Serotypes and antimicrobial susceptibility of invasive 'Streptococcus pneumoniae' isolated in Serbia in 2012-2013

Abstract

The aim of this study was to: determine susceptibility patterns of invasive Streptococcus pneumoniae to antimicrobial agents, evaluate macrolide resistance phenotypes and genotypes and identify capsular serotypes among invasive isolates of S. pneumoniae circulating in Serbia. The total of 85 invasive pneumococcal strains, collected during 2012 and 2013, were sent from regional laboratories to the National Reference Laboratory. Susceptibility testing was performed by disk diffusion and E test, while phenotypes and genotypes of macrolide resistant strains were determined by double-test and PCR, respectively. Serotyping was performed by Quelling reaction. The overall penicillin and erythromycin non-susceptibility rates were 14.12% and 28.23%, respectively. Resistance rates were significantly higher in children than in adults and (p<0,01). Co-resistance to penicillin and erythromycin was detected in 7.06% strains. Resistance rates to tetracycline and chloramphenicol were 29.41% and 15.29%, respectively. The rate of multi resistance was 27.06%. cMLS phenotype was detected in 62.5% of all macrolide resistant isolates, while 37.5% expressed M phenotype. All 15 isolates with cMLS phenotype harbored ermB gene and all M isolates harbored mefA. The most common resistant serotypes were 3, 9A and 23F. This study revealed that penicillin and macrolide resistance among invasive pneumococcal isolates is high. Obtained results emphasize the need for continuous monitoring of invasive pneumococcal disease in Serbia.