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Capsular Serotyping of Streptococcus pneumoniae by Latex Agglutination
Published on: September 25, 2014
Serotype Distribution, Virulence Determinants and Antimicrobial Susceptibility of Streptococcus agalactiae Isolated
Zhengjiang Jin1, Juan Li2, Haijian Zhou2
1Department of Clinical Laboratory, Maternal and Child Health Hospital of Hubei Province, Wuhan 430070, China.
Insights
This study analyzed genetic characteristics of Streptococcus agalactiae (Group B Streptococcus, GBS) in Chinese infants. Serotype III, ST17, and Rib surface protein were predominant, highlighting genetic variations influencing virulence and antibiotic resistance.
Area of Science:
- Microbiology
- Genetics
- Infectious Diseases
Background:
- Streptococcus agalactiae (Group B Streptococcus, GBS) causes significant neonatal infections globally.
- Understanding GBS genetic diversity, including surface proteins and virulence factors, is crucial for managing infections, especially in China where data is limited.
Purpose of the Study:
- To investigate the genetic characteristics of clinical GBS isolates from infected infants in China.
- To analyze serotypes, surface proteins, virulence determinants, and antibiotic resistance genes.
Main Methods:
- Whole-genome sequencing and Multilocus Sequence Typing (MLST) were performed on 97 GBS isolates from infected infants (2017-2021).
- Analysis included assessment of GBS serotypes, sequence types (STs), clonal complexes (CCs), surface protein genes (e.g., Rib, srr1, hvgA), pilus island genes, and antibiotic resistance genes.
Main Results:
- Serotype III (49.5%) and ST17 (23.7%) were the most prevalent GBS types.
- The Rib surface protein was predominant (41.2%), mainly in serotype III strains.
- Significant proportions of isolates carried antibiotic resistance genes (tetM, tetO/tetL, ermB) and specific virulence gene profiles (cfb-cylE-lmb-pavA), particularly in serotype III/CC17.
Conclusions:
- Whole-genome sequencing revealed substantial genetic variation in GBS surface proteins, virulence, and antibiotic resistance in Chinese infant isolates.
- These findings provide critical insights into GBS genetic features and pathogenic dynamics.
- Continuous epidemiological surveillance is essential for improving GBS treatment outcomes.
Abstract:
Background: Streptococcus agalactiae (Group B Streptococcus, GBS) is the most common cause of serious infections in the first 3 months of life worldwide. The pathogenicity of GBS is closely related to serotypes, surface proteins and virulence factors, and the distribution of them may vary temporally and geographically. However, data related to GBS surface proteins and virulence determinants in China are very few. The aim of this study is to investigate the genetic characteristics of clinical GBS isolates from infected infants. Methods: We recovered GBS isolates from infected infants younger than 3 months during 2017−2021 at Maternal and Child Health Hospital of Hubei Province in China. We assessed the GBS serotypes, surface proteins, virulence determinants and antibiotic resistance genes distribution, by Multilocus sequence typing (MLST) and whole-genome sequencing analysis. Results: Among 97 isolates (81 EOD and 16 LOD), 5 serotypes were detected. Serotype III was the most represented (49.5%), followed by type Ib (20.6%). The isolates belonged to 17 different sequence types (STs) that grouped into the 8 clonal complexes (CCs). The most frequently identified ST was ST17 (23.7%). The most predominant surface protein of alpha-protein-like (alp) family (one of the protein components of the GBS surface antigen, resistant to trypsin) present was Rib (41.2%), which was mainly detected in serotype III. The srr1, which encodes Srr1 protein, was identified in 54.6% of isolates. The hvgA encoding for hypervirulent GBS adhesin can be detected in all 24 serotype III GBS. Among the pilus islands genes, 50% and 58.8% of the isolates were positive for pi-1 and pi-2a genes, respectively. The presence of pi-2b was mainly associated with serotype III/CC17 strains; 56.7% of isolates carried tetM, tetO/tetL, ermB antibiotic resistant genes. Among all the virulence genes detected, the cfb-cylE-lmb-pavA pattern was the main virulence gene profile (81.4%), mainly in serotype III/CC17. Conclusions: The whole genomic sequencing data revealed the high variation in surface proteins, determining virulence and antibiotic resistance in clinical isolates from 97 GBS infected infants. These data provide insightful characteristics of genetic features of GBS. Constant epidemiological surveillance is warranted to provide information on the GBS pathogenic dynamics and antibiotic resistance profiles in the surveyed areas for improving therapeutic outcomes.
