Dipstick for Rapid Diagnosis of Shigella flexneri 2a in Stool

BACKGROUND: Shigellosis or bacillary dysentery, an acute bloody diarrhoea, is a major public health burden in developing countries. In the absence of prompt and appropriate treatment, the infection is often fatal, particularly in young malnourished children. Here, we describe a new diagnostic test for rapid detection, in stool, at the bedside of patients, of Shigella flexneri 2a, the most predominant agent of the endemic form of the disease. METHODOLOGY/PRINCIPAL FINDINGS: The test is based on the detection of S.flexneri 2a lipopolysaccharide (LPS) using serotype 2a-specific monoclonal antibodies coupled to gold particles and displayed on one-step immunochromatographic dipstick. A concentration as low as 20 ng/ml of LPS is detected in distilled water and in reconstituted stools in under 15 minutes. The threshold of detection corresponds to a concentration of 5×10(7) CFU/ml of S. flexneri 2a, which provides an unequivocal positive reaction in three minutes in distilled water and reconstituted stools. The specificity is 100% when tested with a battery of Shigella and unrelated strains, in culture. When tested in Vietnam, on clinical samples, the specificity and sensitivity were 99.2 and 91.5%, respectively. A decrease of the sensitivity during the evaluation on stool samples was observed after five weeks at room temperature and was due to moistening of the dipsticks caused by the humidity of the air during the fifth week of the evaluation. This drawback is now overcome by improving the packaging and providing dipsticks individually wrapped in waterproof bags. CONCLUSION: This simple dipstick-bases test represents a powerful tool for case management and epidemiological surveys

Dipstick Test for Rapid Diagnosis of Shigella dysenteriae 1 in Bacterial Cultures and Its Potential Use on Stool Samples

International audienceBACKGROUND: We describe a test for rapid detection of S. dysenteriae 1 in bacterial cultures and in stools, at the bedside of patients. METHODOLOGY/PRINCIPAL FINDINGS: The test is based on the detection of S. dysenteriae 1 lipopolysaccharide (LPS) using serotype 1-specific monoclonal antibodies coupled to gold particles and displayed on a one-step immunochromatographic dipstick. A concentration as low as 15 ng/ml of LPS was detected in distilled water and in reconstituted stools in 10 minutes. In distilled water and in reconstituted stools, an unequivocal positive reaction was obtained with 1.6×10⁶ CFU/ml and 4.9×10⁶ CFU/ml of S. dysenteriae 1, respectively. Optimal conditions to read the test have been determined to limit the risk of ambiguous results due to appearance of a faint yellow test band in some negative samples. The specificity was 100% when tested with a battery of Shigella and unrelated strains in culture. When tested on 328 clinical samples in India, Vietnam, Senegal and France by laboratory technicians and in Democratic Republic of Congo by a field technician, the specificity (312/316) was 98.7% (95% CI:96.6-99.6%) and the sensitivity (11/12) was 91.7% (95% CI:59.8-99.6%). Stool cultures and the immunochromatographic test showed concordant results in 98.4 % of cases (323/328) in comparative studies. Positive and negative predictive values were 73.3% (95% CI:44.8-91.1%) and 99.7% (95% CI:98-100%). CONCLUSION: The initial findings presented here for a simple dipstick-based test to diagnose S. dysenteriae 1 demonstrates its promising potential to become a powerful tool for case management and epidemiological surveys

The physiological role of myoglobin: More than a problem in reaction-diffusion kinetics

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24916/1/0000343.pd

Estudio del rendimiento de sistemas de gestión de bases de datos New SQL

nuevas tecnologías diseñadas para este entorno. A pesar de las grandes ventajas que poseen estos sistemas, han dejado de lado funcionalidades como las transacciones o el lenguaje SQL. El presente trabajo se centra en el estudio de rendimiento de dos nuevos sistemas adaptados a los requerimientos actuales que pretenden ofrecer las funcionalidades de los sistemas tradicionales, como las transacciones y el lenguaje SQL por su facilidad y popularidad. Las pruebas realizadas miden el rendimiento de ambos sistemas en situaciones con distintos tipos de operaciones, algunas con alta carga de escritura y otras con alta de lectura. Asimismo, se ha variado el tamaño de la base de datos para observar la escalabilidad de ambos sistemas. Por último, en base a los datos obtenidos se puede concluir que ambos sistemas ofrecen una capa de compatibilidad completa con el lenguaje SQL y un rendimiento similar en situaciones con alta carga de datos. Sin embargo, el comportamiento entre ambos sistemas es muy diferente, ya que Apache Phoenix necesita más tiempo en operaciones de lectura mientras que Splice Machine lo emplea en operaciones de escritura.---ABSTRACT---The volume of new data generated in last years has forced the development of new systems adapted to this new environment. Although the new developed systems has caracteristics adapted to the current requirements, functionalities like transactions or SQL language are not available for this systems. The current study is focused on the performance of two recently-developed systems, Apache Phoenix and Splice Machine, which tries to offer the best of both worlds: escalabilty and performance of new systems, but integrity of data and easy of use with SQL. The developed benchmark is designed to measure the performance of these systems on situations with heavy read load or with heavy write load. In addition, several database sizes are used to check the behavior of the systems. Finally, based on the results we can conclude that both systems offer the same throughput when the database is big enough but the behavoir of each system is different. Apache Phoenix needs more time to do read operations while Splice Machine uses more time on write operations