Emergence of a Streptococcus pneumoniae isolate resistant to streptogramins by mutation in ribosomal protein L22 during pristinamycin therapy of pneumococcal pneumonia

Objectives: The aim of this study was to characterize the mechanism of resistance to macrolides and streptogramins of a Streptococcus pneumoniae strain isolated from blood cultures in an 80-year-old patient suffering from severe pneumonia unsuccessfully treated with pristinamycin. Methods: Resistance genes erm(B) and mef(A) were searched for by PCR. Portions of genes for domains V and II of the 23S rRNA (rrl) and genes for ribosomal proteins L4 (rplD) and L22 (rplV) were amplified by PCR from total genomic DNA and sequenced. Results: Resistance genes erm(B) and mef(A) were not detected. Only mutation in the rplV gene encoding ribosomal protein L22 was detected. The strain contained a six amino acid insertion ( 107 KRTAHI 108 ) in the C-terminus of the ribosomal protein L22. Conclusions: This is the first report of emergence of a pneumococcus resistant to streptogramins by mutation in ribosomal protein L22 during treatment with pristinamycin.