# Assessment of Clinical Significance of Molecular Streptococcus agalactiae Detection in Patients With Suspected Pneumonia

## TL;DR

This study examines whether detecting Streptococcus agalactiae in pneumonia patients using a specific test indicates a true infection or just harmless presence in the lungs.

## Contribution

The study provides insights into the clinical interpretation of Streptococcus agalactiae detection in pneumonia patients using the BIOFIRE Pneumonia Panel.

## Key findings

- In over half of the cases, Streptococcus agalactiae was considered nonpathogenic despite detection by the test.
- Only a small percentage of positive test results were confirmed by bacterial culture.
- Other microorganisms were commonly detected alongside Streptococcus agalactiae in most cases.

## Abstract

Streptococcus agalactiae (group B Streptococcus [GBS]) may cause pneumonia or may colonize the respiratory tract, making its clinical significance uncertain when detected in respiratory specimens. This study aimed to assess whether clinicians interpreted GBS detected by the BIOFIRE Pneumonia Panel (BF-PP) as a pathogen implicated in pneumonia.

This retrospective cohort study included adult patients hospitalized with suspected pneumonia at Mayo Clinic, Rochester, between September 2020 and February 2025. Cases were independently classified into pathogen and nonpathogen groups by 2 infectious diseases (ID) specialists, with a third reviewer resolving disagreements. Clinical characteristics and outcomes of both groups were recorded. A subgroup analysis of patients who had an ID consultation was performed.

A total of 109 cases were included. GBS was considered a pneumonia pathogen in 47.7% of cases and a nonpathogen in 52.3%. ID consultation was performed in 33.0% of cases, with GBS considered a pathogen in 30.6% of those. Common comorbid conditions included pulmonary, gastrointestinal, neurologic, and cardiovascular disease and obesity. Rates of endotracheal intubation were similar in the pathogen and nonpathogen groups (51.9% vs 50.9%, respectively), with the in-hospital mortality rate being numerically but not significantly higher in the former versus the latter (21.2% vs 14.0%; P = .33); findings were similar in the ID-assessed subgroup. In 76.1% of GBS detections, other microorganisms—most commonly Staphylococcus aureus—were codetected. Only 10.2% of BF-PP GBS-positive specimens were culture positive for GBS.

While GBS is not an uncommon pneumonia pathogen, the clinical significance of its detection by BF-PP is uncertain in many cases.

In more than half of BIOFIRE Pneumonia Panel Streptococcus agalactiae detections, the organism was considered nonpathogenic. Assessing clinical relevance can be challenging, highlighting the need for means to distinguish a true pneumonia pathogen from respiratory tract colonization.