Serotype Distribution, Antimicrobial Susceptibility, Multilocus Sequencing Type and Virulence of Invasive Streptococcus pneumoniae in China: A Six-Year Multicenter Study.

Menglan Zhou,Chenyun Qian,Li Zhang,Bin Jiang,Haoran An,Hong Zhang,Yao Wang,Timothy Kudinha,Ziran Wang,Jingren Zhang,Zhengyin Liu,Yingchun Xu

doi:10.3389/fmicb.2021.798750

Abstract

Background: Streptococcus pneumoniae is an important human pathogen that can cause severe invasive pneumococcal diseases (IPDs). The aim of this multicenter study was to investigate the serotype and sequence type (ST) distribution, antimicrobial susceptibility, and virulence of S. pneumoniae strains causing IPD in China.Methods: A total of 300 invasive S. pneumoniae isolates were included in this study. The serotype, ST, and antimicrobial susceptibility of the strains, were determined by the Quellung reaction, multi-locus sequence typing (MLST) and broth microdilution method, respectively. The virulence level of the strains in the most prevalent serotypes was evaluated by a mouse sepsis model, and the expression level of well-known virulence genes was measured by RT-PCR.Results: The most common serotypes in this study were 23F, 19A, 19F, 3, and 14. The serotype coverages of PCV7, PCV10, PCV13, and PPV23 vaccines on the strain collection were 42.3, 45.3, 73.3 and 79.3%, respectively. The most common STs were ST320, ST81, ST271, ST876, and ST3173. All strains were susceptible to ertapenem, levofloxacin, moxifloxacin, linezolid, and vancomycin, but a very high proportion (>95%) was resistant to macrolides and clindamycin. Based on the oral, meningitis and non-meningitis breakpoints, penicillin non-susceptible Streptococcus pneumoniae (PNSP) accounted for 67.7, 67.7 and 4.3% of the isolates, respectively. Serotype 3 strains were characterized by high virulence levels and low antimicrobial-resistance rates, while strains of serotypes 23F, 19F, 19A, and 14, exhibited low virulence and high resistance rates to antibiotics. Capsular polysaccharide and non-capsular virulence factors were collectively responsible for the virulence diversity of S. pneumoniae strains.Conclusion: Our study provides a comprehensive insight into the epidemiology and virulence diversity of S. pneumoniae strains causing IPD in China.

Highlights

Streptococcus pneumoniae is a common Gram-positive coccus that can cause serious invasive pneumococcal diseases (IPDs) such as pneumonia, meningitis, and sepsis, especially in children and the elderly
The serotypes of 299 S. pneumoniae strains were accurately identified by Quellung reaction, and the remaining one isolate was considered as non-typeable (NT)
Based on the specific serotypes included in the vaccines, the coverage rates of PCV7, PCV10, PCV13, and PPV23 vaccines on this bacterial collection were 42.3% (127/300), 45.3% (136/300), 73.3% (220/300), and 79.3% (238/300), respectively (Figure 1A)

Summary

Introduction

Streptococcus pneumoniae is a common Gram-positive coccus that can cause serious invasive pneumococcal diseases (IPDs) such as pneumonia, meningitis, and sepsis, especially in children and the elderly. At present, developed countries in Europe and the United States have already included PCV and PPV vaccines in their national vaccination programs, greatly reducing IPD caused by serotypes covered by these vaccines (Richter et al, 2013; Esposito et al, 2014). S. pneumoniae can undergo efficient intraand interspecies DNA recombination, leading to changes in the capsule composition, molecular typing, antibiotic resistance, and virulence factors (Varghese et al, 2019) These phenomena present great challenges to the prevention and treatment of pneumococcal diseases. Streptococcus pneumoniae is an important human pathogen that can cause severe invasive pneumococcal diseases (IPDs) The aim of this multicenter study was to investigate the serotype and sequence type (ST) distribution, antimicrobial susceptibility, and virulence of S. pneumoniae strains causing IPD in China

Methods

Results

Discussion

Conclusion