# Detection of Streptococcus pneumoniae in sterile liquids using real-time PCR (qPCR) in hospitalized patients with suspected invasive pneumococcal disease

## TL;DR

This study shows that qPCR is more effective than traditional culture methods for detecting Streptococcus pneumoniae in hospitalized patients with suspected invasive pneumococcal disease.

## Contribution

The study demonstrates the superior sensitivity of qPCR over culture for detecting pneumococcus in sterile fluids in a Peruvian hospital setting.

## Key findings

- qPCR detected pneumococcus in 71.8% of samples, compared to 29.4% by culture.
- Serotype 19A was the most common among positive samples.
- qPCR detected pneumococcus in 78.4% of pleural fluid and 55.0% of cerebrospinal fluid samples.

## Abstract

The standard for diagnosing invasive pneumococcal disease (IPD) is to isolate pneumococcus in culture. However, the etiological agent cannot be identified in some patients, especially those who received empirical antibiotic therapy. This study aimed to detect pneumococcus in normally sterile fluids by qPCR in patients with suspected IPD hospitalized in Lima. qPCR had a detection limit of 1.2 x 101 genome copies/uL. Of the 71 clinical samples (51 were pleural fluid [PF] and 20 were cerebrospinal fluid [CSF]), 29.4% (28/71) were positive for pneumococcus by culture and 71.8% (51/71) were positive by qPCR, including 78.4% (40/51) in PF and 55.0% (11/20) in CSF. Of the positive samples, 13/51 were serotype 19A. The detection of pneumococcus was almost double by qPCR compared to the conventional microbiological method. Therefore, molecular methods such as qPCR should be implemented to improve the identification and timely treatment of IPD in Peru and in the region.

El estándar para diagnosticar enfermedad neumocócica invasiva (ENI) es aislar neumococo en cultivo. Sin embargo, en algunos pacientes, sobre todo los que recibieron terapia antibiótica empírica, no se logra identificar el agente etiológico. El objetivo de este estudio fue detectar neumococo en líquidos normalmente estériles mediante qPCR en pacientes con sospecha de ENI hospitalizados en Lima. La qPCR tuvo un límite de detección de 1,2 x 101 copias del genoma/uL. De las 71 muestras clínicas (51 de líquido pleural [LP] y 20 de líquido cefalorraquídeo [LCR]), el 29,4% (28/71) fueron positivas para neumococo por cultivo y 71,8% (51/71) fueron positivas por qPCR, incluyendo 78,4% (40/51) en LP y 55,0% (11/20) en LCR. De las muestras positivas, 13/51 fueron del serotipo 19A. La detección de neumococo fue casi el doble por qPCR en comparación con el método microbiológico convencional. Por lo tanto, se debe implementar métodos moleculares como esta qPCR para mejorar la identificación y tratamiento oportuno de ENI en Perú y en la región.