In vitro activity of tigecycline against Gram-positive cocci: a multicentre study in Greece

Abstract

than imipenem, meropenem and ceftriaxone. Our findings suggest that against these multidrug-resistant pneumococcal isolates, the ranking of in vitro activity based on MIC90 for the b-lactams would be ME1036 (0.12 mg/L) (most active).imipenem (0.5 mg/L). meropenem (1 mg/L).ceftriaxone (1 mg/L).cefotaxime (2 mg/L).penicillin1⁄4cefepime (4 mg/L).amoxicillin (8–16 mg/L).cefuroxime (16 mg/L).ampicillin ( 16 mg/L) (least active). A previous study that employed agar dilution testing against a smaller number of non-selected penicillin-resistant S. pneumoniae isolates reported an MIC90 value of 0.03 mg/L for ME1036, 4 a value two dilutions lower than the MIC90 value determined in this study against multidrug-resistant strains belonging to troublesome serotypes exhibiting higher amoxicillin than penicillin MIC. MIC90 values determined for ME1036 by broth microdilution against a small number (11 strains) of penicillin-resistant S. pneumoniae isolates in a previous study showed values similar to those in the present study. In conclusion, ME1036 exhibited excellent intrinsic activity against penicillin-resistant S. pneumoniae belonging to serotypes 9V, 14, 6B and 19A, exhibiting higher amoxicillin than penicillin MIC. The spread of multidrug resistance that includes b-lactams (including penicillins, secondand third-generation cephalosporins and previous carbapenems) may challenge empirical hospital treatment of lower respiratory tract infections. The high intrinsic activity of ME1036 against resistant strains of S. pneumoniae may represent an advantage when broadspectrum activity is required.