In vitro activity of delafloxacin against highly levofloxacin-resistant invasive isolates of Streptococcus pneumoniae / Actividad in vitro de delafloxacino frente a aislados invasivos de Streptococcus pneumoniae altamente resistentes a levofloxacino

ABSTRACT

IntroductionWe report the activity of delafloxacin, a new fluoroquinolone with high affinity for both topoisomerase IV and DNA gyrase, against highly-levofloxacin-resistant invasive strains of Streptococcus pneumoniae.MethodsA total of 173 highly-levofloxacin-resistant (MIC>32mg/L) S. pneumoniae invasive isolates were studied. The strains were isolated from blood (n=162) and other sterile fluids (n=11). Serotyping was performed by the Pneumotest-Latex and Quellung reaction.Delafloxacin, levofloxacin, penicillin, cefotaxime, erythromycin and vancomycin MICs were determined by the gradient diffusion method following EUCAST guidelines and breakpoints.ResultsAmong the isolates, 32.9% were penicillin non-susceptible, 19.7% cefotaxime non-susceptible, and 76.9% erythromycin resistant. All were susceptible to vancomycin. Delafloxacin MIC50 and MIC90 (mg/L) values were 0.064 and 0.12, respectively; 60% (15/25) of serotype 9V isolates showed delafloxacin MICs≥0.12mg/L.ConclusionsDelafloxacin was very active against highly-levofloxacin-resistant invasive isolates of S. pneumoniae. Isolates belonging to serotype 9V showed higher delafloxacin MIC values.

RESUMEN

IntroducciónAnalizamos la actividad de delafloxacino, una fluoroquinolona con elevada afinidad por la topoisomerasa i.v. y la ADN girasa, frente a cepas invasivas de Streptococcus pneumoniae altamente resistentes a levofloxacino.MétodosSe estudiaron 173 cepas con CMI de levofloxacino >32mg/l procedentes de sangre (n=162) y otros fluidos estériles (n=11). El serotipado se realizó mediante Pneumotest-Latex y test de Quellung.Las CMI de delafloxacino, levofloxacino, penicilina, cefotaxima, eritromicina y vancomicina se determinaron mediante gradiente de difusión siguiendo las recomendaciones del EUCAST.ResultadosEl 32,9% de las cepas fueron no-sensibles a penicilina, el 19,7% no-sensibles a cefotaxima y el 76,9% resistentes a eritromicina. Todas fueron sensibles a vancomicina. Las CMI50 y CMI90 de delafloxacino (mg/l) fueron 0,064 y 0,120, respectivamente; 60% (15/25) de cepas del serotipo 9V presentaron CMI de delafloxacino ≥0,12mg/l.ConclusionesDelafloxacino fue muy activo frente a S. pneumoniae altamente resistente a levofloxacino. Los aislados del serotipo 9V presentaron mayores valores de CMI de delafloxacino.