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

Natural Compounds Inhibiting <em>Pseudomonas aeruginosa</em> Biofilm Formation by Targeting Quorum Sensing Circuitry

The biofilm lifestyle mode certainly represents one of the most successful behaviors to facilitate bacterial survival in diverse inhospitable environments. Conversely, the ability of bacteria to develop effective biofilms represents one of the major obstacles in the fight against bacterial infections. In Pseudomonas aeruginosa, the biofilm formation is intimately connected to the quorum sensing (QS) mechanisms, a mode of cell-to-cell communication that allows many bacteria to detect their population density in order to coordinate common actions. In this chapter, we propose an overview (i) on P. aeruginosa QS mechanisms and their implication in biofilm formation, and (ii) on natural products that are known to interfere with these QS mechanisms, subsequently disrupting biofilm formation. The concluding remarks focus on perspectives of these compounds as possible antibiotherapy adjuvants

A STUDY ON RECTAL CARRIAGE OF MULTIRESISTANT GRAM-NEGATIVE BACILLI IN CHILDREN ATTENDING PEDIATRIC HOSPITAL AMBOHIMIANDRA, MADAGASCAR

Introduction:&nbsp;Gram-negative bacilli are often responsible for rectal colonization in children. These bacilli normally sensitive to third generation cephalosporins (3GC) have acquired disturbing antibiotic resistance in recent years, hence the interest of our study. The aims are to monitor the epidemiological evolution resistance of Enterobacteriaceae with antibiotics in particular β-lactams, estimate the prevalence of enterobacteria responsible for rectal colonization and their resistance to 3GC.&nbsp;Material and methods: This is a descriptive prospective study of&nbsp;Enterobacteriaceae&nbsp;in children attending Ambohimiandra Hospital for a period of 3 months (from 01 August to 31 October 2015). We have done a rectal swab of all the children whom we have parental consent. The samples were processed at the Laboratory of Medical Biology Faravohitra. The parameters studied are the antecedent of therapy antibiotic, notion of recent hospitalization and the results of microbiological examinations.&nbsp;Results:&nbsp;Of the 55 bacteriological samples obtained, 39 strains of&nbsp;Enterobacteriaceae&nbsp;were isolated,&nbsp;Escherichia coli&nbsp;(n = 12),&nbsp;Enterobacter cloacae&nbsp;(n = 13),&nbsp;Citrobacter spp&nbsp;(n = 1),&nbsp;Salmonella spp.&nbsp;(N = 5) and&nbsp;Shigella spp&nbsp;(n = 2),&nbsp;Proteus mirabilis&nbsp;(n = 1). Six isolated strains (50%) of&nbsp;Escherichia coli&nbsp;showed resistance to ceftriaxone, of which 4 (33.33%) produced ESBL.&nbsp;Conclusion: Gram-negative bacilli responsible for colonization of the digestive tract have several resistances to β-lactams, in particular 3GC, by the production of enzymes (Expanded spectrum beta-lactamase or ESBL and cephalosporinase or CASE) which hydrolyze these antibiotics. Measures to combat the spread of these phenomena resistance must be implemented in the Malagasy community to limit them. KEYWORDS:&nbsp;Rectal porous; Gram negative bacillus; ESBL; Multiresistence

SEROPREVALENCE OF HIV, HBV, HCV, SYPHILIS AMONG DONORS OF BLOOD AT THE NATIONAL CENTER OF BLOOD TRANSFUSION ANTANANARIVO IN 2014

Introduction: Currently, routine screening for HIV, hepatitis B and C and syphilis is done in most blood banks in the world.&nbsp;Methods: We conducted a prospective descriptive study at the National Blood Transfusion Center (CNTS) Antananarivo for a period of 7 months from January to July 2014, which aims to assess the socio-clinical factors accompanying ineligibility of blood products and to determine the seroprevalence of HIV, hepatitis B, C and syphilis of the blood donors who have spent at CNTS HU JRA Antananarivo during this period. All donors who have abnormal results of microbiological examinations were included. The parameters used and studied were age, sex, marital status, blood and results microbiological examinations for HIV, hepatitis B, C, and syphilis. The prevalence of blood donors who presented a serological abnormality is 3.95% with a predominance of donors with hepatitis B (72.93%) followed by syphilis (18.29%) of the hepatitis C (6.95%) and HIV (1.80%) and a predominance of young people.&nbsp;Conclusion:&nbsp;At the CNTS Antananarivo, the HBV is the main definitive reason for exclusion of these donors. This high prevalence is a real public health problem for the country\u27s health authorities. The search for maximum safety in blood transfusion through firstly a better selection of blood donors by implementing a policy of strong loyalty and other early diagnosis of major diseases transmissible by blood and likely to infect the recipient. KEYWORDS:&nbsp;Antananarivo; Blood donor; Microbiology; Seroprevalence

SEROPREVALENCE OF HIV, HBV, HCV, SYPHILIS AMONG DONORS OF BLOOD AT THE NATIONAL CENTER OF BLOOD TRANSFUSION ANTANANARIVO IN 2014

Introduction: Currently, routine screening for HIV, hepatitis B and C and syphilis is done in most blood banks in the world.&nbsp;Methods: We conducted a prospective descriptive study at the National Blood Transfusion Center (CNTS) Antananarivo for a period of 7 months from January to July 2014, which aims to assess the socio-clinical factors accompanying ineligibility of blood products and to determine the seroprevalence of HIV, hepatitis B, C and syphilis of the blood donors who have spent at CNTS HU JRA Antananarivo during this period. All donors who have abnormal results of microbiological examinations were included. The parameters used and studied were age, sex, marital status, blood and results microbiological examinations for HIV, hepatitis B, C, and syphilis. The prevalence of blood donors who presented a serological abnormality is 3.95% with a predominance of donors with hepatitis B (72.93%) followed by syphilis (18.29%) of the hepatitis C (6.95%) and HIV (1.80%) and a predominance of young people.&nbsp;Conclusion:&nbsp;At the CNTS Antananarivo, the HBV is the main definitive reason for exclusion of these donors. This high prevalence is a real public health problem for the country's health authorities. The search for maximum safety in blood transfusion through firstly a better selection of blood donors by implementing a policy of strong loyalty and other early diagnosis of major diseases transmissible by blood and likely to infect the recipient. KEYWORDS:&nbsp;Antananarivo; Blood donor; Microbiology; Seroprevalence

Malagasy traditional treatments of infectious plant diseases exert anti-virulence activities against pseudomonas aeruginosa and Ralstonia solanacearum

peer reviewedTraditional Malagasy farmers have developed a range of biological methods to restrict plant diseases without reliance on external or synthetic inputs. Five common Malagasy traditional practices demonstrated to be efficient against potato crop bacterial disease in experimental fields have been investigated for their antibacterial (i.e. bacteriostatic and bactericidal effects) and anti-virulence (i.e. antiquorum sensing and anti-biofilm) activities against two phytopathogens, Pseudomonas aeruginosa and Ralstonia solanacearum. Results show that polar (methanolic) extracts of recipes exert anti-virulence activities rather than bacteriostatic and/or bactericidal activities. Indeed, three recipes (R5, R7 and R9) reduce the expression of QS-dependent virulence factors whereas only recipe (R5) exhibit antibiofilm activities without affecting bacterial growth. R4 and R6 were not active, suggesting other bacterial targets and/or other bioactivity properties. Innovative approaches, inspired from ancestral practices, should be considered in the struggle against infectious diseases to limit the overuse of antibiotics for controlling infectious plant diseases and to reduce the overspread of multidrug resistant bacteria

Dalbergia trichocarpa, source of natural compounds which affect quorum sensing mechanism and biofilm formation in Pseudomonas aeruginosa

Depuis quelques décennies, les bactéries pathogènes multi-résistantes aux antibiotiques sont de plus en plus répandues dans le monde. Cette situation a suscité le besoin et l'intérêt de trouver des médicaments antibactériens avec de nouvelles cibles potentiels. La découverte des systèmes de communication de type quorum sensing (QS) régulant la virulence bactérienne représente une des cibles privilégiées pour contrôler les bactéries pathogènes autrement qu’en interférant avec leur croissance bactérienne. Dans l’écosystème naturel, un grand nombre d'organismes (Eucaryotes et Procaryotes) co-existent en synthétisant chacun de leur côté des métabolites secondaires. Les plantes, étant en permanence en contact avec des bactéries, synthétisent des métabolites secondaires capables d’inhiber l’expression des gènes de virulence chez les bactéries sans pour autant affecter ni leur croissance ni leur viabilité. Notre objectif a été de contribuer à la valorisation de la biodiversité malgache en identifiant des plantes et en y isolant les composés actifs présentant une capacité à perturber le mécanisme de QS chez P. aeruginosa PAO1, une bactérie pathogène opportuniste de l’homme, des animaux et des plantes. Dans ce but, nous avons tout d’abord réalisé un criblage d’activité anti-QS de différents flavonoïdes commerciaux. De ce criblage, la narigenine et la naringine ont été sélectionnées pour être les molécules de contrôle positif et négatif des tests d’activité anti-QS, respectivement. Par la suite, 4 espèces de Dalbergia endémique de Madagascar ont fait l’objet de criblage pour leur activité anti-QS. Ce travail a fait ressortir l’activité anti-QS très intéressante de l’écorce de D. trichocarpa à partir de laquelle nous avons isolée le composé actif nommé la coumarate de l’aldéhyde-oléanolique (OALC). Le contrôle naringénine et l’OALC ne présente aucun effets inhibiteurs sur la croissance bactérienne de P. aeruginosa PAO1 et sur l’expression du gène QS-indépendant aceA suggérant une activité d’inhibition spécifiquement liée au QS. Cependant, ces deux molécules présentent des spectres d’inhibition différente. En effet, les deux molécules diffèrent dans le sens que la naringenine n’inhibe pas l’expression du gène gacA et la motilité de type twitching contrairement à l’OALC. Ces résultats suggèrent que l’OALC et la naringénine représente des candidats potentiels pour des investigations in vivo quant à leur effet anti-QS et anti-biofilm sur des modèles infectieux d’organismes supérieurs. Par ailleurs, ils démontrent la richesse des plantes malgaches comme sources de nouvelles molécules anti-virulence ainsi que l’importance de telle investigation afin de renforcer notre arsenal thérapeutique en composé antibactérienne dans la lutte continuelle contre les bactéries pathogènes/Since few decades, multidrug resistant bacteria spread all over the world. This situation gives rise to the need and interest in finding antibacterial drugs with novel potent target. Discovery of communication system termed Quorum Sensing (QS) which regulate bacterial virulence factor represent privileged target in another way than interfering with bacterial growth. In natural ecosystem, many organisms (Eukaryotes and Prokaryotes) produce secondary metabolites. As plants are permanently in contact with bacteria, they have synthetized secondary metabolites which inhibit bacterial virulence gene expression without affecting bacterial viability. Our goal was to contribute to the valorization of Malagasy biodiversity and specifically to identify plants and isolate bioactive compound presenting ability to disrupt QS mechanism in P. aeruginosa, opportunistic pathogen bacteria in plants, animals and human. In this purpose, screening of commercial available flavonoids has been firstly carried out. From this screening, naringenin and naringin have been selected to be used as positive and negative QS inhibitor controls, respectively. Subsequently, Four Malagasy endemic Dalbergia species have been screened for their anti-QS activity. This work pointed out the interesting anti-QS activity of D. trichocarpa bark extract which led to the isolation of oleanolic aldehyde coumarate (OALC) as one major bioactive compound. At the concentration tested, naringenin and OALC did not affect P. aeruginosa PAO1 viability and didn’t reduce QS-independent aceA gene expression suggesting a specific anti-QS activity. However, these two compounds present different inhibition spectrum. Indeed, naringenin didn’t inhibit gacA gene expression and twitching motility contrarily to OALC. These results suggest that OALC and naringenin represent potent candidates for in vivo investigations in their anti-QS and anti-biofilm activity onto eukaryotes infectious model. Besides, this finding demonstrated the potent source for novel anti-virulence compounds of Malagasy flora and the importance of this kind of research to strengthen our antimicrobial therapeutic arsenal with the ongoing struggle against bacterial infection.Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Quorum-Sensing Mechanisms and Bacterial Response to Antibiotics in P. aeruginosa

Emergence and worldwide spreading of resistant bacteria to antibiotic have raised the importance for finding therapeutic alternative to compensate antibiotic drawbacks. Quorum sensing (QS) is a cell-to-cell communication involved in the development of various common bacterial behaviors including virulence factors expression, and targeting QS seems to be relevant to the struggle against bacterial infection. In this report, relevant literature on intrication of QS system and antimicrobial sensitivity mechanisms in P. aeruginosa PAO1 are reviewed.SCOPUS: re.jinfo:eu-repo/semantics/publishe