Summary
Carbapenem is an important therapy for serious hospital‐acquired infections and for the care of patients affected by multidrug‐resistant organisms, specifically Acinetobacter baumannii; ...however, with the global increase of carbapenem‐resistant A. baumannii, this pathogen has significantly threatened public health. Thus, there is a pressing need to better understand this pathogen in order to develop novel treatments and control strategies for dealing with A. baumannii. In this review, we discuss an overview of carbapenem, including its discovery, development, classification and biological characteristics, and its importance in hospital medicine especially in critical care units. We also describe the peculiarity of bacterial pathogen, A. baumannii, including its commonly reported virulence factors, environmental persistence and carbapenem resistance mechanisms. In closing, we discuss various control strategies for overcoming carbapenem resistance in hospitals and for limiting outbreaks. With the appearance of strains that resist carbapenem, the aim of this review is to highlight the importance of understanding this increasingly problematic healthcare‐associated pathogen that creates significant concern in the field of nosocomial infections and overall public health.
Aims: Dielectric barrier discharge (DBD) plasma is used for sterilization of contaminated inanimate surfaces but seldomly optimized and depends upon the type of organisms and the plasma treatment ...duration, (net energy deposited) this efficacy varies. The proposed study was designed to see biological responses of one of the robust organism, Bacillus stratosphericus. Methods and Results: DBD plasma was applied over various durations to B. stratosphericus either surface‐dried or suspension in de‐ionized water, and viability, culturability, and viable but nonculturability (VBNC) were assayed using standard techniques. Depending upon the exposure of B. stratosphericus to DBD plasma resulted in three viability states, viable and culturable at low plasma doses and VBNC or disintegrated bacteria at higher plasma doses. Although organism's respiration levels at relatively low levels, immediately after plasma treatment, over the course of 24‐ h respiratory activity was increased c. eight times (and found still nonculturable during colony assays). Conclusions: The loss of culturability is hypothesized to be induced as one of the responses to oxidative stress and it remains to be unclear if the response is temporary or indefinite. Appropriate plasma powers should be used to avoid VBNC‐like status. 2,3‐Bis‐(2‐methoxy‐4‐nitro‐5‐sulfophenyl)‐2H‐tetrazolium‐5‐carboxanilide (XTT) assay is a good alternative method to detect VBNC state. Significance and Impact of the Study: Bacillus stratosphericus has the potential to turn into VBNC upon plasma application, and XTT assay can be an alternative method to detect VBNC state.
AIMS: Characterize the genetic type and resistance mechanisms of 16 carbapenem‐resistant Acinetobacter baumannii (CRAB) isolates recovered between January 2010 and March 2011 from US tertiary‐care ...hospital. METHODS AND RESULTS: A modified Hodge test demonstrated the presence of carbapenemases, but meropenem and ethylenediaminetetraacetic acid (EDTA) double‐disc synergy tests and PCR for metallo‐β‐lactamase (MBL) genes were negative. The genes of ampC β‐lactamase and efflux pump of adeABC and adeIJK were detected. The presence of oxacillinase (OXA)‐like genes, blaOXA‐₅₁‐ₗᵢₖₑ, blaOXA‐₂₃‐ₗᵢₖₑ and blaOXA‐₄₀‐ₗᵢₖₑ genes, and insertion sequence ISAba1 in promoter region of blaOXA‐₅₁‐ₗᵢₖₑ and blaOXA‐₂₃‐ₗᵢₖₑ genes were detected; and confirmed by RT‐PCR analyses. The sequencing of blaOXA‐₅₁‐ₗᵢₖₑ genes revealed two major alleles, blaOXA‐₆₆‐ₗᵢₖₑ (blaOXA‐₈₂) and blaOXA‐₁₁₃ from 31·2 to 68·8% of isolates respectively. The blaOXA‐₂₃ and blaOXA‐₇₂ genes showed high expression and found co‐harbouring blaOXA‐₅₁‐ₗᵢₖₑ gene preceded by ISAba‐1. All CRAB isolates revealed significant reduction in carO transcription, indicated downregulation of CarO porin system, a potentially independent mechanism of carbapenam resistance. Sequencing of carO gene from representative isolates showed no ISAba1 insertional inactivation. Pulsed‐field gel electrophoresis revealed a clonal relationship. CONCLUSIONS: CRAB exhibited diversity of mechanisms of carbapenem resistance, and clonal relationship. SIGNIFICANCE AND IMPACT OF THE STUDY: Studies on distinct outbreaks of CRAB are alarming situation for clinicians.
This paper presents an experimental study on the effects of micro-textured surfaces on lubricated non-conformal point contacts. Thus, we focus on a regime poorly investigated in literature, where the ...contact area and the micro-holes have a comparable size. Tribological characterization are performed on three geometrical patterns, which are textured on stainless steel polished surfaces. Experiments are carried out on a rheometer, where a steel ball slides against the surface of the samples. These samples are tested with two different viscosities of the PAO (Poly-Alpha-Olefin)as a lubricant. Results show the change in the friction with respect to the sliding velocity under different lubrication regimes due to the stress, void ratio and two different kinematic viscosities of PAO. In particular, we show that, depending on the void ratio, a significant friction reduction or, on the contrary, a deterioration of the frictional performances can affect the boundary and mixed lubrication regimes. This is due to the simultaneous occurrence of two competing effects. One is related to the stress intensification, due to the presence of the micro-hole edges on the contact topography, which leads to a consequent increase in wear and friction. On the other hand, micro-texture may play a positive role in the friction optimization given the possibility, offered by the micro-holes, to entrap wear debris and, then, to preverse a smoother interface between the contacting pairs.
•Tribological Investigation of the non-conformal point contacts where contact area and micro-holes have comparable size.•The void ratio influences friction reduction or deterioration of the frictional performances in different lubrication regimes.•Stress intensity increase due to micro-hole edges on the contact topography which causes high wear and friction.•Micro-texture helps in reducing friction by entrapping wear debris thus forming a smoother interface in the tribo-pair.•High void ratio can be useful to enhance the entrapping effect and decrease the friction.
In the present study, a novel series of 4-pyrrol-1-yl benzoic acid hydrazide analogs, some derived 5-substituted-2-thiol-1,3,4-oxadiazoles, 5-substituted-4-amino-1,2,4-triazolin-3-thione and ...2,5-dimethyl pyrroles have been synthesized in good yields and characterized by IR, NMR, mass spectral and elemental analyses. Compounds were evaluated for their preliminary in vitro antibacterial activity against some Gram-positive and Gram-negative bacteria and compounds were screened for antitubercular activity against
Mycobacterium tuberculosis H
37Rv strain by broth dilution assay method. Some compounds showed very good antibacterial and antitubercular activities.
A series of 4-pyrrol-1-yl benzoic acid hydrazide analogs and some derived ring systems were synthesized. The structures of new compounds were established on the basis of their elemental analysis and IR,
1H NMR,
13C NMR and mass spectral data. All compounds were subjected to in vitro antibacterial testing against six pathogenic strains and antitubercular screening against
Mycobacterium tuberculosis. Preliminary results indicate that some of them exhibited promising activities and they deserve more consideration as potential antibacterial and antitubercular agents.
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AIM: Investigation of antifungal mechanism of phenazine 1‐carboxamide (PC) produced by a Pseudomonas strain MCC2142. METHODS AND RESULTS: An antifungal metabolite produced by a Pseudomonas was ...purified and identified as PC. Human pathogenic fungi such as Candida albicans, Candida glabrata, Cryptococcus neoformans, Fusarium oxysporum, Aspergillus fumigatus and Aspergillus niger were found to be inhibited by PC (MIC₉₀32–64 μg ml⁻¹). Addition of PC (20 μg ml⁻¹) during yeast (Y)–hypha (H) transitions inhibited germ tube formation by >90% and >99% in C. albicans National Collection of Industrial Microorganisms (NCIM) 3471 and nonpathogenic model Benjaminiella poitrasii, respectively. After exposure to PC (20 μg ml⁻¹), 75–80% yeast cells of B. poitrasii and C. albicans NCIM 3471 showed rhodamine 123 fluorescence indicating high intracellular reactive oxygen species (ROS) production. ROS further led to hyperpolarization of mitochondrial membrane, subsequently induction of apoptosis as evident by externalization of phosphatidylserine, DNA fragmentation, chromatin condensation and finally death in B. poitrasii. In C. albicans NCIM 3471, PC (20 μg ml⁻¹) induced apoptosis. CONCLUSIONS: The antifungal effect of PC in B. poitrasii and C. albicans may be due to ROS‐mediated apoptotic death. SIGNIFICANCE AND IMPACT OF THE STUDY: Inhibition of Y–H transition of B. poitrasii and C. albicans by PC indicates that it may prove useful in the control of dimorphic human pathogens.
Sludge characteristics available inside the reactor are of vital importance to maximize advantages of UASB reactor. The organic loading rate and sludge loading rate applied during start-up are among ...the important parameters to govern the sludge characteristics. Effects of these loading rates on the characteristics of the sludge developed are evaluated in six laboratory scale UASB reactors. The sludge characteristics considered are VSS/SS ratio of the sludge, sludge volume index, specific gravity, settling velocity and metal contents of the sludge developed under different loading rates. The experimental results indicate that, for developing good characteristics sludge, during primary start-up from flocculent inoculum sludge, organic loading rate and sludge loading rate should be in the range of 2.0–4.5
kg COD/m
3
d and 0.1–0.25
kg COD/kg VSS
d, respectively (chemical oxygen demand, COD). Proper sludge granulation and higher COD removal efficiency will be achieved by these loading rates.
This paper presents the structural and magnetic properties of polyvinyl alcohol/iron (PVA/Fe) nanocomposite films. Iron (Fe) films of different thicknesses were deposited on a PVA substrate using ion ...beam sputtering. The Fe nanoparticle layer thickness ranges from 3 to 50 nm on the PVA substrate. Grazing incidence x-ray diffraction has been carried out to study the structural behavior of the prepared films. An atomic force microscope records the indicated remarkable change in the roughness of the nanocomposite film as a result of initiation of vertical growth of sputtered Fe nanoparticles.Magneto-optic Kerr effect (MOKE) magnetometry and MOKE spectroscopy have been employed to evaluate the magnetic property and simultaneously study the real time growth of the magnetic domain structure for both 0° and 90° azimuthal angles. MOKE microscopic images indicated the magnetization reversal commensurate with the hysteresis loop of the nanocomposites. All the films show soft ferromagnetic behavior. Gradual development of the domain structure is observed in the MOKE micrograph with the increase in the thickness of Fe nanoparticle deposition. Ex situ magnetic force micrographs of the magnetic domain structures supported the observation of MOKE microscopic studies, which indicated switching of in-plane magnetization to out-of-plane magnetization near an Fe nanoparticle deposition thickness of 40 nm. The PVA matrix appears to be an effective material to support the growth of magnetic properties in the PVA/Fe nanocomposite system. The evolution of Fe nanostructures on PVA and the resulting magnetic behavior have been discussed.
•We evaluated 28 newly developed high yielding early maturing CIMMYT wheat lines and 2 checks in South Asia and Mexico.•We identified early maturing lines with higher grain yield and stable ...performance across locations in South Asia.•Early maturity provides a better adaptation under terminal and continual high temperature stress common in South Asia.•Canopy temperature and leaf chlorophyll content were identified as promising traits that may contribute to adaptation.
High temperatures are a primary concern for wheat production in South Asia. A trial was conducted to evaluate the grain yield performance of high yielding, early maturing heat tolerant CIMMYT wheat lines, developed recently in Mexico for adaptation to high temperature stresses in South Asia. The trial, comprised of 28 entries and two checks, was grown in 13 locations across South Asia and two environments in Mexico. Each location was classified by mega environment (ME); ME1 being the temperate irrigated locations with terminal high temperature stress, and ME5 as warm, tropical, irrigated locations. Grain yield (GY), thousand kernel weight (TKW), days to heading (DH) and plant height (PH) were recorded at each location. Canopy temperature (CT) was also measured at some locations. Significant differences were observed between ME for DH, PH, GY, and TKW. The cooler ME1 locations had a mean DH of 83 days, compared to 68 days mean DH in ME5. The ME1 locations had higher mean GY of 5.26 t/ha and TKW of 41.8g compared to 3.63 t/ha and 37.4g, respectively, for ME5. Early heading entries (<79 days, mean DH) performed better across all locations, with GY of 2–11% above the local checks and 40–44g TKW. Across all locations the top five highest yielding entries had 5–11% higher GY than the local checks. The early maturing CIMMYT check ‘Baj’ also performed well across all locations. In the Mexico location, CT was associated with GY, thereby suggesting that cooler canopies may contribute to higher GY under normal as well as high temperature stress conditions. Our results suggest that the early maturing, high yielding, and heat tolerant wheat lines developed in Mexico can adapt to the diverse heat stressed areas of South Asia.
After several years of quiescence, the blazar CTA 102 underwent an exceptional outburst in 2012 September–October. The flare was tracked from γ-ray to near-infrared (NIR) frequencies, including Fermi ...and Swift data as well as photometric and polarimetric data from several observatories. An intensive Glast-Agile support programme of the Whole Earth Blazar Telescope (GASP–WEBT) collaboration campaign in optical and NIR bands, with an addition of previously unpublished archival data and extension through fall 2015, allows comparison of this outburst with the previous activity period of this blazar in 2004–2005. We find remarkable similarity between the optical and γ-ray behaviour of CTA 102 during the outburst, with a time lag between the two light curves of ≈1 h, indicative of cospatiality of the optical and γ-ray emission regions. The relation between the γ-ray and optical fluxes is consistent with the synchrotron self-Compton (SSC) mechanism, with a quadratic dependence of the SSC γ-ray flux on the synchrotron optical flux evident in the post-outburst stage. However, the γ-ray/optical relationship is linear during the outburst; we attribute this to changes in the Doppler factor. A strong harder-when-brighter spectral dependence is seen both the in γ-ray and optical non-thermal emission. This hardening can be explained by convexity of the UV–NIR spectrum that moves to higher frequencies owing to an increased Doppler shift as the viewing angle decreases during the outburst stage. The overall pattern of Stokes parameter variations agrees with a model of a radiating blob or shock wave that moves along a helical path down the jet.
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