Lamblia Strains Research Articles

Mucosal vaccination in a murine gnotobiotic model of Giardia lamblia infection.

Giardia lamblia is an important protozoan cause of diarrheal disease worldwide, delayed development and cognitive impairment in children in low- and middle-income countries, and protracted post-infectious syndromes in developed regions. G. lamblia resides in the lumen and at the epithelial surface of the proximal small intestine but is not mucosa invasive. The protozoan parasite is genetically diverse with significant genome differences across strains and assemblages. Animal models, particularly murine models, have been instrumental in defining mechanisms of host defense against G. lamblia, but mice cannot be readily infected with most human pathogenic strains. Antibiotic pretreatment can increase susceptibility, suggesting that the normal microbiota plays a role in controlling G. lamblia infection in mice, but the broader implications on susceptibility to diverse strains are not known. Here, we have used gnotobiotic mice to demonstrate that robust intestinal infection can be achieved for a broad set of human-pathogenic strains of the genetic assemblages A and B. Furthermore, gnotobiotic mice were able to eradicate infection with a similar kinetics to conventional mice after trophozoite challenge. Germ-free mice could also be effectively immunized by the mucosal route with a protective antigen, α1-giardin, in a manner dependent on CD4 T cells. These results indicate that the gnotobiotic mouse model is powerful for investigating acquired host defenses in giardiasis, as the mice are broadly susceptible to diverse G. lamblia strains yet display no apparent defects in mucosal immunity needed for controlling and eradicating this lumen-dwelling pathogen.

Conserved metabolic enzymes as vaccine antigens for giardiasis.

Giardia lamblia is a leading protozoal cause of diarrheal disease worldwide. Infection is associated with abdominal pain, malabsorption and weight loss, and protracted post-infectious syndromes. A human vaccine is not available against G. lamblia. Prior studies with human and murine immune sera have identified several parasite antigens, including surface proteins and metabolic enzymes with intracellular functions. While surface proteins have demonstrated vaccine potential, they can exhibit significant variation between G. lamblia strains. By comparison, metabolic enzymes show greater conservation but their vaccine potential has not been established. To determine whether such proteins can serve as vaccine candidates, we focused on two enzymes, α-enolase (ENO) and ornithine carbamoyl transferase (OCT), which are involved in glycolysis and arginine metabolism, respectively. We show in a cohort of patients with confirmed giardiasis that both enzymes are immunogenic. Intranasal immunization with either enzyme antigen in mice induced strong systemic IgG1 and IgG2b responses and modest mucosal IgA responses, and a marked 100- to 1,000-fold reduction in peak trophozoite load upon oral G. lamblia challenge. ENO immunization also reduced the extent and duration of cyst excretion. Examination of 44 cytokines showed only minimal intestinal changes in immunized mice, although a modest increase of CCL22 was observed in ENO-immunized mice. Spectral flow cytometry revealed increased numbers and activation state of CD4 T cells in the small intestine and an increase in α4β7-expressing CD4 T cells in mesenteric lymph nodes of ENO-immunized mice. Consistent with a key role of CD4 T cells, immunization of CD4-deficient and Rag-2 deficient mice failed to induce protection, whereas mice lacking IgA were fully protected by immunization, indicating that immunity was CD4 T cell-dependent but IgA-independent. These results demonstrate that conserved metabolic enzymes can be effective vaccine antigens for protection against G. lamblia infection, thereby expanding the repertoire of candidate antigens beyond primary surface proteins.

Discovery and Preclinical Development of Antigiardiasis Fumagillol Derivatives.

Giardiasis, caused by the intestinal parasite Giardia lamblia, is a severe diarrheal disease, endemic in poverty-stricken regions of the world, and also a common infection in developed countries. The available therapeutic options are associated with adverse effects, and G. lamblia resistance to the standard-of-care drugs is spreading. Fumagillin, an antimicrosporidiosis drug, is a therapeutic agent with potential for the treatment of giardiasis. However, it exhibits considerable, albeit reversible, toxicity when used to treat immunocompromised microsporidiosis patients. Fumagillin is also a highly unstable compound. To address these liabilities, we designed and synthesized stable fumagillol derivatives with lower levels of permeation across polarized epithelial Caco-2 cells and better potency against G. lamblia trophozoites than fumagillin. Metronidazole-resistant G. lamblia strains were also susceptible to the new fumagillol derivatives. In addition, these compounds were more potent against the amebiasis-causing parasite Entamoeba histolytica than fumagillin. Two compounds exhibited better thermal and acid stability than fumagillin, which should prolong the drug shelf life and reduce compound degradation in the stomach. Studies with a mouse model of giardiasis with the most stable compound, 4-(((((3R,4S,5S,6R)-5-methoxy-4-((2R,3R)-2-methyl-3-(3-methylbut-2-en-1-yl)oxiran-2-yl)-1-oxaspiro[2.5]octan-6-yl)oxy)carbonyl)amino)benzoic acid (compound 9), revealed that it had better efficacy (effective dose [ED]) than fumagillin at both the fully curative dose (the 100% ED) of 6.6 mg/kg of body weight and a 50% ED of 0.064 mg/kg. Plasma pharmacokinetics revealed the slow absorption of compound 9 through the gut, consistent with the in vitro characterization in Caco-2 cells. An acute-dose study yielded a maximum tolerated dose (MTD) of 1,500 mg/kg, 227-fold higher than the fully curative dose. Thus, along with improved stability, compound 9 also exhibited an excellent therapeutic window.

Differential antibody responses to Giardia lamblia strain variants expressing dissimilar levels of an immunogenic protein.

Giardia lamblia is a protozoan parasite that causes giardiasis, one of the most common worldwide gastrointestinal diseases. For rational development of a Giardia vaccine, increasing our understanding of the host-Giardia interaction is crucial. In this study, we analysed the immunogenicity and antigenicity of two G lamblia strain variants [GS and GS-5G8 (+)], which express different levels of the variant-specific surface protein (VSP) 5G8 and also analysed the intestinal histological changes associated with Giardia infection. We evaluated the antibody responses induced by G lamblia strains in infected, reinfected and immunized C3H/HeJ mice using ELISA, flow cytometry, Western blotting and histological analysis. Our results showed that G lamblia GS-5G8 (+) was more immunogenic and antigenic than the GS strain. The antibody response against the GS-5G8 (+) strain primarily recognized 5G8 protein. Serum antibody from infected and reinfected mice exhibited specific agglutination of trophozoites in vitro. GS-5G8 (+)-infected mice showed higher CD19+ infiltrating cell levels compared to GS-infected animals. G lamblia strains with different expression levels of an immunogenic antigen (VSP 5G8) induce differential antibody responses. A better understanding of the immunogenic proteins of G lamblia will contribute to the rational development of an effective vaccine against this parasitic disease.

Methionyl-tRNA synthetase inhibitor has potent in vivo activity in a novel Giardia lamblia luciferase murine infection model.

Methionyl-tRNA synthetase (MetRS) inhibitors are under investigation for the treatment of intestinal infections caused by Giardia lamblia. To properly analyse the therapeutic potential of the MetRS inhibitor 1717, experimental tools including a robust cell-based assay and a murine model of infection were developed based on novel strains of G. lamblia that employ luciferase reporter systems to quantify viable parasites. Systematic screening of Giardia-specific promoters and luciferase variants led to the development of a strain expressing the click beetle green luciferase. Further modifying this strain to express NanoLuc created a dual reporter strain capable of quantifying parasites in both the trophozoite and cyst stages. These strains were used to develop a high-throughput cell assay and a mouse infection model. A library of MetRS inhibitors was screened in the cell assay and Compound-1717 was tested for efficacy in the mouse infection model. Cell viability in in vitro compound screens was quantified via bioluminescence readouts while infection loads in mice were monitored with non-invasive whole-animal imaging and faecal analysis. Compound-1717 was effective in clearing mice of Giardia infection in 3 days at varying doses, which was supported by data from enzymatic and phenotypic cell assays. The new in vitro and in vivo assays based on luciferase expression by engineered G. lamblia strains are useful for the discovery and development of new therapeutics for giardiasis. MetRS inhibitors, as validated by Compound-1717, have promising anti-giardiasis properties that merit further study as alternative therapeutics.

Metabolomic Profiling of Wildtype and Transgenic Giardia lamblia Strains by 1H HR-MAS NMR Spectroscopy.

Giardia lamblia, a causative agent of persistent diarrhea in humans, domestic animals, and cattle, is usually treated with nitro compounds. Consequently, enzymes involved in anaerobic nitro reduction have been investigated in detail as potential targets. Their role within the normal metabolic context is, however, not understood. Using 1H high-resolution magic angle spinning (HR-MAS) NMR spectroscopy, we analyzed the metabolomes of G. lamblia trophozoites overexpressing three nitroreductases (NR1–NR3) and thioredoxin reductase (TrxR), most likely a scavenger of reactive oxygen species, as suggested by the results published in this study. We compared the patterns to convenient controls and to the situation in the nitro drug resistant strain C4 where NR1 is downregulated. We identified 27 metabolites in G. lamblia trophozoites. Excluding metabolites of high variability among different wildtype populations, only trophozoites overexpressing NR1 presented a distinct pattern of nine metabolites, in particular arginine catabolites, differing from the respective controls. This pattern matched a differential pattern between wildtype and strain C4. This suggests that NR1 interferes with arginine and thus energy metabolism. The exact metabolic function of NR1 (and the other nitroreductases) remains to be elucidated.

Resistance formation to nitro drugs in Giardia lamblia: No common markers identified by comparative proteomics

In order to elucidate the question whether resistance to nitro drugs in G. lamblia is due to common resistance markers, trophozoites of three resistant G. lamblia strains, namely C4, 1062ID10, and 713M3 were grown in the presence of the two nitro drugs metronidazole and nitazoxanide and compared to their corresponding wild-types WBC6, 106, and 713 by mass spectometry shotgun analysis of their proteomes. Depending on the strain and the nitro drug, more than 200 to 500 differentially expressed proteins were identified, but there were no common patterns across strains and drugs. All resistant strains underwent antigenic variation with distinct surface antigens like variant surface proteins or cysteine rich proteins depending on strain and nitro compound. A closer look on enzymes involved in nitroreduction and detoxification of nitro radicals, NO or O2 suggested the existence of distinct strategies for each drug and each strain. Therefore, we conclude that resistance to nitro drugs in G. lamblia is not correlated with a specific pattern of differentially expressed proteins and therefore seems not to be the result of a directed process.

Genome Resequencing Reveals Single Nucleotide Polymorphism and Repeat Regions in Giardia lamblia Indian Isolate

Giardia lamblia (syn. Giardia duodenalis and Giardia intestinalis) is a major human infecting intestinal parasite. It is a frequent cause of endemic and epidemic diarrhea. G. lamblia is divided into eight genotypes (A-H) which infect a wide range of mammals and humans, but human infections are caused by Genotypes A and B only. Giardia lamblia strains are speculated to undergo zoonotic transmission and also considerable genetic variation has been identified. To unambiguously determine the genotype of the Indian isolate, we sequenced the genome to high depth coverage and compared the assemblies with the nearly completed WB and DH genome and draft genome of Genotypes E (P15; pig isolate) and B (GS and GS-B; human isolate). Our results identified the Indian isolate to be very closely related to isolate WB and ~97.71% of the sequencing reads aligned to the isolate WBC6 genome. This gave a list of SNPs, InDels and repeat motifs specific to the Indian isolate with the majority of the genome being conserved. This work will layout a framework for the future studies. This study provides an opportunity to develop targeted and genome-wide genetic marker for better understanding of genotypes of Giardia lamblia prevalent in the developing world.

Nitroimidazole carboxamides as antiparasitic agents targeting Giardia lamblia, Entamoeba histolytica and Trichomonas vaginalis

Diarrhoeal diseases caused by the intestinal parasites Giardia lamblia and Entamoeba histolytica constitute a major global health burden. Nitroimidazoles are first-line drugs for the treatment of giardiasis and amebiasis, with metronidazole 1 being the most commonly used drug worldwide. However, treatment failures in giardiasis occur in up to 20% of cases and development of resistance to metronidazole is of concern. We have re-examined ‘old’ nitroimidazoles as a foundation for the systematic development of next-generation derivatives. Using this approach, derivatisation of the nitroimidazole carboxamide scaffold provided improved antiparasitic agents. Thirty-three novel nitroimidazole carboxamides were synthesised and evaluated for activity against G. lamblia and E. histolytica. Several of the new compounds exhibited potent activity against G. lamblia strains, including metronidazole-resistant strains of G. lamblia (EC50 = 0.1–2.5 μM cf. metronidazole EC50 = 6.1–18 μM). Other compounds showed improved activity against E. histolytica (EC50 = 1.7–5.1 μM cf. metronidazole EC50 = 5.0 μM), potent activity against Trichomonas vaginalis (EC50 = 0.6–1.4 μM cf. metronidazole EC50 = 0.8 μM) and moderate activity against the intestinal bacterial pathogen Clostridium difficile (0.5–2 μg/mL, cf. metronidazole = 0.5 μg/mL). The new compounds had low toxicity against mammalian kidney and liver cells (CC50 > 100 μM), and selected antiparasitic hits were assessed for human plasma protein binding and metabolic stability in liver microsomes to demonstrate their therapeutic potential.

Metronidazole-triazole conjugates: Activity against Clostridium difficile and parasites

Metronidazole has been used clinically for over 50 years as an antiparasitic and broad-spectrum antibacterial agent effective against anaerobic bacteria. However resistance to metronidazole in parasites and bacteria has been reported, and improved second-generation metronidazole analogues are needed. The copper catalysed Huigsen azide-alkyne 1,3-dipolar cycloaddition offers a way to efficiently assemble new libraries of metronidazole analogues. Several new metronidazole-triazole conjugates (Mtz-triazoles) have been identified with excellent broad spectrum antimicrobial and antiparasitic activity targeting Clostridium difficile, Entamoeba histolytica and Giardia lamblia. Cross resistance to metronidazole was observed against stable metronidazole resistant C. difficile and G. lamblia strains. However for the most potent Mtz-triazoles, the activity remained in a therapeutically relevant window.

Identification of T-cell stimulating antigens from Giardia lamblia by using Giardia-specific T-cell hybridomas

T-cell immune response plays an important role in controlling Giardia lamblia infections. Little is known about the G. lamblia-specific antigens that stimulate a cell-mediated immune response. The aim of the present study was to identify T-cell stimulating G. lamblia antigens. For this purpose, we generated a group of Giardia-specific T-cell hybridomas (2F9, 4D5, 6D10, 8B9, 9B10, 10F7 and 10G5). Hybridomas were screened for reactivity with G. lamblia protein extract by the CTLL bioassay. These T-cell hybridomas did not exhibit any significant activation either in the absence of G. lamblia protein extract or in the presence of irrelevant antigen (hen white egg lysozyme). To further characterize the T-cell hybridomas generated, we selected three hybridomas (10G5, 4D5 and 9B10). Giardia lamblia proteins of 90-110, 65-77 and 40-64 kDa showed T-cell stimulating activity for the hybridomas 10G5, 4D5 and 9B10, respectively, in a concentration-dependent manner. Protein extract obtained from different G. lamblia strains (GS/M-83-H7, WB C6 and a clinical isolate (YJJ)) stimulated all T-cell hybridomas, indicating that T-cell-stimulating antigens are expressed among different G. lamblia strains. In conclusion, we identified T-cell stimulating G. lamblia antigens by using Giardia-specific T-cell hybridomas. To our knowledge, these hybridomas are the first-described T-cell hybridomas specific for G. lamblia.

Strain-dependent induction of enterocyte apoptosis by Giardia lamblia disrupts epithelial barrier function in a caspase-3-dependent manner.

We recently demonstrated that Giardia lamblia rearranges cytoskeletal proteins and reduces transepithelial electrical resistance. The effect of G. lamblia on enterocyte apoptosis is unknown, and a possible link between microbially induced enterocyte apoptosis and altered epithelial permeability has yet to be established. The aim of this study was to assess whether G. lamblia induces enterocyte apoptosis in duodenal epithelial monolayers and whether this effect increases epithelial permeability. Monolayers of nontransformed human duodenal epithelial cells were incubated with sonicated or live G. lamblia trophozoites (NF, S2, WB, or PB strains) for 8, 24, and 48 h. Cell cultures were assessed for apoptosis by Hoechst fluorescence staining, enzyme-linked immunosorbent assay for apoptotic nucleosomes, and electron microscopy. In separate experiments, monolayers were pretreated with or without 120 microM caspase-3 inhibitor (Z-DEVD-FMK) for 1 h and were assessed for production of apoptotic nucleosomes, tight junctional integrity (with fluorescent ZO-1 staining followed by confocal laser microscopy), and transepithelial permeability for fluorescein isothiocyanate-dextran. G. lamblia strains NF and S2, but not strains WB or PB, induced enterocyte apoptosis within the monolayers, and this effect was inhibited by Z-DEVD-FMK pretreatment. Using the G. lamblia NF isolate, additional experiments investigated the possible link between enterocyte apoptosis and altered epithelial permeability. G. lamblia NF disrupted tight junctional ZO-1 and increased epithelial permeability, but these effects were also prevented by pretreatment with the caspase-3 inhibitor. These findings indicate that strain-dependent induction of enterocyte apoptosis may contribute to the pathogenesis of giardiasis. This effect is responsible for a loss of epithelial barrier function by disrupting tight junctional ZO-1 and increasing permeability in a caspase-3-dependent manner.

Cysteine-dependent zinc binding by membrane proteins of Giardia lamblia.

The abundant, highly variable surface proteins (VSPs) which cover the surface of Giardia lamblia trophozoites compose a group of extremely cysteine (C)-rich proteins in which more than half of the cysteines are in the motif CXXC. Because of the constancy of these features among the known VSPs and the prominence of cysteine and particularly CXXC in proteins that bind zinc and other metals, we asked whether G. lamblia VSPs bind zinc in vitro. VSPs are the major protein component of Triton X-114 detergent-phase extracts of G. lamblia trophozoites and can be readily identified by surface iodination of intact cells. The partitioning of 65Zn binding into the Triton X-114 detergent phase and the correspondence between surface iodination and zinc binding patterns of four G. lamblia strains or sublines with different VSPs support the idea that VSPs bind zinc. The requirement for renaturation of blots with a reducing agent indicates that Zn2+ is coordinated by cysteine residues, rather than by other amino acids. Binding did not appear to be specific to zinc since it was inhibited by competition with other divalent metal ions. The abundance of the VSPs and the prevalence of metal binding motifs among all known variants suggest that they may play an important role in trophozoite survival and colonization in the host.

Isoenzyme comparison of axenic Giardia lamblia strains.

We obtained isoenzyme patterns by polyacrylamide gradient gel electrophoresis (PGGE) of water-soluble protein fractions prepared from trophozoites of 11 axenic G. lamblia strains. The strains were isolated from animals and humans (both symptomatic and asymptomatic) from various geographic locations. Isoenzymes were also separated by isoelectric focusing. Of 12 enzymes attempted, eight exhibited well-defined and reproducible isoenzyme patterns by PGGE, based on which the strains were grouped into four zymodemes. Although the 11 strains were grouped into four zymodemes based on PGGE, no correlation between zymodeme and the known characteristics of the strains existed. Thus, a high degree of characteristic sharing appears to occur among genetically different G. lamblia strains.

Classification of subgroups of Giardia lamblia based upon ribosomal RNA gene sequence using the polymerase chain reaction

A sensitive and specific polymerase chain reaction-based assay has been developed to detect and analyze polymorphism in the Giardia lamblia 18S ribosomal RNA gene. Efficient amplification required the inclusion of cosolvents (glycerol and dimethyl sulfoxide) in the reaction. Following the optimization of conditions for amplification and subsequent hybridization of amplified product with radiolabeled oligonucleotide probe, a detection limit of less than one organism's worth of DNA was achieved. Thirty-five different G. lamblia strains obtained from various human and animal host types and geographic locations were analyzed by this method. The strains could be divided into 3 groups on the basis of defined nucleotide substitutions within the 183-bp amplified DNA fragment of the 18S ribosomal RNA gene. The groupings based upon the 18S ribosomal RNA gene sequence correlated with groupings previously assigned based upon patterns of surface antigens and restriction enzyme analysis. Analysis of the G. lamblia 18S ribosomal RNA gene sequences present in fecal specimens obtained from giardiasis patients revealed the presence of the different sequence types in these specimens. Some specimens contained more than one sequence type. The identification of subgroups of G. lamblia may facilitate studies of virulence, infectivity, and the epidemiology of giardia infection.

Identification of Heterogeneity in Human Isolates of Giardia lamblia by Isoenzyme Studies

Electrophoretic mobility patterns of six enzymes, viz. alkaline phosphatase E.C. 3.1.3.1., acid phosphatase E.C. 3.1.3.2., malic enzyme E.C. 1.1.1.40., phosphoglucomutase E.C. 2.7.5.1., isocitrate dehydrogenase E.C. 1.1.1.42., glucose-6-phosphate dehydrogenase E.C. 1.1.1.49 of two axenically cultured human Giardia lamblia isolated from India (PD-1 and PD-2) and one strain from Portland, Oregon, USA (P-1) were compared using polyacrylamide gel electrophoresis (PAGE). Based on the difference in the mobility patterns of the enzymes phosphoglucomutase, isocitrate dehydrogenase and malic enzyme, the PD-1 and PD-2 isolates appeared to be quite different from P-1. In the present study, the isocitrate dehydrogenase and alkaline phosphatase enzymes were used for the first time for differentiation of Giardia isolates. In the case of PD-1, two alkaline phosphatase bands could be seen whereas only one band was observed in PD-2 and P-1. Thus, the three strains could be grouped into three different zymodemes. These findings reveal the significant heterogeneity in G. lamblia isolates both from widely separated areas and within a single region. Heterogeneity among G. lamblia strains may explain the variable clinical manifestations, host response and treatment efficacy characteristic of human giardiasis.

Zoonotic aspects of giardiasis: A review

Several studies suggested that some water-borne epidemics of giardiasis in the U.S.A. were of zoonotic origin. Also, cats and dogs were suspected of being sources of giardiasis for man. These observations have been partly supported by experimental cross-transmissions. However, there are also some indications that zoonotic giardiasis may not be common. The host-specificity of Giardia spp. is still controversial. To date, morphological characteristics can only differentiate three very basic types of Giardia: G. intestinalis, G. muris and G. agilis. Host-specific and morphometric criteria resulted in the description of more than 40 species of Giardia; many of them probably invalid. Only a few subtle antigenic differences among G. intestinalis(lamblia) strains have been observed. The comparison of isoenzymes and DNA banding patterns revealed 3 basic groups, not necessarily related to host origin. Further biochemical, immunological, genetic and cross-transmission studies in host and parasite populations are needed to better understand host-specificity of various Giardia isolates. At the present time one may only conclude that although mammals and man do not seem to possess their own unique species of Giardia, in reality the major methods of transmission of giardiasis probably remain basically host-specific.

In vitro excystation and subsequent axenic growth of Giardia lamblia

Six fresh Giardia lamblia strains were isolated by in vitro excystation and subsequent culturing of excysted parasites in bile-supplemented BI-S-33 medium. The cysts passed in faeces appeared to differ in structure when observed using differential interference contrast microscopy. Sometimes the enclosed organisms were closely applied to the cyst wall; in most stool specimens, however, the parasites were separated from the cyst wall by a space. Cysts with parasites closely applied to the wall were the most viable type, with excystation rates up to 90%. Cysts with organisms detached from the wall displayed low excystation rates, 0–15%. During exposure to the induction solution of hydrochloric acid (pH 2), parasites initially closely applied to the cyst walls completely detached, and after transfer into culture medium vigorous flexing movements of the organisms were observed. Stool samples from 42 symptomatic and asymptomatic giardiasis patients were examined; in 26 of the samples parasites hatched, and 6 new strains were established in axenic culture.

The detection of enteropathogens in acute diarrhea in a family cohort population in rural Egypt.

In 8 villages of rural northeastern Egypt, a 2-year study of the etiologic agents associated with episodes of diarrhea was carried out. Stool specimens (3,243) from 3,513 episodes of diarrhea were processed for enteropathogens. The most commonly identified agents in the group with diarrhea were Giardia lamblia (44%), heat stable enterotoxin (ST)-producing enterotoxigenic Escherichia coli (ETEC) (15%), heat labile toxin (LT)-producing ETEC (12%), enteropathogenic E. coli (EPEC) (4%), rotavirus (3%), Shigella (2%) and Salmonella (1%). Isolation rates were increased in cases compared to controls for all agents except G. lamblia and EPEC strains. Rotavirus, Salmonella and ST-producing ETEC were more frequently isolated during cooler months and Shigella and LT-ETEC occurred more commonly in warmer months. Campylobacter, EPEC, Giardia and E. histolytica did not show a discernable seasonal pattern. Rotavirus was primarily associated with diarrhea in infants only. Forty-four percent of children experienced at least 1 bout of rotavirus diarrhea by the age of 3 years. Vomiting was reported in 65% of cases of rotavirus infection. Dehydration was reported in greater than 40% of those with rotavirus-, Salmonella-, Campylobacter-, LT-ETEC- and EPEC-associated illness and in those without an identifiable agent. While rotavirus was implicated in 3% of cases overall, when vomiting or vomiting plus dehydration occurred, rotavirus was identified with a rate of 10% and 12%, respectively. Dysentery was common only in Shigella cases, occurring in 24%. A decrease in occurrence of rotavirus, Campylobacter and possibly EPEC illness was seen in the infants less than 6 months of age who were breast-fed when compared to those who were not.

Giardia lamblia: identification of different strains from man.

Four axenically cultured human Giardia lamblia isolates from Jerusalem (KC-1, 2, 3 and 4) and one from Bethesda (WB) were compared. Three distinct groups were defined by agglutination response to rabbit anti-G. lamblia sera viz. WB; KC-3; and KC-1, 2 and 4. The same major groups were identified by isoenzyme analysis using thin-layer starch-gel electrophoresis, each group differing from the others in three or more of five enzymes studied. In addition, a single enzyme difference distinguished KC-2 from KC-1 and 4. These findings reveal significant heterogeneity in G. lamblia isolates both from widely separated areas and within a single region. Immunoassays for diagnosis of giardiasis should take into account the differences between strains. Heterogeneity among G. lamblia strains may explain the variable clinical manifestations, host response and treatment efficacy characteristic of human giardiasis.