Human Gastrointestinal Diseases Research Articles

RETRACTED ARTICLE: Intestinal Microbiota, Probiotics and Human Gastrointestinal Cancers

Cancers of the gastrointestinal tract account for 25 % of all cancers and for 9 % of all causes of cancer death in the world, so gastrointestinal cancers represent a major health problem. In the past decades, an emerging role has been attributed to the interactions between the gastrointestinal content and the onset of neoplasia. Thus, exogenous microbial administration of peculiar bacterial strains (probiotics) has been suggested as having a profound influence on multiple processes associated with a change in cancer risk. Probiotics are mono or mixed cultures of live microorganisms that might beneficially affect the host by improving the characteristics of indigenous microflora. Although the effects of probiotic administration has been intensively investigated in vitro, in animal models, in healthy volunteers, and in some human gastrointestinal diseases, very little is still known about the possible cross-interactions among probiotic administration, changes of intestinal flora, and the neoplastic transformation of gastrointestinal mucosa. Theoretically, probiotics are able to reduce cancer risk by a number of mechanisms: (a) binding and degradation of potential carcinogens; (b) quantitative, qualitative and metabolic alterations of the intestinal microflora; (c) production of anti-tumorigenic or anti-mutagenic compounds; (d) competitive action towards pathogenic bacteria; (e) enhancement of the host's immune response; (f) direct effects on cell proliferation. This review will attempt to highlight the literature on the most widely recognized effects of probiotics against neoplastic transformation of gastrointestinal mucosa and in particular on their effects on cell proliferation.

Investigation into the role of fiveSalmonella entericaserovar Enteritidis genomic islands in colonization of the chicken reproductive tract and other organs following oral challenge

Salmonella enterica serovar Enteritidis is a major cause of human gastrointestinal tract disease, infection being due in large part to the consumption of contaminated eggs. Recent genome sequencing of S.enterica serovars has identified genomic islands, the presence of which differs between serovars. Using defined mutants, we have investigated the contribution that five such loci play in the colonization of the avian reproductive tract, other organs and avian macrophages. All loci appear to play a small role in infection of liver and spleen, but not in colonization of the reproductive tract or macrophages.

Prevalence of Salmonella spp. in the quail egg interior contents: A provincial study

Background: Poultry products have been recognized as major sources of human gastrointestinal disease caused by Salmonella spp. and several outbreaks have been reported where eggs were the source of human infection. OBJECTIVES: This study was carried out to determine the prevalence of Salmonella spp. in the quail egg interior contents from retail stores of Semnan, Iran and to characterize the isolated Salmonella serovars via serotyping and Multiplex PCR techniques. METHODS: 140 packages of quail eggs (each package containing 12 eggs) were collected from different batches during summer 2010 and tested for the presence of Salmonella through conventional culture and serotyping methods. RESULTS: From these samples, S. enteritidis was detected in the egg contents of one package (0.71 %) out of 140 packages. This isolate was confirmed by Multiplex PCR generated amplification products for a random sequence that is specific for the genus salmonella and spv and sefA genes. CONCLUSIONS: According to our results, S. enteritidis is the most prevalent serotype of quail egg content contaminant in the Semnan area of Iran and the multiplex PCR method could be used as a reliable method of identifying Salmonella serovars.

Dietary Factors: Major Regulators of the Gut's Microbiota

Dietary factors and the associated lifestyle play a major role in the pathophysiology of many diseases. Several diets, especially a Western lifestyle with a high consumption of meat and carbohydrates and a low consumption of vegetables, have been linked to common diseases, such as metabolic syndrome, atherosclerosis, inflammatory bowel diseases, and colon cancer. The gastrointestinal tract harbors a complex and yet mainly molecularly defined microbiota, which contains an enormous number of different species. Recent advances in sequencing technologies have allowed the characterization of the human microbiome and opened the possibility to study the effect of "environmental" factors on this microbiome. The most important environmental factor is probably "what we eat," and the initial studies have revealed fascinating results on the interaction of nutrients with our microbiota. Whereas short-term changes in dietary patterns may not have major influences, long-term diets can affect the microbiota in a substantial manner. This issue may potentially have major relevance for human gastrointestinal health and disease because our microbiota has features to regulate many immune and metabolic functions. Increasing our knowledge on the interaction between nutrients and microbiota may have tremendous consequences and result in a better understanding of diseases, even beyond the gastrointestinal tract, and finally lead to better preventive and therapeutic strategies.

Heterologous expression of the Campylobacter jejuni globins: Roles of CGB and CTB in the nitrosative stress resistance in Escherichia coli

Campylobacter jejuni, one of the main causal agents of human gastrointestinal disease worldwide, is exposed to high concentrations of nitric oxide (NO) produced by the host during transmission and pathogenesis. However, under nitrosative stress conditions, C. jejuni expresses two haemoglobins implicated in tolerance to this condition. One, a single-domain haemoglobin (Cgb) detoxifies NO apparently by its conversion to nitrate via a dioxygenase or denitrosylase activity. The other, (the truncated haemoglobin Ctb) has been linked to oxygen chemistry rather than protection from NO toxicity. Details about the molecular mechanisms of these globins remain obscure, since both lack the reductase domain for restoration of the ferrous state required for ligand-binding activity in the most studied bacterial globin, the Escherichia coli flavohaemoglobin Hmp. In the present work, over-expression of Cgb and Ctb in an hmp mutant of E. coli demonstrated that Cgb but not Ctb complements the NO resistance phenotype. Both Cgb- and Ctb-expressing cell suspensions moderately resist to respiratory inhibition by NO under aerobic conditions. However, only Cgb consumes NO endogenously produced by E. coli in anaerobic conditions. Spectroscopic studies of these proteins reveal that the haem is converted to the ferrous state in the presence of E. coli or C. jejuni soluble extracts. Re-reduction of the haem groups after oxidation by NO suggests the presence of a redox partner or reductant environment in the actual and the heterologous host. Unraveling the molecular mechanisms of these globins constitutes a key step in the understanding of the NO resistance ability of C. jejuni.

Arcobacter in Lake Erie Beach Waters: an Emerging Gastrointestinal Pathogen Linked with Human-Associated Fecal Contamination

The genus Arcobacter has been associated with human illness and fecal contamination by humans and animals. To better characterize the health risk posed by this emerging waterborne pathogen, we investigated the occurrence of Arcobacter spp. in Lake Erie beach waters. During the summer of 2010, water samples were collected 35 times from the Euclid, Villa Angela, and Headlands (East and West) beaches, located along Ohio's Lake Erie coast. After sample concentration, Arcobacter was quantified by real-time PCR targeting the Arcobacter 23S rRNA gene. Other fecal genetic markers (Bacteroides 16S rRNA gene [HuBac], Escherichia coli uidA gene, Enterococcus 23S rRNA gene, and tetracycline resistance genes) were also assessed. Arcobacter was detected frequently at all beaches, and both the occurrence and densities of Arcobacter spp. were higher at the Euclid and Villa Angela beaches (with higher levels of fecal contamination) than at the East and West Headlands beaches. The Arcobacter density in Lake Erie beach water was significantly correlated with the human-specific fecal marker HuBac according to Spearman's correlation analysis (r = 0.592; P < 0.001). Phylogenetic analysis demonstrated that most of the identified Arcobacter sequences were closely related to Arcobacter cryaerophilus, which is known to cause gastrointestinal diseases in humans. Since human-pathogenic Arcobacter spp. are linked to human-associated fecal sources, it is important to identify and manage the human-associated contamination sources for the prevention of Arcobacter-associated public health risks at Lake Erie beaches.

Application of baculovirus as a delivery vehicle for study of transcription and translation mechanism of parvovirus in non-permissive mammalian cells

Human bocavirus (HBoV) is a parvovirus associated with respiratory and gastrointestinal diseases in humans. Recombinant baculoviruses have been used widely for many years to transduce transiently and stably a variety of mammalian cell types at high frequencies. In this study, to explore further the use of baculovirus as a gene delivery vehicle for study of transcription and translation mechanism of human bocavirus which lacks susceptible cell culture system, two recombinant baculoviruses were constructed: Bac-BoV-EGFP in which the EGFP gene was under the control of the HBoV1 promoter, and Bac-HBoV1 encompassing the nearly whole HBoV1 genome without both termini. The data demonstrated that efficient gene delivery and expression were observed in numerous mammalian cells transduced by Bac-BoV-EGFP and the transduction rate was much greater than that in plasmid-based transfected cells. The analysis of transcription and translation in Bac-HBoV1 transduced A549 cells showed that two transcripts from NP1 gene were detected by RT-PCR and the NP1 was localized in the nucleus, suggesting that the Bac-HBoV1 recombinant baculovirus delivered efficiently the HBoV1 genome into A549 cells. In summary, this system provides a useful tool for analysis of the transcription and translation of some viruses lacking a virus-cell replication system.

Yersinia Enterocolitica:A Brief Review of the Issues Relating to the Zoonotic Pathogen, Public Health Challenges, and the Pork Production Chain

Yersinia enterocolitica is a zoonotic agent that causes gastrointestinal disease in humans, as well as reactive arthritis and erythema nodosum. Enteropathogenic Yersinia are the etiological agents for yersiniosis, which can be acquired through the consumption of contaminated foods. As porcine animals are the main carriers of Y. enterocolitica, food safety measures to minimize human infection are of increasing interest to the scientific and medical community. In this review, we examine why it is imperative that information on the reservoirs, prevalence, virulence, and ability of this pathogen to survive in different environments is further investigated to provide rational measures to prevent or decrease associated disease risks.

A comprehensive review of diagnostic techniques for detection of cryptosporidium parvum in stool samples

–Cryptosporidium parvum is a significant cause of gastrointestinal disease in humans. Many diagnostic techniques are available for its detection. Most of these includeMicroscopic methods, Serological methods, and Molecular methods. The present review aims in describing various diagnostic techniques available along with their advantages and limitations. Keywords––Cryptosporidium parvum, diagnostic techniques, stool sample

Current situation ofGiardiainfection in Spain: Implications for public health

Giardia is an enteric protozoan that infects a wide range of vertebrate hosts, being considered a major causative agent of gastrointestinal disease in humans in both developing and developed countries. Giardia infection has also a significant impact on livestock health, causing diarrhoea and resulting in significant economic lost. Transmission is either direct, through the faecal-oral route, or indirect, through ingestion of contaminated water or food. In this article, we review current knowledge about the epidemiology of giardiasis in different populations in Spain, including humans, livestock, companion animals, and wildlife. Environmental contamination of surface waters and raw foods by Giardia cysts is also addressed. Special relevance has been given to the data available on the molecular characterization of the Giardia isolates obtained from clinical and environmental samples, as determining thespecies/assemblages and subassemblages involved is essential for accurately identifying the parasite and assessing zoonotic transmission. The public health significance of these findings has also been thoroughly discussed.

Enterotoxigenic &lt;i&gt;Clostridium perfringens&lt;/i&gt;: Detection and Identification

Recent advances in understanding the genetics of enterotoxigenic Clostridium perfringens, including whole genome sequencing of a chromosomal cpe strain and sequencing of several cpe-carrying large plasmids, have led to the development of molecular approaches to more precisely investigate isolates involved in human gastrointestinal diseases and isolates present in the environment. Sequence-based PCR genotyping of the cpe locus (cpe genotyping PCR assays) has provided new information about cpe-positive type A C. perfringens including: 1) Foodborne C. perfringens outbreaks can be caused not only by chromosomal cpe type A strains with extremely heat-resistant spores, but also less commonly by less heat-resistant spore-forming plasmid cpe type A strains; 2) Both chromosomal cpe and plasmid cpe C. perfringens type A strains can be found in retail foods, healthy human feces and the environment, such as in sewage; 3) Most environmental cpe-positive C. perfringens type A strains carry their cpe gene on plasmids. Moreover, recent studies indicated that the cpe loci of type C, D, and E strains differ from the cpe loci of type A strains and from the cpe loci of each other, indicating that the cpe loci of C. perfringens have remarkable diversity. Multi-locus sequence typing (MLST) indicated that the chromosomal cpe strains responsible for most food poisoning cases have distinct genetic characteristics that provide unique biological properties, such as the formation of highly heat-resistant spores. These and future advances should help elucidate the epidemiology of enterotoxigenic C. perfringens and also contribute to the prevention of C. perfringens food poisoning outbreaks and other CPE-associated human diseases.

Molecular mechanisms that mediate colonization of Shiga toxin-producing Escherichia coli strains.

Shiga toxin-producing Escherichia coli (STEC) is a group of pathogens which cause gastrointestinal disease in humans and have been associated with numerous food-borne outbreaks worldwide. The intimin adhesin has been considered for many years to be the only colonization factor in these strains. However, the rapid progress in whole-genome sequencing of different STEC serotypes has accelerated the discovery of other adhesins (fimbrial and afimbrial), which have emerged as important contributors to the intestinal colonization occurring during STEC infection. This review summarizes recent progress to identify and characterize, at the molecular level, novel adhesion and colonization factors in STEC strains, with an emphasis on their contribution to virulence traits, their host-pathogen interactions, the regulatory mechanisms controlling their expression, and their role as targets eliciting immune responses in the host.

Inhibitory Effects of Nisin Against Clostridium perfringens Food Poisoning and Nonfood‐Borne Isolates

The enterotoxigenic Clostridium perfringens type A is the causative agent of C. perfringens type A food poisoning (FP) and nonfood-borne (NFB) human gastrointestinal diseases. Due to its ability to form highly resistant endospores, it has become a great concern to the meat industry to produce meat free of C. perfringens. In this study, we evaluated the antimicrobial effect of nisin against C. perfringens FP and NFB isolates. No inhibitory effect of nisin was observed against germination of spores of both FP and NFB isolates in laboratory medium. However, nisin effectively arrested outgrowth of germinated spores of C. perfringens in rich medium. Interestingly, germinated spores of NFB isolates possessed higher resistance to nisin than that of FP isolates. Furthermore, nisin exhibited inhibitory effect against vegetative growth of both FP and NFB isolates in laboratory medium, with vegetative cells of NFB isolates showing higher resistance than that of FP isolates. However, the antimicrobial activity of nisin against C. perfringens was significantly decreased in a meat model system. In conclusion, although nisin showed inhibitory effect against spore outgrowth and vegetative cells of C. perfringens FP and NFB isolates in laboratory conditions, no such effect was observed against C. perfringens spores inoculated into a meat model system.

Aeromonas salmonicida-secreted protein AopP is a potent inducer of apoptosis in a mammalian and a Drosophila model

Some pathogens are able to establish themselves within the host because they have evolved mechanisms to disrupt host innate immunity. For example, a number of pathogens secrete preformed effector proteins via type III secretion apparatuses that influence innate immune or apoptotic signalling pathways. One group of effector proteins that usurp innate immune signalling is the YopJ-like family of bacterial effector proteins, which includes AopP from Aeromonas salmonicida. Aeromonas species are known to cause gastrointestinal disease in humans, and are associated mainly with subcutaneous wound infections and septicaemia in other metazoans, particularly fish. AopP has been reported to have inhibitory activity against the NF-κB pathway in cultured cells, although the pathological outcomes of AopP activity have not been examined. Here, we show that AopP has potent pro-apoptotic activity when expressed in cultured mammalian macrophage or epithelial cells, or when ectopically expressed in Drosophila melanogaster haemocytes or imaginal disk epithelial cells. Furthermore, apoptosis was significantly elevated upon concurrent AopP expression and TNF-α cellular stimulation. Together, our results demonstrate how the specificity of a YopJ-like protein towards signalling pathways directly governs cellular pathological outcome in disease.

In Vitro Susceptibility Testing of Dientamoeba fragilis

Dientamoeba fragilis is a commonly encountered trichomonad which has been implicated as a cause of gastrointestinal disease in humans. Despite the frequency of reports recording infections with this parasite, little research has been undertaken in terms of antimicrobial susceptibility. The aim of this study was to evaluate the susceptibility of D. fragilis to several commonly used antiparasitic agents: diloxanide furoate, furazolidone, iodoquinol, metronidazole, nitazoxanide, ornidazole, paromomycin, secnidazole, ronidazole, tetracycline, and tinidazole. Antibiotic susceptibility testing was performed on four clinical strains of D. fragilis, designated A, E, M, and V, respectively. Molecular testing followed, and all strains were determined to be genotype 1. The activities of antiprotozoal compounds at concentrations ranging from 2 μg/ml to 500 μg/ml were determined via cell counts of D. fragilis trophozoites grown in dixenic culture. Minimum lethal concentrations (MLCs) were as follows: ornidazole, 8 to 16 μg/ml; ronidazole, 8 to 16 μg/ml; tinidazole, 31 μg/ml; metronidazole, 31 μg/ml; secnidazole, 31 to 63 μg/ml; nitazoxanide, 63 μg/ml; tetracycline, 250 μg/ml; furazolidone, 250 to 500 μg/ml; iodoquinol, 500 μg/ml; paromomycin, 500 μg/ml; and diloxanide furoate, >500 μg/ml. This is the first study to report the profiles of susceptibility to a wide range of commonly used treatments for clinical isolates of D. fragilis. Our study indicated 5-nitroimidazole derivatives to be the most active compounds in vitro against D. fragilis.

Can a Strychnos species be used as antiulcer agent? Ulcer healing action from alkaloid fraction of Strychnos pseudoquina St. Hil. (Loganiaceae)

Ethnopharmacological relevanceStrychnos pseudoquina St. Hil. (Loganiaceae) is one Brazilian native medicinal species described in the first edition of the Brazilian Official Pharmacopoeia in 1929. This medicinal plant, popularly known as “quina-quina”, “quina-branca” or “casca aromatica was very commonly used in folk medicine in tea form obtained from the bark and/or leaves as tonic, antipyretic, antimalarial and mainly against diseases of the liver, spleen and stomach. Aim of the studyPrevious study already characterized the gastroprotective action of this species The aim of the present study is to elucidate the mechanism of the healing process mediated by the methanolic extract (ME) and their enriched alkaloid fraction (EAF) from Strychnos pseudoquina in chronic gastric ulceration induced by 5% acetic acid in rats, an experimental model that accurately reflects human gastrointestinal disease. Material and methodsThe ME and EAF was administered orally in a single dose (based on previously study of dose–response curve) for 14 days after chronic ulceration was induced in rats. The healing effect of ME and EAF was evaluated by macroscopic and morphometric analyses, immunohistochemical assay (PCNA and SOD) and anti-Helicobacter pylori effect was evaluated by in vitro assay. ResultsOur results demonstrated that EAF significantly reduced border internal (42%) and external (38%) lesion area (mm2) by macroscopic analyses (P<0.05). Animals treated with EAF stimulated some proliferative factors by increasing the height of epithelial regenerative area and the expression of PCNA-positive nuclei. The number of vessels in gastric mucosa of rats treated with EAF reveals an expressive increase (4 times more than vehicle treatment) of vessels that stimulate cells proliferation in the healing region. These results suggest that the recovery of vascularization of the ulcerated area is involved in the healing action of alkaloid fraction of Strychnos pseudoquina. The MIC (minimum inhibitory concentration) of 75μg/ml from EAF showed an effective in vitro anti-Helicobacter pylori action of this fraction. EAF also was quite effective in the process of SOD release that is an important protective factor against bacterial agents. The efficacy of EAF was accomplished safely without presenting any alteration of toxicological parameters during 14 day of treatment. ConclusionsThe expressive gastric healing effect by increasing cellular proliferation together with expression of SOD activity and antibacterial action against Helicobacter pylori confirm the efficacy of this species in heal gastric mucosa and these results are a important contribution to the knowledge of a crude drug presents at the Brazilian Official Pharmacopoeia since 1929.

Confocal laser endomicroscopy and narrow-band imaging-aided endoscopy for in vivo imaging of colitis and colon cancer in mice

New endoscopic techniques such as narrow-band imaging (NBI) and confocal laser endomicroscopy (CLE) have improved the in vivo diagnosis of human gastrointestinal diseases in the colon. Whereas NBI may facilitate the identification of neoplastic lesions, CLE permits real-time histology of the inflamed or neoplastic colonic mucosa through the use of fluorescent dyes. These techniques have been recently adopted for use during ongoing endoscopy in mice. This protocol, which can be completed in 2 h, provides a detailed description of NBI and CLE in the mouse colon. In contrast to other techniques, this approach does not require laparotomy, and it allows direct CLE analysis of lesions identified by NBI. Mice exposed to models of colitis or colorectal cancer are anesthetized and examined with a miniaturized NBI endoscope, which provides an increased contrast of the vasculature. Upon identification of suspicious areas by NBI and the administration of fluorescent dyes, a confocal laser probe can be directed to the area of interest through the endoscope and confocal images can be obtained. Through the use of various fluorescent dyes, different aspects of the mucosa can be assessed. In addition, fluorescence-labeled antibodies can be used for molecular imaging of mice in vivo. Mouse NBI endoscopy and CLE represent reliable and fast high-quality techniques for the endoscopic characterization and molecular imaging of the mucosa in colitis and colon cancer.

Neutralization effects of egg yolk immunoglobulin (IgY) and Fab' fragment against lipopolysaccharide (LPS) in burned mice model

The aim of this study is to evaluate the neutralization effects of egg yolk immunoglobulin (IgY) and Fab’ fragment against lipopolysaccharide (LPS), and identify possible approaches to prevent and treat LPS related injuries. Mice with third-degree burns covering 30% of the total body surface and exposed to LPS were orally administered with the IgY or Fab’ fragment of egg yolk immunoglobulin at 6, 12, 24 and 48 h after burning. The mortality rates and circulating levels of LPS, tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) were determined. The mortality rate of mice in the IgY-treated groups and Fab’treated groups were significantly lower when compared with the control groups (without treatment). The levels of LPS, TNF-α and IL-6 in the IgY-treated group and Fab’-treated group were lower than those in the control group, and Fab’-treated group posses much lower levels of LPS, TNF-α and IL-6 than IgYtreated group. The IgY and Fab’ fragment of egg yolk immunoglobulin raised against LPS may be used to inhibit and treat tissue injury caused by LPS. IgY technology has significant future opportunities for the prevention and treatment of LPS related infectious gastrointestinal diseases in humans and animals.

Identification of Novel Clostridium perfringens Type E Strains That Carry an Iota Toxin Plasmid with a Functional Enterotoxin Gene

Clostridium perfringens enterotoxin (CPE) is a major virulence factor for human gastrointestinal diseases, such as food poisoning and antibiotic associated diarrhea. The CPE-encoding gene (cpe) can be chromosomal or plasmid-borne. Recent development of conventional PCR cpe-genotyping assays makes it possible to identify cpe location (chromosomal or plasmid) in type A isolates. Initial studies for developing cpe genotyping assays indicated that all cpe-positive strains isolated from sickened patients were typable by cpe-genotypes, but surveys of C. perfringens environmental strains or strains from feces of healthy people suggested that this assay might not be useful for some cpe-carrying type A isolates. In the current study, a pulsed-field gel electrophoresis Southern blot assay showed that four cpe-genotype untypable isolates carried their cpe gene on a plasmid of ∼65 kb. Complete sequence analysis of the ∼65 kb variant cpe-carrying plasmid revealed no intact IS elements and a disrupted cytosine methyltransferase (dcm) gene. More importantly, this plasmid contains a conjugative transfer region, a variant cpe gene and variant iota toxin genes. The toxin genes encoded by this plasmid are expressed based upon the results of RT-PCR assays. The ∼65 kb plasmid is closely related to the pCPF4969 cpe plasmid of type A isolates. MLST analyses indicated these isolates belong to a unique cluster of C. perfringens. Overall, these isolates carrying a variant functional cpe gene and iota toxin genes represent unique type E strains.

Human immunodeficiency virus-associated gastrointestinal disease: common endoscopic biopsy diagnoses.

The gastrointestinal (GI) tract is a major site of disease in HIV infection: almost half of HIV-infected patients present with GI symptoms, and almost all patients develop GI complications. GI symptoms such as anorexia, weight loss, dysphagia, odynophagia, abdominal pain, and diarrhea are frequent and usually nonspecific among these patients. Endoscopy is the diagnostic test of choice for most HIV-associated GI diseases, as endoscopic and histopathologic evaluation can render diagnoses in patients with non-specific symptoms. In the past three decades, studies have elucidated a variety of HIV-associated inflammatory, infectious, and neoplastic GI diseases, often with specific predilection for various sites. HIV-associated esophageal disease, for example, commonly includes candidiasis, cytomegalovirus (CMV) and herpes simplex virus (HSV) infection, Kaposi's sarcoma (KS), and idiopathic ulceration. Gastric disease, though less common than esophageal disease, frequently involves CMV, Mycobacterium avium-intracellulare (MAI), and neoplasia (KS, lymphoma). Small bowel biopsies and intestinal aspirates from HIV-infected patients often show HIV enteropathy, MAI, protozoa (Giardia, Isospora, Cryptosporidia, amebae, Microsporidia), and helminths (Strongyloides stercoralis). Colorectal biopsies demonstrate viral (CMV, HSV), bacterial (Clostridia, Salmonella, Shigella, Campylobacter), fungal (cryptococcosis, histoplasmosis), and neoplastic (KS, lymphoma) processes. Herein, we review HIV-associated GI pathology, with emphasis on common endoscopic biopsy diagnoses.