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Introduction: The early detection of resistance in Mycobacterium tuberculosis is of primary importance for both patient management and infection control., Objective: To evaluate nitrate reductase assay (NRA) performance for the testing of Mycobacterium tuberculosis drug-resistance against first-line anti-tuberculosis drugs, such as rifampicin (RIF), isoniazid (INH), streptomycin (STR) and ethambutol (EMB)., Materials and Methods: Fifty isolates were tested by using both the proportion method and the nitrate reductase assay., Results: RIF, INH, STR and EMB sensitivity was found to be 92%, 91%, 63% and 80% and 100%, respectively, and a corresponding specificity of 100%, 100%, 100% and 98% by comparing NRA results to those obtained with the gold standard (i.e., the proportion method). The positive predictive values for RIF, INH, STR and EMB were 100%, 100%, 100% and 80% and the negative predictive values were 97%, 93%, 73% and 98%, respectively. The mean time for obtaining results was shorter when using the nitrate reductase assay (10 days) compared to using the proportion method (28 days). Excellent agreement was observed between both phenotypic tests: 98%, 96%, 81% and 96% for RIF, INH, STR and EMB, respectively ., Conclusions: The results showed that the nitrate reductase assay is suitable for the early determination of multidrug-resistant tuberculosis (MDR-TB) and is a useful tool for the quick and accurate determination of a rapid M. tuberculosis drug-sensitivity test in countries having low resources.

We evaluated the two methods accepted by the Mexican norm for the determination of nitritesin infant meat-based food with vegetables. We determined the content of nitrites in the infant food, raw materials as well as products from the intermediate stages of production. A reagent blank and a reference sample were included at each analytical run. In addition, we determined the sensitivity, recovery percentage and accuracy of each methodology. Infant food results indicated an important difference in the nitrite content determined under each methodology, due to the persistent presence of turbidity in the extracts. Different treatments were proposed to eliminate the turbidity, but these only managed to reduce it. The turbidity was attributed to carbohydrates which disclosed concentration exhibit a wide dispersion and were below the quantifiable limit under both methodologies; therefore it is not recommended to apply these techniques with food suspected to contain traces of nitrites.

Introduction: The aim of the study was to analyse the relationship between the intensity of the respiratory tract inflammation, expressed by oxidative stress markers, and the severity of the disease in patients with bronchiectasis unassociated with cystic fibrosis., Patients and Methods: The study included 25 patients with stable bronchiectasis (15 females and 10 males). As determining factors of severity, the following parameters were collected: degree of dyspnoea, number of exacerbations/admissions in the last year, mean daily sputum volume, sputum colour (graduated colour scale), bacterial colonisation, respiratory function tests, quality of life (St. George questionnaire) and radiological extension of the lesions (Bhalla scale). Inflammation was analysed using the measurement of nitric oxide, pH and concentration of nitrites, nitrates and isoprostane in the exhaled air condensate. The C reactive protein and erythrocyte sedimentation rate were also determined in peripheral blood., Results: There were no significant relationships between the markers in the exhaled air condensate and the clinical, radiological and functional involvement or the quality of life of the patients. Only bacterial colonisation (16 cases) was associated with higher values of nitrates in exhaled air (mean+/-standard deviation: 18+/-4 compared to 7+/-2microM; r(2)=0.6) and a higher number of exacerbations (3.1+/-1.9 compared to 1.7+/-1.9; r(2)=0.3)., Conclusions: In our study, the measurement of inflammation markers in exhaled air is only associated with some parameters of severity in patients with bacterial bronchiectasis.

Introduction: Nitric oxide is an important modulator of numerous physiological and pathophysiological processes. An indirect form to detect NO production has been the quantification of its stable end products, nitrites and nitrates (NO2- + NO3-). These metabolites can be detected with a commercial kit, but it is somewhat expensive and not accessible to some laboratories in our country., Objective: To validate an easy, accessible and less expensive assay for detecting nitrates and nitrites in biological fluids., Material and Methods: In this study we determined nitrates and nitrites by reducing nitrates enzymatically with nitrate reductase, followed by nitrites quantification using the Griess reagent. To validate the assay, NO3- concentration was evaluated in aliquots with known amounts of sodium nitrate, also NO2- + NO3- concentrations were detected in plasma containing known amounts of sodium nitrate, finally NO2- + NO3- levels were evaluated in plasma (n = 17) and ascites (n = 11) samples of cirrhotic patients. In samples of patients, NO2- + NO3- levels were also detected by using a commercial kit., Results: The assay that we describe here detects nitrates in the range between 25 to 400 microM/L and nitrites between 25 to 100 microM/L. When specific concentrations of nitrates were added to plasma samples, the recovery percentage in most cases was greater than 95%. In plasma samples of cirrhotic patients, average concentrations of NO2- + NO3- was 44.6 +/- 22.4 microM (mean +/- SD), similar to that found using the commercial kit, 40.9 +/- 18.3 microM/L (p = 0.107). In ascitis samples, similar results using both methods were seen, 64.5 +/- 42.0 vs. 58.2 +/- 39.3 microM/L (p = 0.172) respectively., Conclusions: Our results suggest that the method described here could be considered as an alternative instead of commercial kits to determine NO2- + NO3- in plasma and ascites samples. In addition, this assay results more attractive because, it does not, require special equipment, it is very accessible to most laboratories, it may be use to assay one or more samples at any given time, but the most important advantage, is its cost effectiveness; thus each sample determination is about one fifth of the cost using the commercial kit.

The aim of the present study was to gain further insight on the reliability of the colorimetric determination of the activity of bacterial nitrate reductase to evaluate bacterial concentrations and interaction between microorganisms and enterocyte-like cells. Nitrite produced after incubation of the samples with a nitrate-formate solution was determined with a diazotization reaction with sulphanilic acid and N-naphthyl-ethylene-diamonium dichloride. Cell association assays were performed with differentiated Caco-2 cells. A biphasic relationship was found between nitrite concentration and bacterial densities. This behavior seems to be due to the sigmoideal character of the kinetics of nitrate reduction. Association to Caco-2 cells was strongly strain dependent being Staphylococcus aureus ATCC 25923 the strain showing the highest values of association. For some strains, percentages of association calculated on the basis of the colorimetric assay were significantly higher than those calculated in terms of viable counts. Bacterial association with enterocyte-like cells can be evaluated by measures of the activity of bacterial nitrate reductase provided that the biphasic relationship between bacterial and nitrite concentrations is taken into account for the calculations. Results presented in this paper show the applicability of the colorimetric method to assess the amount of microorganisms associated to human enterocytes in culture.

Objective: Nitric oxide (NO) is a gas considered to have two roles: cytoprotective, derived from its vasodilating and anti-platelet aggregation effects, and cytotoxic, due to its free oxygen radical. It is produced by NO synthase; nitrites and nitrates are its end products. We investigated the role of NO in ischemia-perfusion injury., Methods: For the study, we utilized dogs weighing 15 to 25 kg. Autotransplantation of the left kidney and right nephrectomy were performed. Group I comprised 9 dogs submitted to renal autotransplantation; group II comprised 6 dogs submitted to renal autotransplantation after 24 h cold ischemia; group III comprised 6 dogs submitted to renal autotransplantation after 24 h cold ischemia and subsequent warm ischemia of 30 min; group IV comprised 9 dogs submitted to renal autotransplantation after 24 h cold ischemia and 60 min warm ischemia., Results: A significant fall in nitrite levels was observed in dogs that had some type of surgical injury. Nitrate levels increased significantly in dogs that had warm ischemia. At 30 min reperfusion, a significant increase in the production of constitutive enzyme was observed in all groups. A significant increase in inducible enzyme at 30 min reperfusion was observed in the first three groups and no inducible enzyme was produced in the group that had more injury from ischemia (group IV)., Conclusion: Nitrites are markers of the injury produced by surgery. Nitrates clearly express the injury to the organs caused by warm ischemia-reperfusion. The cNOS enzyme increases after surgery in response to surgical insult or stress. The iNOS enzyme increases in the kidneys that have suffered ischemia and are viable. Non-viable kidneys express no enzymatic activity (cNOS, iNOS).

Sampling of Fossaria cubensis, main host of Fasciola hepatica in Cuba was carried out in 3 transmission sites. A higher mollusk density was found in dairies numbers 6 and 9, coinciding with the higher values of total hardness and carbonate hardness. Ammonium, nitrite, and nitrite ions showed lower values in dairy number 6. Temperature and pH did not show significant differences in the 3 biotopes. The mollusks of dairy number 6 began to emit cercarias on the 26th day after being collected; they showed an emission peak at 9 a.m. and an average of 60 cercarias emitted by each mollusk at that time of the day.