Carbapenem resistance in Acinetobacter baumannii, and their importance in hospital-acquired infections: a scientific review.

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.

Escherichia coli cellular responses to exposure to atmospheric-pressure dielectric barrier discharge plasma-treated N-acetylcysteine solution.

AIM: To understand the underlying cellular mechanisms during inactivation of Escherichia coli in response to antimicrobial solution of nonthermal plasma-activated N-acetylcysteine (NAC). METHODS AND RESULTS: The recommended techniques were used to demonstrate E. coli cellular and transcriptomic changes caused associated with peroxynitrite and compared with plasma-treated NAC solution. The findings demonstrate that E. coli cells respond to plasma-treated NAC and undergo severe oxidative and nitrosative stress, and leading to stress-induced damages to different components of bacterial cells, which includes loss of membrane potential, formation of oxidized glutathione (GSSG), formation of nitrotyrosine (a known marker of nitrosative stress), DNA damage, and generated a prominent pool of peroxynitrite. Reverse-transcriptase (RT)-polymerase chain reaction analysis of reactive nitrogen species (RNS) responsive genes indicated their differential expressions. CONCLUSION: For the first time, we report that the plasma-treated NAC solution activates predominantly nitrosative stress-responsive genes in E. coli and is responsible for cell death. SIGNIFICANCE AND IMPACT OF THE STUDY: The reactive species generated in solutions by nonthermal plasma treatment depends on the type of solution or solvent used. The plasma-treated NAC solution rapidly inactivates E. coli, mostly involving highly RNS generated in NAC solution, and has high potential as disinfectant.

Plumbagin exerts antiobesity effects through inhibition of pancreatic lipase and adipocyte differentiation.

Plumbagin is a naphthoquinone found in the roots of Plumbago zeylanica. Here, we report an investigation to evaluate its antiobesity activity. The preliminary binding affinity of plumbagin to human pancreatic lipase (PL) was determined using molecular docking simulation. The in vitro PL inhibitory potential and the kinetics of inhibition were studied to validate and confirm the results obtained from molecular docking. The IC50 for PL was found to be 82.08 ± 9.47 µM, and the kinetics of inhibition was found to be of the mixed type. Further, the in vivo evaluation revealed that rats treated with plumbagin 1 mg/kg showed significant decrease in serum triglycerides (TG) and area under the curve of serum TG when compared with vehicle-treated rats. It was also seen that plumbagin possessed significant antiadipogenic effect as demonstrated by reduced oil red O staining and decreased TG contents. Thus, we conclude that plumbagin is a promising molecule to combat obesity and further optimization of plumbagin to yield plumbagin analogues will result in its improved activity profile.

Studies on Acinetobacter baumannii involving multiple mechanisms of carbapenem resistance.

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-ß-lactamase (MBL) genes were negative. The genes of ampC ß-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.

Biological responses of Bacillus stratosphericus to floating electrode-dielectric barrier discharge plasma treatment.

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.

Characteristics of sludge developed under different loading conditions during UASB reactor start-up and granulation.

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/m3 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.

Luteal phase concentrations of a progestagen-associated endometrial protein (PEP) in the serum of cycling women with adequate or inadequate endometrium.

We previously demonstrated that the human endometrium synthesizes and secretes a specific protein designated "Progestagen-associated Endometrial Protein" or PEP. This work was undertaken to determine luteal phase levels of PEP in serum of cycling women with histologic evidence of adequate endometrium (endometrium in phase) or inadequate endometrium (endometrium out of phase by 3-4 days). The results provide a normative curve with 95% confidence limits for serum PEP concentrations vs normalized cycle day in women with adequate endometrium (judged by histologic endometrial dating), and indicate that the PEP concentration increases exponentially after day 22, with a mean doubling time of 2.95 +/- 1.60 (mean +/- SD) days (based on serial data from 13 women). More importantly, the proportion of serum PEP values falling outside of the 95% confidence limits was significantly greater (p less than 0.001) in women with inadequate endometrium (83%) than in women with adequate endometrium (16%). Therefore, determination of PEP in serum, rather than the more invasive endometrial biopsy examination, may serve as a method of choice for evaluating endometrial adequacy in infertile women.

Emergency contraception alters progesterone-associated endometrial protein in serum and uterine luminal fluid.

OBJECTIVE: To evaluate the effect of high-dose oral contraceptives on serum and uterine luminal fluid progesterone-associated endometrial protein in the luteal phase. METHODS: Five ovulatory women participated in the study. In a control cycle, serum and uterine lavage samples were collected on luteal day 11. In the next cycle, on luteal day 9, the participants were given two 50-micrograms ethinyl estradiol-norgestrel tablets, repeated 12 hours later. Serum and uterine lavage samples were collected 48 hours (luteal day 11) after the last dose and analyzed by two-dimensional polyacrylamide gel electrophoresis and radioimmunoassays of the serum. RESULTS: Progesterone-associated endometrial protein levels were lower in sera from treated compared with control cycles. Analysis of serum levels of this protein by two-dimensional polyacrylamide gel electrophoresis did not reveal bands corresponding to the known size and charge characteristics (27 kd and pI of 4.9) in either control or treatment samples. On the other hand, in uterine lavage samples, a complete suppression of the 27-kd, pI-4.9 species was evident after treatment. CONCLUSION: High-dose ethinyl estradiol-norgestrel emergency contraception effectively suppresses progesterone-associated endometrial protein in the midluteal uterus, potentially altering the endometrial environment unfavorably and affecting the survival of the early embryo.

Effects of progesterone on labeling of soluble proteins and glycoproteins in rabbit endometrium.

An in vitro test system was used to study in vivo effects of progesterone on synthesis and secretion of total proteins and glycoproteins in rabbit endometrium. Endometrial explants incubated in Eagle's minimal essential medium containing radioactive leucine and N-acetylglucosamine were found to synthesize soluble proteins readily, including glycoproteins. Furthermore, significant amounts of newly synthesized proteins, including blastokinin, were released by the tissues into the incubation medium. In addition, in vitro synthesis and release of labeled proteins by estrogen-primed endometrial tissue (E-primed tissue) was significantly enhanced by exposure of the tissues to progesterone in vivo. Double-labeling studies demonstrated qualitative as well as quantitative differences in peptide synthesis between E-primed tissues and E-primed, progesterone-treated tissues. Progesterone also stimulated both the synthesis and the release of glycoprotein by E-primed tissues. These studies, therefore, suggest that progesterone regulates qualitatively and quantitatively the synthesis and secretion of total proteins, including glyco-proteins, in rabbit endometrium.

Serum and peritoneal fluid proteins in women with and without endometriosis.

We examined the proteins in serum and peritoneal fluid of women with endometriosis (and of healthy controls) for evidence of an autoimmune response that might account for their impaired fertility. No antibodies against endometrial glycoproteins or against "progestin dependent endometrial protein" (PEP) were found in any serum or peritoneal fluid sample. Levels of PEP were not different in serum from women with moderate to severe endometriosis (n = 6), with mild endometriosis (n = 21), or from disease-free cycling controls (n = 19). PEP levels in peritoneal fluid from mild endometriosis and from controls did not differ but were elevated ten times in fluid obtained in the secretory phase from women with moderate to severe disease. This suggests that PEP levels in peritoneal fluid reflect the extent of ectopic endometrial growth. The salient finding was a heretofore undescribed protein (mol wt 70,000) in secretory phase peritoneal fluid samples (18/20) and its absence during the proliferative phase (0/35).

Progestin-dependent human endometrial protein: a marker for monitoring human endometrial function.

Progesterone (P), which is the major secretory product of the corpus luteum (CL) is the key hormone of pregnancy. CL defects that cause P to be secreted for too brief a period or at too low a rate are associated with an underdeveloped or inadequate endometrium which is incapable of supporting pregnancy. Some investigators, therefore, have recommended the use of exogenous P support in chronic CL defect patients who wish to conceive. However, the mechanisms by which P regulates endometrial function are poorly understood and there is no suitable, non-invasive method to monitor in individual patients the endometrial response to either endogenous or exogenous progesterone. We therefore initiated a search for progesterone-dependent endometrial protein(s) which might serve as a marker to assess effects of progestin therapy on endometrial function, and which might also afford insight into the mechanism of P action. We have detected a hormone-dependent endometrial protein designated "progestagen-associated (or -dependent) endometrial protein" or PEP. PEP is a glycoprotein (molecular weight approximately 47,000) which is synthesized in the endometrial glands and secreted into the blood. Its synthesis increases dramatically during pregnancy, as indicated by a more than 1000-fold greater PEP concentration in the decidua. PEP is not synthesized by the immature placenta, but binds to placental cell membranes. In normally cycling women, the serum PEP concentration increases in an exponential manner during the late luteal phase. In cycling infertile women, a direct relationship was found to exist between serum PEP levels they attained in the late luteal phase and their endometrial development, the serum levels being subnormal in women with inadequate endometrium. Menstrual cycles that are anovulatory or with a CL-defect are associated with low luteal phase serum PEP levels. In both pre- and post-menopausal women, serum PEP levels increase following a progestin challenge, demonstrating that PEP is indeed a progestin-dependent protein. Very low luteal phase serum PEP levels are encountered in some women who do not conceive following in vitro fertilization and embryo transfer (IVF/EF), suggesting that endometrial inadequacy is a major cause of failure in this procedure. In patients who undergo ovarian stimulation by exogenous hormones but do not conceive following IVF/ET, luteal phase serum PEP levels are markedly higher in those who receive luteal phase P support than those with no support.(ABSTRACT TRUNCATED AT 400 WORDS)

Surface-acoustic-wave (SAW) flow sensor.

The use of a surface-acoustic-wave (SAW) device to measure the rate of gas flow is described. A SAW oscillator heated to a suitable temperature above ambient is placed in the path of a flowing gas. Convective cooling caused by the gas flow results in a change in the oscillator frequency. A 73-MHz oscillator fabricated on 128 degrees rotated Y-cut lithium niobate substrate and heated to 55 degrees C above ambient shows a frequency variation greater than 142 kHz for flow-rate variation from 0 to 1000 cm(3)/min. The output of the sensor can be calibrated to provide a measurement of volume flow rate, pressure differential across channel ports, or mass flow rate. High sensitivity, wide dynamic range, and direct digital output are among the attractive features of this sensor. Theoretical expressions for the sensitivity and response time of the sensor are derived. It is shown that by using ultrasonic Lamb waves, propagating in thin membranes, a flow sensor with faster response than a SAW sensor can be realized.

Application of a surface-acoustic-wave device for measurement of liquid flow rate.

The use of a surface-acoustic-wave (SAW) device to measure the flow rate of liquids is described. A delay-line stabilized SAW oscillator heated to a suitable temperature above ambient is cooled by the flowing fluid. This results in a change in the oscillator frequency. The frequency of a 68-MHz oscillator operated at 9 degrees C above ambient is found to vary by more than 40 kHz for variation in water flow rate from 0 to 0.8 ml/min. Attractive features of this device include the ability to measure very low flow rates (less than 0.1 mul/min) and direct digital output. However, since this is a thermal type of flow sensor, the temperature of the fluid will be slightly elevated during its passage through the flow cell. The device should be useful in applications where low flow rates have to be monitored.

Reflection of ultrasonic Lamb waves produced by thin conducting strips.

The reflection of ultrasonic Lamb waves produced by a periodic array of thin conducting strips deposited on a piezoelectric plate was investigated both theoretically and experimentally. A repetitively mismatched transmission line model was used to analyze the performance of the reflector. The reflection coefficient of a single strip is given by R approximately Deltav/v, where Deltav/v is the fractional change in velocity produced by electrical shorting of the propagation surface. An attractive property of Lamb waves is that they can provide a much higher value of Deltav/v than is possible with surface acoustic waves. Therefore, efficient Lamb wave reflectors can be realized with relatively few strips in the reflector. For example, reflection coefficient very close to unity, R approximately 0.98, has been obtained in a Lamb wave reflector consisting of just 12 strips on a Y-X lithium niobate plate. The reflector has been used to realize a unidirectional transducer (UDT). A Lamb wave delay line consisting of two UDTs shows insertion loss of less than 3 dB with fractional bandwidth greater than 7%

Propagation of QSH (quasi shear horizontal) acoustic waves in piezoelectric plates.

The characteristics of QSH (quasi shear horizontal) acoustic waves propagating in thin plates of Y-cut, X-propagation lithium niobate are investigated theoretically and experimentally. The fractional velocity change (Deltanu/nu) produced by electrical shorting of the surface is calculated as a function of the normalized plate thickness h/lambda (h=plate thickness, lambda=acoustic wavelength). It was found that values of Deltanu/nu as high as 0.18 could be obtained. Experimental measurements show good agreement with theory. The properties of QSH waves propagating in the presence of a perfectly conducting electrode separated from the piezoelectric plate by a small air gap have been studied theoretically and experimentally. It was found that by varying the height of the gap, the phase shift through a 3.2-MHz QSH wave delay line can be varied by more than 230 degrees . We have also theoretically investigated the influence of a thin layer of arbitrary conductivity on the velocity and attenuation of the QSH wave. Calculations show that the variations in these parameters can be as high as 18% and 5 dB per wavelength for a change in layer surface conductance from 10(-7) to 10(-5) S. Results obtained in this paper confirm the attractive properties of QSH waves for a variety of sensing and signal processing applications.

Influence of conducting layer and conducting electrode on acoustic waves propagating in potassium niobate plates.

The influence of a thin conducting layer and a conducting electrode on the characteristics of acoustic waves propagating in thin plates of potassium niobate is investigated theoretically. The variations in velocity and attenuation as high as 50% and 30 dB per wavelength, respectively, can be achieved for a change in conductance of the thin film layer from 10(-7) to 10(-5) S.

Shear-horizontal acoustic waves in piezoelectric plates bordered with conductive liquid.

The influence of a conductive liquid on the characteristics of shear-horizontal acoustic waves of zeroth order (SH0 mode) propagating in thin piezoelectric plates of lithium tantalate, lithium niobate, and potassium niobate was investigated. Experimental results obtained for SH0 mode devices fabricated on lithium niobate plates are found to be in good agreement with theory. The data presented in this paper is useful for a proper design of various acoustic wave sensors operating in contact with conductive liquids.

Investigation of acoustic waves in thin plates of lithium niobate and lithium tantalate.

The general properties of fundamental antisymmetric A0, symmetric S0, and shear horizontal SH0 acoustic waves propagating in thin piezoelectric plates have been theoretically investigated on samples of lithium niobate (LiNbO3) and lithium tantalate (LiTaO3). The results obtained will be useful for a proper development of various physical, chemical, and biological sensors and devices for signal processing based on plate acoustic waves.

Improved equivalent circuits for acoustic plate wave devices.

This paper presents improved equivalent circuits for the analysis and design of acoustic plate wave devices. The method uses a mixed equivalent circuit for the interdigital transducer consisting of both active and passive sections placed on the surface of a piezoelectric plate. The values of the various circuit elements are obtained by carrying out a best fit between theoretical and experimental frequency dependence of the real and imaginary parts of transducer input impedance. Knowledge of the equivalent circuit parameters allows one to optimize design of the devices. The method has been successfully employed for the design of one-port shear-horizontal wave resonators on Y-X lithium niobate plates. The proposed method can also be utilized for determining acoustic wave velocity with high accuracy.

Liquid level sensor using ultrasonic Lamb waves.

This paper describes a novel, noninvasive method for measurement of liquid level in closed metal tanks that are under high pressure. It is based on the use of ultrasonic Lamb waves propagating along the tank wall. Contact with liquid substantially changes the characteristics of these waves and this can be used as an indicator of liquid presence. Theoretical analysis shows that the symmetric and antisymmetric Lamb wave modes, both fundamental and higher order, are sensitive to presence of the liquid. The optimal wave frequency depends on the thickness of the tank wall and wall material. A prototype level sensor based on this principle has been developed. It uses two pairs of wedge transducers to generate and detect Lamb waves propagating along the circumference of the gas tank. An operating frequency of 100 kHz is found to be optimal for use with tanks having a wall thickness of 30-50 mm. Prototype sensors developed under this program have been used successfully in oil fields in the far northern region of Russia.