Protozoan infections of the gastrointestinal tract

A cell-cycle-dependent GARP-like transcriptional repressor regulates the initiation of differentiation in Giardia lamblia

Transcriptional regulation of differentiation is critical for parasitic pathogens to adapt to environmental changes and regulate transmission. In response to encystation stimuli, Giardia lamblia shifts the distribution of the cell cycle toward G2 and induces the expression of cyst wall proteins (CWPs) within 2 to 4 h, indicating that key regulatory steps occur within the first 4 h of encystation. However, the role of transcription factors (TFs) in encystation has primarily been investigated at later time points. How TFs initiate encystation and link it to the cell cycle remains enigmatic. Here, we systematically screened six putative early up-regulated TFs for nuclear localization, established their dynamic expression profiles, and determined their functional role in regulating encystation. We found a critical repressor, Golden2, ARR-B, Psr-1–like protein 1 (GARP)–like protein 4 (GLP4), that increases rapidly after 30 min of encystation stimuli and down-regulates encystation-specific markers, including CWPs and enzymes in the cyst N-acetylgalactosamine pathway. Depletion of GLP4 increases cyst production. Importantly, we observe that G2+M cells exhibit higher levels of CWP1, resulting from the activation of myeloblastosis domain protein 2 (MYB2), a TF previously linked to encystation in Giardia. GLP4 up-regulation occurs in G1+S cells, suggesting a role in repressing MYB2 and encystation-specific genes in the G1+S phase of the cell cycle. Furthermore, we demonstrate that depletion of GLP4 up-regulates MYB2 and promotes encystation while overexpression of GLP4 down-regulates MYB2 and represses encystation. Together, these results suggest that Giardia employs a dose-dependent transcriptional response that involves the cell-cycle–regulated repressor GLP4 to orchestrate MYB2 and entry into the encystation pathway.

ECCO Topical Review on Clinicopathological Spectrum and Differential Diagnosis of Inflammatory Bowel Disease

INTRODUCTION

Many diseases can imitate inflammatory bowel disease [IBD] clinically and pathologically. This review outlines the differential diagnosis of IBD and discusses morphological pointers and ancillary techniques that assist with the distinction between IBD and its mimics.

METHODS

European Crohn's and Colitis Organisation [ECCO] Topical Reviews are the result of an expert consensus. For this review, ECCO announced an open call to its members and formed three working groups [WGs] to study clinical aspects, pathological considerations, and the value of ancillary techniques. All WGs performed a systematic literature search.

RESULTS

Each WG produced a draft text and drew up provisional Current Practice Position [CPP] statements that highlighted the most important conclusions. Discussions and a preliminary voting round took place, with subsequent revision of CPP statements and text and a further meeting to agree on final statements.

CONCLUSIONS

Clinicians and pathologists encounter a wide variety of mimics of IBD, including infection, drug-induced disease, vascular disorders, diverticular disease, diversion proctocolitis, radiation damage, and immune disorders. Reliable distinction requires a multidisciplinary approach.

Interactions between Cryptosporidium, Enterocytozoon, Giardia and Intestinal Microbiota in Bactrian Camels on Qinghai-Tibet Plateau, China

Cryptosporidium spp., Enterocytozoon bieneusi, and Giardia duodenalis are zoonotic pathogens commonly found in the intestinal tract of mammalian hosts including livestock and humans. The prevalence of these eukaryote microorganisms in domestic animals and their interaction with intestinal microbiota are not yet fully recognized. We analyzed the intestinal microbiota composition with metagenomics and functional characterization with Cluster of Orthologous (COG) in Bactrian camels, which were raised on Qinghai-Tibet Plateau, Northwest China. Thus, fecal samples were collected from the animals to determine the parasite infection and the profile of microbiota. Analysis of intestinal microbiota at genus level revealed important features of interaction between parasites infection and bacterial community. Coprococcus and Prevotella were more abundant while Akkermansia had lower relative abundance with E. bieneusi infection. Bacteria of Akkermansia, Lactococcus, Oxalobacter, Sphaerochaeta, Paludibacter, Fibrobacter, Anaerovibrio, Pseudomonas, Mogibacterium, Pseudoramibacter_Eubacterium, YRC22, Flexispira, SMB53, AF12, and Roseburia genera were found under-presented and Oscillospira genus over-presented when G. duodenalis infection was present. Meanwhile, Cryptosporidium spp. and E. bieneusi co-infected animals showed lower relative abundance of Allobaculum, Rikenella, Shuttleworthia, Epulopiscium, Bilophila, Dorea, Fibrobacter, and TG5. Results demonstrate important interaction between the intestinal parasites and microbiota, and provide informative link for understanding the co-evolution of zoonotic pathogens and bacteria in domestic animals.

Acute abdominal syndrome revealing an intestinal amoebiasis: Report of two cases in Tunisia

Amoebiasis is a parasitosis, mainly caused by Entamoeba histolytica (E. histolytica). It is a common disease in tropical and subtropical regions. E. histolytica possesses different mechanisms of pathogenicity, and might lead to the invasion and lysis of the intestinal epithelium. Outside of the high-risk regions, acute intestinal amoebiasis is a very rare condition, often leading to misdiagnosis and death, if not promptly treated. We discuss the cases of 18 and 43 year-old men without medical history, who presented to the emergency department complaining of acute abdominal pain along with fever. Following imaging features and clinical presentation, appendicitis and a complicated form of Crohn's disease were respectively suspected. Given the severity of the symptoms, an explorative laparotomy was performed showing in both cases an inflammatory aspect of the intestine. Histological examination concluded intestinal amoebiasis, a diagnosis that wasn't suspected at first. The learning point of these cases is considering invasive intestinal amoebiasis in patients presenting with an acute abdominal syndrome, even with no history of traveling abroad or immunodeficiency.

Host-adapted Cryptosporidium and Enterocytozoon bieneusi genotypes in straw-colored fruit bats in Nigeria

Few data are available on the distribution and human infective potential of Cryptosporidium and Enterocytozoon bieneusi genotypes in bats. In this preliminary study, we collected 109 fecal specimens during April-July 2011 from a colony of straw-colored fruit bats (Eidolon helvum) in an urban park (Agodi Gardens) of Ibadan, Nigeria, and analyzed for Cryptosporidium spp., Giardia duodenalis and E. bieneusi using PCR targeting the small subunit rRNA gene, triosephosphate isomerase gene, and ribosomal internal transcribed spacer, respectively. Genotypes of these enteric parasites were determined by DNA sequencing of the PCR products. Altogether, 6 (5.5%), 0 and 16 (14.7%) specimens were positive for Cryptosporidium spp., G. duodenalis, and E. bieneusi, respectively. DNA sequence analysis of the PCR products indicated the presence of two novel Cryptosporidium genotypes named as bat genotype XIV (in 5 specimens) and bat genotype XV (in 1 specimen) and one known E. bieneusi genotype (Type IV in 1 specimen) and two novel E. bieneusi genotypes (Bat1 in 13 specimens and Bat2 in 2 specimens). In phylogenetic analysis of DNA sequences, the two novel Cryptosporidium genotypes were genetically related to Bat genotype II previously identified in fruit bats in China and Philippines, whereas the two novel E. bieneusi genotypes were genetically related to Group 5, which contains several known genotypes from primates. With the exception of Type IV, none of the Cryptosporidium and E. bieneusi genotypes found in bats in this study are known human pathogens. Thus, straw-colored fruit bats in Nigeria are mainly infected with host-adapted Cryptosporidium and E. bieneusi genotypes.

In vivo treatment with nitazoxanide induces anaerobic metabolism in experimental intraperitoneal cysticercosis

Taenia crassiceps cysticerci are used as experimental model to study the host-parasite relationship and treatment of cysticercosis. One of the described mode of actions of nitazoxanide (NTZ) is to block the pyruvate ferredoxine oxidoreductase (PFOR) enzyme which is an essential enzyme to the parasite metabolism. The aim of this study was to determine the in vivo influence of one dosage of NTZ on the energetic metabolism of T. crassiceps cysticerci. Thirty days after the intraperitoneal inoculation of T. crassiceps cysticerci, BALB/c mice were orally treated with 7.5 mg/kg of NTZ. The control group was treated with physiologic solution (NaCl 0.9%). After 24 h, the animals were euthanized and the cysticerci were removed, washed, and processed for biochemical analysis. The organic acids detection occurred through high-performance liquid chromatographic and spectrophotometric analysis. While there was no difference in the glucose dosages, it was possible to observe a significant increase in the lactate concentrations and a decrease in the pyruvate concentrations of the NTZ-treated groups when compared to the control group. Also, there was a decrease in the urea and alpha-ketoglutarate concentrations. This probably occurred due to the impairment of the parasite's PFOR and nitroreductases leading an impairment of the mitochondrial aerobic pathways. In conclusion, the in vivo NTZ treatment leads to an increase in the lactic fermentation and to a decrease in the protein catabolism in T. crassiceps cysticerci.

An overview of parasitic infections of the gastro-intestinal tract in developed countries affecting immunocompromised individuals

In both developed and developing countries, parasitic infections continue to be a frequent cause of mortality and morbidity. Due to the globalization of the world, doctors must be fully prepared to deal with a plethora of parasitic infections. More commonly the gastrointestinal (GI) tract is infected and in developed countries protozoans are more likely to be the cause of infection compared to helminths. These GI protozoa are progressively becoming recognized as important pathogens in patients that are immunocompromised. The number of immunocompromised patients is increasing and therefore the likelihood of similar infections will also increase. This paper aims to highlight the key GI parasites affecting immunocompromised individuals in developed countries, discussing diagnosis, treatment options and also prevention. Cryptosporidium parvum may be the most common GI parasite found in the immunocompromised host closely followed by Cyclospora, however, Giardia duodenalis is the most common GI parasite found in developed countries. The pathogenesis of parasitic infection is not clear, poorly understood and diagnostic testing remains difficult with management continuing to be a challenge.

[Gastrointestinal infections]

Infectious diarrhea is one of the most common diseases. This article summarizes the current state of the diagnostics and treatment and includes the most important pathogens, i.e. Norovirus, Rotavirus, Campylobacter, Salmonella, Shigella and pathogenic Escherichia coli. Infections caused by toxin-producing strains of Clostridium difficile are described in more detail due to the increasing importance. Symptomatic therapy is still the most important component of treatment. Empirical antibiotic therapy is reserved for severely ill patients with a high stool frequency, fever, bloody diarrhea, underlying immune deficiency or significant comorbidities. Increasing bacterial resistance (in particular against fluoroquinolones) has to be considered. Motility inhibitors are not recommended for infections due to Shiga toxin-producing E. coli, C. difficile infections (CDI) and severe enterocolitis caused by other pathogens. The macrocyclic antibiotic fidaxomicin can reduce the recurrence rate of CDI. Fecal microbiota transplantation (FMT) currently provides a reserve treatment option for multiple recurrences of CDI and is subject to the Medicines Act (Arzneimittelgesetz, AMG) in Germany.

Antimicrobial therapy of acute diarrhoea: a clinical review

Diarrhoea is one of the most commonly occurring diseases. This article presents a review of the current state of the treatment of acute infectious diarrhoea, as well as of the most important pathogens. The general principles of the therapy of diarrhoea are exemplified, followed by a description of the targeted antimicrobial therapy of the most important bacterial gastrointestinal infections, including salmonellosis, shigellosis and Campylobacter infections, as well as infections with pathogenic Escherichia coli strains, yersiniosis and cholera. Diarrhoea caused by toxigenic Clostridium difficile strains has increased in incidence and in severity. These infections will therefore be described in detail, including important new aspects of treatment. Symptomatic therapy is still the most important component of the treatment of infectious diarrhoea. However, empirical antibiotic therapy should be considered for severely ill patients with a high frequency of stools, fever, bloody diarrhoea, underlying immune deficiency, advanced age or significant comorbidities. Increasing resistance, in particular against fluoroquinolones, must be taken into consideration. Therapy with motility inhibitors is not recommended for Shiga toxin-producing Escherichia coli (STEC) infections, Clostridium difficile infections (CDI), and severe colitis. The macrocyclic antibiotic fidaxomicin can reduce the rate of recurrent disease in CDI. Furthermore, evidence for the benefits of faecal microbiota transplantation as a treatment option for multiple recurrences of CDI is increasing. In conclusion, the treatment of acute diarrhoea is still primarily supportive. General empirical antibiotic therapy for acute diarrhoea is not evidence-based.

Parasitic infections in travelers and immigrants: part I protozoa

ABSTRACT 

The growth in international commerce, travel and migration contribute to the global emergence of certain parasitic infections. Importation of vectors and food products may contribute to the emergence of protozoan infections in nonendemic countries. Infections such as malaria are potentially fatal, especially in nonimmune patients, and outcome depends largely on timely diagnosis and treatment. Diagnosis/management of imported parasitic infections may be complex especially as some patients may have underlying immunosuppressive conditions such as HIV infection. Major challenges concern the development of improved diagnostic techniques, safer/more effective drug therapies and identification of biological markers of progression and response to treatment. Imported parasitic diseases which may be transmitted vertically or through blood transfusion/organ donation could become a public health priority in the near future. Climate change may affect arthropod distribution and facilitate the spread of protozoan vector-borne diseases. The first part of this review focuses on protozoan infections in travelers and immigrants.

[Protozoa and protozoan infections of humans in Central Europe]

This article is a condensed review of the medically relevant protozoa in Central Europe and the infections and diseases caused by them. Information is given on modes and sources of infection, organs involved in the disease, prevalence, diagnostics, therapy, and prophylaxis. Moreover, travel-associated infections with protozoa are briefly outlined.

[Drug therapy of infectious diarrhea. Part 2: Chronic diarrhea]

Diarrheal diseases are among the most common diseases worldwide. In this review the current treatment recommendations for acute (Part 1) and chronic (Part 2) infectious diarrhea are summarized and typical enteropathogens are discussed. The second part of the article describes chronic diarrhea, its related pathogens and treatment. In contrast to acute diarrhea which is mainly caused by viral and typical bacterial pathogens, chronic diarrhea has mainly non-infectious origins. Protozoal pathogens, such as Giardia lamblia and Entamoeba histolytica in particular are found and more rarely bacterial pathogens, such as Tropheryma whipplei. Opportunistic pathogens cause diarrhea in immunocompromised patients, such as in HIV patients. In these patients cytomegalovirus (CMV) colitis or infections with Cryptosporidium spp., Cyclospora cayetanensis, Isospora belli or microsporidia have to be considered. Besides targeted specific antimicrobial therapy, anti-retroviral drugs improving the underlying immunosuppression and thus the reconstitution of the adaptive immune response remain a cornerstone of the treatment in HIV-positive patients.

Screening and identification of inhibitors against influenza A virus from a US drug collection of 1280 drugs

Infection with influenza A virus is still a global concern since it causes significant mortality, morbidity and economic loss. New burst pandemics and rapid emergence of drug-resistance strains in recent years call for novel antiviral therapies. One promising way to overcome this problem is searching new inhibitors among thousands of drugs approved in the clinic for the treatment of different diseases or approved to be safe by clinical trials. In the present work, a collection of 1280 compounds, most of which have been clinically used in human or animal, were screened for anti-influenza activity and 41 hits (SI>4.0) were obtained. Next the 18 hit compounds with SI >10.0 were tested for antiviral activity against 7 other influenza virus strains in canine-originated MDCK cells, 9 compounds exhibited broad antiviral spectrum. The antiviral effects of the 9 compounds were also confirmed in human-originated A549 cells and chicken-originated DF1 cells, by infectious virus yield reduction assay and indirect immunofluorescent assay. Results from the time of addition assay showed that the 9 candidates impaired different stages of influenza virus life cycle, indicating they are novel inhibitors with different mechanisms compared with the existing M2 ion-channel blockers or neuraminidase (NA) inhibitors. Taken together, our findings provide 9 novel drug candidates for the treatment of influenza virus infection. Further mechanism of action study of these inhibitors may lead to the discovery of new anti-influenza targets and structure-activity relationship (SAR) study can be initiated to improve the efficacy of these new classes of influenza inhibitors.

Childhood parasitic infections endemic to the United States

Endemic parasitic infections in the United States are more frequent than is commonly perceived. Intestinal parasitic infection with Cryptosporidium, Dientamoeba, and Giardia occurs most often in children in northern states during the summer months. Zoonotic Toxocara and Toxoplasma parasitic infections are more frequent in southern states, in African Americans, and in populations with lower socioeconomic status. Approximately 300, 000 people in the United States have Trypanosoma cruzi infection. Local, vector-borne transmission of T cruzi and Leishmania infections has been documented in southern states. Parasitic diseases endemic to the United States are not uncommon but are understudied.

Prevalence of intestinal protozoa infection among school-aged children on Pemba Island, Tanzania, and effect of single-dose albendazole, nitazoxanide and albendazole-nitazoxanide

Background

Pathogenic intestinal protozoa infections are common in school-aged children in the developing world and they are frequently associated with malabsorption syndromes and gastrointestinal morbidity. Since diagnosis of these parasites is difficult, prevalence data on intestinal protozoa is scarce.

Methods

We collected two stool samples from school-aged children on Pemba Island, Tanzania, as part of a randomized controlled trial before and 3 weeks after treatment with (i) single-dose albendazole (400 mg); (ii) single-dose nitazoxanide (1,000 mg); (iii) nitazoxanide-albendazole combination (1,000 mg–400 mg), with each drug given separately on two consecutive days; and (iv) placebo. Formalin-fixed stool samples were examined for the presence of intestinal protozoa using an ether-concentration method to determine the prevalence and estimate cure rates (CRs).

Results

Almost half (48.7%) of the children were diagnosed with at least one of the (potentially) pathogenic protozoa Giardia intestinalis, Entamoeba histolytica/E. dispar and Blastocystis hominis. Observed CRs were high for all treatment arms, including placebo. Nitazoxanide showed a significant effect compared to placebo against the non-pathogenic protozoon Entamoeba coli.

Conclusions

Intestinal protozoa infections might be of substantial health relevance even in settings where they are not considered as a health problem. Examination of a single stool sample with the ether-concentration method lacks sensitivity for the diagnosis of intestinal protozoa, and hence, care is indicated when interpreting prevalence estimates and treatment effects.

Diarrhoea due to small bowel diseases

Small intestinal diseases are a common, though often overlooked cause of diarrhoeal illness. Fully 1% of the Caucasian population are affected by coeliac disease and a substantial portion of children living in poverty in the developing world are affected by environmental enteropathy. These are but two examples of the many diseases that cause mucosal injury to the primary digestive and absorptive organ in our body. While diarrhoea may be a common, though not universally seen symptom of small bowel mucosal disease, the consequent malabsorption can lead to substantial malnutrition and nutrient deficiencies. The small intestine, unlike the colon, has been relatively inaccessible, and systematic evaluation is often necessary to identify and treat small intestinal mucosal diseases that lead to diarrhoea. Immunodeficiency states, including HIV enteropathy, adult autoimmune enteropathy, drug-associated enteropathy, and tropical sprue continue to occur and require specific therapy. All patients with severe diarrhoea or diarrhoea associated with features suggestive of malabsorption may have a disease of the small intestinal mucosa that requires careful evaluation and targeted management.