We 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.

A 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.

Among 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.

Delafloxacin was very active against highly-levofloxacin-resistant invasive isolates of S. pneumoniae. Isolates belonging to serotype 9V showed higher delafloxacin MIC values.

Analizamos 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.

Se 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.

El 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.

Delafloxacino fue muy activo frente a S. pneumoniae altamente resistente a levofloxacino. Los aislados del serotipo 9V presentaron mayores valores de CMI de delafloxacino.