A review of antibiotic synergy in carbapenemase-producing bacteria

The problem of antibiotic resistance has garnered too much attention over the last few decades for posing a global hazard to the clinical handling and the inhibition of several deadly infections caused by bacteria. It burdens the world not only clinically but also economically... Antibiotic agents known as carbapenems are a very effective and  typically designated for the treatment of multidrug-resistant (MDR) bacterial infections. To identify a suitable antibiotic combination to be used in vivo, one must be able to determine the synergism between the antibiotics in vitro. Several methods, such as the checkerboard method, multiple-combination bactericidal test, time-kill and E-test, have been used for this purpose. However, the lack of proper standardization procedures, types of bacterial agents, bacterial load, stage of infection and other factors make it very difficult to reproduce or correlate the results with other methods.Carbapenem-destroying lactases, which have recently emerged as mechanisms of resistance, are increasing in number and decreasing the treatment alternatives available. These infections are treated with colistin and tigecycline, but monotherapy may result in clinical breakdown because of a variety of factors. To control these infections, clinicians often choose combinations of drugs over monotherapy. There is an extreme lack of information on synergistic antibiotic combinations accounting for the diverse mechanisms of GNB resistance commonly encountered. The incidence of carbapenem-resistant GNB in Indian articles is also unknown. Therefore, we anticipate that this study may provide methodology for the selection of an appropriate antibiotic combination

Characteristics of spectral aerosol optical depths over India during ICARB

Spectral aerosol optical depth (AOD) measurements, carried out regularly from a network of observatories spread over the Indian mainland and adjoining islands in the Bay of Bengal and Arabian Sea, are used to examine the spatio-temporal and spectral variations during the period of ICARB (March to May 2006). The AODs and the derived Angstrom parameters showed considerable variations across India during the above period. While at the southern peninsular stations the AODs decreased towards May after a peak in April, in the north Indian regions they increased continuously from March to May. The Angstrom coefficients suggested enhanced coarse mode loading in the north Indian regions, compared to southern India. Nevertheless, as months progressed from March to May, the dominance of coarse mode aerosols increased in the columnar aerosol size spectrum over the entire Indian mainland, maintaining the regional distinctiveness. Compared to the above, the island stations showed considerably low AODs, so too the northeastern station Dibrugarh, indicating the prevalence of cleaner environment. Long-range transport of aerosols from the adjoining regions leads to remarkable changes in the magnitude of the AODs and their wavelength dependencies during March to May. HYSPLIT back-trajectory analysis shows that enhanced long-range transport of aerosols, particularly from the west Asia and northwest coastal India, contributed significantly to the enhancement of AOD and in the flattening of the spectra over entire regions; if it is the peninsular regions and the island Minicoy are more impacted in April, the north Indian regions including the Indo Gangetic Plain get affected the most during May, with the AODs soaring as high as 1.0 at 500 nm. Over the islands, the Angstrom exponent (α) remained significantly lower (~1) over the Arabian Sea compared to Bay of Bengal (BoB) (~1.4) as revealed by the data respectively from Minicoy and Port Blair. Occurrences of higher values of α, showing dominance of accumulation mode aerosols, over BoB are associated well with the advection, above the boundary layer, of fine particles from the east Asian region during March and April. The change in the airmass to marine in May results in a rapid decrease in α over the BoB

Diagnostics of direct CT - PT contact of the coolant channels of PHWRs

It has now been realised that the garter springs which maintain the gap between the pressure tube (PT) and calandria tube (CT) of a PHWR can get displaced significantly from their deign position in many channels. It has also been recognised that the large unsupported span of the PT restricts the life of the channel due to premature contact of the PT with the CT making it susceptible to delayed hydrogen cracking. This paper reports the details of a non-intrusive diagnostic technique based on vibration measurement for detecting the contacting channels

Quasi-biennial oscillations in spectral aerosol optical depth

Analysis of long-term time series of monthly mean aerosol optical depths (AOD) at four tropical stations over Asia and Africa revealed the presence of significant annual oscillations (AO) and quasi-biennial oscillations (QBO). While the AOs were the dominant features, the QBOs in AOD (QBOAOD) were also quite strong and were well associated with the QBO in stratospheric zonal wind (QBOU). At the equatorial stations, QBOAOD were out of phase with QBOU, while they were in phase at the off-equatorial stations. However, QBO in both outgoing longwave radiation (OLR) and rainfall showed an out-of-phase relationship with QBOAOD at all stations. Copyright © 2009 Royal Meteorological Society

Characterization of aerosol black carbon over a tropical semi-arid region of Anantapur, India

Black carbon (BC) aerosol mass concentrations measured using an aethalometer at Anantapur, a semi-arid tropical station in the southern part of peninsular India, from August 2006 to July 2007 are analyzed. Seasonal and diurnal variations of BC in relation to changes in the regional meteorological conditions have been studied along with the mass fraction of BC to the total aerosol mass concentration (M-t) and fine particle mass (FPM) concentration in different months. The data collected during the study period shows that the annual average BC mass concentration at Anantapur is 1.97 +/- 0.12 mu g m(-3). Seasonal variations of BC aerosol mass concentration showed high during the dry (winter and summer) seasons and low during the post-monsoon followed by the monsoon seasons. Diurnal variations of BC aerosols attain a gradual build up in BC concentration from morning and a sharp peak occurs between 07:00 and 09:00 h almost an hour after local sunrise and a broad nocturnal peak from 19:00 to 21:00 h with a minimum in noon hours. The ratio of BC to the fine particle mass concentration was high during the dry season and low during the monsoon season. The regression analysis between BC mass concentration and wind speed indicates that, with increase in wind speeds the BC mass concentrations would decrease and vice-versa. Aerosol BC mass concentration shows a significant positive correlation with total mass concentration (M-t) and aerosol optical depth (ACID, tau(p)) at 500 nm. (C) 2010 Elsevier B.V. All rights reserved

Characterization of aerosol black carbon over a tropical semi-arid region of Anantapur, India

Black carbon (BC) aerosol mass concentrations measured using an aethalometer at Anantapur, a semi-arid tropical station in the southern part of peninsular India, from August 2006 to July 2007 are analyzed. Seasonal and diurnal variations of BC in relation to changes in the regional meteorological conditions have been studied along with the mass fraction of BC to the total aerosol mass concentration (Mt) and fine particle mass (FPM) concentration in different months. The data collected during the study period shows that the annual average BC mass concentration at Anantapur is 1.97 ± 0.12 μg m−3. Seasonal variations of BC aerosol mass concentration showed high during the dry (winter and summer) seasons and low during the post-monsoon followed by the monsoon seasons. Diurnal variations of BC aerosols attain a gradual build up in BC concentration from morning and a sharp peak occurs between 07:00 and 09:00 h almost an hour after local sunrise and a broad nocturnal peak from 19:00 to 21:00 h with a minimum in noon hours. The ratio of BC to the fine particle mass concentration was high during the dry season and low during the monsoon season. The regression analysis between BC mass concentration and wind speed indicates that, with increase in wind speeds the BC mass concentrations would decrease and vice-versa. Aerosol BC mass concentration shows a significant positive correlation with total mass concentration (Mt) and aerosol optical depth (AOD, τp) at 500 nm

Characterization of PM, PM₁₀ and PM_2.5 mass concentrations at a tropical semi-arid station in Anantapur, India

95-104The particulate matter (PM), PM10 and PM2.5 concentrations are estimated from regular measurements of size segregated as well as total mass concentration of near surface composite aerosols, using a ten-channel Quartz Crystal Microbalance (QCM) Cascade Impactor in a tropical semi-arid station, Anantapur, India for the period May 2006 – April 2007. The monthly variations of PM, PM10 and PM2.5 and season-wise shares of PM10 and PM2.5 to PM have been computed. The highest contribution of PM10 to PM has been noticed during local summer season, while the maximum share of PM2.5 to PM has been noticed during the winter season. The average values of PM, PM10 and PM2.5 mass concentrations have been found to be 21.21±1.21, 18.7±1.06 and 17.02±1.28 g m-3, respectively. Seasonally, the concentration has been highest in winter (24.62±3.53, 22.07±2.56, 21.29±2.31) and lowest in monsoon (18.12±1.62, 16.46±1.82, 14.47±1.57) for PM, PM10 and PM2.5, respectively. The back trajectory cluster analysis revealed that the aerosol loading has been significantly higher in fine mode during periods of continental air mass (winter) but when the winds shift to marine (monsoon), the loading became higher due to major contribution of sea salt aerosols, particularly in the coarse mode. PM10 and PM2.5 concentrations has been highly correlated with PM and inversely correlated with local wind speed. The results of this analysis underlined the importance of local emission sources, mostly from anthropogenic, which are responsible for the high PM10 and PM2.5 concentration levels observed during this one year - sampling period