Prevalencia en España de mecanismos de resistencia a quinolonas en enterobacterias productoras de betalactamasas de clase C adquiridas y/o carbapenemasas / Prevalence of quinolone resistance mechanisms in Enterobacteriaceae producing acquired AmpC Beta-lactamases and/or carbapenemases in Spain

Introducción: En los últimos años se ha observado un incremento de la resistencia a fluoroquinolonas en enterobacterias, estando asociado significativamente a la resistencia a betalactámicos. Nuestro objetivo fue conocer la prevalencia de mecanismos cromosómicos y plasmídicos de resistencia a quinolonas en aislados productores de betalactamasas de claseC adquiridas y/o carbapenemasas. Métodos: Se evaluó la presencia de mecanismos cromosómicos y plasmídicos de resistencia a quinolonas [mutaciones en la región determinante de resistencia a quinolonas de gyrA y parCy genes qnr, aac(6')-Ib-cr y qepA] en 289 aislados de enterobacterias productoras de betalactamasas de claseC adquiridas y/o carbapenemasas recogidos entre febrero y julio de 2009 en 35 hospitales españoles. Resultados: Se detectaron determinantes plasmídicos en 92 aislados (31,8%); en 83 aislados (28,7%) se detectó algún gen qnr, y en 20 (7%), la variante aac(6')-Ib-cr. El gen qnr más prevalente fue qnrB4 (20%), asociado en la mayoría de los casos a DHA-1. El 14,6% de los aislados con una CMI de ciprofloxacino superior a 0,25mg/l no presentaban mutaciones en gyrA ni parC, detectándose en el 90% de los mismos algún determinante plasmídico de resistencia a quinolonas. Conclusión: qnrB4 fue el determinante plasmídico más prevalente, claramente asociado a DHA-1. Los mecanismos plasmídicos en asociación con mecanismos cromosómicos diferentes a las mutaciones en los genes de las topoisomerasas (sobreexpresión de bombas de expulsión, alteración del lipopolisacárido o disminución de porinas) pueden dar lugar a valores de CMI de ciprofloxacino que superan los puntos de corte establecidos por los principales comités internacionales de definición de puntos de corte para interpretación de datos de sensibilidad (AU)

Background: Quinolone resistance in Enterobacteriaceae species has increased over the past few years, and is significantly associated to beta-lactam resistance. The aim of this study was to evaluate the prevalence of chromosomal- and plasmid-mediated quinolone resistance in acquired AmpC Beta-lactamase and/or carbapenemase-producing Enterobacteriaceae isolates. Methods: The presence of chromosomal- and plasmid-mediated quinolone resistance mechanisms [mutations in the quinolone resistance determining region (QRDR) of gyrA and parC and qnr, aac(6')-Ib-cr and qepA genes] was evaluated in 289 isolates of acquired AmpC Beta -lactamase- and/or carbapenemase-producing Enterobacteriaceae collected between February and July 2009 in 35 Spanish hospitals. Results: Plasmid mediated quinolone resistance (PMQR) genes were detected in 92 isolates (31.8%), qnr genes were detected in 83 isolates (28.7%), and the aac(6')-Ib-cr gene was detected in 20 isolates (7%). qnrB4 gene was the most prevalent qnr gene detected (20%), associated, in most cases, with DHA-1. Only 14.6% of isolates showed no mutations in gyrA or parC with a ciprofloxacin MIC of 0.5mg/L or higher, whereas PMQR genes were detected in 90% of such isolates. Conclusion: qnrB4 gene was the most prevalent PMQR gene detected, and was significantly associated with acquired AmpC Beta -lactamase DHA-1. PMQR determinants in association with other chromosomal-mediated quinolone resistance mechanisms, different to mutations in gyrA and parC (increased energy-dependent efflux, altered lipopolysaccharide or porin loss), could lead to ciprofloxacin MIC values that exceed breakpoints established by the main international committees to define clinical antimicrobial susceptibility breakpoints (AU)

Prevalence of quinolone resistance mechanisms in Enterobacteriaceae producing acquired AmpC ß-lactamases and/or carbapenemases in Spain. / Prevalencia en España de mecanismos de resistencia a quinolonas en enterobacterias productoras de betalactamasas de clase C adquiridas y/o carbapenemasas.

BACKGROUND: Quinolone resistance in Enterobacteriaceae species has increased over the past few years, and is significantly associated to beta-lactam resistance. The aim of this study was to evaluate the prevalence of chromosomal- and plasmid-mediated quinolone resistance in acquired AmpC ß-lactamase and/or carbapenemase-producing Enterobacteriaceae isolates. METHODS: The presence of chromosomal- and plasmid-mediated quinolone resistance mechanisms [mutations in the quinolone resistance determining region (QRDR) of gyrA and parC and qnr, aac(6')-Ib-cr and qepA genes] was evaluated in 289 isolates of acquired AmpC ß-lactamase- and/or carbapenemase-producing Enterobacteriaceae collected between February and July 2009 in 35 Spanish hospitals. RESULTS: Plasmid mediated quinolone resistance (PMQR) genes were detected in 92 isolates (31.8%), qnr genes were detected in 83 isolates (28.7%), and the aac(6')-Ib-cr gene was detected in 20 isolates (7%). qnrB4 gene was the most prevalent qnr gene detected (20%), associated, in most cases, with DHA-1. Only 14.6% of isolates showed no mutations in gyrA or parC with a ciprofloxacin MIC of 0.5mg/L or higher, whereas PMQR genes were detected in 90% of such isolates. CONCLUSION: qnrB4 gene was the most prevalent PMQR gene detected, and was significantly associated with acquired AmpC ß-lactamase DHA-1. PMQR determinants in association with other chromosomal-mediated quinolone resistance mechanisms, different to mutations in gyrA and parC (increased energy-dependent efflux, altered lipopolysaccharide or porin loss), could lead to ciprofloxacin MIC values that exceed breakpoints established by the main international committees to define clinical antimicrobial susceptibility breakpoints.

Actividad comparativa del ertapenem frente a Klebsiella pneumoniae productor de betalactamasas de espectro extendido o betalactamasas de AmpC plasmídicas: efecto inóculo y papel de la pérdida de porinas / Comparative activity of ertapenem against extended-spectrum beta lactamase-producing or plasmid-mediated AmpC beta lactamase-producing Klebsiella pneumoniae

Se ha estudiado el efecto de la pérdida de porinas y el efecto inóculo en la actividad comparativa del ertapenem (ERT) frente a las cepas de Klebsiella pneumoniae productoras de betalactamasas de espectro extendido (BLEE) o de betalactamasas de AmpC de codificación plasmídica (pACBL). Métodos Sistema de microdilución mediante la utilización de 2 inóculos diferentes.ResultadosEl imipenem (IMP), la amikacina, el ERT y la cefepima fueron los antimicrobianos más activos en condiciones estándares. La pérdida de porinas afectó más al ERT que al IMP. Conclusiones El ERT muestra una buena actividad frente a las cepas productoras de betalactamasas de tipo BLEE y de tipo pACBL. Las cepas deficientes en porinas analizadas tienen una sensibilidad disminuida a betalactámicos. El efecto inóculo afectó más al IMP que al ERT (AU)

The effect of porin loss and inoculum size on the comparative activity of ertapenem against either extended-spectrum beta lactamase-producing (ESBL) or plasmid-mediated AmpC beta lactamase-producing (pACBL) Klebsiella pneumoniae strains was evaluated. Methods Microdilution using 2 different bacterial inocula. Results Imipenem, amikacin, ertapenem, and cefepime were the most active agents under standard conditions. Ertapenem was more highly affected by porin loss than imipenem. Conclusions Ertapenem showed high activity against K. pneumoniae strains expressing ESBL, pACBL or both. Strains deficient in porins showed decreased susceptibility to beta lactams. The inoculum effect had a greater impact on imipenem than on ertapenem (AU)

[Comparative activity of ertapenem against extended-spectrum beta-lactamase-producing or plasmid-mediated AmpC beta-lactamase-producing Klebsiella pneumoniae]. / Actividad comparativa del ertapenem frente a Klebsiella pneumoniae productor de betalactamasas de espectro extendido o betalactamasas de AmpC plasmídicas: efecto inóculo y papel de la pérdida de porinas.

INTRODUCTION: The effect of porin loss and inoculum size on the comparative activity of ertapenem against either extended-spectrum beta lactamase-producing (ESBL) or plasmid-mediated AmpC beta lactamase-producing (pACBL) Klebsiella pneumoniae strains was evaluated. METHODS: Microdilution using 2 different bacterial inocula. RESULTS: Imipenem, amikacin, ertapenem, and cefepime were the most active agents under standard conditions. Ertapenem was more highly affected by porin loss than imipenem. CONCLUSIONS: Ertapenem showed high activity against K. pneumoniae strains expressing ESBL, pACBL or both. Strains deficient in porins showed decreased susceptibility to beta lactams. The inoculum effect had a greater impact on imipenem than on ertapenem.

Activities of ABT-773 against Listeria monocytogenes and coryneform bacteria of clinical interest.

The in vitro activities of ABT-773 were evaluated against 15 Listeria monocytogenes strains and 196 coryneform bacteria isolated from clinical samples. One hundred percent of the L. monocytogenes strains were inhibited by 32 (Corynebacterium jeikeium), 0.03 and >32 (Corynebacterium minutissimum), >32 and >32 (Corynebacterium pseudodiphtheriticum and Corynebacterium urealyticum), 0.125 and >32 (Corynebacterium striatum), and 0.03 and 0.5 (Rhodococcus equi), respectively.

Energy-dependent accumulation of norfloxacin and porin expression in clinical isolates of Klebsiella pneumoniae and relationship to extended-spectrum beta-lactamase production.

The relationships between porin deficiency, active efflux of fluoroquinolones, and extended-spectrum beta-lactamase (ESBL) production were determined for 53 clinical isolates of Klebsiella pneumoniae. Thirty-two ESBL-positive strains (including 22 strains expressing porins and 10 strains lacking porins) and 21 ESBL-negative strains were evaluated. Active efflux of norfloxacin was defined as a >/=50% increase in the accumulation of norfloxacin in the presence of carbonyl cyanide m-chlorophenylhydrazone (CCCP) in comparison with the corresponding basal value in the absence of CCCP. The quinolone resistance-determining regions of both gyrA and parC from 13 strains, representing all isolates with different porin profiles and with or without active efflux, were determined. Porin loss was significantly more common among ESBL-positive strains (10 of 32 [31.2%]) than among ESBL-negative strains (0 of 2 [0%]) (P < 0.01). Active efflux was observed in 7 of 10 (70%) strains lacking porins and in 4 of 43 (9.3%) strains producing porins (P < 0.001). The 11 strains showing active efflux corresponded to 3 of 21 (14.3%) ESBL-negative strains and 8 of 32 (25.5%) ESBL-positive strains (P > 0.05). Basal values of norfloxacin accumulation were higher in strains lacking active efflux than in those that had this mechanism (P < 0.05). In the absence of topoisomerase changes, the contribution of either porin loss or active efflux to fluoroquinolone resistance in K. pneumoniae was negligible. It is concluded that among K. pneumoniae strains of clinical origin, porin loss was observed only in those producing ESBL, and that a significant number of porin-deficient strains also expressed active efflux of norfloxacin. In terms of fluoroquinolone resistance, both mechanisms are significant only in the presence of topoisomerase modifications.

Actividad de cuatro fluoroquinolonas frente a cepas de Pseudomonas aeruginosa con diferente patrón de sensibilidad a Ceftazidima e Imipenem / The activity of four fluoroquinolones against strains of Pseudomonas aeruginosa with a different sensitivity pattern to ceftazidime and imipenem

FUNDAMENTO. Evaluar la actividad de cuatro fluoroquinolonas (ciprofloxacino, clinafloxacino, norfloxacino y pefloxacino) frente cepas clínicas de Pseudomas aeruginosa con diferentes patrones de sensibilidad a ceftazidima e imipenem. MATERIAL Y MÉTODOS. Se estudiaron 156 cepas de P. aeruginosa aisladas en el Hospital Universitario Virgen Macarena de Sevilla en los años 1998 y 1999. La actividad in vitro de cuatro fluoroquinolonas se determinó mediante microdilución en caldo Mueller Hinton suplementado con cationes siguiendo las recomendaciones del NCCLS. RESULTADOS. Para el total de cepas evaluadas, los valores de concentración mínima inhibitoria (CMI)90 de clinafloxacino (4 mg/l) fueron significativamente inferiores a los de ciprofloxacino (64 mg/l). Para las 76 cepas resistentes a ciprofloxacino, las CMI90 de clinafloxacino y ciprofloxacino fueron de 16 y > 128 mg/l respectivamente. Clinafloxacino fue más activa que ciprofloxacino, norfloxacino y pefloxacino, con independencia del patrón de sensibilidad o resistencia a ceftazidima e imipenem. CONCLUSIÓN. Clinafloxacino fue más activa in vitro que ciprofloxacino frente a P. aeruginosa (AU)