Activity of telithromycin against multi-drug resistant Streptococcus pneumoniae and molecular characterization of macrolide and tetracycline resistance determinants.

Abstract

The antistreptococcal activity of telithromycin and 11 different comparators was evaluated in 26 multi-drug resistant (MDR) Streptococcus pneumoniae strains collected during 2002-2003 as part of the ongoing PROTEKT (Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin) Italian Surveillance Program. The strains were characterized for their susceptibility to antibiotics both at the phenotypic and genotypic levels; furthermore, the association of erm(B), mef(A) class and tet(M) genes, as well as the mobile elements carrying them were determined. The strains in this study were resistant to penicillin (MIC > or = 2 mg/l) in 23.1% of cases, resistant to tetracycline in 88.4%, to cotrimoxazole in 34.6% and cefuroxime in 26.9% while only telithromycin and levofloxacin retained 100% activity against all microorganisms. Co-existence of different resistance determinants was found in 19.2% of all isolates collected in our laboratory, coming from southern Italy. Twenty-three isolates showing the MLSB phenotype of resistance possessing the erm(B) gene (88.5%), associated with tet(M), were carried on the same Tn1545-like element, while two isolates showing the M phenotype possessing the mef(A) gene alone, were carried on Tn1207.1. In only one strain were mef(E) and tet(M) together carried on Tn2009.