Cell size changes during the growth of Escherichia coli partially inhibited by some antibacterial agents

The effects of tetracycline, phenol, chloramphenicol and ampicillin on the rates of division and mass increase in growing cultures of Escherichia coli have been examined by comparing the number, carbon content and the size of the cells from partially inhibited cultures with those of control cultures. In cultures treated with low concentrations of tetracycline, phenol or chloramphenicol the increase in cell mass is inhibited more than cell division, thus causing a decrease in the cell size. At higher concentrations of these agents and at all concentrations of ampicillin, cell division is inhibited more than increase in cell mass so causing an increase in cell size.     

Impact of heat treatment on the physical properties of noncrystalline multisolute systems concentrated in frozen aqueous solutions

The purpose of this study was to elucidate the effect of heat treatment on the miscibility of multiple concentrated solutes that mimic biopharmaceutical formulations in frozen solutions. The first heating thermal analysis of frozen solutions containing either a low-molecular-weight saccharide (e.g., sucrose, trehalose, and glucose) or a polymer (e.g., polyvinylpyrrolidone and dextran) and their mixtures from -70°C showed a single transition at glass transition temperature of maximally freeze-concentrated solution (T(g) ') that indicated mixing of the freeze-concentrated multiple solutes. The heat treatment of single-solute and various polymer-rich mixture frozen solutions at temperatures far above their T(g) ' induced additional ice crystallization that shifted the transitions upward in the following scan. Contrarily, the heat treatment of frozen disaccharide-rich solutions induced two-step heat flow changes (T(g) ' splitting) that suggested separation of the solutes into multiple concentrated noncrystalline phases, different in the solute compositions. The extent of the T(g) ' splitting depended on the heat treatment temperature and time. Two-step glass transition was observed in some sucrose and dextran mixture solids, lyophilized after the heat treatment. Increasing mobility of solute molecules during the heat treatment should allow spatial reordering of some concentrated solute mixtures into thermodynamically favorable multiple phases.     

药品在被少量大肠杆菌污染而造成漏检的有关问题的探讨

目的:探讨药品在被少量大肠杆菌污染后,按中国药典现行方法检验是否存在漏检可能,建立了在该种情况下可行的大肠杆菌检查的方法.方法:对8个品种人为污染少量大肠杆菌后,按中国药典检查.结果:药品在被少量大肠杆菌污染后,按药典法大肠杆菌阳性检出率为0～66%,改进法为100%.结论:药品在被少量大肠杆菌污染后,按中国药典现行方法检验存在漏检可能.     

Teniposide-induced changes in the physical properties of phosphatidylcholine liposomes. A calorimetric study

The anticancer agent teniposide has significant effects on plasma membrane components, in addition to its well known nuclear effects. Alterations in the properties and function of cellular membranes by various amphipathic compounds have been attributed previously to their relatively non-specific interactions with membrane components. We have examined the interaction of teniposide with defined model membranes by monitoring drug-induced changes in the melting profile of phospholipids by differential scanning calorimetry. The main phase transition temperature of dimyristoyl- or dipalmitoylphosphatidylcholine was lowered and broadened by the presence of teniposide in the liposomes. These effects were essentially linear over the concentration range of 1-5 mole %. The calorimetric enthalpy of the gel to liquid-crystalline transition of the phospholipids was not changed by the addition of the drug. The characteristic pretransition of these saturated phospholipids was decreased by teniposide concentrations as low as 0.1 mole % and was abolished at teniposide concentrations greater than 1 mole %. The data confirm the lipophilic nature of teniposide and indicate that the non-specific interactions with membrane lipids should be considered when evaluating the membrane-related effects of this agent.     

Induction of SOS function in Escherichia coli by some mycotoxins

The genotoxic activity of 11 mycotoxins was investigated in Escherichia coli K12. The induction of the SOS function s fi A whose level of expression is monitored by means of a s fi A :: lac Z operon fusion was assayed by measuring the β-galactosidase activity in the PQ 37 strain. Most of these fungal metabolites did not induce SOS response in this bacterial test. Only aflatoxicol, a reduced metabolite of aflatoxin B1, was well detected as an SOS inducer if metabolic activation was performed. Patulin, penicillic acid, and viomellein were only weak inducing agents. The other fungal compounds tested failed to demonstrate a positive SOS inducing activity. The relationship between the SOS Chromotest, mutagenicity to Salmonella typhimurium, and in vivo carcinogenicity was discussed.     

Kinetic analysis and characterization of the bacterial regrowth after treatment of Escherichia coli with beta-lactam antibiotics

The generation curves of Escherichia coli B/r and E. coli NIHJ JC-2 in the presence of several beta-lactam antibiotics were studied from the kinetic point of view. Apparent first-order regrowth of resistant organisms was observed approximately 6 h after addition of these antibiotics. The time courses of apparent viable counts could be interpreted in terms of the sum of the viable counts of sensitive and resistant organisms. To clarify the nature of the regrowth, experiments involving a second addition of antibiotic, single colonization by subculture, and synchronous cell culture were carried out. Several possible explanations for the results are discussed, including beta-lactamase production, selection in terms of membrane permeability, and mutation to acquire drug resistance. A selection process or a modification of membrane permeability caused by contact with the drug seems to be the most probable reason for the regrowth of the organisms.     

The partially inhibited growth of Escherichia coli in the presence of some antibacterial agents

Cultures of Escherichia coli were partially inhibited by treatment with tetracycline, phenol, phenylmercuric acetate or cetyltrimethylammonium bromide. The effects of these agents were investigated by measuring the cell size distributions after growth had occurred in the presence of sufficient ampicillin to suppress cellular division. Tetracycline and phenol inhibited cultures by a uniform decrease in the rate of growth of all of the cells; cetyltrimethylammonium bromide completely inhibited the growth of some of the cells whilst having no effect on the remainder; phenylmercuric acetate probably affected all the cells but inhibited each individual to a different extent. The implications of these results are discussed in terms of a general growth rate equation.     

Resuscitation and enumeration of Escherichia coli after freeze-drying

The suitability and precision of a recently suggested method for the resuscitation of Enterobacteriaceae is discussed. Experiments with freeze-dried cells of Escherichia coli ATCC 8739, showed that the recovery of the damaged cells was quantitative and that growth did not affect the result of the subsequent MPN count in Enterobacteriaceae Enrichment Broth. The method seems to be applicable for the examination of all kinds of products, and is possibly also suitable for the determination of other types of organisms.     

The effect of some excipients on the physical properties of a paracetamol tablet formulation

The effects of the addition of the excipients sorbitol, sodium lauryl sulphate and Aerosil on the physical properties of a paracetamol tablet formulation have been evaluated. Increase in the concentration of sorbitol and sodium lauryl sulphate caused a decrease in the hardness with a corresponding increase in the friability, disintegration and dissolution rates of the tablets. The mode of incorporation of the excipient, Aerosil, greatly influenced the physical properties of the paracetamol tablets. When added internally, the tablets' strength decreased while the friability, disintegration and dissolution rates increased. However, when Aerosil was added externally, the strength of the tablets increased while their friability, disintegration and dissolution rates decreased.