ABSTRACT
Synergy time-kill studies against 40 methicillin-resistant Staphylococcus aureus (MRSA) strains of differing resistance phenotypes were conducted. Subinhibitory concentrations of telavancin were combined with sub-MIC concentrations of other antimicrobial agents that might be used in combination with telavancin to provide Gram-negative coverage. The highest incidence of synergy was found after 24 h with gentamicin (90% of strains), followed by ceftriaxone (88%), rifampin and meropenem (each 65%), cefepime (45%), and ciprofloxacin (38%) for combinations tested at or below the intermediate breakpoint for each agent.
Subject(s)
Aminoglycosides/pharmacology , Anti-Bacterial Agents/pharmacology , Gentamicins/pharmacology , Methicillin-Resistant Staphylococcus aureus/drug effects , Cefepime , Ceftriaxone/pharmacology , Cephalosporins/pharmacology , Ciprofloxacin/pharmacology , Drug Synergism , Lipoglycopeptides , Meropenem , Microbial Sensitivity Tests , Oxacillin/pharmacology , Rifampin/pharmacology , Thienamycins/pharmacology , Time FactorsABSTRACT
Synergy time-kill studies of 47 methicillin-resistant Staphylococcus aureus strains with differing resistance phenotypes showed that combinations of subinhibitory concentrations of ACHN-490 and daptomycin yielded synergy against 43/47 strains at 24 h, while the combination was indifferent against the remaining 4 strains. ACHN-490 and ceftobiprole showed synergy in 17/47 strains tested at 24 h, while 6/47 strains showed synergy for subinhibitory combinations of ACHN-490 and linezolid.
Subject(s)
Acetamides/pharmacology , Aminoglycosides/pharmacology , Daptomycin/pharmacology , Methicillin-Resistant Staphylococcus aureus/drug effects , Oxazolidinones/pharmacology , Sisomicin/analogs & derivatives , Aminoglycosides/chemistry , Anti-Bacterial Agents/pharmacology , Cephalosporins/pharmacology , Drug Resistance, Bacterial/drug effects , Drug Synergism , Linezolid , Microbial Sensitivity Tests , Sisomicin/chemistry , Sisomicin/pharmacology , Time FactorsABSTRACT
For 297 penicillin-susceptible, -intermediate, and -resistant pneumococcal strains, the sulopenem MIC(50)s were 0.008, 0.06, and 0.25, respectively, and the sulopenem MIC(90)s were 0.016, 0.25, and 0.5 microg/ml, respectively. The MIC(50)s of amoxicillin for the corresponding strains were 0.03, 0.25, and 2.0 microg/ml, respectively, and the MIC(90)s were 0.03, 1.0, and 8.0 microg/ml, respectively. The combination of amoxicillin and clavulanate gave MICs similar to those obtained with amoxicillin alone. The sulopenem MICs were similar to those of imipenem and meropenem. The MICs of ss-lactams increased with those of penicillin G, and among the quinolones tested, moxifloxacin had the lowest MICs. Additionally, 45 strains of drug-resistant type 19A pneumococci were tested by agar dilution and gave sulopenem MIC(50)s and MIC(90)s of 1.0 and 2.0 microg/ml, respectively. Both sulopenem and amoxicillin (with and without clavulanate) were bactericidal against all 12 strains tested at 2x MIC after 24 h. Thirty-one strains from 10 countries with various penicillin, amoxicillin, and carbapenems MICs, including those with the highest sulopenem MICs, were selected for sequencing analysis of the pbp1a, pbp2x, and pbp2b regions encoding the transpeptidase active site and MurM. We did not find any correlations between specific penicillin-binding protein-MurM patterns and changes in the MICs.
Subject(s)
Anti-Bacterial Agents/pharmacology , Lactams/pharmacology , Streptococcus pneumoniae/drug effects , Microbial Sensitivity Tests , Penicillin-Binding Proteins/analysis , beta-Lactam ResistanceABSTRACT
Agar dilution MIC methodology was used to compare the activity of sulopenem with those of amoxicillin/clavulanate, ampicillin/sulbactam, piperacillin-tazobactam, imipenem, clindamycin, and metronidazole against 431 anaerobes. Overall, MIC(50)/(90) values were as follows: sulopenem, 0.25/1.0 microg/ml; amoxicillin/clavulanate, 0.5/2.0 microg/ml; ampicillin/sulbactam, 0.5/4.0 microg/ml; piperacillin/tazobactam, 0.25/8.0 microg/ml; imipenem, 0.06/1.0 microg/ml; clindamycin, 0.25/16.0 microg/ml; and metronidazole, 1.0/4.0 microg/ml.
Subject(s)
Anti-Bacterial Agents/pharmacology , Bacteria, Anaerobic/drug effects , Gram-Negative Bacteria/drug effects , Lactams/pharmacology , Humans , Lactams/chemistry , Microbial Sensitivity Tests/methods , Microbial Sensitivity Tests/standards , Prodrugs/chemistry , Prodrugs/pharmacologyABSTRACT
For a panel of 153 Staphylococcus aureus clinical isolates (including 13 vancomycin-intermediate or heterogeneous vancomycin-intermediate and 4 vancomycin-resistant strains), MIC(50)s and MIC(90)s of three novel dihydrophthalazine antifolates, BAL0030543, BAL0030544, and BAL0030545, were 0.03 and 0.25 microg/ml, respectively, for methicillin-susceptible strains and 0.03 and
Subject(s)
Anti-Bacterial Agents/pharmacology , Folic Acid Antagonists/pharmacology , Phthalazines/pharmacology , Staphylococcus aureus/drug effects , Staphylococcus epidermidis/drug effects , Drug Resistance, Bacterial , Microbial Sensitivity Tests , Tetrahydrofolate Dehydrogenase/geneticsABSTRACT
All 982 methicillin-resistant Staphylococcus aureus strains collected from August 2006 to December 2007 were tested for vancomycin susceptibility by using 3-microg/ml vancomycin brain heart infusion screening plates, a vancomycin Etest, and a vancomycin/teicoplanin macro Etest. Three vancomycin-intermediate Staphylococcus aureus (VISA) (0.3%) and two heterogeneous VISA (0.2%) isolates were identified. The screening method yielded 895 cases of < or =1 colony and 87 positive results (with growth of >1 colony after 48 h); further Etests showed 82/87 isolates with growth on screening plates to be false positive. Repeat testing showed a false-positivity rate of only 15 of the original 87 isolates by plate screening.
Subject(s)
Methicillin-Resistant Staphylococcus aureus/drug effects , Staphylococcal Infections/epidemiology , Vancomycin Resistance , Academic Medical Centers , Anti-Bacterial Agents/pharmacology , False Positive Reactions , Humans , Incidence , Methicillin-Resistant Staphylococcus aureus/classification , Methicillin-Resistant Staphylococcus aureus/isolation & purification , Microbial Sensitivity Tests/methods , Pennsylvania/epidemiology , Staphylococcal Infections/microbiology , Vancomycin/pharmacologyABSTRACT
Against 300 strains of pneumococci and 100 group A streptococci of differing beta-lactam, macrolide, and quinolone resistance phenotypes, AR-709 was very active, with all MICs being < or =2 microg/ml. Furthermore, AR-709 was active against strains that were both susceptible and resistant to trimethoprim-sulfamethoxazole.
Subject(s)
Anti-Bacterial Agents/pharmacology , Pyrimidines/pharmacology , Streptococcus pneumoniae/drug effects , Streptococcus pyogenes/drug effects , Drug Resistance, Bacterial , Humans , Microbial Sensitivity Tests/standards , Pyrimidines/chemistry , Streptococcus pneumoniae/classification , Streptococcus pyogenes/classification , Tetrahydrofolate Dehydrogenase/drug effects , Trimethoprim, Sulfamethoxazole Drug Combination/pharmacologyABSTRACT
Against 447 anaerobe strains, the investigational carbapenem doripenem had an MIC 50 of 0.125 microg/ml and an MIC 90 of 1 microg/ml. Results were similar to those for imipenem, meropenem, and ertapenem. Time-kill studies showed that doripenem had very good bactericidal activity compared to other carbapenems, with 99.9% killing of 11 strains at 2x MIC after 48 h.
Subject(s)
Anti-Bacterial Agents/pharmacology , Bacteria, Anaerobic/drug effects , Bacteria, Anaerobic/growth & development , Carbapenems/pharmacology , Bacteria, Anaerobic/classification , Colony Count, Microbial , Doripenem , Humans , Microbial Sensitivity Tests/standardsABSTRACT
Testing of 12 pneumococcal strains with differing resistotypes [including tet(M) positive] showed that tigecycline, amoxicillin-clavulanate, imipenem, and ceftriaxone did not select for resistant clones after 50 sequential subcultures. By comparison, azithromycin, clarithromycin, clindamycin, telithromycin, levofloxacin, moxifloxacin, and gemifloxacin did show resistant clones. Tigecycline also yielded a low frequency of resistance in single-step tests compared to all beta-lactams, macrolides/ketolides, and quinolones tested.
Subject(s)
Anti-Bacterial Agents/pharmacology , Drug Resistance, Bacterial , Streptococcus pneumoniae/drug effects , Aza Compounds/pharmacology , Azithromycin/pharmacology , Clarithromycin/pharmacology , Clavulanic Acid/pharmacology , Clindamycin/pharmacology , Fluoroquinolones/pharmacology , Gemifloxacin , Imipenem/pharmacology , Ketolides/pharmacology , Levofloxacin , Microbial Sensitivity Tests/methods , Moxifloxacin , Naphthyridines/pharmacology , Ofloxacin/pharmacology , Quinolines/pharmacologyABSTRACT
Against 198 viridans group streptococci, 25 Streptococcus bovis strains, and 5 Cardiobacterium hominis strains, MICs of DX-619, a des-F(6)-quinolone, were between 0.004 and 0.25 microg/ml. These MICs were lower than those of other quinolones (< or = 0.008 to > 32 microg/ml). Beta-lactam MICs were between < or = 0.008 and 16 microg/ml. Azithromycin resistance was found in most species, while most were telithromycin susceptible. Glycopeptides and linezolid were active against viridans group strains but inactive against C. hominis.
Subject(s)
Anti-Infective Agents/pharmacology , Cardiobacterium/drug effects , Pyrrolidines/pharmacology , Quinolones/pharmacology , Streptococcus bovis/drug effects , Viridans Streptococci/drug effects , Acetamides/pharmacology , Anti-Bacterial Agents/pharmacology , Azithromycin/pharmacology , Drug Resistance, Bacterial , Glycolipids/pharmacology , Ketolides/pharmacology , Linezolid , Microbial Sensitivity Tests , Oxazolidinones/pharmacology , beta-Lactams/pharmacologyABSTRACT
Against 307 pneumococci of various resistotypes, dalbavancin MICs were 0.008 to 0.125 microg/ml. All strains were susceptible to vancomycin, teicoplanin, linezolid, and quinupristin-dalfopristin. Dalbavancin at 2x MIC was bactericidal against all 10 pneumococci tested after 24 h. Vancomycin and teicoplanin killed 10 and 8 strains, respectively, at 2x MIC after 24 h.
Subject(s)
Anti-Bacterial Agents/pharmacology , Streptococcus pneumoniae/drug effects , Teicoplanin/analogs & derivatives , Microbial Sensitivity Tests , Streptococcus pneumoniae/isolation & purification , Teicoplanin/pharmacologyABSTRACT
Ceftobiprole (formerly BAL9141), the active component of the prodrug BAL5788 (ceftobiprole medocaril), is a novel cephalosporin with expanded activity against gram-positive bacteria. Among 152 Staphylococcus aureus isolates, including 5 vancomycin-intermediate and 2 vancomycin-resistant strains, MIC(50) and MIC(90) values for ceftobiprole were each 0.5 microg/ml against methicillin-susceptible strains and 2 mug/ml against methicillin-resistant strains. Against 151 coagulase-negative staphylococci (including 4 vancomycin-intermediate strains), MIC(50) and MIC(90) values were, respectively, 0.125 microg/ml and 1 microg/ml against methicillin-susceptible and 1 microg/ml and 2 microg/ml against methicillin-resistant strains. Teicoplanin was less active than vancomycin against coagulase-negative strains. Linezolid, quinupristin-dalfopristin, and daptomycin were active against all strains, whereas increased MICs for amoxicillin-clavulanate, cefazolin, minocycline, gentamicin, trimethoprim-sulfamethoxazole, levofloxacin, rifampin, mupirocin, fusidic acid, and fosfomycin were sometimes observed. At 2x MIC, ceftobiprole was bactericidal against 11 of 12 test strains by 24 h. Prolonged serial passage in the presence of subinhibitory concentrations of ceftobiprole failed to select for clones with MICs >4 times those of the parents; the maximum MIC achieved for ceftobiprole after 50 passages (in 1 of 10 strains) was 8 mug/ml. Single-passage selections showed very low frequencies of resistance to ceftobiprole irrespective of genotype or phenotype; the maximal ceftobiprole MIC of recovered clones was 8 mug/ml.
Subject(s)
Anti-Bacterial Agents/pharmacology , Cephalosporins/pharmacology , Gram-Positive Bacteria/drug effects , Staphylococcus aureus/drug effects , Drug Resistance, Bacterial , Microbial Sensitivity Tests , Staphylococcus aureus/geneticsABSTRACT
The in vitro activity of DX-619, a new des-F(6)-quinolone, was tested against staphylococci and compared to those of other antimicrobials. DX-619 had the lowest MIC ranges/MIC(50)s/MIC(90)s (microg/ml) against 131 Staphylococcus aureus strains (=0.002 to 2.0/0.06/0.5) and 128 coagulase-negative staphylococci (0.004 to 0.25/0.016/0.125). Among strains tested, 76 S. aureus strains and 51 coagulase-negative staphylococci were resistant to ciprofloxacin. DX-619 had the lowest MIC(50)/MIC(90) values against 127 quinolone-resistant staphylococci (0.125/0.5), followed by sitafloxacin (0.5/4), moxifloxacin (2/8), gatifloxacin (4/16), levofloxacin (16/>32), and ciprofloxacin (>32/>32). Raised quinolone MICs were associated with mutations in GyrA (S84L) and single or double mutations in GrlA (S80F or Y; E84K, G, or V) in all S. aureus strains tested. A recent vancomycin-resistant S. aureus (VRSA) strain (Hershey) was resistant to available quinolones and was inhibited by DX-619 at 0.25 microg/ml and sitafloxacin at 1.0 microg/ml. Vancomycin (except VRSA), linezolid, ranbezolid, tigecycline, and quinupristin-dalfopristin were active against all strains, and teicoplanin was active against S. aureus but less active against coagulase-negative staphylococci. DX-619 produced resistant mutants with MICs of 1 to >32 microg/ml after <50 days of selection compared to 16 to >32 microg/ml for ciprofloxacin, sitafloxacin, moxifloxacin, and gatifloxacin. DX-619 and sitafloxacin were also more active than other tested drugs against selected mutants and had the lowest mutation frequencies in single-step resistance selection. DX-619 and sitafloxacin were bactericidal against six quinolone-resistant (including the VRSA) and seven quinolone-susceptible strains tested, whereas gatifloxacin, moxifloxacin, levofloxacin, and ciprofloxacin were bactericidal against 11, 10, 7, and 5 strains at 4x MIC after 24 h, respectively. DX-619 was also bactericidal against one other VRSA strain, five vancomycin-intermediate S. aureus strains, and four vancomycin-intermediate coagulase-negative staphylococci. Linezolid, ranbezolid, and tigecycline were bacteriostatic and quinupristin-dalfopristin, teicoplanin, and vancomycin were bactericidal against two, eight, and nine strains, and daptomycin and oritavancin were rapidly bactericidal against all strains, including the VRSA. DX-619 has potent in vitro activity against staphylococci, including methicillin-, ciprofloxacin-, and vancomycin-resistant strains.
Subject(s)
Anti-Infective Agents/pharmacology , Fluoroquinolones/pharmacology , Staphylococcus/drug effects , Bacterial Proteins/genetics , Drug Resistance, Multiple, Bacterial/genetics , Humans , Microbial Sensitivity Tests , Mutation , Staphylococcus/enzymology , Staphylococcus/genetics , Staphylococcus/growth & development , Staphylococcus aureus/drug effects , Staphylococcus aureus/enzymology , Staphylococcus aureus/genetics , Staphylococcus aureus/growth & developmentABSTRACT
Dalbavancin, tested against 146 staphylococci, was more potent than other drugs tested, with an MIC at which 50% of staphylococci were inhibited of 0.03 microg/ml and an MIC at which 90% of staphylococci were inhibited of 0.06 microg/ml by microdilution. For all strains, MICs of vancomycin, linezolid, ranbezolid, oritavancin, daptomycin, and quinupristin-dalfopristin were =4.0 microg/ml. Dalbavancin was bactericidal at four times the MIC against all six strains tested.
Subject(s)
Anti-Bacterial Agents/pharmacology , Glycopeptides/pharmacology , Staphylococcus/drug effects , Colony Count, Microbial , Drug Resistance, Bacterial , Kinetics , Methicillin Resistance , Microbial Sensitivity Tests , Teicoplanin/analogs & derivatives , Vancomycin ResistanceABSTRACT
The MICs of GW 773546, GW 708408, and telithromycin for 164 macrolide-susceptible and 161 macrolide-resistant pneumococci were low. The MICs of GW 773546, GW 708408, and telithromycin for macrolide-resistant strains were similar, irrespective of the resistance genotypes of the strains. Clindamycin was active against all macrolide-resistant strains except those with erm(B) and one strain with a 23S rRNA mutation. GW 773546, GW 708408, and telithromycin at two times their MICs were bactericidal after 24 h for 7 to 8 of 12 strains. Serial passages of 12 strains in the presence of sub-MICs yielded 54 mutants, 29 of which had changes in the L4 or L22 protein or the 23S rRNA sequence. Among the macrolide-susceptible strains, resistant mutants developed most rapidly after passage in the presence of clindamycin, GW 773546, erythromycin, azithromycin, and clarithromycin and slowest after passage in the presence of GW 708408 and telithromycin. Selection of strains for which MICs were >/=0.5 microg/ml from susceptible parents occurred only with erythromycin, azithromycin, clarithromycin, and clindamycin; 36 resistant clones from susceptible parent strains had changes in the sequences of the L4 or L22 protein or 23S rRNA. No mef(E) strains yielded resistant clones after passage in the presence of erythromycin and azithromycin. Selection with GW 773546, GW 708408, telithromycin, and clindamycin in two mef(E) strains did not raise the erythromycin, azithromycin, and clarithromycin MICs more than twofold. There were no change in the ribosomal protein (L4 or L22) or 23S rRNA sequences for 15 of 18 mutants selected for macrolide resistance; 3 mutants had changes in the L22-protein sequence. GW 773546, GW 708408, and telithromycin selected clones for which MICs were 0.03 to >2.0 microg/ml. Single-step studies showed mutation frequencies <5.0 x 10(-10) to 3.5 x 10(-7) for GW 773546, GW 708408, and telithromycin for macrolide-susceptible strains and 1.1 x 10(-7) to >4.3 x 10(-3) for resistant strains. The postantibiotic effects of GW 773546, GW 708408, and telithromycin were 2.4 to 9.8 h.
Subject(s)
Anti-Bacterial Agents/pharmacology , Macrolides/pharmacology , Streptococcus pneumoniae/drug effects , Azithromycin/pharmacology , Clarithromycin/pharmacology , Clindamycin/pharmacology , Drug Resistance, Bacterial , Erythromycin/pharmacology , Genes, Bacterial , Ketolides/pharmacology , Microbial Sensitivity Tests , Mutation/genetics , Streptococcus pneumoniae/genetics , Time FactorsABSTRACT
BACKGROUND: Short course antimicrobial therapy is suggested for group A streptococcal tonsillopharyngitis. METHODS: The bacteriologic and clinical efficacies of clarithromycin [30 or 15 mg/kg/day twice daily (b.i.d.)] or amoxicillin/clavulanate (43.8/6.2 mg/kg/day b.i.d.) for 5 days or penicillin V (30 mg/kg/day 3 times a day) for 10 days were compared. In a randomized, open label, parallel group, multicenter study, 626 children (2-16 years old) with tonsillopharyngitis were enrolled; 537 were evaluable for efficacy. Follow-up evaluations were performed at 4-8 and 21-28 days after therapy. RESULTS: At enrollment, 26% of the Streptococcus pyogenes isolates were clarithromycin-nonsusceptible. All regimens had an apparently similar clinical efficacy. The long term S. pyogenes eradication rates were 102 of 123 (83%) with amoxicillin/clavulanate and 88 of 114 (77%) with penicillin V. In the 30- and 15-mg/kg/day clarithromycin groups, eradication occurred in 71 of 86 (83%) and 59 of 80 (74%) of the clarithromycin-susceptible isolates (P = 0.33), and in 4 of 28 (14%) and 5 of 26 (19%) of the clarithromycin-resistant isolates, respectively (clarithromycin-susceptible versus -resistant, P < 0.0001). Both clarithromycin dosages were well-tolerated. CONCLUSIONS: In group A streptococcal tonsillopharyngitis, 5 days of clarithromycin or amoxicillin/clavulanate treatment had clinical efficacy comparable with that of 10 days of penicillin V treatment; however, amoxicillin/clavulanate and penicillin V were bacteriologically more effective than clarithromycin because of its failure to eradicate the clarithromycin-resistant S. pyogenes isolates. The 5-day clarithromycin regimens are not recommended for treatment of streptococcal tonsillopharyngitis in areas where in vitro resistance of group A streptococci to clarithromycin is common.
Subject(s)
Amoxicillin-Potassium Clavulanate Combination/administration & dosage , Clarithromycin/administration & dosage , Penicillin V/administration & dosage , Pharyngitis/drug therapy , Streptococcal Infections/drug therapy , Tonsillitis/drug therapy , Acute Disease , Adolescent , Child , Child, Preschool , Dose-Response Relationship, Drug , Drug Administration Schedule , Female , Follow-Up Studies , Humans , Male , Pharyngitis/microbiology , Probability , Reference Values , Risk Assessment , Severity of Illness Index , Streptococcal Infections/diagnosis , Streptococcus pyogenes/drug effects , Streptococcus pyogenes/isolation & purification , Tonsillitis/microbiology , Treatment OutcomeABSTRACT
The MICs of LBM415, a new peptide diformylase inhibitor, were evaluated and ranged from 0.03 to 4.0 microg/ml for 300 pneumococci, irrespective of their beta-lactam, macrolide, and quinolone susceptibilities. By comparison, vancomycin, teicoplanin, linezolid, and quinupristin-dalfopristin were also active, with MICs =2.0 microg/ml. Gatifloxacin and moxifloxacin were the most active quinolones tested, while the MICs of the beta-lactams rose with those of penicillin G. LBM415 at two times the MIC was bactericidal (99.9% killing) against six strains after 24 h.
Subject(s)
Amidohydrolases/antagonists & inhibitors , Anti-Bacterial Agents/pharmacology , Enzyme Inhibitors/pharmacology , Peptides/pharmacology , Streptococcus pneumoniae/drug effects , Colony Count, Microbial , Kinetics , Microbial Sensitivity TestsABSTRACT
The MICs of LBM415, a new peptide diformylase inhibitor, were =0.06 to 4.0 microg/ml for 258 isolates of Staphylococcus aureus and coagulase-negative staphylococci. LBM415 MICs were similar irrespective of whether the strains were methicillin susceptible or resistant. All strains were also susceptible to vancomycin, linezolid, ranbezolid, daptomycin, oritavancin, and quinupristin-dalfopristin. LBM415 at the MIC was bacteriostatic after 24 h.
Subject(s)
Amidohydrolases/antagonists & inhibitors , Anti-Bacterial Agents/pharmacology , Enzyme Inhibitors/pharmacology , Peptides/pharmacology , Staphylococcus aureus/drug effects , Colony Count, Microbial , Humans , Staphylococcal Infections/microbiology , Vancomycin ResistanceABSTRACT
Erythromycin-resistant Streptococcus pneumoniae isolates from young carriers were tested for their antimicrobial susceptibility; additionally, inducibility of macrolide and clindamycin resistance was investigated in pneumococci carrying erm(A), erm(B), or mef(A). Of 125 strains tested, 101 (81%) were multidrug resistant. Different levels of induction were observed with erythromycin, miocamycin, and clindamycin in erm(B) strains; however, in erm(A) strains only erythromycin was an inducer. Induction did not affect macrolide MICs in mef(A) strains.
Subject(s)
Anti-Bacterial Agents/pharmacology , Bacterial Proteins/genetics , Genes, Bacterial/genetics , Membrane Proteins/genetics , Methyltransferases/genetics , Streptococcus pneumoniae/drug effects , Erythromycin/pharmacology , Humans , Microbial Sensitivity Tests , Pneumococcal Infections/microbiologyABSTRACT
The activity of ranbezolid (RBX 7644), a new oxazolidinone, against 306 anaerobes was compared with those of 11 other agents. The MICs at which 50% of the isolates tested are inhibited and those at which 90% of the isolates tested are inhibited (in micrograms per milliliter) were as follows: ranbezolid, 0.03 and 0.5; linezolid, 2 and 4; vancomycin, >16 and >16; teicoplanin, 1 and >16; quinupristin-dalfopristin, 1 and >8; amoxicillin-clavulanate, 0.5 and 2; imipenem, 0.125 and 1; clindamycin, 0.25 and 8; metronidazole, 1 and 4; gatifloxacin, 0.5 and 4; and moxifloxacin, 0.5 and 2, respectively. Ranbezolid had very good in vitro activity against both gram-negative and -positive anaerobes.