Association between minimum inhibitory concentration, beta-lactamase genes and mortality for patients treated with piperacillin/tazobactam or meropenem from the MERINO study

INTRODUCTION

This study aims to assess the association of piperacillin/tazobactam and meropenem minimum inhibitory concentration (MIC) and beta-lactam resistance genes with mortality in the MERINO trial.

METHODS

Blood culture isolates from enrolled patients were tested by broth microdilution and whole genome sequencing at a central laboratory. Multivariate logistic regression was performed to account for confounders. Absolute risk increase for 30-day mortality between treatment groups was calculated for the primary analysis (PA) and the microbiologic assessable (MA) populations.

RESULTS

320 isolates from 379 enrolled patients were available with susceptibility to piperacillin/tazobactam 94% and meropenem 100%. The piperacillin/tazobactam non-susceptible breakpoint (MIC > 16 mg/L) best predicted 30-day mortality after accounting for confounders (odds ratio 14.9, 95% CI 2.8 - 87.2). The absolute risk increase for 30-day mortality for patients treated with piperacillin/tazobactam compared with meropenem was 9% (95% CI 3% - 15%) and 8% (95% CI 2% - 15%) for the original PA population and the post-hoc MA populations, which reduced to 5% (95% CI -1% - 10%) after excluding strains with piperacillin/tazobactam MIC values > 16 mg/L. Isolates co-harboring ESBL and OXA-1 genes were associated with elevated piperacillin/tazobactam MICs and the highest risk increase in 30-mortality of 14% (95% CI 2% - 28%).

CONCLUSION

After excluding non-susceptible strains, the 30-day mortality difference was from the MERINO trial was less pronounced for piperacillin/tazobactam. Poor reliability in susceptibility testing performance for piperacillin/tazobactam and the high prevalence of OXA co-harboring ESBLs suggests meropenem remains the preferred choice for definitive treatment of ceftriaxone non-susceptible E. coli and Klebsiella.

Novel Thermoplastic Elastomers Based on Acrylonitrile-Butadiene-Styrene Terpolymer (ABS) from Waste Computer Equipment and Nitrile Rubber

Acrylonitrile-butadiene-styrene terpolymer (ABS) is one of the engineering plastics most frequently used as outer casings for computer equipment such as monitors, keyboards and other similar components. In an attempt to recycle, blends of scrap computer plastics (SCP) based on ABS with nitrile rubber (NBR) were prepared and mechanical properties and morphology were studied. Effect of dynamic vulcanization on the properties of 60/40, 70/30, and 80/20 NBR/SCP blends was assessed. These blends show the thermoplastic elastomeric behavior. Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM) studies show that the dynamically vulcanized NBR particles are dispersed in the ABS matrix. The thermoplastic elastomeric blends show excellent swelling resistance in IRM # 93 oil.

Utilization of Powdered EPDM Scrap in EPDM Compound

Processability, curing characteristics and vulcanizate properties of EPDM compounds containing ground waste EPDM (W-EPDM) have been studied. Ground waste was prepared from factory scraps, using a mechanical grinder with silicon carbide abrasive wheel rotating at 2950 rpm. The particle size shows a range between 2 and 50 μm, with an average size of 10 μm. Particle surface seems to be rough and convoluted and mild oxidation during the abrasion enhances the aggregation of particles. Mooney scorch time and the maximum rheometric torque of the EPDM compound decrease gradually with increasing W-EPDM content. Migration of curatives between the virgin rubber and waste rubber phases is believed to be the reason for the variation in the curing behavior. The processability of the EPDM compound shows improvement on addition of W-EPDM (that is, both die swell and extrudate distortion are less). The vulcanizate properties of the W-EPDM-filled EPDM compounds reveal the reinforcing nature of the ultrafine W-EPDM particles. Comparison of W-EPDM with an inert filler like precipitated CaCO3 in an EPDM compound reveals the potential of W-EPDM as a cheap filler in EPDM compounds. It is also found that W-EPDM can be incorporated into the window seal compound formulation and the drop in properties even at 100 phr of W-EPDM is within acceptable limit, thus providing a scope for on-site recycling of EPDM.

Effect of Degree of Neutralization on the Properties of Ionic Thermoplastic Elastomer Based on Sulfonated Maleated Styrene-Ethylene/Butylene-Styrene Block Copolymer

Novel block copolymer ionomers having both carboxylate and sulfonate groups in the same polymer backbone were obtained by sulfonating maleated poly (styrene-(ethylene-co-butylene)-styrene) block copolymer (m-SEBS), followed by its neutralization with barium acetate. The effects of the degree of neutralization on the properties of the ionomers were studied. Infrared spectroscopic studies confirm the formation of both carboxylate and sulfonate salts and the occurrence of the sulfonation reaction in the para position of the benzene rings of polystyrene segments. Dynamic mechanical thermal analyses show the presence of a high temperature rubbery plateau, particularly at high degree of neutralization, in addition to the glass-rubber transitions due to the polystyrene (PS) and ethylene-butylene (EB) phases. Tg of the PS block remains unchanged and tanδ at the Tg gradually decreases with increasing the degree of neutralization. But Tg of the EB block gradually increases and tanδ at the Tg marginally increases. The decrease in tanδ at δ of the PS block is ascribed to the stiffening of the polystyrene segments on neutralization.Increase in the degree of neutralization causes formation of ionic crosslinks which increases the Tg of the EB block. Dielectric thermal analyses show that incorporation of ionic groups plays an important role in the temperature dependence of the dielectric constant of the ionomers. At lower degrees of neutralization (25 and 50%), the ionomers behave like the base polymer in the sense that dielectric constant increases at elevated temperature(>120°C). At higher degrees of neutralization, however, the increase in dielectric constant in the high temperature region is restricted due to the formation of the rubbery network arising out of the ionic aggregates. Transmission electron micrographs reveal that on neutralization the domain shape changes from predominantly cylindrical type to exclusively spherical one and at 100% neutralization the diameter of the spheres ranges from 15 to 20 nm. Processability studies show that as the degree of neutralization increases, the melt viscosity of the ionomers increases. The tensile strength, hardness, modulus and tear strength increase but the elongation at break and tension set decrease with increase in the degree of neutralization. Thermal stability of the polymers increases with the degree of neutralization. Reprocessability studies show that the ionomer can be recycled without fall in properties. The barium salt of sulfonated maleated SEBS at higher degrees of neutralization (75 and 100%) behaves as an ionic thermoplastic elastomer.

Effect of Surface Oxidation of Carbon Black on Its Bonding with Epoxidized Natural Rubber in the Presence of Silane Coupling Agent

Results of bound rubber determination, Monsanto rheometry, solvent swelling studies and measurement of physical properties reveal that high temperature molding of epoxidized natural rubber (ENR) filled with intermediate super abrasion furnace (ISAF) carbon black and surface oxidized ISAF carbon black, in the presence of silane coupling agent, namely, N-(4-vinylbenzyl)-N′-[3-(trimethoxysilyl)propyl]ethane-1,2-diamine monoHCl salt, results in crosslinking of the rubber phase, even in the absence of the vulcanizing agents. Infrared spectroscopic studies show formation of silyl ether, in the case of ISAF carbon black, whereas the oxidized grade forms both silyl ether as well as silyl ester and amide linkage. Oxidation of ISAF carbon black causes an increase in the extent of coupling bond formation.

Chemical Interaction between Surface Oxidized Carbon Black and Epoxidized Natural Rubber

This study—based on Monsanto Rheometer measurements, determination of bound rubber, enthalpy of reaction, solvent swelling studies, and measurement of physical properties— revealed that the functional groups of intermediate super abrasion furnace (ISAF) carbon black chemically interact with the epoxidized natural rubber. The extent of interaction is greater in the case of an oxidized grade of ISAF black than the nonoxidized grade. Infrared spectral studies show that the interaction between the rubber and carbon black leads to chemical bond formation. It is believed that the oxidized grade of carbon black forms ester-type as well as phenolic ether-type bonds, while the nonoxidized grade forms primarily the phenolic ether-type of linkages.

Interaction between Carboxylated Nitrile Rubber and Precipitated Silica: Role of (3-Aminopropyl)Triethoxysilane

On the basis of measurements of bound rubber and physical properties and the results of Monsanto rheometer, dynamic mechanical and infrared spectroscopic studies, it is observed that strong rubber-filler interaction occurs between XNBR and precipitated silica filler. During molding, XNBR was found to be crosslinked by the filler surface through the formation of primary bonds. The coupling agent, namely (3-aminopropyl)triethoxysilane facilitates the formation of rubber-filler bonds at the expense of filler-filler networks, leading to improved dispersion and enhanced degree of crosslinking.

Chemical Interaction between Chlorosulfonated Polyethylene and Silica—Effect of Surface Modifications of Silica

The surface of precipitated silica was modified by heat treatment (800°C, 4 h) and hexadecanol treatment. Diffuse reflectance infrared Fourier transform spectroscopic (DRIFTS) measurements reveal that the modification of the silica surface reduces the silanol content. Heat treatment causes condensation of the silanol groups forming siloxane linkages, while hexadecanol treatment causes esterification, thereby, shielding the free silanol groups. As a result, the modified silicas exhibit much less interaction with polar molecules (e.g. water, chloroform), compared to the unreacted silica. Bound rubber formation in the chlorosulfonated polyethylene (CSM)/silica system is also adversely affected by the modification of the filler surface. CSM upon heat treatment (180°C, 1 h) loses -SO2Cl groups and the modified polymer lacks in its ability to form bound rubber. Accordingly, it is believed that the rubber-filler interaction occurs between the silanol groups of the silica and sulfonyl chloride groups of CSM.

Chemical Interaction between Carbon Black and Elastomers — Crosslinking of Chlorosulfonated Polyethylene by Carbon Black

Surface oxidation of a carbon black leads to an increased elastomer-filler bonding between the chlorosulfonated polyethylene and the carbon black. The increased interaction appears to be related to the increased concentration and reactivity of the oxygen containing sites in the oxidized carbon black, as deduced from the moisture adsorption and thermometric titration results. The bound rubber content is substantially higher for the oxidized carbon black. The reactive surface sites of the carbon black also promote the crosslinking of the elastomer at elevated temperatures.

Thermally Induced Crosslinking in Blends of Poly(Vinyl Chloride) and Hydrogenated Acrylonitrile—Butadiene Rubber

A blend of Poly(vinyl chloride) (PVC) and hydrogenated acrylonitrile—butadiene rubber (HNBR) undergoes crosslinking at high molding temperatures in the absence of any external curing agents. This is evident from Monsanto rheometric, solvent swelling, and infrared spectroscopic studies. The reaction proceeds through the interaction of allylic and tertiary chlorine in PVC, with amide and acid groups in HNBR formed during molding. The network structure is believed to consist of amide and ester crosslinks. Dynamic mechanical analysis and differential scanning calorimetry show that the blend components are miscible Variation in molding time and temperature has no effect on the miscibility.

FTIR and NMR Studies on Crosslinking Reaction between Chlorosulfonated Polyethylene and Epoxidized Natural Rubber

A blend of chlorosulfonated polyethylene and epoxidized natural rubber undergoes a self-crosslinking reaction at elevated temperatures. Sulfonyl chloride groups of chlorosulfonated polyethylene react with epoxy groups of epoxidized natural rubber to give ether crosslinks between the two polymers. In addition to the self-crosslinking reaction, these two polymers undergo a number of side reactions as evidenced by spectroscopic studies.

Giant hydronephrosis

A case of congenital, unilateral giant hydronephrosis containing 42 1/2 litres of urine in an adult male is reported. Diagnosis and management are discussed. Because of the possible effects of sudden abdominal decompression, a plea is made for a two-stage procedure. The hydronephrosis is first decompressed slowly by drainage and nephrectomy is then performed after the patient's cardiorespiratory and alimentary systems have been stabilised.