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 It was molded after the unpublished work of Belding concerning the effect of tyrothricin on the Oxford Strain of Staphylococcus aureus in saliva.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

Biological Control of Weeds: Theory and Practical Application

Crop Production/Industries,

Non-invasive genetic monitoring for the threatened valley elderberry longhorn beetle.

The valley elderberry longhorn beetle (VELB), Desmocerus californicus dimorphus (Coleoptera: Cerambycidae), is a federally threatened subspecies endemic to the Central Valley of California. The VELB range partially overlaps with that of its morphologically similar sister taxon, the California elderberry longhorn beetle (CELB), Desmocerus californicus californicus (Coleoptera: Cerambycidae). Current surveying methods are limited to visual identification of larval exit holes in the VELB/CELB host plant, elderberry (Sambucus spp.), into which larvae bore and excavate feeding galleries. Unbiased genetic approaches could provide a much-needed complementary approach that has more precision than relying on visual inspection of exit holes. In this study we developed a DNA sequencing-based method for indirect detection of VELB/CELB from frass (insect fecal matter), which can be easily and non-invasively collected from exit holes. Frass samples were collected from 37 locations and the 12S and 16S mitochondrial genes were partially sequenced using nested PCR amplification. Three frass-derived sequences showed 100% sequence identity to VELB/CELB barcode references from museum specimens sequenced for this study. Database queries of frass-derived sequences also revealed high similarity to common occupants of old VELB feeding galleries, including earwigs, flies, and other beetles. Overall, this non-invasive approach is a first step towards a genetic assay that could augment existing VELB monitoring and accurately discriminate between VELB, CELB, and other insects. Furthermore, a phylogenetic analysis of 12S and 16S data from museum specimens revealed evidence for the existence of a previously unrecognized, genetically distinct CELB subpopulation in southern California

Working with Mycorrhizas in Forestry and Agriculture

Crop Production/Industries,

Integration of drone data and field investigations to investigate avalanche potential in steep cliffs, with examples from Western Norway

Masteroppgave i geovitenskapGEOV399MAMN-GEO

Bivalve mollusc culture research in Thailand

An account of research, which explored new biological and socioeconomic perspectives on bivalve mollusc culture to increase production and to improve the livelihood of farmers. It presents a review of the pathways in which aquatic macrophytes may be involved in the food production process, directly as human food, as livestock fodder, as fertilizer (mulch and manure, ash, green manure, compost, biogas slurry), and as food for aquatic herbivores, such as fish, turtles, rodents and manatees. Suggests research areas.Mollusc culture, Research programmes, ICLARM publications, Thailand, Bivalvia

Measuring food security using household expenditure surveys:

Food is one of the most basic needs for human survival. Access to it is a basic human right. Moreover, the pursuit of the Millennium Development Goal to cut hunger requires a sound understanding of the related food security issues. For these reasons, accurate measurement of the food security status of populations—or their ability to gain access to sufficient high-quality food to enable them to live an active, healthy life—is imperative to all international development efforts. It is necessary for effectively targeting food-insecure populations, researching and planning appropriate interventions, and monitoring progress. As past efforts have shown, accurately estimating the amount of food people eat is costly in terms of time and money, and such measurements have thus been carried out mostly in small populations. Where measurement has been extended to large populations, such as entire countries, it has been necessary to rely on less accurate, indirect techniques based on the availability of food at the national level. This technical guide presents a new avenue for measuring food security, for both small and large populations, based on the data collected as part of household expenditure surveys on the quantities of food acquired by households. It shows how these data can be used to measure a variety of food security indicators, including the prevalence of food energy deficiency and indicators of dietary quality and economic vulnerability to food insecurity. In keeping with the approach of IFPRI's Food Security in Practice series for practitioners, the manual guides readers step by step through the process of assessing the food security status of a population. It begins by offering guidance on choosing an appropriate strategy for calculating quantities of foods acquired by households, given time constraints, financial constraints, and the nature of the population's diet. The guide then leads the practitioner through the steps of collecting the data, processing and cleaning the data, and calculating the indicators. It concludes by illustrating how to conduct some basic food security analyses. I hope that this guide will assist practitioners in increasing the accuracy of the measurement of food insecurity for a greater number of populations, including those at the country level. Greater accuracy at the country level will provide the necessary foundations for overcoming food insecurity globallyFood supply, food consumption, Diet, Household surveys,