Dried Saliva Spots: A Robust Method for Detecting Streptococcus pneumoniae Carriage by PCR

Area of Science:

• Microbiology
• Molecular Diagnostics
• Public Health Surveillance

Background:

• Early Streptococcus pneumoniae (S. pneumoniae) carriage studies utilized saliva.
• Conventional culture methods hindered pneumococcal isolation from saliva due to oral microbial complexity.
• A need exists for improved, stable sample collection methods for S. pneumoniae surveillance.

Purpose of the Study:

• To evaluate the feasibility of using dried saliva spots (DSS) for S. pneumoniae carriage detection.
• To assess the stability and DNA recovery of S. pneumoniae from DSS under various storage conditions.
• To determine the suitability of DSS for epidemiological surveillance of pneumococcal carriage.

Main Methods:

• Saliva samples (from children) and S. pneumoniae-spiked saliva (from adults) were collected and applied to paper as dried saliva spots (DSS).
• DSS were stored at various temperatures (-20 to 37 °C) for up to 35 days, with and without desiccant.
• DNA was extracted from DSS and analyzed for S. pneumoniae using quantitative PCR (qPCR).

Main Results:

• S. pneumoniae DNA quantities in freshly processed DSS matched those in raw saliva.
• S. pneumoniae DNA remained stable in DSS stored with desiccant for up to one month across a range of temperatures.
• No significant differences were observed when using various S. pneumoniae strains for spiking.

Conclusions:

• Dried saliva spots (DSS) are a feasible and stable matrix for detecting S. pneumoniae DNA.
• DSS technology simplifies sample collection and transportation, making it ideal for remote surveillance.
• This method overcomes previous challenges in pneumococcal carriage studies using saliva.