In vitro activity of a polyhexanide-betaine solution against high-risk clones of multidrug-resistant nosocomial pathogens / Actividad in vitro de una solución de polihexanida-betaína frente a patógenos nosocomiales multirresistentes pertenecientes a clones de alto riesgo

ABSTRACT

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 0.5-8 mg/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

RESUMEN

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 0,5-8 mg/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