Resumen de In vitro activity of a polyhexanide–betaine solution against high-risk clones of multidrug-resistant nosocomial pathogens

Rafael López Rojas, Felipe Fernández-Cuenca, Lara Serrano Rocha, Álvaro Pascual

• español

  Objective To determine the in vitro activity of a polyhexanide–betaine solution against collection strains and multidrug-resistant (MDR) nosocomial isolates, including high-risk clones.

  Methods We studied of 8 ATCC and 21 MDR clinical strains of Staphylococcus aureus, Enterococcus faecium, Enterococcus faecalis, Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa, including the multiresistant high-risk clones. The MICs and MBCs of a 0.1% polyhexanide–0.1% betaine solution were determined by microdilution. For each species, strains with the highest MICs were selected for further experiments.

  The dilution–neutralization test (PrEN 12054) was performed by incubating bacterial inocula of 106CFU/mL for 1min with undiluted 0.1% polyhexanide–betaine solution. The CFUs were counted after neutralization.

  Growth curves and time-kill curves at concentrations of 0.25, 1, 4, and 8×MIC, were performed. MICs of recovered strains were determined when regrowth was observed in time-kill studies after 24h of incubation.

  Strains with reduced susceptibility were selected by serial passage on plates with increasing concentrations of polyhexanide–betaine, and MICs were determined.

  Results Polyhexanide–betaine MIC range was 0.5–8mg/L. MBCs equalled or were 1 dilution higher than MICs. The dilution–neutralization method showed total inoculum clearance of all strains. In time-kill curves, no regrowth was observed at 4×MIC, except for S. aureus (8×MIC). Increased MICs were not observed in time-kill curves, or after serial passages after exposure to polyhexanide–betaine.

  Conclusions Polyhexanide–betaine presented bactericidal activity against all MDR clinical isolates tested, including high-risk clones, at significantly lower concentrations and time of activity than those commercially used.

• English

  Objetivos Determinar la actividad in vitro de una solución de polihexanida-betaína frente a una colección de cepas nosocomiales multirresistentes, incluyendo clones de alto riesgo.

  Métodos Estudiamos 8 cepas ATCC y 21 cepas clínicas de Staphylococcus aureus, Enterococcus faecium, Enterococcus faecalis, Escherichia coli, Enterobactercloacae, Klebsiella pneumoniae, Acinetobacter baumannii y Pseudomonas aeruginosa, incluyendo clones de alto riesgo multirresistentes. Determinamos las CMI y las CMB de una solución 0,1% de polihexanida y 0,1% de betaína por microdilución. De cada especie, seleccionamos las cepas con mayores CMIs para los siguientes experimentos.

  Realizamos el test de dilución-neutralización (PrEN 12054) incubando 106UFC/ml 1min con solución 0,1% de polihexanida-betaína, calculando las UFCs tras un paso de neutralización.

  Realizamos curvas de crecimiento y de tiempo-muerte a concentraciones 0,25, 1, 4 y 8×CMI. Determinamos las CMIs de las cepas recuperadas tras recrecimiento a las 24h.

  Seleccionamos cepas con sensibilidad reducida tras pases seriados en placas con concentraciones crecientes de polihexanida-betaína y determinamos sus CMI.

  Resultados El rango de CMI fue de 0,5–8mg/l. Las CMBs fueron iguales o una dilución mayor. El test de dilución-neutralización presentó aclaramiento total del inóculo en todas las cepas. En las curvas de tiempo-muerte, no se observó recrecimiento a 4×CMI, excepto para S. aureus (8×CMI). No se incrementó la CMI ni aquí ni en los pases seriados con polihexanida-betaína.

  Conclusiones Polihexanida-betaína presenta actividad bactericida frente a todas las cepas multirresistentes estudiadas, incluyendo clones de alto riesgo, a concentraciones y tiempos de exposición significativamente menores que los usados comercialmente.