Evaluation of Phenotypic Variations in the Antibiotics Sensitivity of Escherichia Coli by Repeated Exposure

Enterobacteriaceae, in particular Escherichia coli, are habitual residents of the gastrointestinal tract, capable of causing a large number of infections. The MIC varies according to the bacterial strains and the antibiotics used, hence the need to carry out antibiotic sensitivity tests. The objective of this study is to evaluate the behavior of Escherichia coli after repeated exposure to the same antibiotic to demonstrate a possible correlation between excessive intake of antibiotics and bacterial resistance. A prospective and descriptive study was carried out in the Laboratory of Microbiology of Fundamental and Applied Biochemistry (Faculty of Sciences Antananarivo) during the month of November 2019. The strains studied were the reference strain Escherichia coli ATCC 25922 provided by the Laboratory and two clinical strains from the Microbiology Laboratory of the Joseph Ravoahangy Andrianavalona University Hospital Center (CHU JRA) Antananarivo. Repeated exposure to Tobramycin and Ofloxacin of these strains were performed. The results of our study showed that most E. coli is exposed to the antibiotic, the more it develops resistance. The evolution of E. coli\u27s sensitivity is different in the presence of Tobramycin with MICs up to 4 times the starting value while in the presence of Ofloxacin, the MIC increases to 125 times the initial value. This difference may be due to the different target of the antibiotic which causes the bacteria to develop variable mechanisms to escape it. Key words: E. coli - MIC - antibiotics - repeated exposur

Etude des levures endogènes de Evodia bilahe (Rutaceae) endémique de Madagascar

Evodia belahe, un arbre endémique de Madagascar, de la famille des Rutaceae, est utilisé à des fins diverses et son écorce est surtout utilisé pour servir de levain dans la fabrication de Betsabetsa (bière artisanale). Cette plante se rencontre surtout sur les deux versants (Est et Ouest) de la chaîne montagneuse de Marojejy. D’après la logique biotechnologique, elle pourrait donc renfermer de la levure fermentaire du genre Saccharomyces. Cette étude aurait pour objectif d’isoler, de purifier et d’identifier les levures sauvages contenues dans l’écorce d’Evodia belahe. Des méthodes classiques d’isolement microbien ont été entreprises, telles que l’isolement sur milieu YGC. Deux souches ont été retenues : une souche blanche et une souche rose. Après identification en se basant sur les caractères culturaux, morphologiques, physiologiques, biochimiques (galerie Api Candida) et génétiques, la souche blanche a été reconnue comme étant l’espèce Saccharomyces cerevisiae, levure responsable de la fermentation alcoolique, et la souche rose appartient à l’espèce Rhodotorula glutinis, qui participe à la formation de l’arome et du goût du produit alcoolisé. La souche blanche, contrairement à la souche rose, est fermentaire.© 2016 International Formulae Group. All rights reserved.Mots clés: Evodia belahe, Rutaceae endémique, Saccharomyces cerevisiae, Rhodotorula glutinis, MadagascarEnglish Title: A study of the endogeneous Evodia belahe (Rutaceae) yeast, endemic of MadagascarEnglish AbstractThis study aims to insulate, purify and detect wild yeast contained in the Evodia belahe bark, a Malagasy endemic tree belonging to the Rutaceae branch which can be used in various targets. Its bark is primarily utilized as leaven Betsabetsa (an artisanal beer) manufacturing. This plant can be found on both sides (Eastern and Western) of the Marojejy mountainous chain. Based on biotechnological logic, it is likely to contain Saccharomyces yeast. Classical germ isolating method, namely YGC isolating medium is carried out. As a result, two strains can be retained: the white and pink ones. According to cultural, morphological, physiological, biochemical (Analytical Profile Index : API Candida) and genetic analyses, the white strain  belongs to Saccharomyces cerevisiae species, whereas the pink strain is among Rhodotorula glutinis species, one that plays a major part in alcoholic drink flavor and taste. In contrast with the pink strain, the white one can be used in fermentation.© 2016 International Formulae Group. All rights reserved.Keywords: Evodia belahe, endemic Rutaceae, Saccharomyces cerevisiae, Rhodotorula glutinis, Madagasca

Evaluation of Phenotypic Variations in the Antibiotics Sensitivity of Escherichia Coli by Repeated Exposure

Enterobacteriaceae, in particular Escherichia coli, are habitual residents of the gastrointestinal tract, capable of causing a large number of infections. The MIC varies according to the bacterial strains and the antibiotics used, hence the need to carry out antibiotic sensitivity tests. The objective of this study is to evaluate the behavior of Escherichia coli after repeated exposure to the same antibiotic to demonstrate a possible correlation between excessive intake of antibiotics and bacterial resistance. A prospective and descriptive study was carried out in the Laboratory of Microbiology of Fundamental and Applied Biochemistry (Faculty of Sciences Antananarivo) during the month of November 2019. The strains studied were the reference strain Escherichia coli ATCC 25922 provided by the Laboratory and two clinical strains from the Microbiology Laboratory of the Joseph Ravoahangy Andrianavalona University Hospital Center (CHU JRA) Antananarivo. Repeated exposure to Tobramycin and Ofloxacin of these strains were performed. The results of our study showed that most E. coli is exposed to the antibiotic, the more it develops resistance. The evolution of E. coli's sensitivity is different in the presence of Tobramycin with MICs up to 4 times the starting value while in the presence of Ofloxacin, the MIC increases to 125 times the initial value. This difference may be due to the different target of the antibiotic which causes the bacteria to develop variable mechanisms to escape it. Key words: E. coli - MIC - antibiotics - repeated exposur

Valorisation de la biodiversité des levures dans la zone Océan indien (Réunion, Madagascar). Le cas du métabolisme des arômes chez la levure Saprochaete suaveolens, isolée du fruit du pitahaya

International audienceno abstrac

Improvement of the growth of Arthrospira (Spirulina) platensis from Toliara (Madagascar): Effect of agitation, salinity and CO2 addition

Arthrospira (Spirulina) platensis Toliara isolated from alkaline and salt lakes in the south-western area of Madagascar is a potential source of proteins that could efficiently fight against food deficiency in developing countries like Madagascar. Up to now, productivity in this country has been low, so a better understanding of the growth conditions of this species is needed to improve its production. Growth experiments were undertaken in bubble columns at laboratory scale. The influence of agitation of the culture, medium salinity (ranging from 13 to 35gL−1) and CO2 addition (ranging from 0 to 2%, v/v) on growth and protein content was examined. Because Arthrospira cells are fragile, a bubble column without additional mixing gave the best growth. Arthrospira (Spirulina) platensis showed higher specific growth rate (μmax) and protein content for lower salinity. Addition of 1% of CO2 improved the productivity by near 60%. The feasability of semi-continuous culture was demonstrated and optimal culture conditions led to a mean productivity of 0.22±0.03gL−1d−1, a mean specific growth rate of 0.015±0.002h−1 and a protein content of 53±2% of total dry weight

5-CQA and mangiferin, two leaf biomarkers of adaptation to full sun or shade conditions in Coffea arabica L.

Phenolic compounds are involved in plant response to environmental conditions and are highly present in leaves of Coffea arabica L., originally an understory shrub. To increase knowledge of C. arabica leaf phenolic compounds and their patterns in adaptation to light intensity, mature leaves of Ethiopian wild accessions, American pure lines and their relative F1 hybrids were sampled in full sun or under 50% shade field plots in Mexico and at two contrasting elevations in Nicaragua and Colombia. Twenty-one phenolic compounds were identified by LC-DAD-MS2 and sixteen were quantified by HPLC-DAD. Four of them appeared to be involved in C. arabica response to light intensity. They were consistently more accumulated in full sun, presenting a stable ratio of leaf content in the sun vs. shade for all the studied genotypes: 1.6 for 5-CQA, F-dihex and mangiferin and 2.8 for rutin. Moreover, 5-CQA and mangiferin contents, in full sun and shade, allowed for differentiating the two genetic groups of Ethiopian wild accessions (higher contents) vs. cultivated American pure lines. They appear, therefore, to be potential biomarkers of adaptation of C. arabica to light intensity for breeding programs. We hypothesize that low 5-CQA and mangiferin leaf contents should be searched for adaptation to full-sun cropping systems and high contents used for agroforestry systems

Optimisation de vaccin contre la colibacillose bovine

Two types of Escherichia coli, C1 and C2, used in the making of a vaccine against bovine colibacillosis in Madagascar, are studied. Bacteria were counted by the Malassez cell. The LD100 of the two strains are respectively 1.09×108 and 1.66×107 bacteria/ml. They were inactivated by 5‰ formalin to produce the respective antigens at a titer of 2×109 bacteria/ml. The antigens thus obtained are added with adjuvant based on potassium alum to obtain vaccine prototypes P1 and P2. Each vaccine prototype was injected subcutaneously into batches of mice followed by a booster after 15 days of the first dose. The batches of vaccinated mice are tested after 15 days of the booster dose and each receive the LD100 of the strain. During the 10 days observation time, mice vaccinated with P1 are protected against C1 and those receiving P2 are protected against C2. On the other hand, P1 does not protect mice against C2 and P2 does not protect them against C1. The duration of protection is 12 months. The 2 prototypes maintain their effectiveness for 6 months of storage at 4°C. Keywords: Escherichia coli, vaccine, bovine colibacillosisDeux types d’Escherichia coli, C1 et C2, entrés dans la confection d’un vaccin contre la colibacillose bovine à Madagascar, sont étudiés. Le comptage des bactéries s’est fait par la cellule de Malassez. Les DL100 des deux souches sont respectivement de 1,09 108 et 1,66 107 bactéries/ml. Elles sont inactivées par le formol à 5‰ pour fabriquer les antigènes respectifs à un titre de 2 109 bactéries/ml. Les antigènes ainsi obtenus sont additionnés d’adjuvant à base d’alun de potassium pour avoir les prototypes de vaccin P1 et P2. Chaque prototype de vaccin a été injecté par voie sous-cutanée à des lots de souris, suivi d’un rappel après 15 jours de la première dose. Les lots de souris vaccinés sont mis à l’épreuve après 15 jours de la dose de rappel et reçoivent chacun la DL100 de la souche. Pendant le temps d’observation de 10 jours, les souris vaccinées avec P1 sont protégées contre C1 et celles recevant P2 sont protégées contre C2. Par contre, P1 ne protège pas les souris contre C2  et P2  ne les protège pas contre C1. La durée de protection est de 12 mois. Les 2 prototypes de vaccin ont gardé leur efficacité durant 6 mois de conservation à 4°C. Mots clés: Escherichia coli, vaccin, colibacillose bovin