Association between Giardia duodenalis and coinfection with other diarrhea-causing pathogens in India.

Giardia duodenalis, is often seen as an opportunistic pathogen and one of the major food and waterborne parasites. Some insights of Giardia infestation in a diarrhoea-prone population were investigated in the present study. Our primary goal was to understand the interaction of this parasite with other pathogens during infection and to determine some important factors regulating the diarrhoeal disease spectrum of a population. Giardia showed a steady rate of occurrence throughout the entire study period with a nonsignificant association with rainfall (P > 0.05). Interestingly coinfecting pathogens like Vibrio cholerae and rotavirus played a significant (P ≤ 0.001) role in the occurrence of this parasite. Moreover, the age distribution of the diarrhoeal cases was very much dependent on the coinfection rate of Giardia infection. As per our findings, Giardia infection rate seems to play a vital role in regulation of the whole diarrhoeal disease spectrum in this endemic region.

Multilocus sequence typing system (MLST) reveals a significant association of Entamoeba histolytica genetic patterns with disease outcome.

The relationship between parasite genotypes and outcome of amoebic infection is still a paradox and needed to be explored. Proper identification and genetic characterization of Entamoeba histolytica clinical isolates is an effective tool for exploring this relation. Along with conventional polymorphic marker (Chitinase), tRNA linked short tandem repeat (STR) loci has been employed as multilocus genotyping tool due to its better resolution and evolutionary significance. Some common as well as exclusive repeat patterns showing significant relation with disease outcome have been identified. Phylogenetic analysis revealed that repeat patterns exclusively found in asymptomatic and amoebic liver abscess derived isolates are placed in a common lineage and has similar association pattern with the disease outcome. Assumption can be made that isolates of E. histolytica remaining asymptomatic is genetically closer siblings of those causing liver abscess rather than the diarrheal isolates.

Differential gene expression in Giardia lamblia under oxidative stress: significance in eukaryotic evolution.

Giardia lamblia is a unicellular, early branching eukaryote causing giardiasis, one of the most common human enteric diseases. Giardia, a microaerophilic protozoan parasite has to build up mechanisms to protect themselves against oxidative stress within the human gut (oxygen concentration 60 µM) to establish its pathogenesis. G. lamblia is devoid of the conventional mechanisms of the oxidative stress management system, including superoxide dismutase, catalase, peroxidase, and glutathione cycling, which are present in most eukaryotes. NADH oxidase is a major component of the electron transport chain of G. lamblia, which in concurrence with disulfide reductase, protects oxygen-labile proteins such as pyruvate: ferredoxin oxidoreductase against oxidative stress by sustaining a reduced intracellular environment. It also contains the arginine dihydrolase pathway, which occurs in a number of anaerobic prokaryotes, includes substrate level phosphorylation and adequately active to make a major contribution to ATP production. To study differential gene expression under three types of oxidative stress, a Giardia genomic DNA array was constructed and hybridized with labeled cDNA of cells with or without stress. The transcriptomic data has been analyzed and further validated using real time PCR. We identified that out of 9216 genes represented on the array, more than 200 genes encoded proteins with functions in metabolism, oxidative stress management, signaling, reproduction and cell division, programmed cell death and cytoskeleton. We recognized genes modulated by at least ≥ 2 fold at a significant time point in response to oxidative stress. The study has highlighted the genes that are differentially expressed during the three experimental conditions which regulate the stress management pathway differently to achieve redox homeostasis. Identification of some unique genes in oxidative stress regulation may help in new drug designing for this common enteric parasite prone to drug resistance. Additionally, these data suggest the major role of this early divergent ancient eukaryote in anaerobic to aerobic organism evolution.

Trend of Entamoeba histolytica infestation in Kolkata.

BACKGROUND: Entamoeba histolytica infection is found almost all over the world and is highly endemic and a major cause of parasitic diarrhoea particularly in the developing countries. METHODS: A systemic surveillance was set up at the Infectious Disease hospital, Kolkata, India between November 2007 and October 2009 for understanding the trend of E. histolytica infection in Kolkata. Fecal samples were collected from diarrhoeal patients attending the hospital, under the surveillance system and processed for detection of E. histolytica. RESULTS: During the last two years about 2500 diarrhoeal samples were collected and screened for E. histolytica. About 3.6% were positive for E. histolytica. As compared to the earlier years, E. histolytica infection was observed to be less amongst patients screened during the last two years. No seasonality was observed in Kolkata although in the neighboring tropical country Bangladesh, a typical seasonality of E. histolytica infection was noticed. CONCLUSION: The study indicates that the detection rate of E. histolytica infection amongst diarrhoeal patients in Kolkata is decreasing during the last two years than that of Bangladesh.