Detection of co-colonization with Streptococcus pneumoniae by algorithmic use of conventional and molecular methods

Area of Science:

• Microbiology
• Vaccinology
• Molecular Diagnostics

Background:

• Accurate detection of pneumococcal carriage is vital for assessing the efficacy of pneumococcal conjugate vaccines (PCV).
• Existing methods for detecting multiple pneumococcal serotypes in respiratory specimens vary in sensitivity, cost, and complexity.

Purpose of the Study:

• To develop and evaluate an algorithmic molecular method for detecting all known pneumococcal serotypes.
• To preserve the relative abundance of co-colonizing serotypes during detection.
• To provide an affordable and practical method for pneumococcal carriage assessment.

Main Methods:

• Culturing respiratory swabs followed by serotyping of 100 colonies using Quellung-guided molecular techniques (capsular and PCR reactions on 96-well plates).
• Evaluation of the method using 102 nasal swabs from children carrying Streptococcus pneumoniae.

Main Results:

• The developed method detected multiple pneumococcal serotypes in 22% of carriers, significantly higher than the 3% detected by the WHO-recommended method.
• The technique could identify subdominant strains representing as little as 1% of the bacterial population.
• The method demonstrated affordability (processing cost of $87) and practicality, preserving the native distribution of serotypes without false positives.

Conclusions:

• The novel algorithmic method is effective in detecting multiple pneumococcal serotypes, including subdominant strains, in respiratory specimens.
• This approach offers a sensitive, affordable, and practical alternative to current methods for assessing pneumococcal carriage and vaccine impact.
• The preservation of serotype abundance provides a more accurate representation of the microbial community.