Alteration of capsular type of encapsulated strains ofStaphylococcus aureus during freeze-drying and storage

Summary Remarkable alteration was shown in capsular type antigen production in encapsulated strains ofStaphylococcus aureus stored by lyophilization for 10 years. This alteration was further elucidated by antibody production in rabbits immunized with the altered strain and by absorbing the antibodies with representative capsular type strains.     

Mobile genetic elements of Staphylococcus aureus

Bacteria such as Staphylococcus aureus are successful as commensal organisms or pathogens in part because they adapt rapidly to selective pressures imparted by the human host. Mobile genetic elements (MGEs) play a central role in this adaptation process and are a means to transfer genetic information (DNA) among and within bacterial species. Importantly, MGEs encode putative virulence factors and molecules that confer resistance to antibiotics, including the gene that confers resistance to beta-lactam antibiotics in methicillin-resistant S. aureus (MRSA). Inasmuch as MRSA infections are a significant problem worldwide and continue to emerge in epidemic waves, there has been significant effort to improve diagnostic assays and to develop new antimicrobial agents for treatment of disease. Our understanding of S. aureus MGEs and the molecules they encode has played an important role toward these ends and has provided detailed insight into the evolution of antimicrobial resistance mechanisms and virulence.     

LysogenicKlebsiella pneumoniae strains of capsular serotype 2(B)

Résumé L'auteur décrit quatre souches deKlebsiella pneumoniae du type capsulaire B lysogènes pour les bactériophages actifs pour une autre souche du même type.

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I am grateful to ProfessorsD. G. Catcheside andJ. P. Duguid, Drs.B. H. Park, I. Ørskov, J. Papavassiliou andY. Hamon for encouragement, information and bacterial strains. This work was begun at the Microbiology Department, University of Birmingham, while the author held an award from the Agricultural Research Council.     

Alteration of resistantStaphylococcus aureus cultures by contact with yeast products

Zusammenfassung Staphylococcus aureus-Stämme wurden 3 Jahre lang in unseren Laboratorien gezüchtet. Hefeextrakt wirkte kurze Zeit auf sie cin, bevor sie wieder in den Nährboden geimpft wurden. Nach dieser Behandlung kam es zu einer Antibiotikaempfindlichkeit, und die Stämme bildeten weder Coagulase noch Hämolysin. Die neu erworbenen Eigenschaften sind erblich und wurden durch mehrere Generationen beibehalten.     

Genetic basis of methicillin resistance in Staphylococcus aureus

Methicillin resistance in staphylococci is due to the acquisition of the mecA gene encoding a new penicillin-binding protein (PBP2', PBP2a) that has a lower affinity to methicillin than the endogenous PBPs. PBP2' is involved in the assembly of the cell wall peptidoglycan in the presence of high concentrations of beta-lactams that otherwise inhibit the endogenous PBPs. The production of PBP2' is under dual control by its own mecR1-mecI- and the penicillinase blaR1-blaI-encoded regulatory elements. Resistance to high levels of methicillin depends, in addition to PBP2', on chromosomally encoded factors that are involved in the synthesis and degradation of the peptidoglycan. Any mutations that reduce peptidoglycan precursor formation or change the chemical composition of the muropeptide precursor result in lowered resistance.     

Effect of sodium chloride on the respiratory function of Staphylococcus aureus.

Sodium chloride at concentrations below 0.5 M, enhanced the respiratory activity (O2-consumption) of Staphylococcus aureus under endogenous and sugar-supported conditions, but did not overcome the inhibitory action of sodium azide. Several sugars, including the glucose analogue alpha-methylglucoside, and their metabolites enhanced bacterial O2-consumption, but acetylmethylcarbinol was ineffective.     

Effects of diethylstilbestrol on the production of various extracellular products of Staphylococcus aureus

Summary The synthetic estrogen diethylstilbestrol at a subinhibitory level of 1.75 g/ml diminished the production of staphylococcal alpha toxin, coagulase, deoxyribonuclease and penicillinase. Thus, the reported host beneficial effects of diethylstilbestrol may be partially related to its retardive action of certain toxins, or enzymes of S. aureus.Acknowledgments. This work was supported by United States Public Health Service, grant AI 06618, a grant in aid from Loyola University, United States Public Health Service, grant GRSG PRO 5368, and grants from Eli Lilly, Upjohn, Syntex, and G. D. Searle drug companies.     

The effect of bacterial host strains on the inactivation of polyvalentStaphylococcus aureus bacteriophages

Zusammenfassung Versuche über Inaktivierung von Staphylokokkenphagen durch Hydroxylamin. Das Resultat wird auch durch die Wahl des Wirtsorganismus bestimmt.     

Use of Cowan strain I of Staphylococcus aureus for radio-immunological determination of retrovirus proteins]

The use of Staphylococcus aureus for the radio-immunoassay of C-type virus polypeptides provided very specific results and proved to present several advantages over the classical methods of precipitation of immune complexes.     

Classification of micrococcus(Staphylococcus aureus) by means of differences in electro-phoretical mobility of extractable proteins

Zusammenfassung Mit Agar-Gel-Mikroelektrophorese war es möglich, typenspezifische Unterschiede in Mobilitäten von löslichen Proteinen der drei Typen,Staphylococcus aureus, «Cowan», zu demonstrieren. Diese Methode kann wahrscheinlich zur Typenbestimmung von Staphylococci und anderen Bakterien benützt werden.     

Fructose transport-deficient Staphylococcus aureus reveals important role of epithelial glucose transporters in limiting sugar-driven bacterial growth in airway surface liquid

Hyperglycaemia as a result of diabetes mellitus or acute illness is associated with increased susceptibility to respiratory infection with Staphylococcus aureus. Hyperglycaemia increases the concentration of glucose in airway surface liquid (ASL) and promotes the growth of S. aureus in vitro and in vivo. Whether elevation of other sugars in the blood, such as fructose, also results in increased concentrations in ASL is unknown and whether sugars in ASL are directly utilised by S. aureus for growth has not been investigated. We obtained mutant S. aureus JE2 strains with transposon disrupted sugar transport genes. NE768(fruA) exhibited restricted growth in 10 mM fructose. In H441 airway epithelial-bacterial co-culture, elevation of basolateral sugar concentration (5–20 mM) increased the apical growth of JE2. However, sugar-induced growth of NE768(fruA) was significantly less when basolateral fructose rather than glucose was elevated. This is the first experimental evidence to show that S. aureus directly utilises sugars present in the ASL for growth. Interestingly, JE2 growth was promoted less by glucose than fructose. Net transepithelial flux of d-glucose was lower than d-fructose. However, uptake of d-glucose was higher than d-fructose across both apical and basolateral membranes consistent with the presence of GLUT1/10 in the airway epithelium. Therefore, we propose that the preferential uptake of glucose (compared to fructose) limits its accumulation in ASL. Pre-treatment with metformin increased transepithelial resistance and reduced the sugar-dependent growth of S. aureus. Thus, epithelial paracellular permeability and glucose transport mechanisms are vital to maintain low glucose concentration in ASL and limit bacterial nutrient sources as a defence against infection.     

Alteration in the secretion of anterior pituitary hormones during dimethylbenzathracene induction of mammary tumors in rats]

In a sensitive strain of Rat (Sprague-Dawley) a deregulation of the secretion of some pituitary hormones was noted in the female during induction of mammary tumors by dimethylbenzanthracene administration. The deregulation occurred quickly and depended on the stage of the estrous cycle. It mainly consists of hyposecretion of gonadotropins. TSH and GH and of hypersecretion of prolactin.     

Uptake of glucose-C14 and fructose-C14 by buffalo spermatozoa in extenders during cold storage

Summary Buffalo spermatozoa exhibit insignificant uptake of glucose-C¹⁴ and fructose-C¹⁴ when semen samples were preserved in cold for 96 h in 2 extenders. Incorporation of C¹⁴ in spermatozoa, TCA precipitable proteins and soluble sugar phosphates was either equal or less in semen samples preserved in cold. CAW appeared to be a better extender than SKMEY as revealed by sugar uptake in cold.Acknowledgment. We are indebted to Dr D. Sundaresan, Director, for his kind encouragement in this study.     

Uptake of glusose-C14 and fructose-C14 by buffalo spermatozoa in extenders during cold storage

Buffalo spermatozoa exhibit insignificant uptake of glucose-C14 and fructose-C14 when semen samples were preserved in cold for 96 h in 2 extenders. Incorporation of C14 in spermatozoa, TCA precipitable proteins and soluble sugar phosphates was either equal or less in semen samples preserved in cold. CAW appeared to be a better extender than SKMEY as revealed by sugar uptake in cold.     

高温变形过程中的动态再结晶类型识别

通过分析高温变形过程中伴随再结晶晶粒长大的内部位错密度变化,判别不同变形条件下动态再结晶过程的进行形式,研究动态再结晶形式对变形参数的依赖规律,发现：低温大应变速率下,高温变形过程中的再结晶形式以连续性动态再结晶为主;高温低应变速率下,以周期性动态再结晶为主.根据动态再结晶软化与加工硬化平衡,得到反映稳态流动时钛合金流动应力对变形参数的响应,建立具有实际物理意义描述钛合金稳态流动本构关系的Arrhenius型方程.通过热模拟压缩实验得到800~900℃,0.0005~10 s-1条件下的TC18钛合金高温变形流动应力应变曲线,验证动态再结晶形式的判据模型,并通过DMM耗散效率分布图分析模型的适用性.通过显微组织分析,研究不同变形参数下的高温变形过程中,不同动态再结晶形式对应的再结晶晶粒粗化/细化的特点.通过各变形条件下真应变？=0.8时的稳态应力验证得到的本构模型,并分析应变速率敏感系数的变化规律.