Evaluation of the Mechanisms Underlying Amino Acid and Microbiota Interactions in Intestinal Infections Using Germ-Free Animals

Intestinal infectious diseases refer to the inflammatory changes in the intestinal tract caused by pathogens(including bacteria,viruses,fungi,protozoa,or parasites)or their toxic products.A large number of microorganisms colonize the intestinal tract of healthy people,which together with the intestinal epithelium constitute the biological barrier of the intestinal tract to resist infectious diseases.As an“invisible organ,”the intestinal flora is closely related to human nutrition metabolism and intestinal infections.A variety of intestinal flora participates in the nutritional metabolism of amino acids,and the small molecular substances produced by the amino acid metabolism through the intestinal flora can enhance intestinal immunity and resist bacterial infections.In turn,amino acids can also regulate the composition of the intestinal flora,maintain the steady-state of the intestinal flora,protect the intestinal barrier,and inhibit colonization by pathogenic bacteria.As a model animal with a clear microbial background,germ-free(GF)animals can clarify the mechanisms of interactions between intestinal microbes and amino acid metabolism in intestinal infections by combining genetic engineering technology and multi-omics studies.This article reviews related researches on the involvement of intestinal microbes in host amino acid metabolism and resistance to intestinal infections and discusses the advantages of GF animal models for studying the underlying mechanisms.The GF animal model is helpful to further study the intervention effects of amino acid metabolism of targeted intestinal flora on intestinal infections.

Virological and histological evaluation of intestinal samples in COVID-19 patients

BACKGROUND Severe acute respiratory syndrome coronavirus-2(SARS-CoV-2)is the pathogen responsible for pandemic coronavirus disease 2019(COVID-19).It is a highly contagious virus which primarily affects the respiratory tract,nevertheless,the lungs are not the only target organs of the virus.The intestinal tract could represent an additional tropism site for SARS-CoV-2.Several observations have collectively suggested that enteric infections can occur in COVID-19 patients.However,the detection of viral RNA in gastrointestinal(GI)tissue samples has not been adequately investigated and results are conflicting.AIM To detect the presence of SARS-CoV-2 RNA in intestinal mucosa samples and to evaluate histological features.METHODS The COVID-19 patients hospitalized at an Italian tertiary hospital from April 2020 to March 2021 were evaluated for enrollment in an observational,monocentric trial.The study population was composed of two groups of adult patients.In the first group(biopsy group,30 patients),patients were eligible for inclusion if they had mild to moderate disease and if they agreed to have a rectal biopsy;in the second group(surgical specimen group,6 patients),patients were eligible for inclusion if they underwent intestinal resection during index hospitalization.Fifty-nine intestinal mucosal samples were analyzed.RESULTS Viral RNA was not detectable in any of the rectal biopsies performed(0/53).Histological examination showed no enterocyte damage,but slight edema of the lamina propria with mild inflammatory lymphoplasmacytic infiltration.There was no difference in inflammatory infiltrates in patients with and without GI symptoms.SARS-CoV-2 RNA was detected in fecal samples in 6 cases out of 14 cases examined(42.9%).In the surgical specimen group,all patients underwent emergency intestinal resection.Viral RNA was detected in 2 surgical specimens of the 6 examined,both of which were from patients with active neoplastic disease.Histological examination also pointed out abundant macrophages,granulocytes and plasma cells infiltrating the muscular layer and adipose tissue,and focal vasculitis.CONCLUSION Mild-moderate COVID-19 may not be associated with rectal infection by the virus.More comprehensive autopsies or surgical specimens are needed to provide histological evidence of intestinal infection.

Localization and Dynamic Expression of a 27.8kDa Receptor Protein for Lymphocystis Disease Virus Infection in Sea Bass(Lateolabrax japonicus) Tissues

Lymphocystis disease virus(LCDV) infects target cells by attaching to a 27.8 k Da receptor(27.8R) protein in flounder Paralichthys olivaceus, and anti-27.8R monoclonal antibodies(MAbs) have been developed. However, the 27.8R existence in tissues of sea bass(Lateolabrax japonicus) and its role in LCDV infection have remained unclear. In this study, the results of western blotting demonstrated that the same 27.8R was shared by flounder and sea bass. LCDV-free sea bass individuals were intramuscularly injected with LCDV, and viral copies were detected in tissues from 3 h post infection and showed a time-dependent increase during 9 days infection. Distribution and synthesis of 27.8R in sea bass tissues were investigated by using anti-27.8R MAbs as probes. It was found that 27.8R was distributed in all the tested tissues. The levels of 27.8R protein were highest in gill and skin, then a bit lowly in stomach, head kidney and heart, followed by spleen, intestine, blood cells, gonad and liver, and least in kidney and brain in healthy sea bass. Upon LCDV infection, 27.8R synthesis was up-regulated in each tissue, and higher in the tissues with higher LCDV copies. The 27.8R and LCDV were detected in some peripheral blood leukocytes but not in red blood cells. These results suggested that 27.8R was widely distributed in sea bass tissues, and it served as a receptor and correlated with tissue tropism of LCDV infection. Furthermore, leukocytes had the potential of being a LCDV carrier and were responsible for a systemic infection of LCDV in sea bass.

Prevalence of and risk factors for malaria,filariasis,and intestinal parasites as single infections or co-infections in different settlements of Gabon,Central Africa

Background:Malaria,filariasis,and intestinal parasitic infections(IPIs)are common and frequently overlap in developing countries.The prevalence and predictors of these infections were investigated in three different settlements(rural,semi-urban,and urban)of Gabon.Methods:During cross-sectional surveys performed from September 2013 to June 2014,451 individuals were interviewed.In addition,blood and stool samples were analysed for the presence of Plasmodium,filarial roundworm,intestinal protozoan,and helminth infections.Results:Intestinal parasitic infections(61.1%),including intestinal protozoa(56.7%)and soil-transmitted helminths(STHs)(22.2%),predominated,whereas Plasmodium falciparum(18.8%),Loa loa(4.7%),and Mansonella perstans(1.1%)were less prevalent.Filariasis and STHs were mainly found in rural settlements,whereas a higher plasmodial infection prevalence rate was observed in the periurban area.The most common IPI was blastocystosis(48.6%),followed by ascaridiasis(13.7%),trichuriasis(11.8%),amoebiasis(9.3%),giardiasis(4.8%),and strongyloidiasis(3.7%).Hookworm was detected in one adult from rural Dienga.Adults had a higher prevalence of Blastocystis hominis and STHs,whereas Giardia duodenalis was more frequently observed among children aged below 5 years(P<0.01).The polyparasitism rate was 41.5%,with 7.0%Plasmodium-IPIs and 1.8%Plasmodium-STH co-infections.The multivariate analysis showed that living in a suburban area,belonging to the age group of 5-15 years,having none or a secondary education,or having an open body water close to home were significant risk factors for malaria(P≤0.01).For STH infections,identified risk factors were drinking untreated water and living in a rural area(P≤0.04).No significant predictors were identified for IPIs and malaria-IPI co-infection.Conclusions:This study reports a high prevalence of IPIs and intestinal protozoa,but a low rate of malaria-IPI co-infections in the study sites.Improvements in the living conditions of the population such as adequate water supply and proper health education and sanitation should be integrated into control strategies for malaria,STHs,and IPIs.

Coinfection with malaria and intestinal parasites, and its association with anaemia in children in Cameroon

Background:The purpose of this study was to determine the prevalence of coinfection with malaria and intestinal parasites,as well as to determine its association with anaemia in children aged 10 years and below in Muyuka,Cameroon.Materials and methods:This was a cross-sectional study.Participants were febrile children who were admitted to the Muyuka district hospital between April and October 2012.Blood and stool samples were collected from those participants who gave consent to take part in the study.Haemoglobin concentration(Hb)and complete blood count(CBC)were performed using an automated haematology analyser(Mindray®,BC-2800).Giemsa-stained blood film was examined to detect malaria parasites,while the formol-ether concentration technique was used to detect intestinal parasitic infections(IPIs).The Pearson’s chi-square,Student’s T-test and correlation analysis were all performed as part of the statistical analyses.Results:Four hundred and eleven(411)children successfully took part in this study.The prevalence of malaria,IPIs,malaria and IPI coinfection,and anaemia observed were 98.5%,11.9%,11.9%and 44.8%,respectively.Anaemia and IPIs were significantly associated with age;anaemia was more prevalent in children under five years of age(p=0.000),whereas IPIs were more prevalent in children aged between five and 10 years(p=0.006).The parasite species isolated included Ascaris lumbricoides(36[73.5%]),Entamoeba histolytica/dispar(9[18.4%])and hookworm(4[8.2%]).The mean Hb observed was 10.64 g/dl(±1.82).A significant negative correlation was observed between malaria parasite density and Hb.There was no significant difference in the prevalence of anaemia among children infected with malaria,IPIs,or malaria and IPI coinfection,or among non-infected children.Similarly,the mean Hb did not differ among infected and non-infected children.Conclusion:This study showed that malaria and IPIs still constitute a major public health problem in the study area despite a lack of any significant association between these infections and anaemia.The findings suggest that there is a need for the implementation of control measures to curb the rate of malaria and IPIs in the study area.

Non-opportunistic intestinal parasitic infections among HIV-infected individuals at Wolaita Sodo Hospital, South Ethiopia

Objective:To determine the prevalence of non-opportunistic intestinal helminthic and protozoal infections among HIV-infected individuals and to determine socio-demographic determinants of intestinal parasitosis.Methods:A cross-sectional study was conducted on HIV-infected individuals attending antiretroviral therapy clinic of Wolaita Sodo Hospital.Stool in wet mount preparation and formalether concentration technique were used to diagnose intestinal parasitic infection.Sociodemographic variables were collected by using questionnaire.Chi-square test was used to test the associations between intestinal parasitosis and socio-demographic variables.Results:The overall prevalence of non-opportunistic intestinal parasitic infection was 32.4%out of which 11.0%was protozoal infection and 21.4%was helminthic infection.The most common intestinal parasite detected was Ascaris lumbricoides with 12.7%prevalence followed by Giardia lamblia with 7.5%prevalence.The prevalence of Strongyloides stercoralis,hookworm species,Entamoeba histolytica/Entamoeba dispar,Schistosoma mansoni and Taenia species was 2.9%,1.2%,3.5%,1.7%and 2.3%respectively.There was no significant difference in prevalence of intestinal parasite infection with regard to age,sex,residence area,job type and religion of participants but there was a significant association between the educational status and intestinal parasitic infection.The prevalence of intestinal parasitic infection was higher among illiterate participants.Conclusions:Ascaris lumbricoides was the most common intestinal parasite detected in HIV-infected individuals.Giardia lamblia was the most common protozoal parasite observed.Prevalence of intestinal helminthic infection was higher than protozoal infection.Intestinal parasitosis was significantly associated with an educational status of individuals.

New insights on serodiagnosis of trichinellosis during window period:early diagnostic antigens from Trichinella spiralis intestinal worms

The clinical diagnosis of trichinellosis is difficult because its clinical manifestations are nonspecific.Detection of anti-Trichinella IgG by ELISA using T.spiralis muscle larval excretory-secretory(ES)antigens is the most commonly used serological method for diagnosis of trichinellosis,but the main disadvantage is false negativity during the early stage of infection.There is an obvious window period between Trichinella infection and antibody positivity.During the intestinal stage of Trichinella infection,the ES antigens of intestinal worms(intestinal infective larvae and adults)are exposed to host’s immune system at the earliest time and elicit the production of specific anti-Trichinella antibodies.Anti-Trichinella IgG antibodies in infected mice were detectable by ELISA with ES antigens of intestinal worms as soon as 8-10 days post infection(dpi),but ELISA with muscle larval ES antigens did not permit detection of infected mice before 12 dpi.Therefore,the new early antigens from T.spiralis intestinal worms should be screened,identified and characterized for early serodiagnosis of trichinellosis.

Prevalence and risk factors of undernutrition among schoolchildren in the Plateau Central and Centre-Ouest regions of Burkina Faso

Background:Multiple factors determine children’s nutritional status,including energy and nutrient intake,recurrent infectious diseases,access(or lack thereof)to clean water and improved sanitation,and hygiene practices,among others.The“Vegetables go to School:improving nutrition through agricultural diversification”(VgtS)project implements an integrated school garden programme in five countries,including Burkina Faso.The aim of this study was to determine the prevalence of undernutrition and its risk factors among schoolchildren in Burkina Faso before the start of the project.Methods:In February 2015,a cross-sectional survey was carried out among 455 randomly selected children,aged 8-14 years,in eight schools in the Plateau Central and Centre-Ouest regions of Burkina Faso.Nutritional status was determined by anthropometric assessment.Helminth and intestinal protozoa infections were assessed using the Kato-Katz and a formalin-ether concentration method.A urine filtration technique was used to identify Schistosoma haematobium eggs.Prevalence of anaemia was determined by measuring haemoglobin levels in finger-prick blood samples.Questionnaires were administered to children to determine their knowledge of nutrition and health and their related attitudes and practices(KAP).Questionnaires were also administered to the children’s caregivers to identify basic household socio-demographic and economic characteristics,and water,sanitation and hygiene(WASH)conditions.To determine the factors associated with schoolchildren’s nutritional status,mixed logistic regression models were used.Differences and associations were considered statistically significant if P-values were below 0.05.Results:Complete datasets were available for 385 children.The prevalence of undernutrition,stunting and thinness were 35.1%,29.4%and 11.2%,respectively.The multivariable analysis revealed that undernutrition was associated with older age(i.e.12-14 years compared to<12 years;adjusted odds ratio(aOR)=3.45,95%confidence interval(CI)2.12-5.62,P<0.001),multiple pathogenic parasitic infections(aOR=1.87,95%CI 1.02-3.43,P=0.044)and with moderate and severe anaemia in children(aOR=2.52,95%CI 1.25-5.08,P=0.010).Conclusions:We found high prevalence of undernutrition among the children surveyed in the two study regions of Burkina Faso.We further observed that undernutrition,anaemia and parasitic infections were strongly associated.In view of these findings,concerted efforts are needed to address undernutrition and associated risk factors among school-aged children.As part of the VgtS project,WASH,health education and nutritional interventions will be implemented with the goal to improve children’s health.Trial registration:ISRCTN17968589(date assigned:17 July 2015).