Photochemical degradation of the carbapenem antibiotics imipenem and meropenem in aqueous solutions under solar radiation.

This paper deals with the photochemical fate of two representative carbapenem antibiotics, namely imipenem and meropenem, in aqueous solutions under solar radiation. The analytical method employed for the determination of the target compounds in various aqueous matrices, such as ultrapure water, municipal wastewater treatment plant effluents, and river water, at environmentally relevant concentrations, was liquid chromatography coupled with hybrid triple quadrupole-linear ion trap-mass spectrometry. The absorption spectra of both compounds were measured in aqueous solutions at pH values from 6 to 8, and both compounds showed a rather strong absorption band centered at about 300 nm, while their molar absorption coefficient was in the order from 9 × 103-104 L mol-1 cm-1. The kinetics of the photochemical degradation of the target compounds was studied in aqueous solutions under natural solar radiation in a solar reactor with compound parabolic collectors. It was found that the photochemical degradation of both compounds at environmentally relevant concentrations follows first order kinetics and the quantum yield was in the order of 10-3 mol einsten-1. Several parameters were studied, such as solution pH, the presence of nitrate ions and humic acids, and the effect of water matrix. In all cases, it was found that the presence of various organic and inorganic constituents in the aqueous matrices do not contribute significantly, either positively or negatively, to the photochemical degradation of both compounds under natural solar radiation. In a final set of photolysis experiments, the effect of the level of irradiance was studied under simulated solar radiation and it was found that the quantum yield for the direct photodegradation of both compounds remained practically constant by changing the incident solar irradiance from 28 to 50 W m-2.

Diseminación de enterobacterias productoras de carbapenemasas tipo KCP en Venezuela / Spread of carbapenemase-producing Enterobacteriaceae type KCP in Venezuela

La resistencia a carbapenems en la familia Enterobacteriaceae constituye un problema creciente a nivel mundial, siendo el mecanismo de mayor impacto clínico, epidemiológico y microbiológico, la producción de serino-carbapenemasas KPC. Investigar la presencia de carbapenemasas tipo KPC en aislados de Enterobacterias resistentes a carbapenems, provenientes de diversos centros de salud a nivel nacional, durante el período mayo 2010 - junio 2011. En esta investigación se analizaron 91 aislados de Enterobacterias: K pneumoniae (48), E. cloacae (30), E. aerogenes (4), E. coli (2), C. koseri (1), C. freundil (6), con resistencia a carbapenems provenientes de 14 centros de salud. La susceptibilidad antimicrobiana se evaluó siguiendo los criterios de la CLSI 2011. La detección fenotípica de carbapenemasas se realizó mediante el test de Hodge modificado y evaluando la sinergia con el ácido 3-aminofenilborónico 300 µg/disco. Se realizó el Test de Hodge "doble modificado" a los aislados de Enterobacter y Citrobacter. La detección genotípica de carbapenemasas se llevó a cabo mediante PCR utilizando iniciadores para el gen blaKPC. Todos los aislados presentaron a los deinhibición < 22 mm para meropenem y ertapenem. El 95% de los aislados resultaron positivos para el test de Hogde modificado, el test con ácido borónico, y para el gen blaKPC. En el test de Hodge "doble modificado", se observó 100% de positividad. La resistencia a carbapenems mediada por Carbapenemasas KPC, se ha incrementado en los últimos años en el país y el carácter plasmídico de estas enzimas les permite su fácil diseminación entre diversos géneros de Enterobacterias.

Resistance to carbapenems is the family Enterobacteriaceae is a growing problem around the world, being production of KPC serino-carbapenemase, the mayor impact clinical, epidemiological and microbiological mechanism. To investigate the presence of KPC carbapenemases in isolates of Enterobacterias resistant to carbapenems, from various health centers nationwide, during the period May-2010 June 2011. In this study were analyzed 91 Enterobacterias isolates: K. pneumoniae (48), E. cloacae (30), E. aerogenes (4), E. coli (2), C. koseri (1), C. freundii (6), with resistance to carbapenems from 14 health centers. Antimicrobial susceptibility was evaluated according to the criteria of the CLSI 2011. Phenotypic detection of carbapenemases was performed by Modified Hodge Test and it was evaluated the synergy with the 3-aminophenylboronic 300 µg/disc. Test were done with "double Modified" Hodge to Enterobacter and Citrobacter isolates. Genotypic detection of carbapenemases was performed out by using PCR primers for the gene blaKPC. All isolated showed inhibition zones <22 mm for meropenem and ertapemen. The 95% of the isolates were positive for Hogde Modified Test, test with boronic acid, and to blaKPC gene. By performing "Double Modified" Hodge`s essay , we observed a 100% of positivity. Resistance to carbapenems mediated by KPC carbapenemases has increased in the last few years in the country, and plasmidic characterization of these enzymes allows easily dissemination among different genera of Enterobacteriaceae.