Background:The purpose of this work was to study the acquisition of new antibiotic-resistant genes carried by extended spectrum β–lactamase (ESBL)-producing Enterobacteriaceae via horizontal transfer to understand their rampant spread in the hospitals and in the community.Materials and Methods:A retrospective analysis of 120 ESBL screen-positive isolates of Escherichia coli and Klebsiella pneumoniae, which were subjected to antimicrobial susceptibility testing, was carried out. The Double Disc Synergy Test (DDST) and Inhibitor-Potentiation Disc Diffusion Test (IPDD) were employed for confirmation of ESBL activity. The transferability of the associated antibiotic resistance for amoxicillin, amikacin, gentamicin, cefotaxime and ceftriaxone was elucidated by intra- and intergenus conjugation in Escherichia coli under laboratory as well as under simulated environmental conditions. Transformation experiments using plasmids isolated by alkaline lysis method were performed to study the transferability of resistance genes in Klebsiella pneumoniae isolates.Results:ESBL production was indicated in 20% each of the Escherichia coli and Klebsiella pneumoniae isolates. All the ESBL isolates showed co- resistance to various other groups of antibiotics, including 3GC antibiotics, though all the isolates were sensitive to both the carbapenems tested. Conjugation-mediated transfer of resistance under laboratory as well as environmental conditions at a frequency of 3–4 × 10-5, and transformation-mediated dissemination of cefotaxime and gentamicin resistance shed light on the propensity of ESBL producers for horizontal transfer.Conclusions:The transfer of resistant markers indicated availability of a large pool of resistance genes in the hospital setting as well as in the environment, facilitating long-term persistence of organisms.
BACKGROUND: This work fulfils the need to develop an eco-friendly biosorbent, elucidating the mechanism of biosorption. Removal of Cr(VI) by Rhizopus arrhizus was investigated in batch mode. Enhancement in the performance of the biosorbent was attempted by pre-treating the biomass with inorganic and organic acids, chelating agent, cross-linker and an organic solvent followed by autoclaving. The surface characterization of the biomass was carried out by potentiometric titration, surface area analysis, infrared spectroscopy, chemical modification of the biomass and scanning electron microscopy.
The removal of Ni (II) from aqueous solutions by the physico‐chemically treated fungal biomass of Mucor hiemalis was investigated in the batch mode. Treatment of the autoclaved biosorbent with alkali chemicals, detergents, salts, cross linker, organic acid, organic solvent and oxidizing agent showed varying effects on the uptake capacity of Ni (II) and loss in biomass. Pre‐treating the autoclaved biomass with 0.5 M Na2CO3 for 24 h yielded biosorption capacity of 13.60 mg/g biomass at pH 8.0. The possible binding sites on the biosorbent involved in Ni (II) complexation were evaluated by chemical and instrumental analysis including potentiometric titration, infrared spectroscopy and scanning electron microscopy. The amine, amide and carboxyl groups were recognized as important in the biosorption of Ni (II) by M. hiemalis biomass. Chemical modification of the biomass by methylation of the amine groups and esterification of the carboxyl groups significantly decreased the biosorption of Ni (II) thus confirming their role in biosorption.
Background Increasing environmental awareness is forcing waste creators to consider new options such as biosorption for the disposal of colored wastewaters. Due to prohibitive costs of commercially available activated carbon, low-cost biosorbents with high adsorption capacities have gained increasing attention. The present investigation deals with utilization of a low-cost, fungal biosorbent of Rhizopus arrhizus NCIM 997 and optimization of conditions for the removal of Reactive Orange 13 dye from an aqueous solution using sequential statistically designed experiments.Results Plackett-Burman design with six independent variables (pH, temperature, biosorbent dosage, dye concentration, contact time and speed of agitation) was used to identify the most important factors influencing dye biosorption. Path of steepest ascent and central composite design were used to move toward the vicinity of the optimum operating conditions and to determine the optimum levels of the variables, respectively. The maximum biosorption capacity (133.63 mg/g) was obtained under the following conditions: pH 2.0, dye concentration 114 mg/L, biosorbent dosage 0.8 g/L and speed of agitation 85 rpm. Validation experiments and application of artificial neural network showed excellent correlation between predicted and experimental values. Conclusions Response surface methodology using central composite design was employed at the specified combinations of four independent significant factors identified by Plackett-Burman design. The fitted model was used to arrive at the best operating conditions to achieve a maximum response. Sequential optimization was successfully used to increase biosorption by 49.04 %. The study indicated that the fungal biosorbent was an effective and economical alternative for the removal of Reactive Orange 13 dye.
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