C-2 derivatized 8-sulfonamidoquinolines as antibacterial compounds.

A series of C-2 derivatized 8-sulfonamidoquinolines were evaluated for their antibacterial activity against the common mastitis causative pathogens Streptococcus uberis, Staphylococcus aureus and Escherichia coli, both in the presence and absence of supplementary zinc (50 µM ZnSO4). The vast majority of compounds tested were demonstrated to be significantly more active against S. uberis when in the presence of supplementary zinc (MICs as low as 0.125 µg/mL were observed in the presence of 50 µM ZnSO4). Compounds 5, 34-36, 39, 58, 79, 82, 94 and 95 were shown to display the greatest antibacterial activity against S. aureus (MIC ≤ 8 µg/mL; both in the presence and absence of supplementary zinc), while compounds 56, 58 and 66 were demonstrated to also exhibit activity against E. coli (MIC ≤ 16 µg/mL; under all conditions). Compounds 56, 58 and 66 were subsequently confirmed to be bactericidal against all three mastitis pathogens studied, with MBCs (≥3log10 CFU/mL reduction) of ≤ 32 µg/mL (in both the presence and absence of 50 µM ZnSO4). To validate the sanitizing activity of compounds 56, 58 and 66, a quantitative suspension disinfection (sanitizer) test was performed. Sanitizing activity (>5log10 CFU/mL reduction in 5 min) was observed against both S. uberis and E. coli at compound concentrations as low as 1 mg/mL (compounds 56, 58 and 66), and against S. aureus at 1 mg/mL (compound 58); thereby validating the potential of compounds 56, 58 and 66 to function as topical sanitizers designed explicitly for use in non-human applications.

Substituted sulfonamide bioisosteres of 8-hydroxyquinoline as zinc-dependent antibacterial compounds.

A series of substituted sulfonamide bioisosteres of 8-hydroxyquinoline were evaluated for their antibacterial activity against the common mastitis causative pathogens Streptococcus uberis, Staphylococcus aureus and Escherichia coli, both in the presence and absence of supplementary zinc. Compounds 9a-e, 10a-c, 11a-e, 12 and 13 were demonstrated to have MICs of 0.0625 µg/mL against S. uberis in the presence of 50 µM ZnSO4. Against S. aureus compounds 9g (MIC 4 µg/mL) and 11d (MIC 8 µg/mL) showed the greatest activity, whereas all compounds were found to be inactive against E. coli (MIC > 256 µg/mL); again in the presence of 50 µM ZnSO4. All compounds were demonstrated to be significantly less active in the absence of supplementary zinc. Compound 9g was subsequently confirmed to be bactericidal, with an MBC (≥3log10 cfu/mL reduction) of 0.125 µg/mL against S. uberis in the presence of 50 µM ZnSO4. To validate the sanitising activity of compound 9g in the presence of supplementary zinc, a quantitative suspension disinfection (sanitizer) test was performed. In this preliminary test, sanitizing activity (>5log10 reduction of CFU/mL in 5 min) was observed against S. uberis for compound 9g at concentrations as low as 1 mg/mL, validating the potential of this compound to function as a topical sanitizer against the major environmental mastitis-causing microorganism S. uberis.

Simultaneous HPLC assay for pretomanid (PA-824), moxifloxacin and pyrazinamide in an inhaler formulation for drug-resistant tuberculosis.

A simple and sensitive reversed phase HPLC method has been developed for the simultaneous quantitation of pretomanid (PA-824), moxifloxacin and pyrazinamide in a combination spray-dried powder formulation for inhalation, without any use of an internal standard. Good resolution of the analytes was achieved on a Luna C18 (2), 150×4.6mm, 5µm, 100Å column using gradient elution with a mobile phase containing methanol and triethylamine phosphate buffer (pH 2.5) at a flow rate of 1.0mL/min in a total run time of 25min. Pyrazinamide, moxifloxacin and pretomanid (PA-824) were detected at wavelengths (retention times) of 269nm (3.80min), 296nm (7.94min) and 330nm (17.46min), respectively. The assay was linear for all analytes in the concentration range 2.5-100µg/mL (correlation coefficients >0.999) with LODs and LLOQs (µg/mL) of pretomanid (PA-824) 0.51 and 1.56, moxifloxacin 0.06 and 0.19 and pyrazinamide 0.35 and 1.06, respectively. Recoveries of the three drugs were 99.6-106.8% with intra- and inter-day precisions (as relative standard deviation) of <7%. The method was successfully applied to an evaluation of content uniformity and freedom from interference by l-leucine of a spray-dried combination powder for inhalation.

Delayed delivery of intravenous gentamicin in neonates: impact of infusion variables.

OBJECTIVE: To investigate infusion variables that delay delivery of gentamicin through neonatal infusion lines. METHODS: Infusions were set up to simulate administration of gentamicin to neonates. The primary infusion was 10% dextrose (Baxter Colleague pump). A syringe driver was used to deliver a coloured marker via the T-connection over 35 min followed by a 1 ml normal saline flush over 35 min. Effects of dextrose concentration, primary infusion rate, dose volume and angle of the primary line were investigated. Gentamicin adsorption to in-line filters (Poisdyne Neo) and administration protocols from different neonatal intensive care units were also investigated. KEY FINDINGS: Low dose volumes (<0.4 ml) infused into slow-flowing glucose (dextrose) lines (3.8-4 ml/h) did not mix well at the T-connection. Coloured solutions formed an upper layer that moved in a retrograde direction towards the primary infusion bag. Gentamicin did not adsorb onto Posidyne Neo filters. Comparison of infusion protocols for gentamicin administration showed that slow infusion (30 min) into slow-flowing lines (4 ml/h) containing 10% glucose gave low recovery of drug during the infusion (<30% of intended dose). CONCLUSIONS: Poor mixing at the T-connection appears to be the cause of delayed and/or incomplete gentamicin delivery for low dose volumes and slow infusion rates.

Metabolism of L-selenomethionine and selenite by probiotic bacteria: in vitro and in vivo studies.

Since selenium supplements have been shown to undergo biotransformation in the gut, probiotic treatment in combination with selenium supplements may change selenium disposition. We investigated the metabolism of L-selenomethionine (SeMet) and selenite by probiotic bacteria in vitro and the disposition of selenium after probiotic treatment followed by oral dosing with SeMet and selenite in rats. When SeMet was incubated anaerobically with individual antibiotic-resistant probiotic strains (Streptococcus salivarius K12, Lactobacillus rhamnosus 67B, Lactobacillus acidophilus L10, and Bifidobacterium lactis LAFTI® B94) at 37°C for 24 h, 11-18% was metabolized with 44-80% of SeMet lost being converted to dimethyldiselenide (DMDSe) and dimethylselenide (DMSe). In similar incubations with selenite, metabolism was more extensive (26-100%) particularly by the lactobacilli with 0-4.8% of selenite lost being converted to DMSe and DMDSe accompanied by the formation of elemental selenium. Four groups of rats (n = 5/group) received a single oral dose of either SeMet or selenite (2 mg selenium/kg) at the time of the last dose of a probiotic mixture or its vehicle (lyoprotectant mixture used to maintain cell viability) administered every 12 h for 3 days. Another three groups of rats (n = 3/group) received a single oral dose of saline or SeMet or selenite at the same dose (untreated rats). Serum selenium concentrations over the subsequent 24 h were not significantly different between probiotic and vehicle treated rats but appeared to be more sustained (SeMet) or higher (selenite) than in the corresponding groups of untreated rats. Probiotic treated rats given SeMet also had selenium concentrations at 24 h that were significantly higher in liver and lower in kidney than untreated rats given SeMet. Thus, treatment with probiotics followed by SeMet significantly affects tissue levels of selenium.

Biotransformation of L-selenomethionine and selenite in rat gut contents.

L-selenomethionine (SeMet) and sodium selenite are widely used selenium nutritional supplements with potential benefit in preventing cancer. However, supplementation is not without risks of toxicity if intake is too high. The aim of the present study was to investigate SeMet and selenite metabolism in the gastrointestinal tract with particular focus on the formation of the volatile selenium excretion products, dimethylselenide (DMSe) and dimethyldiselenide (DMDSe). Adult male Wistar rats (n = 5) were euthanized, their intestinal tracts removed and the contents of jejunum, ileum, caecum and colon used to prepare 10% suspensions in saline. SeMet and selenite (0.5-0.6 mM) were then incubated with these suspensions at 37°C for 3 h. Caecum and colon contents were the most metabolically active towards SeMet with 30% and 15% metabolized over 3 h. DMDSe was the only volatile selenium metabolite detected accounting for 8.7 ± 1.3% of the selenium lost in caecum contents. Selenite was completely metabolized by caecum contents and 73% by colon contents under the same conditions forming DMSe (5.7 ± 0.9% of the selenium lost in caecum) and a precipitate of red amorphous elemental selenium. Based on previous literature and these results, we conclude that the gut microbiota contributes to the excretion of excess selenium through the production of methylated selenium compounds and elemental selenium.

An improved HPLC method for the investigation of L-selenomethionine metabolism in rat gut contents.

Selenomethionine (SeMet) is a widely used nutritional supplement that has potential benefit for people living in selenium-deficient areas. Previous research has shown that selenium administered as SeMet undergoes significant enterohepatic recycling which may involve the gut microflora. In order to investigate this we have developed a simple method for the quantitation of l-SeMet in rat gut content suspensions prepared from jejunum, ileum, caecum and colon. After incubation of l-SeMet with gut content suspensions, samples were deproteinized with sulfosalicylic acid and derivatized with o-phthaldialdehyde (OPA) and N-acetyl-l-cysteine (NAC). Mass spectrometry confirmed the formation of a 1:1:1 derivative of l-SeMet with OPA and NAC. Samples were analysed by reversed-phase high-performance liquid chromatography with fluorescence detection. The assay was linear in the concentration range 0.5-100 microg/mL (r(2) = 0.9992) with a limit of detection of 0.025 microg/mL (signal-to-noise ratio of 5). Intra-day and inter-day accuracies were 91.1-92.8 and 91.7-95.5%, respectively with corresponding precisions as relative standard deviation of <5%. Incubation of l-SeMet with gut content suspensions from different parts of the rat intestine showed that l-SeMet metabolism occurs mainly in the caecum.

Does zinc deficiency play a role in stunting among primary school children in NE Thailand?

Stunting in school-age years may result in a decrease in adult size, and thus reduced work capacity and adverse reproductive outcomes. We have compared the mean intakes of energy, protein and selected growth-limiting nutrients in fifty-eight stunted children and 172 non-stunted controls drawn from 567 children aged 6-13 years attending ten rural schools in NE Thailand. Control children were selected randomly after stratifying children by age in each school. Dietary data were calculated from 24-h recalls using nutrient values from Thai food composition data and chemical analysis. Inter-relationships between stunting and sociodemographic, anthropometric and biochemical variables were also examined. Biochemical variables investigated were serum albumin, zinc, ferritin, transferrin receptor and retinol, and iodine in casual urine samples. Significantly more males than females were stunted (males, n 38, 65.5% v. females, n 20. 34.5%: P=0.025). Stunted males had lower mean intakes of energy, protein, calcium, phosphorus and zinc, and a lower mean (95% CI) serum zinc (9.19 (8.53, 9.84) v. 9.70 (8.53, 9.29) micromol/1) than non-stunted males; no other biochemical differences were noted. Stunted males also had a lower mean arm muscle area (P= 0.015), after adjusting for age, than non-stunted males. In conclusion, the lower dietary intakes of the stunted males compared to their non-stunted counterparts may be associated with anorexia and hypogeusia induced by zinc deficiency. Hence, zinc deficiency may be a factor limiting linear growth, especially among boys in NE Thailand, but more research is needed to establish whether other factors also play a role.

Low zinc, iron, and calcium intakes of Northeast Thai school children consuming glutinous rice-based diets are not exacerbated by high phytate.

Phytate, a salt of phytic acid (myo-inositol 1,2,3,4,5,6-hexakisphosphate), is found in certain plant-based foods. It strongly chelates minerals, forming insoluble complexes in the small intestine that cannot be digested or absorbed. Information on the phytate content of rice-based diets of children in Northeast Thailand is limited. In this study 1-day weighed duplicate diet composites were collected from 40 Northeast Thai children (age 6-13 years) randomly selected from participants (n=567) of an efficacy trial in Ubon Ratchathani province. Diet composites were analyzed for zinc, iron, and calcium by atomic absorption spectrophotometry, and for phytate (as inositol penta-phosphate and hexa-phosphate) by high-performance liquid chromatography; the accuracy and precision were established using a certified reference material for the minerals and an inter-laboratory comparison for phytate. The median (1st, 3rd quartiles) zinc, iron, and calcium contents of the diet composites were 4.3 (3.7, 6.1), 4.3 (3.2, 6.5) and 130 (82, 216) mg/day, respectively. The inositol penta-phosphate and hexa-phosphate levels were so low they were below the detection limit, attributed in part to leaching of water-soluble potassium and magnesium phytate from glutinous rice after soaking overnight before cooking. Clearly, phytate will not compromise mineral absorption from these diets. Instead, low zinc intakes are probably primarily responsible for the low zinc status of these children. In contrast, although intakes of dietary iron appear low, the prevalence of biochemical iron deficiency was also low, suggesting that iron absorption may have been higher than previously assumed. Whether the low calcium intakes compromise optimal bone health in these growing Northeast Thai school children is unknown.

Primary school children from northeast Thailand are not at risk of selenium deficiency.

Selenium has important roles as an antioxidant, in thyroid hormone metabolism, redox reactions, reproduction and immune function, but information on the selenium status of Thai children is limited. We have assessed the selenium status of 515 northeast Thai children (259 males; 256 females) aged 6 to 13 years from 10 rural schools in Ubon Ratchthani province. Serum selenium (n=515) was analyzed by Graphite Furnace Atomic Absorption Spectrophotometry and dietary selenium intake by Hydride Generation Absorption Spectrophotometry from one-day duplicate diet composites, from 80 (40 females; 40 males) randomly selected children. Inter-relationships between serum selenium and selenium intakes, and other biochemical micronutrient indices were also examined. Mean (SD) serum selenium was 1.46 (0.24) micro mol/L. Concentrations were not affected by infection or haemoglobinopathies, but were dependent on school (P< 0.001), sex (P=0.038), and age group (P=0.003), with serum zinc as a significant covariate. None of the children had serum selenium concentrations indicative of clinical selenium deficiency (i.e. <0.1 micro mol/L). Significant correlations existed between serum selenium and serum zinc (r= 0.216; P < 0.001), serum retinol (r = 0.273; P < 0.001), urinary iodine (r = -0.110; P = 0.014), haemoglobin (r = 0.298; P <0.001), and haematocrit (r = 0.303; P< 0.001). Mean (SD) dietary selenium intake was 46 (22) micro g/d. Children with low serum selenium concentrations had a lower mean selenium intake than those with high serum selenium concentrations (38 +/- 17 vs.51 +/- 24 micro g/d; P< 0.010). In conclusion, there appears to be no risk of selenium deficiency among these northeast Thai children.