Molecular epidemiological characterization in mucoid-type Streptococcus pneumoniae isolates obtained from invasive pneumococcal disease patients in Japan

Serotype distribution and antimicrobial resistance of Streptococcus pneumoniae isolated from children in Japan, 2023

Background

The prevalence of serotypes and antimicrobial resistance of Streptococcus pneumoniae was characterized among children thirteen years after the licensure of the pneumococcal conjugate vaccine (PCV) in Japan.

Methods

A total of 353 pneumococcal isolates were collected from Japanese children between March and July 2023. All the isolates were serotyped using genetic methods and tested for susceptibility to 14 antimicrobial agents.

Results

Among the 353 isolates, the prevalence rates of non-PCV13 and non-PCV20 serotypes were 96.9 % and 77.9 %, respectively, including the dominant non-PCV13/PCV20 serotypes 23A (16.1 %), 35B (15.3 %), 15A (10.5 %), 15C (9.3 %), and 34 (9.1 %), which accounted for 60.3 % of all isolates. The high non-susceptibility rates were observed for macrolides (erythromycin, azithromycin, and clarithromycin; ≥81.9 %) and tetracycline (80.7 %). Penicillin non-susceptibility and multidrug resistance (MDR) were detected in 49.9 % (6.8 % resistant and 43.1 % intermediate) and 68.3 % of the isolates, respectively. The three most common non-PCV13/PCV20 serotypes 15A, 23A, and 35B exhibited high prevalence rates of penicillin non-susceptibility (≥89.5 %) and MDR (≥81.5 %). Extensive drug resistance was observed in 10.5 % of all isolates belonging to six different serotypes (12F, 23A, 11A, 15A, 35B, and 15B) and in the non-encapsulated strains of S. pneumoniae.

Conclusions

Our study revealed a higher prevalence of non-susceptibility to penicillin with MDR in the three most common non-PCV13/PCV20 serotypes 15A, 23A, and 35B, in Japan, suggesting their persistence in the PCV13 era.

Invasive pneumococcal serotype 3 infection following pneumococcal vaccination in a hematopoietic stem cell transplant patient: A case report

Given the high mortality rate of invasive pneumococcal disease (IPD) in hematopoietic stem cell transplant (HSCT) recipients, vaccination is recommended. These recipients respond to most vaccines; however, their immune response is typically weaker during the first months or years after transplantation, compared with that of healthy individuals. Here, we report a case of IPD with serotype 3 pneumonia and empyema in an HSCT recipient who had received three doses of the 13-valent pneumococcal conjugate vaccine (PCV) and one dose of the 23-valent pneumococcal polysaccharide vaccine; furthermore, the recipient had no relapse, graft-versus-host disease, or use of immunosuppressive agents after allogeneic HSCT for acute myeloid leukemia. Moreover, we discussed the characteristics of serotype 3 Streptococcus pneumoniae, a case series of breakthrough infections with S. pneumoniae in HSCT recipients who received pneumococcal vaccines, and the potential implications for the upcoming PCV15 and PCV20 vaccines for serotype 3.

Historical Population-Level Impact of Infant 13-Valent Pneumococcal Conjugate Vaccine (PCV13) National Immunization Programs on Invasive Pneumococcal Disease in Australia, Canada, England and Wales, Israel, and the United States

INTRODUCTION

This study estimates the annual population-level impact of 13-valent pneumococcal conjugate vaccine (PCV13) infant national immunization programs (NIPs) on vaccine-type and non-vaccine type invasive pneumococcal disease (IPD) incidence across all ages using national surveillance data.

METHODS

We identified countries (Australia, Canada, England and Wales, Israel, and the US) with national IPD active surveillance data that introduced the seven-valent PCV (PCV7) followed by PCV13, which also reported annual serotype- and age group-specific incidence. We extracted IPD incidence by serotype groupings [PCV13 minus PCV7 (PCV13-7) serotypes; PCV13-7 serotypes excluding serotype 3; non-PCV13 serotypes; and the 20-valent (PCV20) minus PCV13 (PCV20-13) serotypes] and by age groups (< 2 years, 2-4 years, 5-17 years, 18-34 years, 35-49 years, 50-64 years, and ≥ 65 years). For each country, we calculated the annual relative change in IPD incidence (percent change), and the corresponding incidence rate ratio (IRR), for 7 years post introduction compared to the year prior to PCV13 program initiation.

RESULTS

PCV13-7 vaccine-type IPD incidence consistently decreased over time following introduction of PCV13 across countries, reaching an approximate steady state after 3-4 years in ages < 5 years, with roughly 60-90% decrease (IRRs = 0.1-0.4) and after 4-5 years in ages ≥ 65 years with approximately 60-80% decrease (IRRs = 0.2-0.4). Incidence declines were more substantial for the PCV13-7 grouping when excluding serotype 3. Non-PCV13 serotype incidence was variable by country and age group, ranging from virtually no serotype replacement compared to the PCV7 period across ages in the US to increases for other countries ranging from 10 to 204% (IRRs = 1.10-3.04) in children < 5 years and 41% to 123% (IRRs = 1.41-2.23) in ages ≥ 65 years.

CONCLUSIONS

Countries with longstanding PCV13 infant NIPs have observed substantial direct and indirect benefits, which are demonstrated in this study by the reduction in PCV13-7 IPD incidence compared to PCV7 period in all age groups. Over time, non-PCV13 serotypes have emerged in response to the reduction of incidence of PCV13-unique serotypes. Higher-valent PCVs are needed to address this emerging pneumococcal disease burden as well as the direct vaccination of both pediatric and adult populations against the most prevalent circulating serotypes.

Multiple comorbidities increase the risk of death from invasive pneumococcal disease under the age of 65 years

INTRODUCTION

Risk factors for death from invasive pneumococcal disease (IPD) have not been clearly established in patients aged under 65 years. We aimed to evaluate contributions of host and bacterial factors to the risk of death from IPD in patients aged under 65 years in Japan.

METHODS

In this prospective, observational, multicenter cohort study, patients with IPD (n = 581) aged 6-64 years were enrolled between 2010 and 2017. We investigated the role of host and bacterial factors in 28-day mortality.

RESULTS

The mortality rate increased from 3.4% to 6.2% in patients aged 6-44 years to 15.5%-19.5% in those aged 45-64 years. Multivariable analysis identified the following risk factors for mortality: age 45-64 years (hazard ratio [HR], 3.4; 95% confidence interval [CI], 1.6-6.8, p = 0.001), bacteremia with unknown focus (HR, 2.0; 95% CI, 1.1-3.7, p = 0.024), meningitis (HR, 2.1; 95% CI, 1.1-4.0, p = 0.019), underlying multiple non-immunocompromising conditions (HR, 2.6; 95% CI, 1.1-7.4, p = 0.023), and immunocompromising conditions related to malignancy (HR, 2.4; 95% CI, 1.0-5.2, p = 0.039). Pneumococcal serotype was not associated with poor outcomes.

CONCLUSIONS

Host factors, including age of 45-64 years and underlying multiple non-immunocompromising conditions, are important for the prognosis of IPD. Our results will contribute to the development of targeted pneumococcal vaccination strategies in Japan.

Properties of Mucoid Serotype 3 Streptococcus pneumoniae From Children in 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.