# Rapid detection of Staphylococcus aureus in blood culture samples using human IgG-based lateral flow assay

## TL;DR

A new rapid test using human IgG detects Staphylococcus aureus in blood samples within 15 minutes, potentially enabling faster diagnosis and treatment.

## Contribution

The study introduces a cost-effective lateral flow immunoassay using human IgG for S. aureus detection, offering a faster alternative to traditional methods.

## Key findings

- The LFIA achieved 100% sensitivity and 92.4%-100.0% specificity in spiked blood culture samples.
- The detection limit for purified protein A was 10−3 µg/mL and for bacterial colonies was 107 CFU/mL.
- The test showed 98.1% sensitivity in 221 bacterial colony isolates and 89.7% in 118 positive blood culture bottles.

## Abstract

Staphylococcus aureus is one of the most common pathogens. The conventional workflow for identifying this organism is time-consuming and takes up to several days. Therefore, we developed a colloidal gold-based lateral flow immunoassay (LFIA) using human IgG as a conjugated antibody to detect S. aureus. One hundred and thirty-eight clinical isolates, including 79 S. aureus and 59 non-S. aureus were spiked in blood samples, and incubated at 37°C for 24 h. The bacterial antigens were simply extracted before being tested by the developed LFIA strips. The results were read by the naked eye within 15 min. Conventional PCR was used as a reference method. The sensitivity and specificity of the developed LFIA were 100% (95% CI: 94.2%–100.0% and 92.4%–100.0%, respectively) in spiked blood culture samples. The detection limits of the LFIA for the purified protein A and bacterial colonies were 10−3 µg/mL and 107 CFU/mL, respectively. The performance of the LFIA testing in 221 bacterial colony isolates and 118 positive blood culture bottles from three hospitals by their medical technologists showed 98.1% (95% CI: 94.1%–99.5%) and 89.7% (95% CI: 79.3%–95.4%) sensitivity, respectively. The LFIA is a quick, easy, and sensitive method for detecting S. aureus without expensive equipment. It might have the potential for early diagnosis of routine service in low-resource laboratories, leading to a rapid and effective treatment.

In this study, we modified our previously developed lateral flow immunoassay (LFIA) test for the detection of Staphylococcus aureus by using an in-house human IgG as a conjugated antibody instead of the specific commercial antibody. It gave comparable results to the former developed-LFIA test and helped cost reduction.