In vitro activity of linezolid and 12 other antimicrobials against coryneform bacteria

ObjectivesTo compare the in vitro activity of linezolid with 12 other antimicrobials against 190 strains of the coryneform bacteria, including 60 strains of C. amycolatum, 30 of C. striatum, 30 of C. jeikeium, 10 of C. urealyticum, 20 of B. casei, 20 of D. hominis and 20 of T. otitidis.MethodsMinimum inhibitory concentrations (MICs) and time–death curves were carried out according to the recommendations of the Clinical and Laboratory Standards Institute (CLSI).ResultsLinezolid was very active against the 130 strains of the Corynebacterium species studied. Only the glycopeptides showed similar efficacy. In contrast, penicillin G, ampicillin, macrolides, lincosamides, fluoroquinolones and aminoglycosides showed generally high MICs. Among the β-lactams, only imipenem was active against the majority of strains of C. striatum and C. amycolatum, and, approximately half of the C. jeikeium and C. urealyticum isolates. Both Dermabacter hominis and Brevibacterium casei showed marked resistance against most of the antimicrobials tested, while Turicella otitidis only showed high MICs against macrolides and clindamycin. For all of them, linezolid, vancomycin and teicoplanin proved effective.The time–death curves showed linezolid to behave as a bacteriostatic agent (approximately 90% death rate). Such activity was more accentuated for C. amycolatum and C. striatum (reduction of 1.3 and 1.7 log10 CFU/mL, respectively) than for C. jeikeium and C. urealyticum (reduction of 1.0 and 0.8 log10, respectively).ConclusionsOur results indicate that linezolid is active against coryneform bacteria. The efficacy of linezolid is equal to or even superior to that of the glycopeptides.