[Activity of ertapenem and 19 other antimicrobial agents against beta-lactam-resistant Streptococcus pneumoniae and Haemophilus influenzae respiratory tract isolates]

Abstract

Introduction: Ertapenem is a new carbapenem with a long half-life that has a broad spectrum of action against Gram-positive and Gram-negative bacteria. Although, clinically indicated for the treatment of the polymicrobial abdominal infection, other uses are possible, due to the broad spectrum of action of this antimicrobial agent.

Objective: The purpose of this study was to examine the susceptibility to ertapenem of Streptococcus pneumoniae and Haemophilus influenzae strains with resistance to beta-lactam antibiotics.

Methods: The study comprised 105 S. pneumoniae strains with a reduced susceptibility to penicillin G, 86 S. pneumoniae strains resistant to penicillin, and 100 H. influenzae strains resistant to ampicillin isolated fron clinical respiratory samples collected in the 21 participating microbiology laboratories. Susceptibility to antimicrobials was tested using an agar dilution method.

Results: The S. pneumoniae strains with intermediate resistance to penicillin were highly susceptible to carbapenems, with MIC90 of 0,25 and 0,5 mg/l for imipenem and ertapenem, respectively. Among the penicillin-resistant strains the MIC90 values for imipenem and ertapenem were 1 and 2 mg/l respectively. Carbapenems were very active against the whole group of H. influenzae strains, particullary ertapenem, which inhibited 90% of the series at a concentration of 0,12 mg/l.

Conclusions: Ertapenem is a powerful agent against the most common respiratory bacterial pathogens, including those with resistance mechanisms effective against other compouunds. Few strains can currently be considered resistant to this carbapenem, which is at least comparable to imipenem, cefotaxime or the modern fluorquinolones. Such performance, and its favorable pharmacokinetic characteristics, make ertapenem an interesting option for the treatment of respiratory tract infections.