凝固酶阴性葡萄球菌耐药性及流行变迁情况的观察

通过对我院1992－1994年间的108株CNS和1997－1999年8月间的72株CNS的比较研究发现：表皮葡萄球菌的分离率仍居首位,溶血葡萄球菌和模仿葡萄球菌占的比例有所提高,耐药性的研究发现,对环丙氟哌酸和红霉素的耐药率有显著提高。     

我国鱼类病原——嗜水气单胞的耐药性研究

采用琼脂扩散法和稀释法研究26株嗜水气单胞菌对21种菌药物的敏感性,分析了其耐药状况。结果表明：从不同地区分离收集到的26株嗜水气单胞菌（Aeromonas hydrophila）对青霉素类和头孢菌素类药物全部具耐药性,对万古霉素多数不敏感。21种药物中最敏感的是氟哌酸、氯霉素、呋喃呋酮,总体耐药率分别为7.7％、7.7％和11.5％。氨基糖甙类药物和四环素类药物的耐药频率介于其间,对磺胺药的耐药菌比例也很高,高达73.1％的A.hydrophila对磺胺及复方磺胺其有耐药性,但耐磺胺比耐复方磺胺的现象更为普遍,对3种常用药物具有耐药性的菌株比例最高。同时对鱼类病原菌耐药性的判定标准以及两种方法在鱼类病原菌耐药性研究中的适用性问题进行了讨论。     

LEAF RESISTANCE TO WATER VAPOR TRANSFER IN SUCCULENT PLANTS: EFFECT OF THERMOPERIOD

Leaf resistance (R_L) of Kalanchoe blossfeldiana to water vapor transfer was determined with a resistance hygrometer. The diurnal leaf-resistance change followed a normal pattern (i.e., low in light and higher in dark) when plants were pretreated with cool thermoperiods or with thermoperiods having little diurnal temperature fluctuation. Large diurnal temperature fluctuations (30-18, 26-15 C) resulted in apparent nocturnal stomatal opening. Nocturnal stomatal opening was more apparent than real since leaf-resistance measurements indicated day stomatal closing rather than complete night opening. Low nocturnal leaf resistances ( < 10 sec/cm) were not measured in the dark; however, resistances tended to decrease toward the end of the dark period indicating some degree of nocturnal stomatal opening. Leaf resistances were generally higher than those reported for nonsucculent plants. The data suggested that gaseous diffusion (Q) into or out of the leaves of K. blossfeldiana would be adequately described by an equation of the form, Q = D Δ e R_L⁻¹. There was little or no indication that physiological long days (15 min of 660 mμ light in the middle of a 16-hr dark period), which prevented flowering and reduced organic acid accumulation, significantly affected leaf resistance. It was concluded that the photoperiod response effects of dark CO₂ fixation were probably not due to leaf-resistance changes and, therefore, not due to stomatal aperture changes.     

重症监护患者病原菌感染及耐药性分析

目的：了解重症监护患者感染的病原菌及其耐药特点,为临床防治感染提供依据。方法：对我院ICU1998年1月-2000年1月所有分离的细菌菌株、真菌菌株及细菌耐药性进行回顾性调查。结果：医院内感染仍以G^-菌为主占83.3%,其次为真菌11.1%,G^ 菌5.5%。G^-菌以不动杆菌属为主,占26.7%。G^ 菌以金黄色葡萄球菌（金葡菌）为主。金葡菌中耐苯唑青霉素的金葡萄（MRSA）占66.6%,表皮葡萄球菌（表葡萄）中耐苯唑青霉素的表葡菌（MRSE）占33.3%。真菌以白色念珠菌为主占80.0%。在细菌耐药性方面,G^-菌对泰能的耐药率最低为2.6%。结论：重症监护患者感染病原菌以G^-菌为主,真菌和G^ 菌与应引起重视,且大多数病原菌耐药率较高,使临床经验性选择抗生素治疗医院感染非常困难。     

550例支原体药敏结果分析

目的：了解本地区感染泌尿生殖系的解脲、人型支原体耐药情况。方法：对性病科和妇科门诊近3年来550例支原体感染者用支原体药敏试剂盒进行司巴沙星（SPA）、克拉霉素（CLA）、可乐必妥（CRA）、交沙霉素（JOS）、阿奇霉素（AZI）、罗红霉素（ROX）、强力霉素（DOX）、美满霉素（MIN）、氧氟沙星（ODL）、乙酰螺旋霉素（ASP）、四环素（TET）、红霉素（ERY）12种抗生素的药敏试验。结果：统计近3年耐药率,总计依次是4.2%、8.4%、10.4%、23.2%、23.8%、29.6%、29.6%、33.0%、43.1%、55.3%、61.9%、82.7%。结论：耐药率司巴沙星、克拉霉素、可乐必妥较稳定,基本低于10%,其余均较高且大部分呈逐年增长趋势,且解脲和人型支原体耐药性有较大差异。     

THE EVOLUTION OF RESISTANCE TO HERBIVORY IN IPOMOEA PURPUREA. II. NATURAL SELECTION BY INSECTS AND COSTS OF RESISTANCE

An important component of the process of coevolution between plants and their insect herbivores is the imposition of selection on plants by insects. Although such selection has been inferred from indirect evidence, little direct evidence for it exists. One goal of this study was to seek direct evidence by determining, for a single plant-herbivore system, whether insect herbivores impose selection on their host plants. A second goal was to determine whether costs are associated with genotypes that confer resistance to herbivores, as has been commonly postulated. The annual morning glory, Ipomoea purpurea, exhibits genetic variation in resistance to four different types of insects. For three of these types, most of the genetic variation is additive. Removal of insect herbivores increased the number of seeds produced by I. purpurea by 20% and eliminated additive genetic variation for seed number (fitness). This result implies that herbivores impose selection on some trait(s) of their host plants. Coupled with selection for decreased damage by corn earworms, as revealed by a negative additive genetic covariance between damage and fitness, this result suggests that insect herbivores impose selection on resistance to corn earworms in I. purpurea. Two types of cost of resistance to herbivores were sought in I. purpurea: 1) internal trade-offs in allocation of resources and 2) ecological trade-offs between resistances to different insects. No costs of either type were detected. This result suggests that cost-benefit arguments that attempt to predict the evolution of levels of resistance to herbivores are not applicable to I. purpurea.     

The Interaction of Acridine Dyes with the Densely Packed DNA of Bacteriophage

The interactions of acridine dyes with intact phage DNA differ from those with extracted DNA in the following respects. Strong binding (intercalation) is greatly reduced in intact phage but probably not eliminated. The cooperative, weak binding is stronger and the stacking tendency is increased. In gels of DNA the stacking tendency is seen to increase with decreasing hydration. These influences of the dense packing of DNA must be taken into account when using basic dyes to study chromosome structure.     

STUDIES ON THE PERMEABILITY OF MEMBRANES : II. DETERMINATION OF IONIC TRANSFER NUMBERS IN MEMBRANES FROM CONCENTRATION CHAINS.

The ionic transfer number in an electrolyte solution in the pores of a narrow pored collodion membrane depends much more on the concentration than it does in a free aqueous solution. The potential difference of two solutions of the same electrolyte in different concentration depends largely on the concentration range. The ratio of the concentrations on the two sides was always 1:2 in the experiments; the concentration range was varied. It is shown that the transfer number of Cl, calculated from the P.D. measured, is very small in dilute solution (down to .02 and less in some cases), whereas it approaches the value .5 holding for free aqueous solutions when the concentration range is raised. The differences for the transfer number of Cl, according to the cation (H, K, Na, Li), can be recognized and show the same order as in free aqueous solution. But even in LiCl, where in an ordinary aqueous solution the transfer number of Cl is always > .5, this number is very low in the case of the membrane (e.g. < .05 in .01 M solution).     

INTRASPECIFIC TRANSFER OF HERBICIDE RESISTANCE IN THE RED MICROALGA PORPHYRIDIUM SP. (RHODOPHYCEAE) VIA PROTOPLAST FUSION

Stable progeny doubly resistant to the herbicides sulfometuron methyl (SMM) and diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] (DCMU) were obtained at a frequency of 2% on fusion of protoplasts derived from mutants of Porphyridium sp. (UTEX 637) that were resistant only to SMM (strain SMR) or DCMU (strain DC-2). In the presence of both herbicides, only the fusion progeny could grow; both parental mutants were inhibited. In the absence of SMM, the activity of acetohydroxy acid synthase (AHAS) in the wild-type strain was similar to that in DC-2, exceeding that of SMR by up to 4.5-fold. AHAS activities of all fusion progeny were lower than those of the wild-type strain and DC-2 but higher than that of SMR. In the presence of SMM, AHAS activities of all tested fusion progeny ranged between those of the two parental mutants. This result indicates that both types of AHAS, the type resistant to SMM and the sensitive type, originating from SMR and DC-2, respectively, were expressed in the fusion progeny. In the presence of DCMU, the photosynthetic activity of SMR was completely inhibited, whereas that of DC-2 was unaffected. The photosynthetic activity of the fusion progeny in the presence of DCMU was slightly lower than that of DC-2. Both the cell volume and the DNA content of the fusion progeny were similar to those of the parents. However, the genetic nature of the fusion products has not yet been elucidated. To the best of our knowledge, this is the first report on transfer of herbicide resistance via protoplast fusion in algae.     

大肠埃希菌在肿瘤患者肠外的分布及耐药谱分析

目的：了解大肠埃希菌在肿瘤患者肠外的分布和感染情况及耐药性。方法：参照全国临床检验操作规程,采用K-B法对云南省肿瘤医院58例肿瘤患者继发大肠埃希菌感染进行分析及对9种抗生素的耐药谱测定。结果：各类肿瘤患者中,以宫颈癌及继发大肠埃希菌感染多见,其中,宫颈癌为28.30%。肺癌为26.87%。从标本来源来看,以尿液标本最多,为63.79%,其次为痰液12.07%及分泌物12.07%。结论：大肠埃希菌在肿瘤患者肠外分布广泛,所致感染较严重,经耐药谱测定发现大肠埃希菌多重耐药类型多,提示对肿瘤患者治疗应重视局部微生态平衡及控制感染。     

THE EFFECT OF REPEATED SPRAYING OF INSECTS IN INCREASING THEIR RESISTANCE TO INSECTICIDES: I. DEVELOPMENT OF RESISTANCE TO DDT IN A STRAIN OF DROSOPHILA MELANOGASTER MEIG.

Successive spraying with DDT suspensions of the adults of a wild colony of Drosophila melanogaster and the progeny of survivors enhanced the resistance to that insecticide.
The rate at which resistance increased depended on: (1) the relative proportion of resistants to susceptible individuals, or (2) the intensity of selection as measured by the concentration of DDT, the proportion killed or on both. The resistance of the populations of the insects fluctuated considerably whether subjected to successive sprayings or not, and in one sprayed series there was some indication of a rhythm with peaks of susceptibility occurring at regular intervals.
Enhanced resistance may show a change of slope in the probit log concentration regression line, leading to different relative values at different levels of mortality, or by a parallel shift of the regression line. The former appears to be a preliminary stage of selection and indicates a change in the frequency distribution within a population.
Increasing the concentration of DDT, slowly or rapidly, may have enhanced resistances at an increased rate, but the series sprayed with the lower initial concentration reached finally the same end point, as judged by the values of log lc . 50.
During the course of these experiments the insects developed sensitivity to carbon dioxide (used in anaesthesis). Its bearing on our work is considered in Part II.     

HOST-PATHOGEN INTERACTIONS IN NATURAL POPULATIONS OF LINUM MARGINALE AND MELAMPSORA LINI: II. LOCAL AND REGIONAL VARIATION IN PATTERNS OF RESISTANCE AND RACIAL STRUCTURE

Spatial variation in the resistance structure of Linum marginale (wild flax) populations to the rust fungus Melampsora lini, and in the racial structure of this pathogen, was investigated by sampling 10 populations distributed throughout the Kosciusko National Park, New South Wales, Australia. Considerable differences were found among populations in the structure of both host and pathogen. Host populations were divided into three broad categories: (1) populations susceptible to all testing races; (2) populations containing a strictly limited number of resistant phenotypes; and (3) populations with a considerable diversity of resistant phenotypes. The pathogen populations also showed a range of diversity. The major differences between these populations were determined by the occurrence and frequency of four common races of pathogen (races A, E, K, and N). These differences were apparent both at a regional spatial scale (over the 100 km separation of the most distant populations) and at a local scale where major differences were detected between two populations only 300 m apart. The distribution of the four common races of M. lini was consistent with the hypothesis that a fitness cost was associated with unnecessary virulence. In general, however, differences in the structure of pathogen populations from genetically very similar host populations implied that, in addition to host resistance genes, other evolutionary forces are also important in determining the genetic structure of individual pathogen populations.     

THE VARIATION OF ELECTRICAL RESISTANCE WITH APPLIED POTENTIAL : II. THIN COLLODION FILMS

The resistance of very thin collodion membranes to direct current bears some resemblance to that of living cells since it varies with the applied potential. With membranes separating two different solutions the resistance varies with the direction (and the voltage) of the applied potential, rising when less mobile ions are carried across the membrane and falling when more mobile ones are so carried. (With some membranes the resistance varies with potential when the same solution is on both sides.) These changes are very prompt and regular. There is a hysteretic effect of previous current flow. But the membranes differ from Valonia cells in that the rise of resistance is largely ohmic, there being little or no polarization potential.