Activity of oxazolidinone TR-700 against linezolid-susceptible and -resistant staphylococci and enterococci.
BACKGROUND
TR-700 is the active moiety of TR-701 (DA-7157), a new oral/intravenous oxazolidinone prodrug. We examined its activity against linezolid-susceptible and -resistant staphylococci and enterococci.


METHODS
MICs were determined by the CLSI agar dilution method.


RESULTS
MICs of TR-700 were tightly clustered around 0.5 mg/L for linezolid-susceptible staphylococci and enterococci compared with 2 mg/L for linezolid. MICs for 52 linezolid-resistant isolates were raised, but only exceeded 4 mg/L for two Enterococcus faecium isolates homozygous for the G2576T 23S rRNA mutation and for one with an unknown mechanism of linezolid resistance.


CONCLUSIONS
TR-700 is 4- to 16-fold more active than linezolid and overcame most linezolid resistance in vitro.
Livermore
David M
DM
Antibiotic Resistance Monitoring and Reference Laboratory, Health Protection Agency Centre for Infections, 61 Colindale Avenue, London NW95EQ, UK. david.livermore@hpa.org.uk
Mushtaq
Shazad
S
Warner
Marina
M
Woodford
Neil
N
D000081:Acetamides / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D016983:Enterococcus / Q000187:drug effects*; D006801:Humans; D000069349:Linezolid; D008826:Microbial Sensitivity Tests; D023303:Oxazolidinones / Q000494:pharmacology*; D017354:Point Mutation; D012329:RNA, Bacterial / Q000235:genetics; D012338:RNA, Ribosomal, 23S / Q000235:genetics; D013210:Staphylococcus / Q000187:drug effects*
D000081:Acetamides; D000900:Anti-Bacterial Agents; D023303:Oxazolidinones; D012329:RNA, Bacterial; D012338:RNA, Ribosomal, 23S; D000069349:Linezolid