Bacteriological and molecular characterization of temperature- and CO₂-dependent Streptococcus pneumoniae serotype 24F ST162 isolated from Japanese children

Area of Science:

• Microbiology
• Infectious Diseases
• Vaccinology

Background:

• Invasive pneumococcal disease (IPD) remains a significant global health concern.
• Streptococcus pneumoniae serotype 24F, particularly sequence type (ST) 162, has emerged as a notable pathogen.
• The 13-valent pneumococcal conjugate vaccine (PCV13) has altered the epidemiological landscape of IPD.

Purpose of the Study:

• To characterize Streptococcus pneumoniae serotype 24F ST162 isolates from Japanese children with IPD.
• To investigate the growth characteristics and antimicrobial susceptibility testing challenges associated with this specific isolate.
• To inform clinical practice and future strategies in the post-PCV13 era.

Main Methods:

• Isolation and characterization of Streptococcus pneumoniae serotype 24F ST162 from pediatric IPD cases.
• Assessment of bacterial growth under standard laboratory conditions (35°C in ambient air).
• Evaluation of implications for antimicrobial susceptibility testing methodologies.

Main Results:

• Serotype 24F ST162 isolates demonstrated impaired growth at 35°C in ambient air.
• Standard broth microdilution antimicrobial susceptibility testing is not feasible under ambient air conditions for these isolates.
• This presents a diagnostic and therapeutic challenge for clinicians and laboratories.

Conclusions:

• Serotype 24F ST162 possesses unique bacteriological characteristics that impact standard laboratory diagnostics.
• Awareness of these traits is crucial for accurate diagnosis and effective treatment of IPD caused by this serotype.
• This serotype may pose an increasing challenge in the post-PCV13 vaccination era.