Validation of pneumococcal iron acquisition (piaA) gene for accurate identification of Streptococcus pneumoniae

Area of Science:

• Microbiology
• Molecular Diagnostics

Background:

• Streptococcus pneumoniae causes significant global health burdens.
• Accurate and rapid identification of pneumococci is crucial for effective treatment and public health surveillance.
• The pneumococcal iron acquisition (piaA) gene has been proposed as a highly specific marker for pneumococcal identification.

Purpose of the Study:

• To evaluate the efficacy of the piaA gene as a genetic marker for the identification of pneumococci.
• To assess the sensitivity and specificity of piaA-based polymerase chain reaction (PCR) for pneumococcal detection.

Main Methods:

• Initial sequencing of the lytA gene for 20 isolates.
• Development and application of a piaA-specific PCR assay using in-house primers and protocol.
• Selection of 30 pneumococcal and 11 non-pneumococcal isolates based on initial results for further testing.
• Statistical analysis of sensitivity, specificity, and agreement using OpenEpi v3.01 and GraphPad Quickcalc.

Main Results:

• The piaA PCR demonstrated 100% specificity in initial testing of non-pneumococcal isolates.
• Sensitivity for piaA PCR was 71.43% for pneumococcal isolates in initial testing, increasing to 73.33% when tested on a larger sample size (41 samples).
• A moderate level of agreement (κ = 0.694) was observed between piaA PCR and lytA sequencing.

Conclusions:

• The piaA gene serves as a specific genetic marker for pneumococcal identification.
• While specific, the piaA PCR assay exhibits moderate sensitivity, suggesting limitations for sole diagnostic use.
• Further extensive research with larger sample cohorts is recommended to definitively establish piaA as a reliable diagnostic marker for pneumococcus.