Burden and risk factors for Pseudomonas aeruginosa community-acquired pneumonia:a Multinational Point Prevalence Study of Hospitalised Patients

Pseudornonas aeruginosa is a challenging bacterium to treat due to its intrinsic resistance to the antibiotics used most frequently in patients with community-acquired pneumonia (CAP). Data about the global burden and risk factors associated with P. aeruginosa-CAP are limited. We assessed the multinational burden and specific risk factors associated with P. aeruginosa-CAP. We enrolled 3193 patients in 54 countries with confirmed diagnosis of CAP who underwent microbiological testing at admission. Prevalence was calculated according to the identification of P. aeruginosa. Logistic regression analysis was used to identify risk factors for antibiotic-susceptible and antibiotic-resistant P. aeruginosa-CAP. The prevalence of P. aeruginosa and antibiotic-resistant P. aeruginosa-CAP was 4.2% and 2.0%, respectively. The rate of P. aeruginosa CAP in patients with prior infection/colonisation due to P. aeruginosa and at least one of the three independently associated chronic lung diseases (i.e. tracheostomy, bronchiectasis and/or very severe chronic obstructive pulmonary disease) was 67%. In contrast, the rate of P. aeruginosa-CAP was 2% in patients without prior P. aeruginosa infection/colonisation and none of the selected chronic lung diseases. The multinational prevalence of P. aeruginosa-CAP is low. The risk factors identified in this study may guide healthcare professionals in deciding empirical antibiotic coverage for CAP patients

Fluoride dynamics in the granitic aquifer of the Wailapally watershed, Nalgonda District, India

High concentrations of fluoride (up to 7.6 mg/L) are a recognized feature of the Wailapally granitic aquifer of Nalgonda District, Andhra Pradesh, India. The basement rocks provide abundant sources of F in the form of amphibole, biotite, fluorite and apatite. The whole-rock concentrations of F in the aquifer are in the range 240–990 mg/kg. Calcretes from the shallow weathered horizons also contain comparably high concentrations of F (635–950 mg/kg). The concentrations of water-soluble F in the granitic rocks and the calcretes are usually low (1% of the total or less) but broadly correlate with the concentrations observed in groundwaters in the local vicinity. The water-soluble fraction of fluoride is relatively high in weathered calcretes compared to fresh calcretes. Groundwater major-ion composition shows a well-defined trend with flow downgradient in the Wailapally aquifer, from Na–Ca–HCO3-dominated waters in the recharge area at the upper part of the catchment, through to Na–Mg–HCO3 and ultimately to Na–HCO3 and Na–HCO3–Cl types in the discharge area in the lowest part. The evolution occurs over a reach spanning some 17 km. Groundwater chemistry evolves by silicate weathering reactions, although groundwaters rapidly reach equilibrium with carbonate minerals, favouring precipitation of calcite, and ultimately dolomite in the lower parts of the watershed. This precipitation is also aided by evapotranspiration. Decreasing Ca activity downgradient leads to a dominance of fluorite-undersaturated conditions and consequently to mobilisation of F. Despite the clear downgradient evolution of major-ion chemistry, concentrations of F remain relatively uniform in the fluorite-undersaturated groundwaters, most being in the range 3.0–7.6 mg/L. The rather narrow range is attributed to a mechanism of co-precipitation with and/or adsorption to calcrete in the lower sections of the aquifer. The model may find application in other high-F groundwaters from granitic aquifers of semi-arid regions

Soil gas radon emanometry: A tool for delineation of fractures for groundwater in granitic terrains

International audienceIn several arid and semi-arid hard rock areas of the world, overexploitation of groundwater has caused de-saturation of the phreatic weathered zone. Attempts are now underway to draw supplies from deeper fracture zones. But random drilling often fails to encounter such productive zones. Further, currently available hydrogeological and geophysical methods are of limited applicability. Alternative geochemical methods, employing soil gas 222radon (Rn) and helium (4He) have been explored but not investigated sufficiently.This paper reports the results of a systematic survey of 222Rn concentration in soil gas (at a depth of 60 and 160 cm) in a watershed located in a semi-arid granitic area in India. We were able to demarcate three high 222Rn anomalies, which were supplemented by 4He measurements. Drilling was carried out on the sites of these high 222Rn anomalies as well as on low 222Rn anomalies. The bore wells drilled at the site of high 222Rn concentration were found to be quite productive and those drilled on low 222Rn concentration sites were dry; those sites of the intermediate 222Rn concentrations had intermediate yields. These preliminary results suggest that 222Rn emanometry method may turn out to be useful. The method still needs to be investigated in detail and its usefulness in various settings still needs to be established on a statistical basis. We have made an attempt to understand the process that may cause such 222Rn anomalies. Our observations of 222Rn concentration in the soil gas and of 222Rn emanation rates from the soil and uranium concentrations in the soil indicate that fracturing of the rock, rather than advection of 222Rn from deeper strata may be responsible for such 222Rn anomalies

A study on the mixing proportion in groundwater samples by using Piper diagram and Phreeqc model

Piper (1944) diagram has been the basis for several important interpretations of the hydrogeochemical data. As seen in this diagram, most natural waters contain relatively few dissolved constituents, with cations (metals or bases) and anions (acid radicles) in chemical equilibrium with one another. Apart from the facies representation, the composition of the mixed sample can be identified in terms of the composition of the parental solution. To bring out this advantage of the Piper diagram, a study was conducted in the Kalpakkam region of Tamilnadu, South India. By taking the geology and water table into consideration, two sample locations were selected as parent solution and third one as the mixture sample. All three samples were analyzed for calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), chloride (Cl), sulphate (SO4) and phosphate (PO4) by Ion Chromatograph (Metrohm IC 861). HCO3 was determined by volumetric titration. The Piper diagram shows that parent solutions clustered towards Na-Mg-Ca-HCO3-Cl and Na-HCO3 facies, and the mixing sample belongs to Na-Mg-HCO3 facies. Phreeqc interactive (Ver 2.8) along with the original composition of the mixture sample was used to correlate the mixing proportion identified by the Piper diagram