Effect of some antibiotics on the resistance of white mice to staphylococcal toxin]

Penicillin and streptomycin in experimental staphylococcal intoxication had different effects on the disease depending on the period of their use. Penicillin injections prior to administration of the toxin increased significantly the resistance of the animals to it, while with the use of streptomycin there was only a tendency to its increase. The use of both antibiotics against the background of the intoxication had a reverse effect: there was a tendency to a decreased animal resistance to a greater extent with the use of streptomycin. The use of tetracycline hydrochloride had no effect on the animal resistance to the staphylococcal toxin.     

Study of the resistance of Candida guilliermondii to polyene antibiotics

250 Candida guilliermondii strains resistant to the polyene antibiotics nystatin, levorin and amphotericin B were obtained using UV irradiation. When the mutant strains became resistant to one of the polyene antibiotics, their resistance to the other ones changed. Phenotypic analysis showed that the resistance of the strains to polyene antibiotics did not make them susceptible to a rise in osmotic pressure and to a change of the temperature of incubation. Some of the polyene-resistant strains were stained in a medium with methylene blue. Analysis of the sterol composition in the mutants by UV spectroscopy showed that the resistance to polyene antibiotics sometimes involved changes in the sterol composition. Two new UV spectrum types were recorded for the sterols of the mutant strains; they differed from the UV spectrum for the sterols of the parent sensitive strain.     

Changes in antibiotic sensitivity in strains of Staphylococcus aureus, 1952-78.

Two hundred strains of Staphylococcus aureus isolated from outpatients with infections of the skin and subcutaneous tissues were tested for sensitivity to penicillin, erythromycin, tetracycline, sodium fusidate, methicillin, clindamycin, chloramphenicol, and gentamicin. One hundred and sixty-three (81.5%) of the strains were resistant to penicillin and 16 (8%) resistant to tetracycline. Incidence of resistance to other antibiotics was low. No strain was resistant to chloramphenicol, gentamicin, or methicillin. When compared with results of earlier studies, there was an increase in the incidence of resistance to penicillin and tetracycline, but no appreciable increase in resistance to other antibiotics.     

Comparative effectiveness of various antibiotics in the treatment of patients with meningococcal meningitis]

The results of treating 322 patients with various forms of meningococcal infection accepted to a hospital within a year are presented. The patients were divided into 3 groups by the character of etiotropic therapy. The patients of group I were treated with benzylpenicillin and those of group 2 were treated with levomycetin sodium succinate. Group 3 included the patients, the therapy of whom with the above two antibiotics failed and they were subjected to treatment with cefazolin, cefotaxime, amikacin and other broad spectrum antibiotics. Benzylpenicillin generally proved to be the drug of choice in the antibacterial therapy of meningococcal infection. In comparison to levomycetin (chloramphenicol) it provide more rapid clinical recovery of the patients and normalization of the indices of the cerebrospinal fluid. Only failure of benzylpenicillin therapy was considered as an indication to the broad-spectrum antibiotics to be in the complex treatment of the patients. As additional methods for estimating the efficacy of antibacterial therapy it was recommended to employ calculation of the integral indices of hemograms (the leukocyte index of intoxication and the hematologic index of intoxication).     

Effect of prodigiosin on the lysozyme activity in melioidosis]

Decreased lysozyme activity was observed under conditions of melioidosis intoxication in rats induced by intraperitoneal administration of an acetone-killed 3-day culture of the bacterial mass of the melioidosis causative agent. When prodigiozan was administered 48 hours by the 4th day which was indicative of prodigiozan activation of the factors of the microbial non-specific resistance.     

Effect of alcoholic intoxication on the body's natural resistance to exposure to infectious and toxic agents]

The influence of alcoholic intoxication on the resistance of albino mice to bacterial toxins and staphylococcus cultures was investigated. Five-day administration of 40% ethyl alcohol to the animals was accompanied by a significant increase of their resistance to the intoxication caused by C1. perfringens toxins and staphylococcus. Thirty-day alcoholic intoxication promoted a marked reduction of albino mice resistance to the both toxins used and the staphylococcus cultures.     

Effect of various antibiotics on the circulation of proteins between the blood and lymph in macro-organisms

The effect of tetracycline, amphotericin B and kefzol on distribution of some proteins between the blood and lymph of the thoracic duct was studied on rabbits. Tetracycline was injected intramuscularly in the form of hydrochloride dissolved in 2% novocain in a dose of 25 mg/kg once or daily for 7 and 20 days. Kefzol (sodium cephazolin) was injected intramuscularly in a single dose of 100 mg/kg. Amphotericin B was injected intravenously in a dose of 1000 Units/kg once or for 5 days. The lymph samples were collected from the thoracic duct of rabbits treated with single doses of the antibiotics 1 and 24 hours after their injection. When the animals were treated with the antibiotics repeatedly the lymph samples were collected 24 hours after the last injection. The level of the total protein and the ratio of the protein fractions, i. e. albumins, alpha 1-, alpha 2-, beta- and gamma-globulins in the lymph and blood serum were determined. On the basis of these findings the protein coefficient (albumin/globulin) of the lymph and blood, the coefficients of the protein permeability of the blood vessels (R) and the constants of selective permeability of the blood capillaries (S) were calculated. It was shown that the shifts in the protein circulation between the blood and lymph had mainly the same trends independent of the antibiotics used and their retention time in the host. A significant decrease in the permeability of the blood vessel walls in respect to the total protein and gamma-globulins and a marked increase in their selectivity in passing of the protein molecules of different size were observed in all cases.     

甲基苯丙胺中毒大鼠纹状体COX-2、PGE2、EP2 受体及小胶质细胞 表达的研究

目的:通过研究COX-2、PGE2、EP2受体及小胶质细胞在甲基苯丙胺中毒大鼠纹状体内的表达变化探讨甲基苯丙胺中毒大鼠纹状体中COX-2/PGE2系统与小胶质细胞活化之间的关系。方法:将40只健康成年雄性SD大鼠,随机分成对照组10只和实验组30只(实验组分成三个亚组,分为末次给药后1天组、2天组和3天组,n=10)。实验组给予10mg/kg的MA腹腔注射,对照组给予同样剂量的生理盐水,每天注射两次,注射时间为8:00、20:00,连续注射4天。分别于末次给药后的第1天、第2天、第3天处杀。用免疫组化技术对中毒大鼠纹状体(CPU)中COX-2、EP2受体及Iba1(钙离子接头蛋白,小胶质细胞内一种特异性标记物)的表达进行检测,并进行图像分析。另外,取大鼠的纹状体运用酶联免疫法检测PGE2的含量。结果:COX-2、PGE2、EP2受体及小胶质细胞在各组均有表达。与对照组相比,实验组中:COX-2、PGE2、EP2受体的1天组表达均不同程度下降;2天组中COX-2表达水平大幅度上升,PGE2、EP2受体表达仍低于正常水平;3天组COX-2表达水平继续升高,而PGE2、EP2受体表达趋于正常组水平。而小胶质细胞表达水平则是三个实验组均高于正常组,且3天组高于2天组,2天组高于1天组。对照组与实验组有显著性差异(P<0.05)。结论:COX-2/PGE2系统与甲基苯丙胺中毒大鼠纹状体内小胶质细胞活化无明显相关性;COX-2与甲基苯丙胺的神经毒性有关。     

In vitro antibiotic susceptibility of bacteria isolated from EUS-affected fishes in India

AIMS: Twelve antibiotics were evaluated for in vitro sensitivity against 16 bacterial strains isolated from surface lesions of fishes affected with epizootic ulcerative syndrome (EUS). METHODS AND RESULTS: Disc diffusion assay in Mueller-Hinton agar showed that the pseudomonads and aeromonads were mainly resistant to penicillin, ampicillin and erythromycin. Additionally, some were resistant to gentamycin and amoxycillin. However, resistance towards antibiotics previously recommended for EUS treatment, such as oxytetracycline and chloramphenicol, was not observed. Four aeromonads and two pseudomonads were found to induce ulcers when injected intramuscularly in healthy Anabas testudineus. CONCLUSIONS: All six pathogenic isolates were sensitive towards oxytetracycline, chloramphenicol and nalidixic acid. Oxytetracycline seems to be an effective antibiotic, and further investigations to determine the mode of treatment and dose appear to be worthwhile.     

绵羊皮肤成纤维细胞对G418及Blasticidin S抗性的研究

抗生素常被用于对转基因动物、植物及微生物细胞进行筛选。在进行抗生素抗性筛选前,需要摸索合适的抗生素使用浓度,其原因在于:过低的筛选浓度无法抑制非转基因细胞的生长;反之,过高的筛选浓度会导致转基因细胞死亡。为了摸索绵羊皮肤成纤维细胞(sheep skin fibroblasts, SSFs)对G418及Blasticidin S的抗性,本实验以体外培养的SSFs为实验材料,采用不同浓度的上述两种抗生素处理SSFs,采用活细胞计数的方式检测SSFs对上述两种抗生素的抗性。单独使用G418或Blasticidin S导致SSFs全部死亡的最低致死浓度分别为200μg/mL及4μg/mL;当两种抗生素联合使用时,其最低致死浓度为100μg/mL G418+3μg/mL Blasticidin S或150μg/mL G418+2μg/mL Blasticidin S。该实验为采用这两种抗生素筛选转基因SSFs提供了理论基础。     

Toxins induce ‘malaise’ behaviour in the honeybee (Apis mellifera)

To avoid poisoning and death when toxins are ingested, the body responds with a suite of physiological detoxification mechanisms accompanied by behaviours that in mammals often include vomiting, nausea, and lethargy. Few studies have characterised whether insects exhibit characteristic ‘malaise-like’ behaviours in response to intoxication. Here, we used the honeybee to investigate how intoxication produced by injection or ingestion with three toxins with different pharmacological modes of action quinine, amygdalin, and lithium chloride affected behaviour. We found that toxin-induced changes in behaviour were best characterised by more time spent grooming. Bees also had difficulty performing the righting reflex and exhibited specific toxin-induced behaviours such as abdomen dragging and curling up. The expression of these behaviours also depended on whether a toxin had been injected or ingested. When toxins were ingested, they were least 10 times less concentrated in the haemolymph than in the ingested food, suggesting that their absorption through the gut is strongly regulated. Our data show that bees exhibit changes in behaviour that are characteristic of ‘malaise’ and suggest that physiological signalling of toxicosis is accomplished by multiple post-ingestive pathways in animals.     

Use of antibiotic resistance analysis to identify nonpoint sources of fecal pollution.

A study was conducted to determine the reliability and repeatability of antibiotic resistance analysis as a method of identifying the sources of fecal pollution in surface water and groundwater. Four large sets of isolates of fecal streptococci (from 2,635 to 5,990 isolates per set) were obtained from 236 samples of human sewage and septage, cattle and poultry feces, and pristine waters. The patterns of resistance of the isolates to each of four concentrations of up to nine antibiotics were analyzed by discriminant analysis. When isolates were classified individually, the average rate of correct classification (ARCC) into four possible types (human, cattle, poultry, and wild) ranged from 64 to 78%. When the resistance patterns of all isolates from each sample were averaged and the resulting sample-level resistance patterns were classified, the ARCCs were much higher (96 to 100%). These data confirm that there are measurable and consistent differences in the antibiotic resistance patterns of fecal streptococci isolated from various sources of fecal pollution and that antibiotic resistance analysis can be used to classify and identify these sources.     

Products containing biocides: perceptions and realities

The mechanisms of action for chemical germicides and antibiotics for inactivating microorganisms are significantly different and methods for determining resistance by microorganisms to these agents are also different. Chemical germicides usually have multiple targets and the mechanisms for inactivation and resistance are not measured in absolute terms but rather in the rapidity with which they reduce levels of microorganisms. The term tolerance is much more suited for germicides than the term resistance. The mechanism of resistance to chemical germicides is often dependent on the concentration of the germicide. At high concentrations multiple cellular and metabolic targets are involved, and at low concentrations fewer cellular targets. In contrast antibiotics usually have a singular cellular or metabolic target and resistance implies the ability of the microorganism to grow in the presence of the antibiotic, and in a clinical sense, to initiate or continue infection in the presence of the antibiotic. When methods used to assess resistance to antibiotics are applied to chemical germicides, inappropriate interpretations can be made regarding the ability of microorganisms to develop resistance to antibiotics as a result of developing resistance to chemical germicides. The use of chemical germicides in health-care institutions and especially the home setting has increased in recent years. Although there may be an overuse of germicides in these settings the consequence is a cost issue and not one that involves the development of antibiotic resistant microorganisms.     

Natural antibiotic resistance of bacteria isolated from larvae of the oil fly, Helaeomyia petrolei

Helaeomyia petrolei (oil fly) larvae inhabit the asphalt seeps of Rancho La Brea in Los Angeles, Calif. The culturable microbial gut contents of larvae collected from the viscous oil were recently examined, and the majority (9 of 14) of the strains were identified as Providencia spp. Subsequently, 12 of the bacterial strains isolated were tested for their resistance or sensitivity to 23 commonly used antibiotics. All nine strains classified as Providencia rettgeri exhibited dramatic resistance to tetracycline, vancomycin, bacitracin, erythromycin, novobiocin, polymyxin, colistin, and nitrofurantoin. Eight of nine Providencia strains showed resistance to spectinomycin, six of nine showed resistance to chloramphenicol, and five of nine showed resistance to neomycin. All 12 isolates were sensitive to nalidixic acid, streptomycin, norfloxacin, aztreonam, cipericillin, pipericillin, and cefotaxime, and all but OF008 (Morganella morganii) were sensitive to ampicillin and cefoxitin. The oil fly bacteria were not resistant to multiple antibiotics due to an elevated mutation rate. For each bacterium, the number of resistant mutants per 10(8) cells was determined separately on rifampin, nalidixic acid, and spectinomycin. In each case, the average frequencies of resistant colonies were at least 50-fold lower than those established for known mutator strain ECOR 48. In addition, the oil fly bacteria do not appear to excrete antimicrobial agents. When tested, none of the oil fly bacteria produced detectable zones of inhibition on Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, or Candida albicans cultures. Furthermore, the resistance properties of oil fly bacteria extended to organic solvents as well as antibiotics. When pre-exposed to 20 microg of tetracycline per ml, seven of nine oil fly bacteria tolerated overlays of 100% cyclohexane, six of nine tolerated 10% xylene, benzene, or toluene (10:90 in cyclohexane), and three of nine (OF007, OF010, and OF011) tolerated overlays of 50% xylene-50% cyclohexane. The observed correlation between antibiotic resistance and organic solvent tolerance is likely explained by an active efflux pump that is maintained in oil fly bacteria by the constant selective pressure of La Brea's solvent-rich environment. We suggest that the oil fly bacteria and their genes for solvent tolerance may provide a microbial reservoir of antibiotic resistance genes.     

对安贞医院革兰阴性杆菌的耐药趋势调查

目的分析安贞医院感染菌中,居前5位的革兰阴性杆菌的耐药趋势,为临床合理使用抗生素提供必要依据。方法对2000～2002年该院分离的医院感染菌株中,居前5位的革兰阴性杆菌的耐药性,进行回顾性分析。结果革兰阴性杆菌中前5位细菌,对3代头孢菌素的耐药性增高。大多数细菌对亚胺培南和美洛培南敏感。阿米卡星的耐药性有所下降。大肠埃希菌对喹诺酮类抗生素耐药率在85％以上。结论不规范使用抗生素,使细菌的耐药性越来越高,交替使用抗生素可能是降低细菌对抗生素耐药性的有效方法。医院应宏观控制使用抗生素。     

急性酒精中毒合并中度创伤性脑损伤大鼠海马AQP4的表达

目的:探讨大鼠急性酒精中毒合并颅脑外伤后AQP4在海马区表达的变化.方法:健康成年雄性SD大鼠96只,随机分为4组:假手术组(N组)、急性酒精中毒组(A组)、中度创伤性脑损伤组(T组)和急性酒精中毒合并中度创伤性脑损伤(AT组).腹腔注射酒精(2.5g/kg),2h后以重物自由落体击打大鼠头部建立急性酒精中毒合并中度创伤性脑损伤(traumatic brain injury,TBI)动物模型.各组动物分别存活1、3、5、14天.免疫组化方法检测海马CA1区AQP4的表达.结果:AQP4阳性产物分布于胶质纤维和毛细血管壁,各实验组表达均高于N组.术后1天T组比AT组表达显著增高(P＜0.01),术后3天AT组比T组表达增高(P＜0.05),术后14天AT组比T组表达显著增高(P＜0.01).结论:大鼠急性酒精中毒合并颅脑外伤后晚期,海马CA1区AQP4表达增高,可能加重晚期继发性脑水肿,是急性酒精中毒合并颅脑外伤预后不良的原因之一.     

Protoplast fusion in Streptomyces fradiae strains producing neomycin and tylosin]

Interspecies fusion of protoplasts of the Streptomyces fradiae strains producing neomycin (an aminoglycoside antibiotic) and tylosin (a macrolide antibiotic) was performed with a view to isolate strains producing novel antibiotics. Fusion of the protoplasts of the neomycin- and tylosin-producing strains labelled by the resistance to monomycin and lincomycin, respectively, caused no formation of stable strains producing antibiotics differing in chromatographic mobility from the antibiotics produced by the initial strains. In fusion of the protoplasts of the unlabelled strains, heat-inactivated protoplasts of the active line of one strain (donor) and native protoplasts of the inactive line of the other strain (recipient) were used. When the neomycin-producing culture was used as a recipient the fusion led to formation of strain 195-34 producing antibiotics of the benzo(a)anthraquinone group. One of these antibiotics, i.e. antibiotic 34-I, proved to be a novel biologically active substance. After regeneration of the protoplasts of the initial strains, no stable strains producing antibiotics differing from neomycin and tylosin were isolated.     

Alteration of 23 S ribosomal RNA and erythromycin-induced resistance to lincomycin and spiramycin in Staphylococcus aureus

Functionally active “hybrid” 50 S ribosomal subunits can be reconstituted using 23 S RNA from Staphylococcus aureus (strain 1206) and 5 S RNA, as well as 50 S ribosomal proteins from Bacillus stearothermophilus. Using this system, resistance of S. aureus 50 S subunits to lincomycin and spiramycin was analyzed. When 23 S RNA from either phenotypically resistant (“induced resistance”) S. aureuscells or derived genetically resistant (“constitutive resistance”) S. aureus cells, were used, the reconstituted 50 S subunits showed the resistant phenotype similar to that seen in native 50 S subunits obtained from resistant cells; only very weak inhibition by the antibiotics was observed in poly (U) - directed polyphenylalanine synthesis involving these 50 S subunits. In contrast, the 50 S particles reconstituted using 23 S RNA from uninduced (sensitive) S. aureus were subject to greater inhibition by the antibiotics in cell-free poly-peptide synthesis. It is concluded that modification of 23 S RNA, presumably the previously observed methylation to form dimethyladenine, is responsible for the resistance to the antibiotics in this strain of S. aureus.     

Long-term shifts in patterns of antibiotic resistance in enteric bacteria

Several mechanisms are responsible for the ability of microorganisms to tolerate antibiotics, and the incidence of resistance to these compounds within bacterial species has increased since the commercial use of antibiotics became widespread. To establish the extent of and changes in the diversity of antibiotic resistance patterns in natural populations, we determined the MICs of five antibiotics for collections of enteric bacteria isolated from diverse hosts and geographic locations and during periods before and after commercial application of antibiotics began. All of the pre-antibiotic era strains were susceptible to high levels of these antibiotics, whereas 20% of strains from contemporary populations of Escherichia coli and Salmonella enterica displayed high-level resistance to at least one of the antibiotics. In addition to the increase in the frequency of high-level resistance, background levels, conferred by genes providing nonspecific low-level resistance to multiple antibiotics, were significantly higher among contemporary strains. Changes in the incidence and levels of antibiotic resistance are not confined to particular segments of the bacterial population and reflect responses to the increased exposure of bacteria to antimicrobial compounds over the past several decades.     

Inactivation of chloramphenicol and florfenicol by a novel chloramphenicol hydrolase

Chloramphenicol and florfenicol are broad-spectrum antibiotics. Although the bacterial resistance mechanisms to these antibiotics have been well documented, hydrolysis of these antibiotics has not been reported in detail. This study reports the hydrolysis of these two antibiotics by a specific hydrolase that is encoded by a gene identified from a soil metagenome. Hydrolysis of chloramphenicol has been recognized in cell extracts of Escherichia coli expressing a chloramphenicol acetate esterase gene, estDL136. A hydrolysate of chloramphenicol was identified as p-nitrophenylserinol by liquid chromatography-mass spectroscopy and proton nuclear magnetic resonance spectroscopy. The hydrolysis of these antibiotics suggested a promiscuous amidase activity of EstDL136. When estDL136 was expressed in E. coli, EstDL136 conferred resistance to both chloramphenicol and florfenicol on E. coli, due to their inactivation. In addition, E. coli carrying estDL136 deactivated florfenicol faster than it deactivated chloramphenicol, suggesting that EstDL136 hydrolyzes florfenicol more efficiently than it hydrolyzes chloramphenicol. The nucleotide sequences flanking estDL136 encode proteins such as amidohydrolase, dehydrogenase/reductase, major facilitator transporter, esterase, and oxidase. The most closely related genes are found in the bacterial family Sphingomonadaceae, which contains many bioremediation-related strains. Whether the gene cluster with estDL136 in E. coli is involved in further chloramphenicol degradation was not clear in this study. While acetyltransferases for chloramphenicol resistance and drug exporters for chloramphenicol or florfenicol resistance are often detected in numerous microbes, this is the first report of enzymatic hydrolysis of florfenicol resulting in inactivation of the antibiotic.