In vitro activity of nemonoxacin (TG-873870), a novel non-fluorinated quinolone, against clinical isolates of Staphylococcus aureus, enterococci and Streptococcus pneumoniae with various resistance phenotypes in Taiwan.
OBJECTIVE
The aim of this study was to assess the in vitro activities of nemonoxacin against Gram-positive cocci with various resistance phenotypes.


METHODS
MICs of nemonoxacin were determined for 798 recently collected (2005-07) and non-duplicate isolates of Gram-positive cocci by the agar dilution method. These isolates included: methicillin-susceptible Staphylococcus aureus (MSSA; n = 100); methicillin-resistant S. aureus (MRSA), including ciprofloxacin-susceptible (n = 50), ciprofloxacin-resistant (n = 100), vancomycin-intermediate (n = 50) and daptomycin-non-susceptible (DNS-MRSA; n = 5) isolates, and community-acquired MRSA (CA-MRSA; n = 101); invasive Streptococcus pneumoniae isolates (n = 150); levofloxacin-non-susceptible (MICs of 4-64 mg/L) S. pneumoniae isolates (n = 30); and enterococci (n = 212), including vancomycin-resistant enterococci (VRE; n = 112).


RESULTS
Nemonoxacin had potent activity against MSSA (MIC(90) of < or =0.03 mg/L), ciprofloxacin-susceptible MRSA (MIC(90) of < or =0.03 mg/L) and CA-MRSA (MIC(90) of 0.06 mg/L). For all invasive S. pneumoniae isolates, the activity of nemonoxacin (MIC(90) of 0.06 mg/L) was similar to that of gemifloxacin and much better than that of levofloxacin (MIC(90) of 2 mg/L) and moxifloxacin (MIC(90) of 0.25 mg/L). Nemonoxacin had a 32- to 64-fold higher activity than levofloxacin against levofloxacin-non-susceptible isolates. Nemonoxacin exerted limited activity against ciprofloxacin-resistant MRSA (MIC(90) of 1 mg/L), vancomycin-intermediate MRSA (MIC(90) of 2 mg/L), DNS-MRSA (MIC(90) of 1 mg/L), vancomycin-susceptible enterococci (MIC(90) of 2 mg/L for Enterococcus faecalis and 4 mg/L for Enterococcus faecium) and VRE (MIC(90) of 4 mg/L for E. faecalis and 16 mg/L for E. faecium).


CONCLUSIONS
Our findings point to a potentially useful role for nemonoxacin in the treatment of infections caused by MSSA, ciprofloxacin-susceptible MRSA and S. pneumoniae with various resistance phenotypes.
Chen
Yen-Hsu
YH
Department of Internal Medicine, Chung-Ho Memorial Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan.
Liu
Chia-Ying
CY
Lu
Jang-Jih
JJ
King
Chi-Hsin R
CH
Hsueh
Po-Ren
PR
D019943:Amino Acid Substitution; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D027081:DNA Gyrase / Q000235:genetics; D027101:DNA Topoisomerase IV / Q000235:genetics; D024881:Drug Resistance, Bacterial; D016983:Enterococcus / Q000187:drug effects* / Q000302:isolation & purification; D016908:Gram-Positive Bacterial Infections / Q000382:microbiology; D006801:Humans; D008826:Microbial Sensitivity Tests; D020125:Mutation, Missense; D015363:Quinolones / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000302:isolation & purification; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000302:isolation & purification; D013624:Taiwan
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015363:Quinolones; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase; C543520:nemonoxacin