Relatedness between Streptococcus pneumoniae and viridans streptococci: transfer of penicillin resistance determinants and immunological similarities of penicillin-binding proteins

The occurrence of highly variable penicillin-binding proteins (PBPs) in penicillin-resistant Streptococcus pneumoniae suggested that transfer of homologous genes from related species may be involved in resistance development. Antiserum and monoclonal antibodies raised against PBPs 1a and 2b from the susceptible S. pneumoniae R6 strain were used to identify related PBPs in 41 S. mitis, S. sanguis I and S. sanguis II strains mostly isolated in South Africa with MIC values ranging from less than 0.15 to 16 mg/ml. Furthermore, the possibility of genetic exchange was examined with 30 penicillin-resistant strains of this collection (MIC greater than 0.06 mg/ml) as donors using S. pneumoniae R6 as recipient in transformation experiments. The majority of S. mitis and S. sanguis II strains but none of the S. sanguis I strains could transform penicillin resistance genes into S. pneumoniae R6. All positive donor strains and all susceptible isolates of S. mitis and S. sanguis II strains contained PBPs which cross-reacted with the anti-PBP 1a and/or anti-PBP 2b antibodies. On the other hand, only five of the 14 S. sanguis I strains contained a PBP that reacted with one of the antibodies. This strongly suggested the presence of genes homologous to the pneumococcal PBP 1a and 2b genes in viridans streptococci, and documents that penicillin resistance determinants can be transformed from viridans streptococci into the pneumococcus.     

Modeling the mechanism of postantibiotic effect and determining implications for dosing regimens

A stochastic model is proposed to explain one possible underlying mechanism of the postantibiotic effect (PAE). This phenomenon, of continued inhibition of bacterial growth after removal of the antibiotic drug, is of high relevance in the context of optimizing dosing regimens. One clinical implication of long PAE lies in the possibility of increasing intervals between drug administrations. The model describes the dynamics of synthesis, saturation and removal of penicillin binding proteins (PBPs). High fractions of saturated PBPs are in the model associated with a lower growth capacity of bacteria. An analytical solution for the bivariate probability of saturated and unsaturated PBPs is used as a basis to explore optimal antibiotic dosing regimens. Our finding that longer PAEs do not necessarily promote for increased intervals between doses, might help for our understanding of data provided from earlier PAE studies and for the determination of the clinical relevance of PAE in future studies.      

Influence of magnesium ions on heat shock and ethanol stress responses of Saccharomyces cerevisiae

This study has highlighted the role of magnesium ions in the amelioration of the detrimental effects of ethanol toxicity and temperature shock in a winemaking strain of Saccharomyces cerevisiae. Specifically, results based on measurements of cellular viability and heat shock protein synthesis together with scanning electron microscopy have shown that, by increasing the bioavailability of magnesium ions, physiological protection is conferred on yeast cells. Elevating magnesium levels in the growth medium from 2 to 20 mM results in repression of certain heat shock proteins following a typical heat shock regime (30–42°C shift). Seed inocula cultures prepropagated in elevated levels of magnesium (i.e. ‘preconditioned’) also conferred thermotolerance on cells and repressed the biosynthesis of heat shock proteins. Similar results were observed in response to ethanol stress. Extra- and intracellular magnesium may both act in the physiological stress protection of yeast cells and this approach offers potential benefits in alcoholic fermentation processes. The working hypothesis based on our findings is that magnesium protects yeast cells by preventing increases in cell membrane permeability elicited by ethanol and temperature-induced stress.     

Effect of azasqualene on hopanoid biosynthesis and ethanol tolerance of Zymomonas mobilis

Pathogenic and non-pathogenic isolates of Streptococcus suis type 2 were screened to determine whether differences in superoxide dismutase (SOD) synthesis could explain the observed differences in their pathogenicity and intracellular fate in macrophages. A single band of SOD activity of similar Rf value was visualised in PAGE gels in all isolates and inhibition studies suggested that the cofactor present was manganese. There was no correlation between specific SOD activity and virulence. It is unlikely, therefore, that SOD produced by S. suis type 2 mediates intracellular survival of pathogenic isolates in macrophages.     

Larvae of related Diptera species from thermally contrasting habitats exhibit continuous up-regulation of heat shock proteins and high thermotolerance

A population of Stratiomys japonica, a species belonging to the family Stratiomyidae (Diptera), common name ‘soldier flies’, occurs in a hot volcanic spring, which is apparently among the most inhospitable environments for animals because of chemical and thermal conditions. Larvae of this species, which naturally often experience temperatures more than 40 °C, have constitutively high concentrations of the normally inducible heat-shock protein Hsp70, but very low level of corresponding mRNA. Larvae of three other species of the same family, Stratiomys singularior, Nemotelus bipunctatus and Oxycera pardalina, are confined to different type semi-aquatic habitats with contrasting thermal regime. However, all of them shared the same pattern of Hsp70 expression. Interestingly, heat-shock treatment of S. japonica larvae activates heat-shock factor and significantly induces Hsp70 synthesis, whereas larvae of O. pardalina, a species from constant cold environment, produce significantly less Hsp70 in response to heat shock. Adults of the four species also exhibit lower, but detectable levels of Hsp70 without heat shock. Larvae of all species studied have very high tolerance to temperature stress in comparison with other Diptera species investigated, probably representing an inherent adaptive feature of all Stratiomyidae enabling successful colonization of highly variable and extreme habitats.     

Respiratory activity of yeast Yarrowia lipolytica under oxidative stress and heat shock

Heat shock (45°C) and the effect of oxidants (H₂O₂) resulted in a decrease of the respiratory activity of yeast cells and their survival rate. Increased resistance to stress effects after mild heat treatment (37°C) or treatment with a nonlethal dose of oxidants (0.5 mM H₂O₂) for 60 min) was accompanied by appearance of an alternative (cyanide-resistant) oxidative pathway in the mitochondria, which promotes survival due to retention of the capacity for ATP synthesis in the first coupling point at the level of endogenous NADH dehydrogenase. The alternative oxidative pathway is more resistant to the effect of stressors that disrupt electron transfer in the cytochrome site of the respiratory chain.     

Respiratory activity of yeast Yarrowia lipolytica under oxidative stress and heat shock

Heat shock (45 degrees C) and the effect of oxidants (H2O2) resulted in a decrease of the respiratory activity of yeast cells and their survival rate. Increased resistance to stress effects after mild heat treatment (37 degrees C) or treatment with a nonlethal dose of oxidants (0.5 mM H2O2 for 60 min) was accompanied by appearance of an alternative (cyanide-resistant) oxidative pathway in the mitochondria, which promotes survival due to retention of the capacity for ATP synthesis in the first coupling point at the level of endogenous NADH dehydrogenase. The alternative oxidative pathway is more resistant to the effect of stressors that disrupt electron transfer in the cytochrome site of the respiratory chain.     

Heat shock proteins and effects of heat shock in plants

Soybean seedlings when exposed to a heat shock respond in a manner very similar to that exhibited by cultured cells, and reported earlier [2]. Maximum synthesis of heat shock proteins (HSPs) occurs at 40C. The heat shock response is maintained for a relatively short time under continuous high temperature. After 2.5 hr at 40 C the synthesis of HSPs decreases reaching a very low level by 6 hr. The HSPs synthesized by cultured cells and seedlings are identical and there is a large degree of similarity in HSPs synthesized between the taxonomically widely separated species, soybean and corn. Storage protein synthesis in the developing soybean embryo is not inhibited but is actually stimulated during a heat shock, unlike most other non-HSPs, whose synthesis is greatly reduced. Seedlings respond differently to a gradual increase in temperature than they do a sudden heat shock. There is an upward shift of several degrees in the temperature at which maximum protein synthesis occurs and before it begins to be inhibited. In addition, there appears to be a protection of normal protein synthesis from heat shock inhibition when the temperature increase is gradual. An additional function of the heat shock phenomenon might be the protection of seedlings from death caused by extreme heat stress. The heat shock response appears to have relevance to plants in the field.     

Metabolome analysis of differential responses of diploid and haploid yeast to ethanol stress

Metabolomic analysis was carried out to investigate the metabolic differences of diploid (α/a) and homogenous haploid (α,a) yeasts, and further assess their response to ethanol stress. The dynamic metabolic variations of diploid and haploid caused by 3 and 7% (v/v) ethanol stress were evaluated by gas chromatography coupled to time-of-flight mass spectrometry combined with statistical analysis. Metabolite profiles originating from three strains in presence/absence of ethanol stress were distinctive and could be distinguished by principal components analysis. Results showed that the divergence among the strains with ethanol stress was smaller than without it. Furthermore, the levels of most glycolytic intermediates and amino acids in haploid were lower than these in diploid with/without ethanol stress, which was considered as species-specific behaviors. The increases of protective metabolites including polyols, amino acids, precursors of phospholipids, and unsaturated fatty acids under ethanol stress in three strains revealed the ethanol stress-specific responses. Higher fold change in most of these protectants in haploid indicated that haploid was more susceptible to ethanol stress than diploid. These findings provided underlying basis for better understanding diploid and haploid yeasts, and further breeding tolerant strains for efficient ethanol fermentation.     

Molecular responses of plants to an increased incidence of heat shock

Abstract. Climatic change as a result of the greenhouse effect is widely predicted to increase mean temperatures globally and, in turn, increase the frequency with which plants are exposed to heat shock conditions, particularly in the semi-arid tropics. The consequences of extreme high-temperature treatments on plants have been considered, particularly in relation to the synthesis of heat shock proteins (HSPs) and the capacity to acquire thermotolerance. The heat shock response is described using results obtained with seedlings of the tropical cereals, sorghum ( Sorghum bicolor ) and pearl millet ( Pennisetum glaucum ). A gradual temperature increase, as would occur in the field, is sufficient to induce thermotolerance. The synthesis of HSPs is a transient phenomenon and ceases once the stress is released. Despite the persistence of the HSPs themselves, de novo synthesis of HSPs is required for the induction of thermotolerance each time high temperatures are encountered. The effect of a repeated, diurnal heat shock was investigated and genotypic differences found in the ability to induce the heat shock response repeatedly.     

侵袭性和非侵袭性肺炎链球菌耐药率的比较分析

目的研究侵袭性和非侵袭性肺炎链球菌的耐药谱的差异,指导合理应用抗生素及感染管理。方法回顾性统计分析2009至2011年来天台县人民医院就诊患者分离肺炎链球菌的标本来源及耐药性,比较侵袭性和非侵袭性肺炎链球菌耐药率之间的差异。结果共分离出肺炎链球菌642株,痰液中分离出584株,非痰液中分离出58株,其中血液中分离出32株,脑脊液中分离出20株,其他分离出6株,所有肺炎链球菌对万古霉素和利奈唑胺均敏感,对青霉素、红霉素、克林霉素、四环素及复方新诺明耐药严重,对左氧氟沙星、氯霉素比较敏感;侵袭性分离株对青霉素、红霉素、克林霉素、左氧氟沙星、四环素及氯霉素的耐药率显著高于非侵袭性肺炎链球菌。结论该院分离的肺炎链球菌主要来自痰液标本,耐青霉素肺炎链球菌的检出率高,大环内酯类耐药严重,存在一定比例的侵袭性感染,非侵袭菌株与侵袭性菌株耐药谱之间存在一定差异,临床治疗应该区别对待,系统的监测细菌耐药性,合理选择抗菌药物。     

114株肺炎链球菌的临床分布及药敏分析

目的波市妇女儿童医院肺炎链球菌的临床分布和耐药情况,为临床合理用药提供依据。方法对该院2009年6月1日至2011年3月31日期间分离的114株肺炎链球菌进行分析,菌株鉴定采用法国生物梅里埃公司的VITEK60分析仪,药敏试验采用K-B法,用参考菌株做质量控制。结果该院分离的肺炎链球菌主要来自儿童（84.21%）,标本来源主要是痰液（61.4%）,其次是血液（9.65%）,其他（28.95%）。肺炎链球菌的耐药率：林可霉素92.19%,红霉素90.12%,青霉素G85.53%,左旋氧氟沙星20.24%,氨苄西林16.67%,头孢唑啉8.7%,头孢曲松5.8%,头孢噻肟4.11%,万古霉素0%,氨苄西林/舒巴坦0%,哌拉西林/他唑巴坦0%。结论宁波市妇女儿童医院肺炎链球菌对某些药物的耐药率很高,有必要对其进行耐药率监测,指导临床合理选择抗菌药物。     

Stress proteins in oligodendrocytes: differential effects of heat shock and oxidative stress

Heat shock proteins (HSP) or stress proteins serve as biomarkers to identify the contribution of stress situations underlying the pathogenesis of degenerative diseases of the CNS. We have analyzed by immunoblot technique the constitutive and inducible occurrence of stress proteins in cultured rat brain oligodendrocytes subjected to heat shock or oxidative stress exerted by hydrogen peroxide, or a combination of both. The data demonstrate that oligodendrocytes constitutively express HSP32, HSP60 and the cognate form of the HSP70 family of proteins, HSC70. After heat shock, HSP25, alpha B-crystallin and HSP70 were up-regulated, while after oxidative stress the specific induction of HSP32 and alpha B-crystallin was observed. HSP32 represents heme oxygenase 1 (HO-1), a small stress protein with enzymatic activity involved in the oxidative degradation of heme which participates in iron metabolism. The presence of the iron chelators phenanthroline or deferoxamine (DFO), which previously has been shown to protect oligodendrocytes from oxidative stress-induced onset of apoptosis, caused a marked stimulation of HSP32 without affecting HSP70. This indicates that DFO possibly exerts its protective role by directly influencing the antioxidant capacity of HO-1. In summary, HSP in oligodendrocytes are differentially stimulated by heat stress and oxidative stress. Heme oxygenase-1 has been linked to inflammatory processes and oxidative stress, its specific up-regulation after oxidative stress in oligodendrocytes suggests that it is an ideal candidate to investigate the involvement of oxidative stress in demyelinating diseases.     

Expression and interaction of small heat shock proteins (sHsps) in rice in response to heat stress

The inherent immobility of rice (Oryza sativa L.) limited their abilities to avoid heat stress and required them to contend with heat stress through innate defense abilities in which heat shock proteins played important roles. In this study, Hsp26.7, Hsp23.2, Hsp17.9A, Hsp17.4 and Hsp16.9A were up-regulated in Nipponbare during seedling and anthesis stages in response to heat stress. Subsequently, the expressing levels of these five sHsps in the heat-tolerant rice cultivar, Co39, were all significantly higher than that in the heat-susceptible rice cultivar, Azucena. This indicated that the expressive level of these five sHsps was positively related to the ability of rice plants to avoid heat stress. Thus, the expression level of these five sHsps can be regarded as bio-markers for screening rice cultivars with different abilities to avoid heat stress. Hsp18.1, Hsp17.9A, Hsp17.7 and Hsp16.9A, in the three rice cultivars under heat stress were found to be involved in one protein complex by Native-PAGE, and the interactions of Hsp18.1 and Hsp 17.7, Hsp18.1 and Hsp 17.9A, and Hsp17.7 and Hsp16.9A were further validated by yeast 2-hybridization. Pull down assay also confirmed the interaction between Hsp17.7 and Hsp16.9A in rice under heat stress. In conclusion, the up-regulation of the 5 sHsps is a key step for rice to tolerate heat stress, after that some sHsps assembled into a large hetero-oligomeric complex. In addition, through protein–protein interaction, Hsp101 regulated thiamine biosynthesis, and Hsp82 homology affected nitrogen metabolism, while Hsp81-1 were involved in the maintenance of sugar or starch synthesis in rice plants under heat stress. These results provide new insight into the regulatory mechanism of sHsps in rice.     

Changes in protein composition ofSaccharomyces brewing strains in response to heat shock and ethanol stress

Summary Heat shock and ethanol stress of brewing yeast strains resulted in the induction of a set of proteins referred to as heat shock proteins (HSPs). At least six strongly induced HSPs were identified in a lager brewing strain and four HSPs in an ale brewing strain. Four of these HSPs with molecular masses of approximately 70, 38, 26 and 23 kDa were also identified in two laboratory strains ofSaccharomyces cerevisiae. The appearance of HSPs correlated with increased survival of strains at elevated temperatures and high concentrations of ethanol. These results suggest that HSPs may play a role in the ethanol and thermotolerance of yeasts. The properties of these proteins and membrane fatty acids in relation to heat and ethanol shock are being investigated.     

Mucosal modulation of immune responses to heat shock proteins in autoimmune arthritis

Induction of oral tolerance to antigens that are targets of self-reactive immune responses is an attractive approach to antigen-specific immune therapy of autoimmune diseases. Oral tolerization has indeed proven to be safe and effective in amelioration of autoimmune diseases in animal models. In humans, results have been somewhat controversial. The emphasis given to clinical outcome rather than to immunomodulation, and the difficulty in identifying appropriate candidate antigens contribute to the controversy. Heat shock proteins are promising targets for immune intervention. Immune reactivity to heat shock proteins has indeed been correlated with autoimmune arthritis in animal models, and abnormal immune responses to heat shock proteins have been described in human arthritis as well. Despite significant recent progress, little is known at a molecular level regarding the mechanisms which are responsible for a switch from autoimmunity to tolerance in humans. This is particularly true with respect to sequential analysis of several molecular and immunologic markers during both the course and treatment of disease. Novel approaches are currently under way to fill the gaps. We will briefly detail here the experience gained to date, and identify some of the avenues which future research will explore.     

Mitochondrial and cytoplasmic protein syntheses are not required for heat shock acquisition of ethanol and thermotolerance in yeast

Two main forms of immunoreactive insulin have been identified in cultures of foetal mouse brain using HPLC and gel filtration. The major component which resembled proinsulin was converted by trypsin to the minor form which was similar to authentic pancreatic insulin in chromatographic behaviour. Both components showed immunological properties comparable to insulin and proinsulin including sensitivity of the former to reduction and alkylation.