Resistance to Antibiotics in Thermophilic Campylobacters

Campylobacter jejuni (C. jejuni) is one of the most frequent causes of bacterial enterocolitis globally. The disease in human is usually self-limiting, but when complications arise antibiotic therapy is required at a time when resistance to antibiotics is increasing worldwide. Mechanisms of antibiotic resistance in bacteria are diverse depending on antibiotic type and usage and include: enzymatic destruction or drug inactivation; alteration of the target enzyme; alteration of cell membrane permeability; alteration of ribosome structure and alteration of the metabolic pathway(s). Resistance of Campylobacter spp. to antibiotics, especially fluoroquinolones is now a major public health problem in developed and developing countries. In this review the mechanisms of resistance to fluoroquinolones, macrolides, tetracycline, aminoglycoside and the role of integrons in resistance of Campylobacter (especially at the molecular level) are discussed, as well as the mechanisms of resistance to β-lactam antibiotics, sulphonamides and trimethoprim. Multiple drug resistance is an increasing problem for treatment of campylobacter infections and emergence of resistant strains and resistance are important One Health issues.

Effect of Fluid/Rock Interactions on Physical Character of Tight Sandstone Reservoirs during CO2 Flooding

Structures of pore-throat and permeability alteration caused by precipitation and the dissolution of rock matrix are serious problems during CO2 flooding into reservoirs for enhanced oil recovery (EOR). Experiments were conducted under pressure boost and reduction conditions, which simulate CO2-brine scaling in different parts of the reservoir during CO2 flooding. And experiments on the dissolution and scaling of CO2-brine-rock were carried out. The results show that the pH of brine with CO2 under high pressure is small, and no precipitation is formed, so there is no precipitation generated near the gas injection well. Pressure drops sharply near the production well, CO2 dissolved in the formation fluid escapes in large quantities, pH increases, carbonate precipitates are generated, so inorganic scale is formed near the production well. The increase of permeability of core saturated high scale-forming ions is smaller than that of saturated no scale-forming ions brine after CO2 flooding. The accumulation and attachment of salt crystals were found in some large pores of the core with scale-forming ions water after CO2 flooding. The ratio of medium size pores decreased, while that of large and small pores increases, and the pore radius distribution differentiates toward polarization.

Effects of CO2/Rock/Formation Brine Parameters on CO2 Injectivity for Sequestration

Summary The injection of carbon dioxide (CO2) into saline aquifers is highlighted as an effective technique to permanently secure anthropogenic gas produced from high CO2 gas fields in the Southeast Asia region. However, previous studies indicate that CO2 injectivity can be impaired primarily due to the interactions between CO2/brine/rock. In this paper, we investigate the effect of a CO2 injection scheme, rock permeability, brine type, and salinity on CO2 injectivity, which is presented by permeability alteration. A CO2 coreflood experiment and the characterization of the rock and effluent produced are presented. Furthermore, core samples with different permeabilities of the typical geological storage for sequestration were selected and analyzed using X-ray fluorescence (XRF), X-ray diffraction (XRD), and field-emission scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (FESEM-EDX). The cores were then saturated with synthetic brine composed of 6,000, 30,000 or 100,000 parts per million (ppm) of either sodium chloride (NaCl), potassium chloride (KCl), or calcium chloride (CaCl2). Subsequently, the core samples were injected by either supercritical CO2 (scCO2), CO2-saturated brine, or CO2-saturated brine followed by scCO2. The fines particles from the collected effluent were separated for further analysis. The results indicate that a CO2 injection scheme, injection flow rate, brine salinity, and initial rock permeability are the principal factors that contribute to the permeability alteration of the core samples. It was also found from FESEM-EDX analysis of the produced fines that the precipitated salt, silica grains, and kaolinite migrated during scCO2 injection, suggesting the dissolution and precipitation of minerals. This phenomenon led to the migration of particles, some of which plugged the pore spaces and reduced the permeability. Besides, the core saturated with CaCl2 brine was the only sample with improvement in permeability after the CO2 flooding experiment.