Effects of Mannose on Pathogenesis of Acanthamoeba castellanii

Acanthamoeba spp. are single-celled protozoan organisms that are widely distributed in the environment. In this study, to understand functional roles of a mannose-binding protein (MBP), Acanthamoeba castellanii was treated with methyl-alpha-D-mannopyranoside (mannose), and adhesion and cytotoxicity of the amoeba were analyzed. In addition, to understand the association of MBP for amoeba phagocytosis, phagocytosis assay was analyzed using non-pathogenic bacterium, Escherichia coli K12. Amoebae treated with mannose for 20 cycles exhibited larger vacuoles occupying the most area of the amoebic cytoplasm in comparison with the control group amoebae and glucose-treated amoebae. Mannose-selected amoebae exhibited lower levels of binding to Chinese hamster ovary (CHO) cells. Exogenous mannose inhibited >50% inhibition of amoebae (control group) binding to CHO cells. Moreover, exogenous mannose inhibited amoebae (i.e., man-treated) binding to CHO cells by <15%. Mannose-selected amoebae exhibited significantly decreased cytotoxicity to CHO cells compared with the control group amoebae, 25.1% vs 92.1%. In phagocytic assay, mannose-selected amoebae exhibited significant decreases in bacterial uptake in comparison with the control group, 0.019% vs 0.03% (P<0.05). Taken together, it is suggested that mannose-selected A. castellanii trophozoites should be severely damaged and do not well interact with a target cell via a lectin of MBP.

Some virulence characteristics of uropathogenic Escherichia coli in different patient groups.

BACKGROUND & OBJECTIVE: Uropathogenic Escherichia coli have virulence properties, that are absent in non pathogenic E. coli. The distribution of these markers can vary according to patient populations. Hence, a study was undertaken to describe the presence of virulence factors like Pfimbriae, type 1 fimbriae and haemolysin in E.coli causing urinary infections in three groups of patients. Antibiogram was also recorded to determine differences, if any, between the groups. METHODS: E. coli isolated from three groups of subjects, in counts of >10(5) CFU/ml and in pure growth were tested for mannose resistant haemagglutination (MRHA) to indicate P fimbriae and mannose sensitive haemagglutination (MSHA) to indicate type 1 fimbriae. Haemolysin production and antimicrobial susceptibility patterns were also recorded. RESULTS: Significantly more isolates from antenatal and postnatal women possessed P fimbriae compared to groups with urologic abnormalities (P=0.05). Haemolysin production was also significantly higher (P<0.001) in this group. Greater proportions of isolates from pregnant women were susceptible to commonly used antimicrobials. However, resistance to third generation cephalosporins was present even in these isolates from community infections. INTERPRETATION & CONCLUSION: In patients with urological abnormality, E. coli with lower virulence can cause infections. Isolates from these patients exhibited greater drug resistance. In pregnant women and in community acquired infections, simple antimicrobial drugs like nitrofurantoin might still be useful. However, urgent and stringent policies for antimicrobial use and infection control in hospitals are required in India.

Inter-conversion of free sugars and accumulation of galactomannan in response to supplied metabolic mediators during pod filling in guar.

Detached inflorescences of guar (Cyamopsis tetragonoloba), each bearing 4 uniformly-developing pods at 42 days post anthesis (DPA), were cultured for 6 days in complete liquid medium manipulated with a fixed concentration of mannose and varying concentration of myo-inositol. Such inflorescences, but with 2 pods, were also maintained in the solutions of (i) glucose(U-14C) containing myo-inositol or phytohormones, and (ii) mannose(U-14C) containing galactose for 36 hr. Effect of such exogenously supplied metabolic mediators on interconversion of free sugars in pod wall, endosperm and cotyledons and galactomannan accumulation in endosperm was studied. Myo-inositol decreased, over control, the relative proportion of invert sugars in pod wall, endosperm and cotyledons and at lower concentration (27.75 mM) it decreased the level of free sugars in pod wall and galactomannan in endosperm. In all pod tissues, 14C from both glucose and mannose got incorporated into myo-inositol as well as various sugars and maximum incorporation occurred in sucrose. High concentration of total free sugars and their 14C activity in pod wall indicated that this pod tissue was a potent accumulator of free sugars. With myoinositol, the relative proportion of 14C from glucose into raffinose sugars of pod wall and endosperm increased with a simultaneous decrease in this incorporation into galactomannan of the latter. Accompanying this, relative proportion of 14C into hexoses and myo-inositol decreased in pod tissues. Galactose increased 14C incorporation from mannose into total free sugars, sucrose and galactomannan with a concomitant decline in the labelling of hexoses. IAA and ABA enhanced 14C incorporation from glucose into total free sugars and this enhancement was much higher with IAA than ABA. The latter inhibited 14C incorporation into galactomannan. Based on these results, it was suggested that myo-inositol at lower concentration was inadequate to mediate the metabolism of sugars and, thereby, galactomannan synthesis. Galactose and mannose exhibited a mutual beneficial effect on their transportation to pods. Phytohormones stimulated the accumulation of sucrose in pod wall for its obligatory unloading into the seed.

The FML vaccine (fucose-mannose ligand) protects hamsters from experimental kala-azar

Visceral leishmaniais or kala-azar, is a chronic and frequently lethal disease, caused by Leishmania donovani. Clinical signs include malaise, hepatosplenomegaly, hypergammaglobulinemia, fever, cachexia and progressive suppresion of the cellular immune response. Only few studies on prophylactic immunization against this disease have been understaken, mostly with crude antigens, and no vaccine against kala-azar is yet available. In previous studies, we have isolated the Fucose-Mannose Ligand (FML) of L. donovani that strongly and specifically inhibits the in vitro infection of macrophages by promastigotes and amastigotes. The FML behaves as a pontent immunogen for rabbits and mice, and is specifically recognized by kala-azar patient sera. The protective pontential of FML on kala-azar was now analyzed in the CB-hamster model. We studied the efect of three intraperitoneal weekly doses of FML (100 mg) in saponin (100 mg), folowed by an intracardiac injection of 107 amastigotes. Saponin- and saline-treated controls were also included. Protection was highly significant regarding the enhancement of anti-FML antibodies titers, the splenocyte proliferative response, and the intradermal delayed hypersensitivity reaction to antigen, as well as the decrease of the parasite burden in spleen and of splenomegaly. Protection to kala-azar was due to specific FML antigenic properties, since the results obtained by saponin alone were significantly different. We conclude that the use of FML and saponin as a vaccine reduced the disease impact and retarded its onset.

Mannose-resistant haemagglutination by Campylobacter jejuni--a preliminary communication.

Ten strains of C. jejuni each isolated respectively from patients with diarrhoea and from chicken intestine (10 strains from each source) were examined for presumptive colonization factor(s) by measuring their cell surface hydrophobicity and haemagglutination. None of the strains expressed cell surface hydrophobicity. However, 14 strains (7 from either source) showed variable haemagglutination pattern with human, sheep and rabbit erythrocytes in the presence of 0.5 per cent D-mannose. Thus, mannose resistant haemagglutinin(s) may be involved in the colonization of intestinal mucosal surfaces by C. jejuni.

Inhibition of macrophage phagocytosis of Escherichia coli by mannose and mannan

1. We investigated the possibility that Candida albicans and Escherichia coli are interiorized by thioglycollate-elicited peritoneal macrophages by interacting with the same receptor. 2. D-mannose (50 mM), a sugar recognized by mannose receptors, reduced the phatfocytosis of C. albicans and E. coli to 46% and 38% of control values, respectively. The presence of 50 mM galactose did not affect the phagocytosis of either microorganism. However, mannan from saccharomyces cerevisiae (0.5 mg/ml) inhibited phagocytosis by 70% for both microorganisms. 3. The ingestion of C. albicans and E. coli was reduced by 85% and 95%, respectively, in the presence of 10 mM EGTA. 4. These results suggest that the mannose receptor, which mediates the recognition of C. albicans by macrophages, might also mediate the phagocytosis of Escherichia coli 0111

Virulence factors of Eschericha coli in urinary isolates

Escherichia coli strains isolated from 100 urine samples taken from patients with urinary tract infections (UTI) and from 20 normal fecal (NF) samples were examined for serum resistance, mannose-resistant hemagglutination of human erythrocytes (MRHA) and for production of aerobactin, hemolysis and colicin. Among the UTI E. coli strains, 79% produced aerobactin, 69% showed serum resistance, 44% produced MRHA, 32% were beta-hemolytic and 22% were colicinogenic. A greater proportion of UTI E. coli strains produced aerobactin, colicin V, beta-hemolysis and MRHA when compared to NF strains. Production of MR hemagglutins was significant correlated with that of aerobactin and hemolysin. These results suggest that the presence of aerobactin may be a significant etiological factor in UTI, and that the production of MR adhesins and of hemolysin also might contribute to the virulence of these strains