Lectin-Mediated Bacterial Modulation by the Intestinal Nematode Ascaris suum

Ascariasis is a global health problem for humans and animals. Adult Ascaris nematodes are long-lived in the host intestine where they interact with host cells as well as members of the microbiota resulting in chronic infections. Nematode interactions with host cells and the microbial environment are prominently mediated by parasite-secreted proteins and peptides possessing immunomodulatory and antimicrobial activities. Previously, we discovered the C-type lectin protein AsCTL-42 in the secreted products of adult Ascaris worms. Here we tested recombinant AsCTL-42 for its ability to interact with bacterial and host cells. We found that AsCTL-42 lacks bactericidal activity but neutralized bacterial cells without killing them. Treatment of bacterial cells with AsCTL-42 reduced invasion of intestinal epithelial cells by Salmonella. Furthermore, AsCTL-42 interacted with host myeloid C-type lectin receptors. Thus, AsCTL-42 is a parasite protein involved in the triad relationship between Ascaris, host cells, and the microbiota.

Comparison of the effect of the chosen species of saprotrophic fungi on the development of Toxocara canis and Ascaris suum eggs

The study aim was to compare the antagonistic interaction between saprotrophic soil fungi and embryonic development of geohelminths Toxocara canis and Ascaris suum. The experimental cultures were fertilized eggs of T.canis and A. suum incubated together with mycelium of strains: Fusarium culmorum, Metarhizium anisopliae,Paecilomyces fumosoroseus, Trichoderma viride and Trichothecium roseum. In the control cultures the eggs of both nematode species were incubated without fungi. The experiment was conducted at temp. 26°C for 60 days. Compared with the control, all of the tested species of fungi significantly extended the embryonic development of both T. canis and A. suum. Most inhibitory effect on the rate of embryonic development of T. canis and A. suum had three fungal species: P. fumosoreus, M. anisopliae and T. viride. Compared with the control, on the 60th day of incubation in the presence of each of the tested fungal species, a larger percentage (p<0.05) of morphological abnormalities was stated in developing embryos of T. canis (49–69%) than in A. suum (15.1–67.7%). Among the examined fungal species, only incubation with P. fumosoroseus resulted in significantly greater (p<0.05) incidence of embryonic malformations(embryopathies) in T. canis, as compared with A. suum. Also the percentage of dead larvae of T. canis in the control and in cultures with fungi (12% and 100%, respectively) was significantly higher in comparison with A. suum (0.5% and 10.3–36%, respectively). The highest percentage of non-viable larvae of A. suum was found in the presence of P.fumosoroseus, and the lowest in the presence of M. anisopliae. Findings may indicate that T. canis eggs are more sensitive to antagonistic interaction of the examined fungal strains than A. suum eggs.

[The influence of the Metarhizium fungi on the embryonic development of Ascaris suum]

PURPOSE

The present study focused on the effect of two fungal species Metarhizium flavoviride and Metarhizium anisopliae on the embryonic development and viability of Ascaris suum larvae.

RESULTS

Microscope examination revealed that the presence of the mycelium inhibited the egg development, compared to control. The fungus-exposed eggs featured zygote vacuolisation, irregular blastomere cleavage, and morphological disturbances in the stages of blastula, gastrula, and larva. The embryopathies were significantly more frequent in the eggs incubated with M. flavoviride. Also the mortality of the developed larvae was significantly higher after 60-day culture with M. flavoviride.

[Limitation in the population of parasitic geohelminths by saprotrophic soil fungi and their secretions]

INTRODUCTION

The aim of the study was to examine the effect of mould fungi isolated from soil and of two of their metabolites, aflatoxin G1 and ochratoxin A, on the embryonic development of eggs and mortality of larvae of Ascaris suum. An attempt was made to demonstrate synergism between fungi species in the action on embryogenesis of Ascaris suum.

MATERIAL AND METHODS

Fungi were isolated from soil and cultured on the standard Czapek-Dox agar medium at 26 degrees C for 60 days. Fertilized eggs of Ascaris suum were incubated in PBS solution with the mycelium of each species or without fungi in the control culture. To demonstrate synergism between fungi species, eggs were cultured with three combinations of two species. Additional cultures were done with aflatoxin G1 and ochratoxin A at concentrations of 0.5, 1, and 2 ppm.

RESULTS

Microscopy showed a slower rate of development of eggs from experimental cultures as compared to the control culture. Fungi, as well as mycotoxins, caused vacuolization of the zygote, uneven division of blastomeres, and morphological abnormalities of the embryo. The highest mortality (36%) of invasive larvae of Ascaris suum was caused by Paecylomyces fumosoroseus. The present study revealed that the antagonistic effect of a fungi on the development of Ascaris suum eggs is increased or decreased in the presence of another fungi species. Exposure to aflatoxin G1 and ochratoxin A at concentrations as low as 0.5 ppm leads to a greater percentage of deformed embryos and 100% mortality of larvae.

Bactericidal activity in the pig roundworm Ascaris suum

A potent, humoral, bactericidal activity against Micrococcus luteus was discovered in pseudocoelomic fluid of the pig roundworm, Ascaris suum. The activity, which was not bacteriolytic, was not due to lysozyme or to a dietary antibiotic. It was not inactivated by exposure to 100 degrees C, to low or high pH, or to ethanol. Dialysis, electrophoresis and agar-diffusion experiments suggested that the main antibacterial activity in the fluid was associated with a basic substance of molecular weight somewhat less than 14,000 Da. Two other Gram-positive organisms, Bacillus megaterium and Staphylococcus aureus, were also killed by the Ascaris fluid, but the Gram-negative Escherichia coli, Proteus vulgaris and Bordetella bronchiseptica were insensitive.

Bacterial flora, a possible source of serotonin in the intestine of adult female Ascaris suum

The effect of intestinal bacteria on 5-hydroxytryptamine (5-HT, serotonin) level and 5-HT turnover rates in Ascaris suum intestine are presented. Ascaris suum were incubated in media containing antibiotics for 24 hr, and the bacterial flora in the anterior regions of the intestine of A. suum was eliminated. The bacteria were significantly reduced (> 99%) but not eliminated in the middle and posterior segments of the worm. The 5-HT level decreased in the intestine after 24 hr incubation in antibiotics, whereas the 5-HT turnover rate increased (131 ng/mg protein/hr). Two possible sources of 5-HT from the intestine were examined: the intestinal tissue itself and the microflora inhabiting the intestine. The 5-HT level in the microflora was 30% higher (72.6 ng/g) than the intestinal tissue (43.3 ng/g) in control samples (0 hr, no antibiotics). These values decreased significantly after 24 hr incubation in A. suum saline. The 5-HT values decreased to 18.6 ng/g in the presence and 28.6 ng/g in the absence of antibiotics. The 5-HT turnover rate during this time period indicated that as the number of bacteria declined, the 5-HT turnover rate also declined in the microflora, but the 5-HT turnover rate in the intestinal tissues increased. Results from these studies suggest that bacterial 5-HT may be contributing to the 5-HT level in A. suum intestinal tissue.