nutritional value. Food-borne diseases are considered a major public health challenge worldwide due to their incidence, associated mortality, and negative economic repercussions. Food safety is the guarantee that foods will not cause harm to the health of those who consume them, and it is a fundamental property of food quality. Food safety can be at risk of being lost at any stage of the food chain if the food is contaminated by pathogenic microorganisms. Many diverse bacteria are present in the environment and as part of the microbiota of food that can be transmitted to humans during the handling and consumption of food. Plesiomonas shigelloides has been mainly associated with outbreaks of gastrointestinal diseases due to the consumption of fish. This bacterium inhabits the environment and aquatic animals and is associated with the microbiota of fish such as tilapia, a fish of importance in fishing, aquaculture, commercialization, and consumption worldwide. The purpose of this document is to provide, through a bibliographic review of databases (Scopus, Web of Science, and Google Scholar, among others), a general informative perspective on food-borne diseases and, in particular, the consumption of fish and tilapia. Diseases derived from contamination by Plesiomonas shigelloides are included, and control and prevention actions and sanitary regulations for fishery products established in several countries around the world are discussed to promote the safety of foods of aquatic origin intended for human consumption and to protect public health.

A Waterborne Gastroenteritis Outbreak Caused by a GII Norovirus in a Holiday Camp in Catalonia (Spain), 2017.

On 2 February 2017, Epidemiological Surveillance Services were notified of an outbreak of acute gastroenteritis (AGE) among schoolchildren who had taken part of a school trip from 30 January to 3 February 2017 at a holiday camp in Catalonia. A retrospective cohort study was performed to identify the causative agent, estimate the magnitude of the outbreak and identify its source, as well as to determine the route of transmission. Data collected by standardised questionnaires identified 41 episodes of AGE among 174 individuals who attended the camp. Cases had mainly symptoms of abdominal pain (73.8%), nausea (64.3%), vomiting (54.8%), diarrhoea (45.2%) and headache (42.9%). Consumption of water was associated with gastroenteritis (crude RR: 1.72, 95%CI: 1.01-2.92; adjusted RR: 1.88, 95%CI 1.03-3.56). NoV GII was detected in faeces (5 out of 13) and water samples. Additionally, faecal indicator bacteria and protozoa were detected in water samples. The outbreak showed a high attack rate and was caused by a natural water fountain not properly treated and not monitored for safety quality. There could have been a discharge of wastewater at a point close to the fountain; however, the source of contamination of the water could not be identified. Health education may be useful to eliminate risks associated with the consumption of untreated water from natural fountains.

Infectious Gastroenteritis in Transplant Patients.

Infectious gastroenteritis is common after transplantation and can lead to increased morbidity and mortality. A wide range of organisms can lead to gastroenteritis in this patient population. Clostridioides difficile, cytomegalovirus, and norovirus are the most common pathogens. Newer diagnostic methods, especially multiplex polymerase chain reaction, have increased the diagnostic yield of infectious etiologies. In this review, we describe the epidemiology and risk factors for common infectious pathogens leading to gastroenteritis.

Anti-Inflammatory and Immunomodulatory Effects of Probiotics in Gut Inflammation: A Door to the Body.

Hosting millions of microorganisms, the digestive tract is the primary and most important part of bacterial colonization. On one side, in cases of opportunistic invasion, the abundant bacterial population inside intestinal tissues may face potential health problems such as inflammation and infections. Therefore, the immune system has evolved to sustain the host-microbiota symbiotic relationship. On the other hand, to maintain host immune homeostasis, the intestinal microflora often exerts an immunoregulatory function that cannot be ignored. A field of great interest is the association of either microbiota or probiotics with the immune system concerning clinical uses. This microbial community regulates some of the host's metabolic and physiological functions and drives early-life immune system maturation, contributing to their homeostasis throughout life. Changes in gut microbiota can occur through modification in function, composition (dysbiosis), or microbiota-host interplays. Studies on animals and humans show that probiotics can have a pivotal effect on the modulation of immune and inflammatory mechanisms; however, the precise mechanisms have not yet been well defined. Diet, age, BMI (body mass index), medications, and stress may confound the benefits of probiotic intake. In addition to host gut functions (permeability and physiology), all these agents have profound implications for the gut microbiome composition. The use of probiotics could improve the gut microbial population, increase mucus-secretion, and prevent the destruction of tight junction proteins by decreasing the number of lipopolysaccharides (LPSs). When LPS binds endothelial cells to toll-like receptors (TLR 2, 4), dendritic cells and macrophage cells are activated, and inflammatory markers are increased. Furthermore, a decrease in gut dysbiosis and intestinal leakage after probiotic therapy may minimize the development of inflammatory biomarkers and blunt unnecessary activation of the immune system. In turn, probiotics improve the differentiation of T-cells against Th2 and development of Th2 cytokines such as IL-4 and IL-10. The present narrative review explores the interactions between gut microflora/probiotics and the immune system starting from the general perspective of a biological plausibility to get to the in vitro and in vivo demonstrations of a probiotic-based approach up to the possible uses for novel therapeutic strategies.