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Properties of Mucoid Serotype 3 Streptococcus pneumoniae From Children in China
Ying Yang1,2, Chun-Zhen Hua1, Chao Fang3
1Department of Infectious Diseases, The Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center For Child Health, Hangzhou, China.
Objective:
To investigate the characteristics of hosts, antimicrobial susceptibility, and molecular epidemiology of mucoid serotype 3 Streptococcus pneumoniae (S. pneumoniae) isolated from children in China.
Method:
S. pneumoniae isolates collected between January 2016 and December 2019 were analyzed. S. pneumoniae isolates with mucoid phenotype were selected visually, and serotype 3 isolates were confirmed by Quellung reaction. The antimicrobial susceptibility was measured by E-test. Multilocus sequence typing was used for clonal analysis.
Results:
Twenty (3.04%) isolates of mucoid serotype 3 S. pneumoniae were identified from 657 clinical isolates, and all of them were noninvasive strains. The mean age of the hosts was 5.69 ± 3.28 years. The isolates included: 50.0% from the dissected tonsil or adenoid tissue in children with obstructive sleep apnea-hypopnea syndrome, 45.0% from sputum or bronchial lavages in children with pneumonia, and 5.0% from vaginal secretions of one patient with vulvovaginitis. All isolates were susceptible to penicillin, cefuroxime, ceftriaxone, meropenem, vancomycin, levofloxacin, trimethoprim/sulfamethoxazole, and rifampin but resistant to erythromycin. Sequence type (ST)505 and its clonal complex (CC) were the main genotypes (95%). Antimicrobial susceptibility of ST180 and ST505 were compared, and the minimum inhibitory concentration (MIC) of ST505 isolates was significantly higher than that of ST180 for tetracycline, trimethoprim/sulfamethoxazole, and meropenem.
Conclusions:
Mucoid serotype 3 Streptococcus pneumoniae can be isolated from various body parts, among which the respiratory system is the most common. It can cause noninvasive infection in children, and it has high susceptibility to a variety of antibiotics, especially β-lactams, but is resistant to macrolides. CC505 is the novel clonal complex found in China, which may be related to the worldwide mainstream clonal complex (CC180) but has its own biological characteristics.
Insights
Mucoid serotype 3 Streptococcus pneumoniae in Chinese children causes noninvasive infections. These strains show high susceptibility to many antibiotics but resistance to erythromycin, with CC505 being a novel genotype.
Area of Science:
- Microbiology
- Epidemiology
- Genetics
Background:
- Streptococcus pneumoniae (S. pneumoniae) is a significant pathogen, with specific serotypes and phenotypes influencing disease presentation and treatment.
- Mucoid variants of S. pneumoniae, particularly serotype 3, have been less characterized, especially in pediatric populations in China.
Purpose of the Study:
- To investigate the characteristics of hosts, antimicrobial susceptibility, and molecular epidemiology of mucoid serotype 3 S. pneumoniae in Chinese children.
Main Methods:
- Analysis of S. pneumoniae isolates (2016-2019) with mucoid phenotype and serotype 3 confirmation.
- Antimicrobial susceptibility testing using E-test and molecular typing via multilocus sequence typing (MLST).
Main Results:
- Twenty mucoid serotype 3 S. pneumoniae isolates were identified, all from noninvasive infections in children (mean age 5.69 years).
- Isolates were commonly found in respiratory samples (tonsils, adenoids, sputum) and showed susceptibility to most tested antibiotics except erythromycin.
- Sequence type (ST)505 and its clonal complex (CC505) were predominant (95%), with CC505 exhibiting higher MICs for tetracycline, trimethoprim/sulfamethoxazole, and meropenem compared to ST180.
Conclusions:
- Mucoid serotype 3 S. pneumoniae causes noninvasive infections in children, primarily affecting the respiratory system.
- These isolates demonstrate broad antibiotic susceptibility, particularly to beta-lactams, but resistance to macrolides.
- CC505 represents a novel clonal complex in China with distinct characteristics, potentially related to the global CC180.
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