No description available.

No description available.

The present study was on the isolation of a bacterium capable of producing filtrable forms which passed through the 0.45µ filter membrane and regenerated the parental form; the testing of the true filtrability of the isolate; the relationship between growth of the isolate and appearance of filtrability; partial characterization of the isolate and visualization of the elements that passed through the membrane filter with electron microscopy and shadow casting technique.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 89-100). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references (leaves 89-100). Also available on the Internet.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1948. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

No description available.

A unique undescribed gram-negative rod is extensively characterized in this study. The cells of this unusual water isolate measure 1.2 x 6.5 microns. The most distinguishing characteristic of the bacterium is a polar tuft of 35-40 flagella that aggregate to function as a single organelle which is visible under phase contrast.

L'indice de réfraction est l'un des paramètres physiques les plus importants qui régissent les comportements à la lumière de cellules et d'autres micro-organismes. Son importance réside dans le fait qu'il peut être utilisé pour déterminer ou mettre en corrélation avec d'autres paramètres biophysiques importants de la cellule tels que la masse sèche, la masse humide, l'élasticité et est utilisé pour étudier les activités dynamiques cellulaires. L'objectif principal de cette recherche est d'étudier et de mesurer les indices de réfraction de bactérie et de cellules unitaires ainsi que leur réponse à des stimulations micro-environnementales.Notre étude expérimentale comprend deux approches. La première consiste en une plate-forme microfluidique intégrée de réfractomètrie par immersion pour mesurer les paramètres biophysiques (taille, forme et indice de réfraction) de trois espèces de bactéries, à savoir Escherichia coli, Shigella flexneri et Vibrio cholerae. Ces paramètres peuvent fournir des signatures biophysiques des bactéries ciblées. L'importance de ce travail de recherche réside dans l'établissement d'un système rapide, sans label fluorescent et à bas coût pour la détection d'une quantité infime de bactéries nocives dans l'eau potable.L'autre approche consiste à obtenir la distribution de l'indice de réfraction au sein d'une seule cellule avec l'accent mis sur l'étude des gouttelettes lipidiques intracellulaires ainsi que leur réponse à une stimulation micro-environnementale. A cet effet, nous avons recouru à un système de diffraction tomographique optique intégré avec imagerie par fluorescence. Ce type d'étude sur l'indice de réfraction de gouttelettes lipidiques cellulaires initie une nouvelle approche pour une meilleure compréhension des gouttelettes lipidiques et leurs rôles essentiels dans le métabolisme cellulaire / Refractive index is one of the most important physical parameters in governing the light-reaction behaviors of cells and other microorganisms. Its significance lies in the fact that it can be used to determine or correlate with other important biophysical parameters such as dry mass, wet mass, elasticity and used to study dynamic cell activities. The main objective of this research is to study and measure refractive indices of single bacterium and cell as well as cell’s response to microenvironment stimulations.The experimental study includes two approaches. One approach is the development of an integrated microfluidic immersion refractometer platform to measure the biophysical parameters (the size, shape and refractive index) of three bacteria species, namely Echerichia coli, Shigella flexneri and Vibrio cholera. These parameters could provide biophysical signatures of the targeted bacteria. The significance of this research work lies in establishing a rapid, label-free and low-cost system for detection of minute amount of harmful waterborne bacteria in drinking water.The other experimental approach is to obtain the refractive index distribution of a single cell with the focus on studying the intracellular lipid droplets and their response towards microenvironmental stimulation using an optical diffraction tomographic system integrated with fluorescence imaging. The investigation of the refractive index of cellular lipid droplets initiates a novel approach for deeper understanding of the lipid droplets and their critical roles in metabolism

Carbapenem-resistant Acinetobacter baumannii is the top-ranked pathogen in the World Health Organization priority list of antibiotic-resistant bacteria. It emerged as a global pathogen due to the successful expansion of a few epidemic lineages, or international clones (ICs), producing acquired class D carbapenemases (OXA-type). During the past decade, however, reports regarding IC-I isolates in Latin America are scarce and are non-existent for IC-II and IC-III isolates. This study evaluates the molecular mechanisms of carbapenem resistance and the epidemiology of 80 non-duplicate clinical samples of A. baumannii collected from February 2014 through April 2016 at two tertiary care hospitals in Lima. Almost all isolates were carbapenem-resistant (97.5%), and susceptibility only remained high for colistin (95%). Pulsed-field gel electrophoresis showed two main clusters spread between both hospitals: cluster D containing 51 isolates (63.8%) associated with sequence type 2 (ST2) and carrying OXA-72, and cluster F containing 13 isolates (16.3%) associated with ST79 and also carrying OXA-72. ST2 and ST79 were endemic in at least one of the hospitals. ST1 and ST3 OXA-23-producing isolates were also identified. They accounted for sporadic hospital isolates. Interestingly, two isolates carried the novel OXA-253 variant of OXA-143 together with an upstream novel insertion sequence (ISAba47). While the predominant A. baumannii lineages in Latin America are linked to ST79, ST25, ST15, and ST1 producing OXA-23 enzymes, we report the emergence of highly resistant ST2 (IC-II) isolates in Peru producing OXA-72 and the first identification of ST3 isolates (IC-III) in Latin America, both considered a serious threat to public health worldwide. / This study was supported by Cienciactiva of CONCYTEC, contract no. 164-2016-FONDECYT; Planes Nacionales de I+D+i 2008-2011/2013-2016, Instituto de Salud Carlos III, Subdirección General de Redes y Centros de Investigación Cooperativa, Ministerio de Economía y Competitividad, Spanish Network for Research in Infectious Diseases (REIPI RD12/0015/0013 and REIPI RD16/0016/ 0010); the 2017 call for Strategic Action on Health (PI17/01932), co-financed by European Development Regional Fund “A way to achieve Europe” and operative program Intelligent Growth 2014-2020; and grant 2014 SGR 0653 from the Departament d’Universitats, Recerca i Societat de la Informació, of the Generalitat de Catalunya. I.R. was supported by the Department of Health, Generalitat de Catalunya, grant SLT002/16/00349. Part of these data have been presented as a poster communication at the 18th International Congress on Infectious Diseases, 3–4 March, 2018, Buenos Aires, Argentina, and at the XXVIII-European Congress of Clinical Microbiology and Infectious Diseases (ECCMID), Madrid (Spain), 21–24 April, 2018 / Revisión por pares