Molecular typing and drug resistance of Streptococcus pneumoniae serogroup 6

Objective To evaluate the performance of 2 methods to identify serotypes of Streptococcus pneumoniae serogroup 6 and understand the drug susceptibility and molecular characteristics of S. pneumoniae serogroup 6. Methods Quellung method and PCR assay were conducted to identify serotypes and related genotypes of 33 strains of S. pneumoniae serogroup 6, the drug susceptibility test to 6 common antibiotics was conducted for these strains and pulsed field gel electrophoresis (PFGE) was performed to analyze the genome characteristics of S. pneumoniae with different serotypes. Results The serological detection results of quellung method and PCR assay were consistent. All the strains were resistant to azithromycin, but sensitive to rifampin and levofloxacin. The drug resistant rate in strains of serotype 6B was higher. According to the PFGE patterns, the 33 strains were in 2 clusters. The PFGE patterns were quite similar between 6C strains and 6B strains. Conclusion PCR assay could be used to identify the serotypes of S. pneumoniae serogroup 6 instead of quellung method. The drug resistance of S. pneumoniae strains detected was very serious, and most of them were multi drug resistant. PFGE is quite sensitive in identifying the differences of S. pneumoniae with different serotypes.