Macrolide-resistant phenotypes of invasive Streptococcus pneumoniae isolates in Serbia

Abstract

Macrolide resistance in Streptococcus pneumoniae has emerged as an important worldwide problem over the past decade. The aim of this study was to investigate macrolide-resistant phenotypes and the antimicrobial susceptibility patterns of invasive pneumococci in Serbia. A total of 68 invasive pneumococcal strains, collected from 2009 to 2011, were sent from regional laboratories to the National Reference Laboratory. Susceptibility testing was performed using the VITEK2 system and phenotypes were determined by triple-test. Overall penicillin and erythromycin nonsusceptibility rates were 26% and 43%, respectively. Resistance rates were higher in children than in adults. Co-resistance to penicillin and erythromycin was detected in 18% strains. Resistance rates to the third generation of cephalosporins, TMP-SXT and tetracycline were 16%, 37% and 29%, respectively. All isolates were fully susceptible to vancomycin, linezolid, fluoroquinolones, telithromycin and rifampicin. Twenty-two isolates (79%) an expressed macrolide-lincosamide-streptogramin B (MLSB) resistance phenotype and M phenotype was found in 21% of macrolide resistant strains.