Objective   To establish erythromycin resistance models of Streptococcus pneumoniae for analysis of the mutations in the binding domain of erythromycin.     Methods   Streptococcus pneumonia tigr4 and two clinical sensitive isolates were induced with erythromycin by minimum inhibitory concentration (MIC) method for antimicrobial susceptibility

and then the rplD

rplV genes

and 23S rRNA in sensitive and resistant strains were amplified by PCR and RT-PCR for sequencing. CPHmodels-2.0 was used to predict the spatial structures of ribosomal protein L4 and L22 coded by rplD and rplV genes.

     Results   MIC of Streptococcus pneumonia tigr4 increased from 0.0312 mg/L to 256mg/L while MICs of the two clinical isolates increased from 0.0312 mg/L to 32 mg/L.  Comparison of the pre- and post-induction results showed V32A mutation in ribosomal protein L4

D35G mutation in ribosomal protein L22

and

67

QK

68

to

67

RE

68

mutations in ribosomal protein L4. Changes in spatial structure was found in SiThe ribosomal protein L22 and ribosomal protein L4 due to D35G

Q67R

and K68E mutations respectively.     Conclusion   Streptococcus pneumonia can be induced to resistant to erythromycin in vitro. The mechanisms of resistance may be relate to the new mutations in the binding domain of erythromycin.