Molecular epidemiology of Streptococcus pneumoniae isosslated from children with community-acquired pneumonia under 5 years in Chengdu, China.

Streptococcus pneumoniae (S. pneumoniae) is one of the most common community-associated pathogens responsible for pneumonia in children. This retrospective study aimed to investigate the molecular characteristics of S. pneumoniae isolated from children with community-acquired pneumonia (CAP) under 5 years in Chengdu, China. Molecular characteristics of S. pneumoniae included serotype and virulence factor performed by using PCR method and sequence types (STs) determined by sequencing seven housekeeping genes. In addition, the potential relationships between molecular characteristics were depicted by minimum spanning tree and correspondence analysis. The prevailing serotypes were 19F (18.52%), 6B (17.59%), 19A (13.89%), 6A (6.48%) and 23F (5.56%) among 108 isolates. The overall coverage rates of 7-valent, 10-valent, 13-valent, 15-valent and 20-valent pneumococcal conjugate vaccines (PCVs) were 47.32, 48.1, 75, 75 and 78.7%, respectively. Meanwhile, the coverage rates of PCV13 among the isolates from CAP patients aged <1 year were high up to 84.2%. MLST analysis results showed that there were 56 different STs identified, of which the dominant STs were ST271 (22.22%) and ST320 (12.04%). Five international clones among STs were observed, including Spain23F-1, Spain6B-2, Taiwan19F-14, Netherlands3-31 and Denmark14-32. Additionally, most of the isolates carried ply, psaA, nanA, pavA, piaA and CC271 isolates expressed more of nanA than non-CC271 isolates. Moreover, there were strong relevant relationships among STs, serotypes and virulence factors. Considering serotypes and virulence factors together can be used as the foundation for the formulation of vaccine strategy.