Analysis of macrolide-resistant isolates of Streptococcus pneumoniae gained from the Far East of Russia
Abstract number: 902_p1155
Macrolide resistance has been reported to be high among pneumococci in Asian countries, but the distribution of these macrolide resistance determinants is not known. The incidence of erythromycin-resistant strains among Streptococcus pneumoniae isolates in such a large territory as the Far East of Russia was approximately 5% until the early 1990s, but nowadays erythromycin-resistant strains have been greatly increasing.
To further define molecular mechanisms of macrolides resistance in pneumococci strains at the territory of the Far East of Russia.
MICs of penicillin, erythromycin, clarithromycin, and clindamycin were determined by the agar dilution method. PCRs were performed with appropriate primers.
A total of 35.82% (48 of 134 strains) of the S. pneumoniae strains were resistant to erythromycin with an MIC of 1.0 g/mL. Of these, 31.25% (15 of 48) showed an MLSB phenotype with erythromycin and clindamycin 50% MICs (MIC50s) and MIC90s of 64 g/mL; 66.6% (32 of 48) showed resistance to erythromycin alone (M phenotype), with a MIC50 and MIC90 of 8.0 g/mL. One isolate was positive with both ermB and mefE primers. Of the isolates expressing the MLSB phenotype, only the ermB gene was detected in 86.63% (13 strains of 15) of the isolates by PCR. Two isolates were repeatedly negative on testing for ermB but were positive for ermA gene. All the isolates expressing the M phenotype were positive for the mefE gene by PCR. The majority of the M-phenotype strains (84.37%, or 27 of 32) had constitutive resistance (cML phenotype); only 15.625% of these strains had inducible resistance (iML phenotype). Before 2000, it was recorded (5) that among the erythromycin resistant S. pneumoniae isolates, the majority (78%) had an ML phenotype and 22% had an M phenotype. All S. pneumoniae isolates exhibiting a cML or iML phenotype harboured the ermB gene.
This study indicated a high percentage of erythromycin resistance among clinical isolates of S. pneumoniae in the Far East of Russia. It requires a more careful approach to diagnostics of macrolide resistance in pneumococci in the clinical microbiology laboratory, particularly in areas with high rates of macrolide resistance."
|Session name:||XXIst ISTH Congress|
|Back to top|