Evaluation of the effect of tyrothricin on beta-hemolytic streptococci in salva. Part I: The effect of salvia upon bacteria. Part II: Effect of tyrothricin on the New York 5 strain of Streptococcus pyogenes in saliva

Part II of thesis by Brancato, Noyes, and Swift. Part I of thesis by Swift. Thesis (M.A.)--Boston UniversityThe antibacterial effect of saliva has been known for many years. Still the exact nature of the antagonistic action of saliva upon bacteria is as yet unsettled. Most workers agree, however, that the salivary bacterial inhibitory action is brought about in at least six ways: The first antibacterial effect is changes in pH, which affect the growth of oral organisms. Furthermore, this change in pH is dependent on diet and on the type of organisms in the oral cavity. The second is the mechanical factors involved, for saliva not only flushes bacteria from the mouth, but dilutes the number of organisms as well. The third is the antibacterial action of the cellular components in saliva. The leukocytes in saliva have a phagocytic action, and the non-phagocytic epithelial cells slough off in sheets, carrying with them thousands of organisms which have lodged in the partially turned edges of the necrotic cells . The fourth antibacterial action is ascribed to the presence of immune bodies in the saliva which lyse or agglutinate the oral bacteria. The fifth is the presence of oral bacteria which are antagonistic to new invaders. And the sixth is the presence of enzymes that lyse some oral bacteria or alter their cell membranes thereby inhibiting further growth. In recent years a great deal of investigation has been made to ascribe the enzymatic effect as the chief antibacterial agent in saliva; however, contradictory work has been done to try to attribute the chief antibacterial action of salivary cocci. Indeed the antibacterial effect of saliva is not always present, for the bacteriostatic effect of saliva is variable from day to day and from individual to individual. The only way of reducing the number of oral bacteria is to add to the saliva an antibiotic. Tyrothricin was used. In an attempt to delineate the range of concentration of tyrothricin per ml. effective against the New York 5 strain of Streptococcus pryogenes in saliva, this experiment was carried out. It was molded after the unpublished work of Belding concerning the effect of tyrothricin on the Oxford Strain of Staphylococcus aureus in saliva. The required inoculum of approximately one million organisms per ml was obtained by growing cultures of the streptococci under uniform conditions and setting up a table of the absorbances and viable cell counts, from which dilution factors for further cultures could be estimated. Controls were set up for determining possible inhibition of tyrothricin and/or test organisms by the various diluting fluids including saliva. Final concentrations per ml of 10, 25, 50, 75, and 100 µg of tyrothricin integrated with saliva and an approximated number of streptococci were plated out after 30 and 60 minutes exposure periods and were counted after 24 and 48 hours of incubation at 37°C. Whereas 1 µg per ml of tyrothricin reduced markedly the number of streptococci suspended in water during a 30 minute exposure period and 10 µg per ml, under similar conditions, caused complete inhibition, 10 µg per ml of the antibiotic was ineffective against this test organism suspended in saliva during a 30 minute exposure period but caused about an 80 per cent reduction in viable organisms during 60 minutes exposure. The length of the exposure period necessary for effective inhibition varied inversely with the concentration of tyrothricin per ml, 100 µg per ml causing a 98 per cent reduction of viable organisms during an exposure period of 1 minute. For the 30 minute exposure period, the quantity of tyrothricin effective against this strain of streptococci mixed in saliva would fall in the 10 µg - 25 µg per ml range and for shorter exposure periods, the concentration per ml would have to be greater. Cultures completely negative during 24 hours incubation at 37°C, showed a typical growth during 48 hours. This is considered indicative of the bacteriostatic action of tyrothricin which, prolonged, resulted in the death of large numbers of the streptococci. The results which were obtained in these experiments serve chiefly to point out the way for further work and to form a basis for the general conclusions listed below: 1. The action of tyrothricin on bacteria is inhibited by saliva to a large degree. 2. The minimal amounts of tyrothricin necessary to produce complete inhibition of growth of Streptococcus pyogenes in saliva is between 25 and 50 µg per ml acting for 30 minutes. 3. There is an effective reduction of Streptococcus pyogenes in saliva by concentrations of tyrothricin between 10 and 25 µg per ml acting for 30 minutes. 4. Tyrothricin acts immediately upon contact with Streptococcus pyogenes. 5. The action of tyrothricin on Streptococcus pyogenes in saliva is apparently bacteriostatic and not of a permanent nature as manifested by growth of atypical colonies during 48 hours incubation. 6. Tyrothricin above a concentration of 50 µg per ml had a definite reducing effect on the bacterial population of this saliva. 7. Saliva also has a bactericidal or bacteriostatic (or both) action against Streptococcus pyogenes

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MRI Sequence Influences Geometrical Information of Osseous Tissues

Although CT-scan data gives accurate geometrical information of bones, MRI data is commonly used instead due to its non-ionizing nature. The geometrical information has a number of applications, including image registration and computer simulations of the human joints, presurgical planning, prosthesis design, linking geometry with function and pain and kinematics. Hence, it is important to for the geometrical information extracted from the MRI data to be accurate. However, this information is influenced by the choice of the MRI sequence. Therefore, the aim of this study is to investigate the effect of different MRI sequences on the accuracy of geometrical information of bones

Novel Relationships among Lampreys (Petromyzontiformes) Revealed by a Taxonomically Comprehensive Molecular Data Set

The systematics of lampreys was investigated using complete mitochondrial cytochrome b sequences from all genera and nearly all recognized species. The families Geotriidae and Petromyzontidae are monophyletic, but the family Mordaciidae was resolved as two divergent lineages at the base of the tree. Within Petromyzontidae, the nonparasitic Lethenteron sp. S and Okkelbergia aepyptera were recognized as distinct lineages, Lethenteron morii and Lampetra zanandreai were moved to new genera, a sister species relationship was recovered between Caspiomyzon wagneri and Eudontomyzon hellenicus, and a clade was recovered inclusive of Entosphenus hubbsi and western North American Lampetra (L. ayresii and L. richardsoni). The placement of E. hellenicus as the sister species to C. wagneri reduces the number of genera comprised entirely of parasitic species to two, Geotria and Petromyzon. The recognition of distinct lineages for O. aepyptera and Lethenteron sp. S recognizes, for the first time, lineages comprised entirely of nonparasitic species. Apart from the results mentioned above, monophyly was supported for the multispecific genera Entosphenus, Eudontomyzon, Ichthyomyzon, Lampetra (restricted to European species), and Lethenteron. Intergeneric relationships within Petromyzontidae were poorly resolved, but separate clades inclusive of Entosphenus and Tetrapleurodon (subfamily Entospheninae) and one comprised of Eudontomyzon, Lampetra, and Okkelbergia were recovered

A journey to citizenship: Constructions of citizenship and identity in the British Citizenship Test

The British Citizenship Test was introduced in 2005 as one of a raft of new procedures aimed at addressing the perceived problems of integration and social cohesion in migrant communities. In this study, we argue that this new citizenship procedure signals a shift in British political discourse about citizenship - particularly, the institutionalization of a common British citizen identity that is intended to draw citizens together in a new form of political/national community. In line with this, we examine the British Citizenship Test from a social psychological perspective to interrogate the ways in which the test constitutes identity, constitutes citizenship, and constitutes citizenship-as-identity. Analysis of the test and its associated documents highlights three ways in which Britishness-as-identity is constituted, that is, as a collective identity, as a superordinate and national identity, and finally as both a destination and a journey. These findings are discussed in terms of their implications for models of citizenship and models of identity. © 2013 The British Psychological Society

Post-streptococcal glomerulonephritis is a strong risk factor for chronic kidney disease in later life

Although unusual in western countries and in Australia in general, post-streptococcal glomerulonephritis (PSGN) is still common in Australian Aboriginal children living in remote communities. Here, we evaluated whether episodes of acute PSGN increased the risk for chronic kidney disease in later life in 1519 residents of a remote Aboriginal community (85% of those age eligible), with high rates of renal and cardiovascular disease, who participated in a health screen over a 3-year period. Of these, 200 had had at least one episode of PSGN, with 27 having had multiple episodes, usually in childhood. High levels of albuminuria (albumin/creatinine ratio) with increasing age were confirmed. All PSGN episodes were associated with group A streptococcal skin infections, often related to scabies. In both genders, aged 10-39 years at screening, about one in five had such a history. Among them, PSGN (5 years or more earlier) was significantly associated with higher levels of albuminuria than those without. In women, aged 30-39 years, a history of PSGN was associated with a significantly higher frequency of estimated glomerular filtration rates < 60 ml/min. The adjusted odds ratios for an albumin/creatinine ratio over 34 g/mol (overt albuminuria) in males and females with a history of PSGN were 4.6 and 3.1, respectively, compared with those without a history. Thus, PSGN contributes to the very serious burden of chronic kidney disease in this community. Rigorous strategies to prevent scabies and Group A streptococcal infections will reduce this burden