Role of Soluble Factors in Immune and Normal Sera in the Control of Giardiasis Due to Giardia Iamblia

Hyperimmune sera (HIS), raised against crude giardia antigen, on in vitro interaction, caused more agglutination of Giardia lamblia trophozoites. Heat inactivated HIS possessed a comparable agglutinating activity as the non-inactivated controls. Non-inactivated normal (unimmunized) serum caused immobilization of Giardia trophozoite, which was checked on heat inactivation. Antibodies in immune sera are mainly responsible for agglutination, whereas the heat labile non-immune components control the mobility of the intestinal parasite.

Extra-intestinal and long term consequences of Giardia duodenalis infections

Giardiasis is the most common waterborne parasitic infection of the human intestine worldwide.The etiological agent,Giardia duodenalis(syn.G.intestinalis,G.lamblia),is a flagellated,binucleated protozoan parasite which infects a wide array of mammalian hosts.Human giardiasis is a true cosmopolitan pathogen,with highest prevalence in developing countries.Giardiasis can present with a broad range of clinical manifestations from asymptomatic,to acute or chronic diarrheal disease associated with abdominal pain and nausea.Most infections are self-limiting,although re-infection and chronic infection can occur.Recent evidence indicating that Giardia may cause chronic post-infectious gastrointestinal complications have made it a topic of intense research.The causes of the post-infectious clinical manifestations due to Giardia,even after complete elimination of the parasite,remain obscure.This review offers a state-of-the-art discussion on the long-term consequences of Giardia infections,from extra-intestinal manifestations,growth and cognitive deficiencies,to post-infectious irritable bowel syndrome.The discussion also sheds light on some of the novel mechanisms recently implicated in the production of these postinfectious manifestations.

Antibacterial and anti-parasitic activities of Terfezia claveryi methanolic extract against some common pathogenic agents of infectious diarrhea

Objective:To assess the antidiarrheal effects of Terfezia claveryi methanolic extract against Escherichia coli,Salmonella typhimurium,Shigella flexneri,and Giardia lamblia.Methods:Antibacterial effects of the Terfezia claveryi methanolic extract were carried out by determining the minimum inhibitory concentration(MIC)and minimum bactericidal concentration through micro broth dilution technique.Furthermore,reactive oxygen species production and protein leakage were evaluated.To evaluate the in vitro anti-giardial effects of Terfezia claveryi methanolic extract,Giardia lamblia WB(ATCC®30957)trophozoites were treated with various concentrations of Terfezia claveryi methanolic extract for 10-360 min.In addition,the plasma membrane permeability of trophozoites treated with Terfezia claveryi methanolic extract was determined.The cytotoxicity effects of Terfezia claveryi methanolic extract against normal(HEK293T)and cancer(MCF-7)cells were also assessed using the MTT assay.Results:The MIC and minimum bactericidal concentration of Terfezia claveryi methanolic extract against bacterial strains were in the range of 0.52-1.04 and 1.04-2.08 mg/mL,respectively.The results revealed that reactive oxygen species production and protein leakage were significantly increased after the bacteria were treated with the Terfezia claveryi methanolic extract,especially at 1/3 and 1/2 MICs(P<0.001).Furthermore,Terfezia claveryi methanolic extract decreased the viability of Giardia lamblia trophozoites in a dose-dependent manner.Terfezia claveryi methanolic extract at 1,2,and 4 mg/mL resulted in 100%mortality in Giardia lamblia trophozoites after 360,240,and 120 min,respectively.Moreover,Terfezia claveryi methanolic extract altered the permeability of plasma membrane of Giardia lamblia trophozoites by increasing the concentration.MTT assay revealed that the 50%cytotoxic concentrations values for HEK293T and MCF-7 cells were 4.32 mg/mL and 6.40 mg/mL,respectively,indicating that Terfezia claveryi methanolic extract had greater cytotoxicity against cancer cells than normal cells.Conclusions:Terfezia claveryi methanolic extract had potent in vitro antibacterial and anti-parasitic effects on Escherichia coli,Salmonella typhimurium,Shigella flexneri,and Giardia lamblia by affecting cell membrane permeability and reactive oxygen species generation with no significant cytotoxicity on normal cells.

Human leukocyte antigen class-Ⅱ DRB1 alleles and Giardia lamblia infection in children: A case-control study

Objective:To compare the genotype frequencies of HLA class-ⅡDRB1 alleles in Giardia(G.)lamblia-infected children.Methods:A total of 490 Egyptian children aged 2-16 years were subjected to microscopic stool examination to detect G.lamblia infection,and to exclude other intestinal pathogens.On the basis of their microscopic findings,a group of 80 children were chosen as giardiasis cases,another 80 children were confirmed as Giardia free control group by immunochromatographic test,and the remaining children were excluded.Both giardiasis and control groups were then subjected to blood examination to identify their genetic type of HLA-DRB1 alleles.Results:HLA class-ⅡDRB1*03:01 and DRB1*13:01 alleles were significantly associated with G.lamblia infection(P<0.001 for each variable).On the other hand,HLA class-ⅡDRB1*04:02,DRB1*10:01,DRB1*14:01 and DRB1*15:01 alleles were significantly demonstrated in Giardia free children.However,other HLA-DRB1 alleles did not show any significant association with giardiasis.Conclusions:HLA class-ⅡDRB1*03,DRB1*13,DRB1*04,DRB1*10,DRB1*14 and DRB1*15 alleles may be involved in the establishment of host immune response to G.lamblia infection.

Uncovering the genetic diversity of Giardia intestinalis in isolates from outbreaks in New Zealand

Background:Giardia intestinalis is one of the most common causes of diarrhoea worldwide. Molecular techniques have greatly improved our understanding of the taxonomy and epidemiology of this parasite. Co-infection with mixed (sub-) assemblages has been reported, however, Sanger sequencing is sometimes unable to identify shared subtypes between samples involved in the same epidemiologically linked event, due to samples showing multiple dominant subtypes within the same outbreak. Here, we aimed to use a metabarcoding approach to uncover the genetic diversity within samples from sporadic and outbreak cases of giardiasis to characterise the subtype diversity, and determine if there are common sequences shared by epidemiologically linked cases that are missed by Sanger sequencing.Methods:We built a database with 1109 unique glutamate dehydrogenase (gdh) locus sequences covering most of the assemblages of G. intestinalis and used gdh metabarcoding to analyse 16 samples from sporadic and outbreak cases of giardiasis that occurred in New Zealand between 2010 and 2018.Results:There is considerable diversity of subtypes of G. intestinalis present in each sample. The utilisation of metabarcoding enabled the identification of shared subtypes between samples from the same outbreak. Multiple variants were identified in 13 of 16 samples, with Assemblage B variants most common, and Assemblages E and A present in mixed infections.Conclusions:This study showed that G. intestinalis infections in humans are frequently mixed, with multiple subtypes present in each host. Shared sequences among epidemiologically linked cases not identified through Sanger sequencing were detected. Considering the variation in symptoms observed in cases of giardiasis, and the potential link between symptoms and (sub-) assemblages, the frequency of mixed infections could have implications for our understanding of host–pathogen interactions.