Caracterización clínica y molecular de bacteriemias causadas por enterobacterias productoras de β -lactamasas de espectro extendido: 2004-2007 / Clinical and molecular characterization of ESBL-producing enterobacteria isolated from bacteremia in a university hospital

Introduction: Extended-spectrum-β-lactamases (ESBL) are plasmid-encoded enzymes that confer resistance to multiple antimicrobials. ESBL-producing enterobacteria that cause bacteremia limit therapeutic options and increase mortality. Objective: To perform a clinical and molecular description of bacteremia caused by ESBL-producing enterobacteria. Method: We retrospectively studied the cases of bacteremia due to ESBL-producing Escherichia coli, Klebsiella pneumoniae and Proteus spp in adults admitted to a university hospital during the years 2004-2007. We reviewed the clinical records and antimicrobial susceptibility patterns. Molecular typing was performed by polymerase chain reaction and study of clonality by pulsed-field electrophoresis. Results: We found a prevalence of 9.8 percent ESBL in enterobacteria causing bacteremia. Decreased susceptibility to quinolones and aminoglycosides was observed, without resistance to carbapenems. The predominant ESBL types were CTX-M (96 percent), TEM (62 percent) and GES (28 percent). 79 percent of the strains presented more than one type of ESBL. Clinical analysis revealed high prevalence of risk factors, previous use of antimicrobials and of invasive devices. There was no significant clonality. Conclusion: The presence of ESBLs in bloodstream infections is a clinical problem that must be considered when choosing empiric therapy.

Introducción: β-lactamasas de espectro extendido (BLEE) son enzimas plasmidiales que confieren resistencia a múltiples antimicrobianos. Las bacteriemias por enterobacterias productoras de BLEE restringen las opciones terapéuticas y aumentan la mortalidad. Objetivo: Realizar una descripción clínica y molecular de las bacteriemias causadas por enterobacterias productoras de BLEE. Método: Se estudiaron retrospectivamente los casos de bacteriemia por Escherichia coli, Klebsiella pneumoniae y Proteus spp. confirmadas para BLEE, en adultos ingresados en un hospital universitario durante los años 2004-2007. Se revisaron los registros clínicos y de susceptibilidad. Se realizó tipificación molecular por reacción de polimerasa en cadena y estudio de clonalidad por electroforesis de campo pulsado. Resultados: Se identificó una prevalencia de BLEE de 9,8 por ciento en enterobacterias causantes de bacteriemias. Se observó susceptibilidad disminuida a quinolonas y aminoglucósidos, sin resistencia a carbapenémicos. Los tipos de BLEE predominantes fueron CTX-M (96 por ciento), TEM (62 por ciento) y GES (28 por ciento). El 79 por ciento de las cepas presentó más de un tipo de BLEE. El análisis clínico reveló alta frecuencia de patologías de riesgo, uso previo de antimicrobianos y uso de dispositivos invasores. No se encontró clonalidad significativa. Conclusión: La presencia de BLEE en bacteriemias constituye un problema clínico que debe ser considerado al elegir la terapia empírica.

Preliminary report of NAD[+]-dependent amino acid dehydrogenase producing bacteria isolated from soil

Amino acid dehydrogenases [L-amino acid: oxidoreductase deaminating; EC 1.4.1.X] are members of the wider superfamily of oxidoreductases that catalyze the reversible oxidative deamination of an amino acid to its keto acid and ammonia with the concomitant reduction of either NAD[+], NADP[+] or FAD. These enzymes have been received much attention as biocatalysts for use in biosensors or diagnostic kits to screen amino acid metabolism disorders such as phenylketonuria [PKU], maple syrup urine disease [MSUD], homocystinuria [HCY] and hyperprolinemia. This study was aimed to isolation and screening of novel amino acid dehydrogenases from soil bacteria. The enzyme producing bacteria were selected among L-methionine and L-phenylalanine utilizers isolated from soil by thin layer chromatography, activity staining and confirmed by enzyme assay. Bacterial strains were identified by phenotypic and biochemical characteristics. The steady-state kinetic studies of enzymes were also performed. In total of 230 tested strains, four of them were recognized as amino acid dehydrogenase producers that belong to species of Pseudomonas, Citrobacter and Proteus. They exhibited the desired NAD[+]-dependent dehydrogenase activities toward L-isoleucine, L-methionine, L-cysteine, L-serine and L-glutamine in oxidative deamination reaction. The specific activity of L-isoleucine dehydrogenase, L-methionine dehydrogenase and L-glutamine dehydrogenase for oxidative deamination of L-isoleucine, L-methionine and L-glutamine were 1.59, 1.2 and 0.73 U/mg, respectively. The Kcat /Km [s-1.mM -1] values in these strains were as follows: L-isoleucine, 113.6, L-methionine, 62.05 and L-glutamine, 95.83. This is the first report of occurrence a specific isoleucine dehydrogenase, glutamine dehydrogenase and methionine dehydrogenase in bacteria