Multicenter Study in Taiwan of theIn VitroActivities of Nemonoxacin, Tigecycline, Doripenem, and Other Antimicrobial Agents against Clinical Isolates of Various Nocardia Species

Abstract

ABSTRACTThe aim of this study was to assess thein vitroactivities of nemonoxacin (a novel nonfluorinated quinolone), doripenem, tigecycline, and 16 other antimicrobial agents againstNocardiaspecies. The MICs of the 19 agents against 151 clinical isolates ofNocardiaspecies were determined by the broth microdilution method. The isolates were identified to the species level using 16S rRNA gene sequencing analysis. The results showed thatN. brasiliensis(n= 60; 40%) was the most common species, followed byN. cyriacigeorgica(n= 24; 16%),N. farcinica(n= 12; 8%),N. beijingensis(n= 9),N. otitidiscaviarum(n= 8),N. nova(n= 8),N. asiatica(n= 7),N. puris(n= 6),N. flavorosea(n= 5),N. abscessus(n= 3),N. carnea(2), and one each ofN. alba,N. asteroidescomplex,N. rhamnosiphila,N. elegans,N. jinanensis,N. takedensis, andN. transvalensis. The MIC90s of the tested quinolones against theN. brasiliensisisolates were in the order nemonoxacin = gemifloxacin < moxifloxacin < levofloxacin = ciprofloxacin, and the MIC90s of the tested carbapenems were in the order doripenem = meropenem < ertapenem < imipenem. Tigecycline had a lower MIC90(1 μg/ml) than linezolid (8 μg/ml). The MIC90s of the tested quinolones againstN. cyriacigeorgicaisolates were in the order nemonoxacin < gemifloxacin < moxifloxacin < levofloxacin < ciprofloxacin, and the MIC90s of the tested carbapenems were in the order imipenem < doripenem = meropenem < ertapenem. Nemonoxacin had the lowest MIC90values among the tested quinolones against the other 17Nocardiaisolates. Among the four tested carbapenems, imipenem had the lowest MIC90s. All of the clinical isolates ofN. beijingensis,N. otitidiscaviarum,N. nova, andN. purisand more than half of theN. brasiliensisandN. cyriacigeorgicaisolates were resistant to at least one antimicrobial agent. The results of thisin vitrostudy suggest that nemonoxacin, linezolid, and tigecycline are promising treatment options for nocardiosis. Further investigation of their clinical role is warranted.