Antiamoebic and toxicity studies of a carbamic acid derivative and its therapeutic effect in a hamster model of hepatic amoebiasis. (17/80)

Amoebiasis is an important public health problem in developing countries. Entamoeba histolytica, the causative agent of amoebiasis, may develop resistance to nitroimidazoles, a group of drugs considered to be the most effective against this parasitic disease. Therefore, research on new drugs for the treatment of this common infection still constitutes an important therapeutic demand. In the present study we determined the effects of a carbamate derivative, ethyl 4-chlorophenylcarbamate (C4), on trophozoites of E. histolytica strain HM-1:IMSS. C4 was subject to various toxicity tests, including the determination of mutagenicity for bacterial DNA and changes in the enzymatic activities of eukaryotic cells. Genotoxicity studies were performed by the mutagenicity Ames test (plate incorporation and preincubation methods) with Salmonella enterica serovar Typhimurium, with or without metabolic activation produced by the S9 fraction of rat liver. C4 toxicity studies were performed by measuring enzymatic activity in eukaryotic cells by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide-formazan test with Fischer 344 rat hepatocytes. C4 did not induce either frame-shift mutations in S. enterica serovar Typhimurium TA97 or TA98 or base pair substitutions in strains TA100 and TA102. The compound was not toxic for cultured rat hepatic cells. Trophozoites treated with 100 microg of C4 per ml were inhibited 97.88% at 48 h of culture; moreover, damage to the amoebae was also confirmed by electron microscopy. The antiamoebic activity of C4 was evaluated by using an in vivo model of amoebic liver abscess in hamsters. Doses of 75 and 100 mg/100 g of body weight reduced the extent of the amoebic liver abscess by 84 and 94%, respectively. These results justify further studies to clearly validate whether C4 is a new suitable antiamoebic drug.  (+info)

Aminoglycosides decrease glutathione peroxidase-1 activity by interfering with selenocysteine incorporation. (18/80)

Cellular glutathione peroxidase is a key intracellular antioxidant enzyme that contains a selenocysteine residue at its active site. Selenium, a selenocysteine incorporation sequence in the 3'-untranslated region of the glutathione peroxidase mRNA, and other translational cofactors are necessary for "read-through" of a UGA stop codon that specifies selenocysteine incorporation. Aminoglycoside antibiotics facilitate read-through of premature stop codons in prokayotes and eukaryotes. We studied the effects of G418, an aminoglycoside, on cellular glutathione peroxidase expression and function in mammalian cells. Insertion of a selenocysteine incorporation element along with a UGA codon into a reporter construct allows for read-through only in the presence of selenium. G418 increased read-through in selenium-replete cells as well as in the absence of selenium. G418 treatment increased immunodetectable endogenous or recombinant glutathione peroxidase but reduced the specific activity of the enzyme. Tandem mass spectrometry experiments indicated that G418 caused a substitution of l-arginine for selenocysteine. These data show that G418 can affect the biosynthesis of this key antioxidant enzyme by promoting substitution at the UGA codon.  (+info)

Efficacy of nitazoxanide and paromomycin in biliary tract cryptosporidiosis in an immunosuppressed gerbil model. (19/80)

OBJECTIVES: To evaluate the efficacy of nitazoxanide and paromomycin in biliary tract cryptosporidiosis in an immunosuppressed Mongolian gerbil (Meriones unguiculatus) model. METHODS: Gerbils (1-month-old) were dexamethasone-immunosuppressed for 10 days and challenged orally with 10(5) Cryptosporidium parvum oocysts. From day 0 to day 12 post-infection, one group (n=14) was treated with 200 mg/kg/day nitazoxanide and another (n=15) with 100 mg/kg/day paromomycin. Infection and efficacy of nitazoxanide and paromomycin were assessed by measuring oocyst shedding in faeces, biliary tract and ileum histological examination. RESULTS: In nitazoxanide-treated and paromomycin-treated groups as compared with untreated animals (P<0.05), oocyst shedding was partially suppressed in a similar manner (P>0.05). Parasites were present in histological sections of the ileal mucosa of 16/16 infected untreated animals versus 3/14 and 6/15 in the nitazoxanide-treated and the paromomycin-treated groups, respectively (P<0.05). In addition, gall bladder infection was less frequent in nitazoxanide-treated (2/14, P<0.01) and paromomycin-treated (5/15, P=0.07) animals than in untreated controls (9/16). No histological alteration of biliary mucosa was observed in both treated and untreated infected gerbils. CONCLUSIONS: Present data support the efficacy of nitazoxanide and, to a lesser extent, paromomycin on biliary C. parvum infection in gerbils, and prompt further investigation of the potential clinical benefits of nitazoxanide in treating human biliary cryptosporidiosis.  (+info)

In vitro acanthamoebicidal activity of a killer monoclonal antibody and a synthetic peptide. (20/80)

OBJECTIVES: To evaluate the in vitro microbicidal activity against Acanthamoeba castellanii of a murine monoclonal anti-idiotypic antibody (KTmAb) and a synthetic killer mimotope (KP), which mimic a yeast killer toxin (KT) characterized by a wide spectrum of antimicrobial activity through interaction with specific cell wall receptors, mainly constituted by beta-glucans. METHODS: Amoebicidal activity was investigated after incubation of trophozoites under different experimental conditions with laminarinase, KTmAb, KP and a scrambled decapeptide (SP). To confirm the specific interaction of KP with beta-glucans, the experiments were also carried out in the presence of laminarin (beta1-3-glucan) or pustulan (beta1-6-glucan); both glucan molecules were co-incubated with KP or SP. RESULTS: KTmAb and KP exhibited a time-dependent killing activity, in comparison with SP or heat-inactivated KTmAb; this activity was completely abolished by pre-incubation with laminarin, but not by pustulan. Notably, in vitro amoebicidal activity was observed in the presence of laminarinase, an enzyme that specifically hydrolyses beta-glucans. Furthermore, KP specifically inhibited the growth of Acanthamoeba on infected contact lenses and the remaining adherent KP-treated trophozoites appeared strongly damaged. CONCLUSIONS: The results indicate that the expression of beta1-3-glucan receptors in the cell membrane is probably modulated during cell growth of A. castellanii and is critical for the killing activity of KT-like molecules. Our data confirm the broad antimicrobial spectra of KTmAb and KP, emphasize the crucial role of beta1-3-glucan in microbial physiology and suggest the potential use of KTmAb and KP in the prevention and therapy of Acanthamoeba infections or in preventing Acanthamoeba contamination during storage of contact lenses.  (+info)

Early diagnosis of Acanthamoeba infection during routine cytological examination of cerebrospinal fluid. (21/80)

Early identification of Acanthamoeba in cerebrospinal fluid is mandatory to prevent fatal granulomatous amebic encephalitis. In the case presented here amebic trophozoites were detected in a routine cerebrospinal fluid sample. The antibiotic treatment and the apparently low virulence of this isolate were responsible for the benign progression of the infection.  (+info)

Amoebiasis cutis in HIV positive patient. (22/80)

Protozoan infections of the skin, particularly cutaneous amoebiasis, are rare in HIV-positive patients. We report a case of amoebiasis cutis in an HIV-positive truck driver with a history of frequent unprotected sexual exposures. He presented with multiple painful ulcers and sinuses with purulent discharge, necrotic slough and scarring in the perianal and gluteal region for the last 2 years. He was positive for HIV-1 and -2. Cutaneous biopsy revealed numerous Entamoeba histolytica in the trophozoite form, in addition to an inflammatory infiltrate and necrotic debris. He responded well to oral metronidazole and chloroquine. Amoebiasis cutis should be considered in the differential diagnosis of perianal ulcers, particularly in HIV-positive patients.  (+info)

Amoebicidal activity of milk, apo-lactoferrin, sIgA and lysozyme. (23/80)

OBJECTIVES: To identify amoebicidal components in human milk and the effect of iron on the amoebicidal activity. DESIGN: Investigation in axenic cultures of Entamoeba histolytica trophozoites. METHODS: Amoebas were treated with 5%-20% of human, bovine and swine milk, with 10% of human milk fractions (i.e., casein, proteins except casein and fat) or with 1 mg/ml of human milk apo-lactoferrin, human secretory immunoglobulin type A (sIgA) and chicken egg-white lysozyme (i.e., purified proteins). Milk proteins were detected using immunoblot. Confocal microscopy was used to define the interaction of milk proteins (100 microM each) and amoebas. Experiments were done at least three times in triplicate, and mean and standard deviations were calculated. RESULTS: Human and bovine milk were amoebicidal showing a concentration-dependent effect. The amoebicidal effect was increased in the absence of iron. Milk protein fractions, with the exception of casein, were the components responsible for the amoebicidal activity found. Apo-lactoferrin, sIgA and lysozyme were identified in the amoebicidal milk protein fraction. Apo-lactoferrin showed the major amoebicidal effect. These proteins, either alone or in combination, showed a killing effect on the trophozoites. They bound to the amoebic membrane causing cell rounding, lipid disruption and damage. CONCLUSIONS: Milk proteins such as apo-lactoferrin, sIgA and lysozyme are able to kill Entamoeba histolytica trophozoites. This study confirms the importance of feeding breast milk to newborns.  (+info)

Effects of human serum on Balamuthia mandrillaris interactions with human brain microvascular endothelial cells. (24/80)

Balamuthia mandrillaris is a free-living amoeba and a causative agent of fatal granulomatous encephalitis. In the transmission of B. mandrillaris into the central nervous system (CNS), haematogenous spread is thought to be the primary step, followed by blood-brain barrier penetration. The objectives of the present study were (i) to determine the effects of serum from healthy individuals on the viability of B. mandrillaris, and (ii) to determine the effects of serum on B. mandrillaris-mediated blood-brain barrier perturbations. It was determined that normal human serum exhibited limited amoebicidal effects, i.e. approximately 40 % of trophozoites were killed. The residual subpopulation, although viable, remained static over longer incubations. Using human brain microvascular endothelial cells (HBMEC), which form the blood-brain barrier, it was observed that B. mandrillaris exhibited binding (>80 %) and cytotoxicity (>70 %) to HBMEC. However, normal human serum exhibited more than 60 % inhibition of B. mandrillaris binding and cytotoxicity to HBMEC. ELISAs showed that both serum and saliva samples exhibit the presence of anti-B. mandrillaris antibodies. Western blots revealed that normal human serum reacted with several B. mandrillaris antigens with approximate molecular masses of 148, 115, 82, 67, 60, 56, 44, 42, 40 and 37 kDa. Overall, the results demonstrated that normal human serum has inhibitory effects on B. mandrillaris growth and viability, as well as on their binding and subsequent cytotoxicity to HBMEC. A complete understanding of B. mandrillaris pathogenesis is crucial to develop therapeutic interventions and/or to design preventative measures.  (+info)