Antimicrobial activity of oritavancin and comparator against a challenge set of molecularly characterized Gram-positive clinical isolates displaying elevated linezolid MIC results

Organisma (no. of isolates tested) and antimicrobial agentMIC (μg/ml)% of isolates with indicated status according tob:
S. aureus (25)
    Oritavancin0.015 to
    Clindamycin≤0.25 to >2>2>
    Daptomycin0.25 to
    Erythromycin≤0.25 to >2>2>24.819.
    Levofloxacin0.25 to >4>4>412.
    Linezolid4 to 3281636.
    Tetracycline≤2 to >8≤2>884.
    TMP-SMXc≤0.5 to 4≤0.5≤0.596.
    Vancomycin0.5 to 212100.00.00.0100.00.0
CoNS (80)
    Oritavancin≤0.008 to
    Clindamycin≤0.25 to >21>232.530.037.520.012.567.5
    Erythromycin≤0.25 to >2>2>220.041.438.623.816.260.0
    Levofloxacin≤0.5 to >4>4>43.83.892.53.83.892.5
    Linezolid4 to >128321287.592.57.592.5
    Oxacillin≤0.25 to >2>2>
    Teicoplanin≤2 to >84892.36.41.358.241.8
    Tetracycline≤2 to >8≤2≤
    TMP-SMXc≤0.5 to >2>2>216.283.818.336.645.1
E. faecalis (13)
    Oritavancin≤0.008 to 10.0150.1292.3d
    Ampicillin≤1 to 4≤12100.00.0100.00.00.0
    Daptomycin0.5 to 212100.0
    Levofloxacine1 to >4>4>415.40.084.6
    Linezolid4 to 168160.046.253.846.253.8
    Teicoplanin≤2 to >8≤2>891.70.08.384.615.4
    Tetracycline≤0.25 to >8>8>815.40.084.6
    Vancomycin1 to >161>1684.60.015.484.615.4
E. faecium (32)
    Oritavancin≤0.008 to 0.120.0150.12
    Ampicillin>8 to >8>8>80.0100.00.00.0100.0
    Daptomycin0.5 to 422100.0
    Levofloxacine>4 to >4>4>40.00.0100.0
    Linezolid4 to 648320.
    Teicoplanin≤2 to >8>8>829.63.766.725.075.0
    Tetracycline≤2 to >8≤2>850.00.050.0
    Vancomycin1 to >16>16>1621.
  • a All S. aureus isolates, except 1, were methicillin (oxacillin) resistant. CoNS, coagulase-negative staphylococci, including 2 S. capitis, 1 S. cohnii, 69 S. epidermidis, 5 S. haemolyticus, and 3 S. hominis isolates.

  • b Breakpoint criteria were those from CLSI (22) and EUCAST (23), as available.

  • c TMP-SMX, trimethoprim-sulfamethoxazole.

  • d Breakpoint available for vancomycin-susceptible E. faecalis only. A total of 92.3% of all E. faecalis and 100.0% of vancomycin-susceptible E. faecalis isolates were susceptible to oritavancin. One E. faecalis isolate displaying a VanA phenotype (i.e., vancomycin and teicoplanin MIC values of ≥8 and ≥16 μg/ml, respectively) had an oritavancin MIC result of 1 μg/ml.

  • e For uncomplicated urinary tract infection only.